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Testing and analysis of the Bangladeshi Treadle pump Kroeker, Murray George 1989

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TESTING AND ANALYSIS OF THE BANGLADESHI TREADLE PUMP By MURRAY GEORGE KROEKER B.Sc.Ag.Eng., The University of Manitoba, 1987 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Applied Science, C i v i l Engineering) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March 1989 (cj Murray George Kroeker, 1989 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of C I V I L ENGINEERING The University of British Columbia Vancouver, Canada D A T E A P R I L 2 0 , 1 9 B 9 DE-6 (2/88) ABSTRACT The Treadle pump was invented i n 1980 by development workers to provide low cost, low technology and l o c a l l y manufacturable i r r i g a t i o n for farmers i n northern Bangladesh. The twin cylinder steel-bodied suction pump, c a l l e d the Treadle pump, operated by a walking motion upon two c e n t r a l l y pivoted levers, i s well suited to the high water tables of much of Bangladesh. The increased popularity of the pump, r e s u l t i n g from extensive marketing e f f o r t s , with annual sales of over 50,000 units i n 1987/88, has prompted suggestions f o r design a l t e r a t i o n s , s p e c i f i c a l l y pump material changes to decrease costs and increase sales. A technical f i e l d and laboratory study supported by calc u l a t i o n s from hydraulic theory was required as a basis upon which to s t a r t design a l t e r a t i o n s . In laboratory t e s t s , d i f f e r e n t pump body configurations were found to have n e g l i g i b l e impact on o v e r a l l pump performance c h a r a c t e r i s t i c s . These findings were supported by r e s u l t s obtained from cal c u l a t i o n s of f r i c t i o n and turbulent l o s s . Any worthwhile a l t e r a t i o n s must rather be j u s t i f i e d by cost and manufacturing benefits. The combination of computer-aided instrumentation and high speed data c o l l e c t i o n i n laboratory t e s t i n g , i i t h e o r e t i c a l analysis, and f i e l d t e s t i n g i n Bangladesh revealed that the losses i n pump performance are a r e s u l t of poor valve sealing, valve opening and cl o s i n g delays and leakage past the piston se a l , r e s u l t i n g i n lower discharges than had been previously assumed. The reduced discharge for i r r i g a t i o n and the operator power input l i m i t , measured at the pump, of 55 watts r e s u l t s i n a four meter maximum depth of water table to which the standard 89 mm (3.5 inch) pump can be used, with some v a r i a t i o n due to i r r i g a t i o n requirements and operator strengths. Improvements to piston valve and foot valve design to reduce leakage and valve-delay times and the use of a smaller 77 mm (3 inch) cylinder diameter, are achievable and are recommended. These improvements combine to permit operation of the pump to nearly s i x meters without exceeding the l i m i t of input power or reducing the discharge below the crop i r r i g a t i o n requirements. TABLE OF CONTENTS PAGE ABSTRACT i i LIST OF TABLES v i LIST OF FIGURES v i i ACKNOWLEDGEMENT i x 1 INTRODUCTION 1 2 BACKGROUND 3 2.1 TREADLE PUMP DEVELOPMENT AND IMPACT 3 2.2 PREVIOUS TEST RESULTS 8 3 DESCRIPTION OF THE TREADLE PUMP 14 3.1 PHYSICAL DESCRIPTION 14 3.2 PUMP OPERATION 19 4 PUMP OPERATION MODEL 23 4.1 OPERATIONAL CONSTRAINTS 23 4.2 CALCULATION OF UNBALANCED HEAD 24 4.2.1 MINOR LOSSES 24 4.2.2 VALVE TIMING AND LEAKAGE 25 4.2.3 INERTIA 26 4.2.4 MECHANICAL LOSSES 29 4.3 GOVERNING EQUATIONS 3 0 5 LABORATORY TESTING 35 5.1 APPARATUS DESIGN CONSIDERATIONS 35 5.2 TESTING PROCEDURE 3 9 5.3 DATA REDUCTION AND ANALYSIS . . . . . 41 6 FIELD TESTING 43 6.1 APPARATUS DESIGN CONSIDERATIONS 4 3 6.2 TEST LOCATIONS AND PROCEDURE 45 6.3 DATA ANALYSIS 49 i v V 7 RESULTS 51 7.1 PUMP FORCES 51 7.2 VALVE CLOSURE DELAYS 56 7.3 THE EFFECT OF WATER TABLE DEPTH ON APPLIED FORCE 60 7.4 THE EFFECT OF WATER TABLE DEPTH ON DISCHARGE AND VOLUMETRIC EFFICIENCY 60 7.5 POWER INPUT REQUIREMENTS 63 7.6 THE EFFECT OF PUMP AGE ON DISCHARGE AND VOLUMETRIC EFFICIENCY 67 7.7 THE EFFECT OF PUMP BODY CONFIGURATION ON VOLUMETRIC EFFICIENCY, POWER REQUIREMENTS AND DISCHARGES 68 8 DISCUSSION 71 8.1 VALIDATION OF THEORETICAL MODEL BY LABORATORY TESTS 71 8.2 COMPARISON OF LABORATORY AND FIELD TEST RESULTS 72 8.3 IMPLICATIONS OF THE RESULTS ON PUMP RE-DESIGN . 74 9 CONCLUSION 79 LIST OF REFERENCES 82 APPENDIX 1: AVERAGED LABORATORY TEST DATA 85 APPENDIX 2: AVERAGED FIELD TEST DATA 86 LIST OF TABLES Table I: Treadle pump sales of International Development Enterprises (IDE), Rangpur Dinajpur R e h a b i l i t a t i o n Service (RDRS) and others. (Source: IDE 1988) 7 Table I I : Percent loss from piston and foot valve delays. 57 v i LIST OF FIGURES Figure 1: Geographical location of Bangladesh 5 Figure 2: Water table depths i n Bangladesh 6 Figure 3: Rope and pulley type Treadle operation 8 Figure 4: Centrally pivoted "dheki" type Treadle operation.9 Figure 5: "Dheki" s t y l e f i e l d i n s t a l l a t i o n of the Treadle pump 15 Figure 6: The two piston configurations, the two-plate design and the No. 6 s t y l e piston, and the two types of junctions tested 16 Figure 7: F i e l d operation of Treadle pump i n Bangladesh 18 Figure 8: The pump cycle defined by valve p o s i t i o n s . . 19 Figure 9: C h a r a c t e r i s t i c piston motion parameters. . . 27 Figure 10: An example of calculated force r e s u l t s with laboratory measured parameters 34 Figure 11: Instrumentation for the laboratory t e s t s . . . 36 Figure 12: Laboratory apparatus 38 Figure 13: Location of f i e l d t e s t s . 46 Figure 14: Force-displacement loop using the two-plate type pistons 52 Figure 15: Force-displacement loop using the No. 6 type piston 53 Figure 16: Variations i n force with water table depth. 61 Figure 17: The e f f e c t of water table depth on volumetric e f f i c i e n c y 62 v i i v i i i Figure 18: Laboratory and estimated f i e l d power input requirements 65 Figure 19: E f f e c t of pump age on volumetric e f f i c i e n c y and discharge from f i e l d t e sts 67 Figure 20: E f f e c t of pump configuration on laboratory measured volumetric e f f i c i e n c y and discharge. . . . 69 Figure 21: Comparison of calculated and laboratory r e s u l t s 71 ACKNOWLEDGEMENT I g r a t e f u l l y acknowledge the Canadian International Development Agency (CIDA) for f i n a n c i a l support through the Awards for Canadians Program. I also would l i k e to acknowledge Bob Nanes and the res t of the s t a f f of International Development Enterprises i n Bangladesh, Canada and the United States for t h e i r assistance, valuable in s i g h t s and l o g i s t i c a l support, Dr. Stephen V. A l l i s o n , previously Director of Operations f o r IDE and currently consultant for the World Bank, for h i s guidance and help as program supervisor and Dr. M. C. Quick of the C i v i l Engineering department at the University of B r i t i s h Columbia for h i s support i n arranging laboratory space and equipment and f o r h i s i n t e r e s t i n the project. i x 1 INTRODUCTION This t h e s i s examines the performance of two configurations of s t e e l Treadle pump bodies and piston configurations, including the designs currently marketed for use i n Bangladesh. Investigation of the pumps by intensive laboratory t e s t i n g and data analysis, f i e l d t e s t s , and analysis from hydraulic theory provides a basis f o r evaluating the pump design and a l t e r a t i o n a l t e r n a t i v e s . An i n i t i a l study of the pump uses, proposed design a l t e r a t i o n s and pump theory was conducted i n Bangladesh during the summer of 1987, followed by laboratory t e s t i n g of alternate pump and piston designs at the University of B r i t i s h Columbia at Vancouver, Canada, i n mid-1988. F i e l d t e s t i n g of Treadle pumps, using the currently marketed configuration of pump body and pistons, was conducted i n the ce n t r a l , eastern and northern regions of Bangladesh at the s t a r t of i r r i g a t i o n for the 1988-89 dry season crops i n la t e November and December 1988. Included i s a hi s t o r y and description of the Treadle pump, to f a m i l i a r i z e readers with t h i s technology, and an examination of the pump hydraulics to describe the pump operation i n more d e t a i l and provide the basis f o r the 1 2 analysis of laboratory and f i e l d t e s t s . Adescription of the laboratory and f i e l d t e s t s and the presentation of the t e s t r e s u l t s , as well as those from the theory based c a l c u l a t i o n s , provides a comprehensive view of the pump performance c h a r a c t e r i s t i c s . The r e s u l t s also i d e n t i f y the mechanisms a f f e c t i n g pump performance as well as providing the basis f o r proposed design a l t e r a t i o n s . The t e s t i n g and study included i s based on the Treadle pump designs and operation configuration described i n section two. This uses c e n t r a l l y pivoted levers to operate the pump, referred to as the "dheki" operation structure, as i s p r i m a r i l y used i n Bangladesh at t h i s time. The t e s t i n g parameters and design alt e r n a t i v e s examined are l i m i t e d to those manufacturable with materials and technology available i n Bangladesh. 2 BACKGROUND 2.1 TREADLE PUMP DEVELOPMENT AND IMPACT The Treadle pump was invented i n 1980 by Gunnar Barnes and Dan Jenkins, development workers with the non-governmental organizations (NGOs), the Rangpur-Dinajpur R e h a b i l i t a t i o n Service (RDRS) and USAid respectively, operating i n northern Bangladesh (RDRS 1984). Bangladesh, located east of India and north-west of Burma, encompassing the Ganges and Brahmaputra r i v e r deltas where they enter the Bay of Bengal, i l l u s t r a t e d i n figure 1, i s well suited to human powered i r r i g a t i o n because: a) Labor i s widely available, e i t h e r by the pump owner or at low cost. b) The high water table throughout most of the country i s within the 10 meter l i m i t of suction pumps, as shown i n the water table depth map i n figure 2 and, c) farm pl o t s are t y p i c a l l y so small that the quantities of water required d a i l y are within the l i f t i n g capacity of a single human operator. The s i z e of plots i r r i g a t e d by manual i r r i g a t i o n range i n s i z e from 0.25 to 1 hectare (Orr and Islam 1988). High value crops such as vegetables, spices and tobacco are grown as they generally have lower i r r i g a t i o n requirements, less 3 4 than 6 mm/day on average (EPC 1988 Tables 24-26), and greater f i n a n c i a l return than r i c e crops. Given these parameters, the i r r i g a t i o n water requirements vary from 15 to 60 cubic meters per day for 0.25 and 1 hectare i r r i g a t e d area respectively. In more understandable terms f o r the physical e f f o r t needed to meet these requirements using manual i r r i g a t i o n , t h i s equates to l i f t i n g from 15 to 60 tonnes of water a v e r t i c a l distance of up to four meters every day during periods of peak i r r i g a t i o n requirements. The o r i g i n a l aim i n designing the pump was to provide low cost manual i r r i g a t i o n , to benefit low income farmers i n the Rangpur and Dinajpur regions of northern Bangladesh. Since i t s introduction, use of the pump has spread to many other new regions of Bangladesh previously without i r r i g a t i o n or i r r i g a t e d by more expensive or les s appropriate means. In a recent socio-economic study of the treadle pump, the low cost of 1488 taka ($60 CAD) (EPC 1988, table 29), including i n s t a l l a t i o n on an unplasticized Polyvinyl Chloride (uPVC) tubewell, was found to provide 100% investment return i n one season with a minimum i r r i g a t e d area of 0.08 hectares (.16 acres) (Orr and Islam 1988), proving that the aim of the o r i g i n a l design has been achieved. Benefits of Treadle pump i r r i g a t i o n include dry season cropping, previously not possible f o r lack of i r r i g a t i o n , d i v e r s i f i c a t i o n of crops to modern high y i e l d r i c e v a r i e t i e s 5 and vegetables, job creation, with 30% of pumping labour being hired, and increased s e l f s u f f i c i e n c y i n r i c e (Orr and Islam 1988). Figure 1: Geographical location of Bangladesh. Figure 2: Water table depths i n Bangladesh. (Source: United Nations 1982, Plate 7) 7 Sales of the Treadle pump have increased dramatically i n the past four years as i s shown i n table 1. YEAR IDE RDRS OTHERS TOTAL 1980-85 1985- 86 1986- 87 1987- 88 0 120 12,000 12,000 39,870 10,316 3,000 3,000 4,000 16,000 27,000 0 39,870 14,436 30,000 43,938 Table I: Treadle pump sales of International Development Enterprises (IDE), Rangpur Dinajpur R e h a b i l i t a t i o n Service (RDRS) and others. (Source: IDE 1988) The large and increasing sales of the Treadle pump are at t r i b u t a b l e to the low i n i t i a l cost, the ease of maintenance and repair, comfort of operation, the a v a i l a b i l i t y of replacement parts and the a b i l i t y to make some repairs using salvaged parts such as inner tube rubber. Although i n i t i a l l y i n s t a l l e d on bamboo tubewells, the increased a v a i l a b i l i t y and increased market demand for uPVC pipe has resulted i n increasing uPVC usage f o r manual pump tubewells. This has resulted i n more consistent well l i f e and increased benefits but at an increase i n cost and a greater dependence upon imported materials. In addition to the obvious benefits of the pump, increasingly focused marketing e f f o r t s throughout Bangladesh by various Non-Governmental Organizations (NGO's) and Bangladeshi private businessmen have contributed greatly to the a v a i l a b i l i t y and 8 qual i t y of the pumps sold, and have further increased sales. 2.2 PREVIOUS TEST RESULTS The increase i n popularity of manual i r r i g a t i o n i n Bangladesh and the concern with drinking water supply world-wide, brought on i n part by the United Nations declared Decade of Sanitation and Water Supply i n 1980, has resulted i n increased t e s t i n g and documentation of pump performance throughout the world. Although the primary focus has been on drinking water pumps, manual i r r i g a t i o n pumps, such as the Treadle, Rower and No. 6 pumps used i n Bangladesh, have received attention from regional NGOs, farmers and small business i n t e r e s t s . Figure 3: Rope and pulley type Treadle operation. (Source: Barnes 1985) Figure 4: Centrally pivoted "dheki" type Treadle operation. (Source: Stickney, R.E., et a l . 1987) Over the past four years, the Treadle pump has been tested by RDRS, the Mennonite Central Committee (MCC), the International Rice Research I n s t i t u t e (IRRI), the Bangladesh University of Engineering and Technology (BUET), and most recently by Engineering and Planning Consultants Limited of Dhaka, Bangladesh (EPC) on contract with the Bangladesh Rural Development Board (BRDB) and the World Bank. The f i v e t ests have varied i n focus as follows: 10 1) The RDRS tes t s dealt with depth to water table to discharge r e l a t i o n s h i p of the o r i g i n a l pump design and larger piston diameter prototypes f o r use at shallower depths (RDRS 1983). 2) The MCC t e s t s focused on the impact of pump i n s t a l l a t i o n parameters, such as tubewell length, diameter and f i l t e r length, on the Rower, Treadle and No. 6 pumps from a p r i m a r i l y s t a t i s t i c a l analysis of a small s i z e t e s t sample (Spare and Pritchard 1981). 3) The IRRI te s t s focused on the adaptation and i n i t i a l promotion of the Treadle pump i n the P h i l i p p i n e s . Comparisons of the power input requirements f o r the rope and pulley and the c e n t r a l l y pivoted "dheki" s t y l e s of Treadle pump i n s t a l l a t i o n s , shown i n figures 3 and 4, indicated no s i g n i f i c a n t differences between them (Stickney et a l . 1987). The "dheki" s t y l e operation was, however, found to more comfortable to operate, which i s also the reason for the large increase i n "dheki" s t y l e i n s t a l l a t i o n s over rope and pulley s t y l e i n s t a l l a t i o n s i n Bangladesh. 4) The BUET t e s t s concentrated on the r e l a t i o n of power e f f i c i e n c y and discharge to operator c h a r a c t e r i s t i c s (Bureau of Research Testing and Consultation. 1986). The use of hir e d urban operators (rickshaw operators) i n the laboratory t e s t s , the lack of comparable f i e l d t e s t s , the use of observational recording of force transducer readings to c a l c u l a t e power input at the pump, and the lack of 11 t h e o r e t i c a l analysis to support the laboratory data, a l l reduced confidence i n the report's conclusions. 5) The EPC report focused on the f i e l d performance of the Treadle, Rower and No.6 pumps. The te s t s were commissioned to provide a basis f o r planning of i r r i g a t i o n pump promotion as part of o v e r a l l a g r i c u l t u r a l development planning (EPC 1988) f o r the BRDB and the World Bank. The pumps were f i e l d tested f o r two months, at four locations, to compare the discharge, pump wear and operator input c h a r a c t e r i s t i c s of each pump type. The f i n a l report concluded that the Treadle pump be recommended for manual i r r i g a t i o n i n s t a l l a t i o n s on the grounds of lowest cost, ease of repair and large discharge for a given amount of operator power. Of p a r t i c u l a r i n t e r e s t are the discharge r e s u l t s , with an average of 4 3 l i t r e s per minute at a water table depth of 3.3 6 meters. This i s achieved with a maximum power input of 69.73 watts over a 20 minute period or 51.6 watts over 30 minutes of sustained pumping. The power input values were estimated from the operator metabolism parameter of body surface area (EPC 1988, Table 12, sec. 3.18). The discharge r e s u l t s were much less than those presented by BUET. The two reports report s i m i l a r power input measurements but the r e s u l t s are not comparable. The EPC r e s u l t s were based on the measurement of the metabolic rate of the operator, which would give the power input to the treadle levers (EPC 1988, sec. 3.18) while the BUET te s t s 12 measured the average force input to the piston rod giving the power input to the pump (Bureau of Research Testing and Consultation, sec. 3.3). The power at the operator and at the pump can not be equal due to f r i c t i o n losses between the treadle levers, axle pin and between the rope and pulley system used with these t e s t s , as well as unmonitored metabolic losses. Given the differences between the discharge measurements, power input r e s u l t s , the more representative f i e l d t e s t conditions and the large number of te s t s , the EPC report seems to provide a more complete i n d i c a t i o n of f i e l d Treadle pump performance. A l l of the Treadle pump te s t s to date used the o r i g i n a l design rope-pulley s t y l e treadle lever configuration, shown i n f i g u r e 3, as opposed to the c e n t r a l l y pivoted "dheki" s t y l e configuration used on most i n s t a l l a t i o n s since 1986, shown i n figures 3,4 and 6. The "dheki" s t y l e operation has been adopted by the Bangladeshi farmer i n an e f f o r t to reduce the number of moving parts subjected to wear and requiring p e r i o d i c replacement and to increase operator comfort. Unfortunately, the shorter stroke lengths of the "dheki" s t y l e r e s u l t s i n lower discharge and greater losses with the increases i n comfort. The increase i n operator comfort and ease of operation has been obtained from the change of pumping s t y l e to a s h i f t i n g of body weight from side to side, pivoting at the hips and without bending the knees, from the the longer 13 bent-knee s t e p - l i k e operation of rope and pulley s t y l e . The large popularity of the "dheki" s t y l e operation c l e a r l y i l l u s t r a t e s the greater importance of comfort and ease of operation to the Bangladeshi pump operator compared to the mechanical e f f i c i e n c y of the pump mechanism. This p r i o r i t y of operator comfort over mechanical e f f i c i e n c y i n the case of the operation configuration, c l e a r l y shows that c h a r a t e r i s t i c s of the Treadle pump that must be c a r e f u l l y considered i n any design a l t e r a t i o n s extend beyond the purely technical performance c h a r a c t e r i s t i c s . The lower discharge data given i n the EPC report i s contrary to previous pump performance assumptions. The lack of agreement between t h e o r e t i c a l analysis, laboratory and f i e l d t e s t r e s u l t s i n a l l of the above reports precludes t h e i r use as a basis for design improvements and comparisons of a l t e r n a t i v e pump designs. The need f o r further technical knowledge was i d e n t i f i e d i n 1988 by the MPG, an organization comprised of manufacturers and marketers of manual i r r i g a t i o n pumps i n Bangladesh. 3 DESCRIPTION OF THE TREADLE PUMP 3.1 PHYSICAL DESCRIPTION The Treadle pump i s a two cylind e r manual suction pump constructed from sheet s t e e l . I t i s t y p i c a l l y mounted on a sing l e 40 mm (1.5 inch) diameter tubewell, also referred to as the r i s i n g main or r i s e r . Attached to the bottom of the r i s i n g main i s a s l o t t e d unplasticized p o l y v i n y l - c h l o r i d e (uPVC) or poly-propylene c l o t h covered s l o t t e d bamboo screen located below the water table, as shown i n figure 5. The pump body consists of two p a r a l l e l s t e e l cylinders made from r o l l e d and welded sheet attached to the top of a Y or box shaped junction. A short s t e e l 40 mm (1.5 inch) pipe i s welded to the bottom of the junction to connect the pump to the uPVC or bamboo tubewell. P l a s t i c tubewell components predominate i n the more recent pump i n s t a l l a t i o n s i n most of Bangladesh due to the superior d u r a b i l i t y and sealing of the r i s e r , although the cost of the p l a s t i c components are greater than the bamboo components. Two designs of piston were tested: (a) The o r i g i n a l two-plate piston design which consists of a perforated plate mounted on a s t e e l pump rod above a s o l i d plate with a p l a s t i c i z e d p o l y - v i n y l chloride (pPVC) cup seal 14 15 T R E A D L E PUMP BODY - PUMP S U P E R S T R U C T U R E C B A M B O C Q > H A N D H O L D A X L E P I N C C E N T R A L P I V O T ^ T R E A D L E L E V E R S C B A M B O C O T U B E W E L L C A S I N G OR R I S I N G M A I N C u P V C } S I L T V W A T E R T A B L E — 1 . • - -4 . o m e t e r F I N E S A N D C O U R S E S A N D 7 . 0 - 2 0 . • m e t e r s S C R E E N Figure 5: "Dheki" s t y l e f i e l d i n s t a l l a t i o n of the Treadle pump. placed between them and, (b) the No. 6 piston, adapted for use i n the Treadle pump. The No. 6 piston consists of a molded uPVC poppet valve, used with the same type of pPVC cup seal as used i n the two plate design, sandwiched between a threaded upper cage, attached to the pump rod, and a s i m i l a r l y threaded lower plate. The poppet valve, seal and valve seat are configured as shown i n figure 6. I t i s c a l l e d the No.6 piston because of i t s use i n the widely used cast iron Number 6 drinking water pump, which i s s i m i l a r to the hand pump s t i l l used for most manual pump applications i n North America. STANDARD CONFIGURATI ON Figure 6: The two piston configurations, the two-plate design and the No. 6 s t y l e piston, and the two types of junctions. 17 Both piston types are connected to the horizontal bamboo rods, c a l l e d treadles, by a hook and pin arrangement at the top of the piston rod. The lower valves, or foot valves, consist of weighted inner-tube rubber flaps mounted at the base of the cylinder s , where the cylinders j o i n to the smaller diameter junction box. Connection of the fl a p to the pump body i s by nuts and bo l t s to the cylinder base plate. The box shaped junction and the two-plate piston design are the standard configuration used i n Bangladesh due to the low cost and ease of manufacture. As shown i n figure 7, the pump i s operated by the treading action of the operator on the opposite side of the central pivot from the pump. The energy exerted by the operator i s used i n three ways, to pump water, to overcome f r i c t i o n at the central pivot and the piston rod connections, and to increase the pot e n t i a l energy of the treadle levers by l i f t i n g the treadle mass on the pump side of the pivot not balanced by the mass on the operator side. This difference i n treadle mass on the pump side of the central pivot i s termed the unbalanced treadle mass. I f the pump i s properly set up, the energy used to r a i s e the treadle lever w i l l be equal the energy required for the downward stroke of the piston and minimal energy i s wasted. In actual practice, many of the pumps are i n s t a l l e d with increased unbalanced treadle mass to increase the upward 18 p r e s s u r e on the o p e r a t o r ' s f o o t d u r i n g the r e t u r n s t r o k e o f the p i s t o n . T h i s i n c r e a s e s o p e r a t o r c o n t r o l over the l o o s e a c t i o n o f the l e v e r and i n c r e a s e s the speed o f t h e r e t u r n s t r o k e . In extreme cases, the l e v e r s may be s e t up so t h a t the end of the l e v e r s on the op e r a t o r ' s s i d e o f t h e c e n t r a l p i v o t touch the ground a t the lower end o f t h e o p e r a t o r s t r o k e and h i t the pump a t the upward end. Alt h o u g h t h i s r e s u l t s i n wasted energy as a r e s u l t o f h i t t i n g t he pump and ground and a l s o i n c r e a s e s wear on the t r e a d l e l e v e r s , p i v o t s and the pump body r e s u l t i n g i n rough o p e r a t i o n , i t has the b e n i f i t t h a t i t decreases the s e n s i t i v i t y and s k i l l r e q u i r e d o f the o p e r a t o r t o o b t a i n the c o r r e c t b a l a n c e i n the t r e a d l e l e v e r s and the more optimal smooth o p e r a t i o n . T h i s shows t h a t g r e a t e r s i m p l i c i t y o f o p e r a t i o n can take precedence over e f f i c i e n c y and smoothness w i t h some o p e r a t o r s . The pump can a l s o be operated u s i n g two o p e r a t o r s , one on each s i d e o f the s u p e r s t r u c t u r e , but t h i s i s not common p r a c t i c e . F i g u r e 7: F i e l d o p e r a t i o n o f the T r e a d l e pump i n Bangladesh. (Photo by Author) 19 3.2 PUMP OPERATION There are four d i s t i n c t stages i n the stroke cycle of the Treadle pump, which consists of a single up and down stroke cycle i n both cylinders, with a h a l f cycle phase difference between cy l i n d e r s . The stage of the cycle can be defined by the p o s i t i o n and d i r e c t i o n of movement of the piston at any point i n time. The four stages, for one cyl i n d e r i n the pump cycle using the two-plate piston, i s shown i n figure 8. S T A G E 1 S T A G E 2 S T A G E 3 S T A G E A Figure 8: The pump cycle defined by valve p o s i t i o n s . In the f i r s t stage, occurring with the i n i t i a l upward movement of the piston from the lowered p o s i t i o n , the piston valve closes with the upward movement of the piston plate to connect with the pPVC cup sea l . When no water i s l i f t e d above the piston by the piston movement, only the f r i c t i o n 20 f o r c e o f t h e cup s e a l moving a g a i n s t the c y l i n d e r and the drag f o r c e of the p i s t o n moving upward through th e water are e x e r t e d on the p i s t o n . The power i n p u t i n t h i s stage i s v e r y s m a l l . In the second stage, f u r t h e r upward movement causes a decrease i n p r e s s u r e immediately below the p i s t o n and the l i f t i n g o f water above the p i s t o n t o the d i s c h a r g e spout. The combination of the low p r e s s u r e below the p i s t o n and atmospheric p r e s s u r e a c t i n g on the water t a b l e r e s u l t s i n a net p o s i t i v e d i f f e r e n t i a l p r e s s u r e , c a u s i n g flow from the water t a b l e through the r i s i n g main and i n t o the c y l i n d e r . The i n i t i a l flow, w i t h the c l o s i n g o f the p i s t o n v a l v e , causes the f o o t v a l v e t o open and remain open f o r the d u r a t i o n o f the upward s t r o k e . Force i s r e q u i r e d t o produce the low p r e s s u r e below the p i s t o n and t o overcome both the p i s t o n s e a l f r i c t i o n f o r c e and the drag f o r c e through the f o o t - v a l v e , and t h i s f o r c e remains c l o s e t o c o n s t a n t throughout t h i s s t r o k e stage. The a d d i t i o n a l f o r c e r e q u i r e d t o a c c e l e r a t e the water i n the r i s i n g main t o equal the motion of t h e p i s t o n and t o l i f t t he water t o the d i s c h a r g e spout from above the p i s t o n are a t a maximum a t the b e g i n n i n g of t h i s stage w i t h a r e d u c t i o n towards the top of the s t r o k e . The r e d u c t i o n i n f o r c e i s a r e s u l t of reduced p i s t o n and water column a c c e l e r a t i o n w i t h the s l o w i n g o f the p i s t o n toward the top of the s t r o k e and the r e d u c t i o n of the mass a c c e l e r a t e d w i t h the d i s c h a r g e of the water from above the piston. An additional force i s required i n t h i s stage to accelerate and l i f t the unbalanced mass of the treadle lever, used as the actuating force i n stages three and four, the return stroke. The magnitude of t h i s force depends on the p o s i t i o n of the central pivot on the treadle levers. The degree of unbalance r e s u l t s from the qu a l i t y of i n s t a l l a t i o n and, i d e a l l y , should nearly equal the force required to move the piston downward during the return stroke. The major portion of work and the maximum power i s imparted to the pump i n t h i s stage. In stage three, the downward return stroke begins with the opening of the piston valve. The upwards movement of the valve i s l i m i t e d by the upper perforated plate. This r e s u l t s i n a d i f f e r e n t i a l pressure across the piston and forces water to flow through the perforated plate and the annulus between the lower plate and the cy l i n d e r wall previously sealed by the pPVC cup sea l . The downward movement of the water i n the cylinder caused by the increased pressure causes the foot valve to close, stopping the reverse flow of water from the cylind e r into the r i s i n g main. Only the f r i c t i o n force of the cup seal r e s u l t i n g from the piston motion, the drag force of the water through the piston, and the i n i t i a l drag force through the foot-valve, need to be overcome during t h i s stage. The force for the downward movement of the piston i n stages three and four i s provided by the unbalanced mass of the treadle lever which was raised i n stages one and two. In stage four, the piston returns to the bottom of the stroke, i n h i b i t e d only by the resistance of flow through the piston valve and the f r i c t i o n of the cup seal against the cylinde r wall. Some water i s discharged by displacement from the piston and piston rod. The second cylin d e r follows the same cycle as the f i r s t , but i s o f f s e t one h a l f cycle, r e s u l t i n g i n a continuous flow of water from the pump. 4 PUMP OPERATION MODEL 4.1 OPERATIONAL CONSTRAINTS As b r i e f l y described i n section three, the operation of the Treadle pump u t i l i z e s the difference between atmospheric pressure, and the low pressure created below the piston to provide flow from the water table to the pump. Atmospheric pressure, at 20 degrees Celsius, i s 101 kPa. When expressed i n height of water over a unit area, termed atmospheric head, i s equal to 10.23 meters. The pressure d i f f e r e n t i a l between atmospheric and that produced below the piston i s termed unbalanced head (UH). Ideally, when the depth to the water table equals atmospheric head, the unbalanced head and r e s u l t i n g l i f t i n g force are reduced to zero. This r e s u l t s i n the t h e o r e t i c a l maximum height f o r the operation of the Treadle pump being constrained to the 10.23 meter l i m i t of atmospheric head. In p r a c t i c e , the actual vapour pressure of water and the use of a portion of the unbalanced head to overcome turbulence, f r i c t i o n and to accelerate the water column with the piston, the l i m i t of water table depth to which the unbalanced head remains p o s i t i v e i s about 7 meters (World Health Organization 1977). 23 24 Further constraints on the operation of the Treadle pump include the l i m i t s of operator c a p a b i l i t i e s such as power input, which varies with weight, d i e t , conditioning, health and environmental conditions such as temperature and humidity. The condition and design of the pump seals and valves, which can influence the amount of s l i d i n g f r i c t i o n and leakage past the piston and the amount of suction head attainable, also constrain pump operation. 4.2 CALCULATION OF UNBALANCED HEAD 4.2.1 MINOR LOSSES Minor losses are those caused by the f r i c t i o n and turbulence of water against components of the pump system. Included are those from when i t enters the pump system at the f i l t e r u n t i l i t i s discharged at the pump spout. The losses from turbulent flow through the expansions, contractions and f i t t i n g s were calculated using tabulated loss c o e f f i c i e n t s (Roberson and Crowe 1985, 377), calculated as a proportion of v e l o c i t y head, and added to the t o t a l head loss of the system. Losses r e s u l t i n g from the f r i c t i o n between the water flow and the uPVC r i s e r pipe and the s t e e l pump body were calculated using the Darcy-Weisbach equation with a f r i c t i o n factor of 0.005 derived from the Moody diagram (Roberson and Crowe 1985, 368). Although there are va r i a t i o n s i n i n s t a l l a t i o n such as r i s e r pipe and f i l t e r q u a l i t i e s that can a f f e c t the amount losses that occur, the losses i n the laboratory t e s t apparatus were kept constant from t e s t to t e s t using a single r i s e r to pump system. This allowed comparison of the measured losses to those calculated. 4.2.2 VALVE TIMING AND LEAKAGE Valve timing and leakage i n a constant d i f f e r e n t i a l manual pump system a f f e c t s pump performance by decreasing discharge f o r a given energy input. In the Treadle pump, delays i n piston valve closure r e s u l t s i n the operator exerting e f f o r t to the pump without l i f t i n g any water and reduces the volume of water above the piston f o r discharge. This delay reduces the force required, with the reduction i n discharge, but consequently increases the time pumping time required to meet the i r r i g a t i o n requirements. Delays i n foot valve closure allow water i n the piston to return to the r i s e r pipe reducing the discharge on the following stroke. This has the e f f e c t of increasing the energy requirement, as a reduced amount of water remains i n the pump as compared to the amount for which energy was expended. Leakage through the valves and past the piston cup seal also reduces pump e f f i c i e n c y . The leakage past the piston cup seal during the upward stroke r e s u l t s i n a reduction of 26 the suction head created below the piston and also reduces the volume of water above the piston to be discharged. From examination of the valve l i f t distances, the valve opening and c l o s i n g times, and the t o t a l losses through laboratory experiments, the proportion of loss through leakage past the piston seal can be compared to that from valve c l o s i n g delays. A measure for the amount of water l o s t by valve delays and leakage i s termed volumetric e f f i c i e n c y , defined as the r a t i o of the volume of water discharged to the volume swept by the piston i n the same time period. Although i t i s possible to obtain volumetric e f f i c i e n c i e s of greater than one, from the momentum e f f e c t s of a water column, i t i s not common i n manual pumps which have small input power and r e l a t i v e l y small water column momentum. 4.2.3 INERTIA The suction head required to accelerate the column of water i n the r i s e r pipe i s dependent upon the length of the pipe and the acceleration. As the r i s e r length i s fixed and sealed, the acceleration of the water column i s a d i r e c t r e s u l t of the acceleration of the pistons, but l i m i t e d by the t o t a l unbalanced head av a i l a b l e . The piston motion c h a r a c t e r i s t i c s of the Treadle pump were assumed to be perio d i c with respect to time. To f i n d the general shape and timing of the acceleration curve, an 27 cm m/s : m/s"2 0.05 0.25 0.5 TIME (Seconds) Figure 9: C h a r a c t e r i s t i c piston motion parameters. approximation of the form: Y(t) = ^avg + A s:"-n (w"t) where y(t) = avg A w = piston displacement with respect to time (centimeters) median distance of piston t r a v e l (cm) Amplitude of piston displacement about Y a v g (cm). Angular v e l o c i t y (as i f piston was connected to a c i r c u l a r crank mechanism) (radians/second) 28 t = time (seconds) was assumed to be s u f f i c i e n t given the motion v a r i a t i o n s due to operator and pump i r r e g u l a r i t i e s . The piston motion, for one piston, measured i n the laboratory i s shown i n figure 9. I r r e g u l a r i t i e s from operator and pump va r i a t i o n s are e s p e c i a l l y evident i n the calculated acceleration curve. The small v a r i a t i o n s i n p o s i t i o n over time, that are not evident with the res o l u t i o n of p o s i t i o n graph, are revealed. An approximation of the motion shown i n figure 9, given below using the assumed sinusoidal form, could be used to mathematically model the pump c h a r a c t e r i s t i c s . y(t) = 3.6 + 1.5 s i n (14t - 2.6) Although the approximation i s not a precise f i t to the measured motion parameters, i t i s s u f f i c i e n t l y accurate given the v a r i a t i o n s i n motion from the pump and operator. Mathematically, t h i s should r e s u l t i n a maximum or minimum acceleration, the second deri v a t i v e of the p o s i t i o n equation, when the p o s i t i o n of the piston i s at a minimum or maximum respectively. At the same minimum or maximum piston p o s i t i o n , the v e l o c i t y , the f i r s t d e r i v a t i v e of the po s i t i o n equation, should be zero. The p l o t of laboratory measured po s i t i o n , v e l o c i t y and acceleration versus time, figure 9, shows close agreement on the maximums and minimums to the 29 those expected from the mathematical derivations. As such, the assumption as to the periodic nature of the Treadle pump motion c h a r a c t e r i s t i c s was considered v a l i d . However, for the purposes of accurately p r e d i c t i n g the forces i n the pump from c a l c u l a t i o n , inputs f o r po s i t i o n , v e l o c i t y and acceleration were taken from the laboratory data rather than from the mathematical expressions. This assured that the c a l c u l a t i o n of the force inputs could be compared d i r e c t l y with the measured r e s u l t s without any errors induced by breaks or i r r e g u l a r i t i e s i n the laboratory stroke motion. 4.2.4 MECHANICAL LOSSES The one mechanical loss accounted f o r i n the pump model was the s l i d i n g f r i c t i o n between the pPVC piston seal and the s t e e l c y l i n d e r . Variations i n the form, consistency and dimensions of the piston cup seals and pump cylinders r e s u l t i n g from the manufacturing process, made a n a l y t i c a l c a l c u l a t i o n of the s l i d i n g f r i c t i o n d i f f i c u l t . Given the inexactness of the pump and the inconsistency between pumps, an empirical approximation of 15 newtons, taken from laboratory data of dry pump tes t s , was adopted. Other mechanical losses, such as the f r i c t i o n i n the hook and p in piston connection to the bamboo treadles, and the f r i c t i o n of the central s t e e l axle treadle pivot against the o s c i l l a t i n g treadles, also reduce the power e f f i c i e n c y from 30 the operator to the pump. The separate measurement of these losses was beyond the scope of t h i s t h e s i s but are estimated i n the assessment of the t o t a l losses occurring i n the Treadle pump. 4.3 GOVERNING EQUATIONS For stage one of the pump cycle, previously described i n section 3.2 and shown i n figure 8, the force applied to the piston i s the sum of the l i f t i n g of the piston mass, the s l i d i n g f r i c t i o n between the piston seal and the c y l i n d e r wall and the drag force from the water flow through the piston. I t i s assumed that no water above the piston i s l i f t e d by the small upward piston movement i n t h i s stage which occurs before the piston seal seals against the lower piston plate, i . e . no discharge i s produced. The force required to l i f t the piston i s dependent upon the mass of the piston, the unbalanced mass of the treadle lever and the acceleration imparted to them, the c o e f f i c i e n t of f r i c t i o n of the seal against the c y l i n d e r wall and the v e l o c i t y of the piston through the water. The equation to c a l c u l a t e the force required i s : F = ((M+Mt)*ap) + (Hd*w*ap) + F f (1) where F = force applied to the piston (newtons) M = the piston mass (kg) 31 = unbalanced mass of the treadle lever (kg) 2 a = the acceleration of the piston (m/s ) H d = head loss r e s u l t i n g from the drag forces (m) F f = s l i d i n g f r i c t i o n force 3 w = s p e c i f i c weight of water (newtons/m ) with c d * v 2 H = E — ( 2 ) 2*g where C d = drag c o e f f i c i e n t V = v e l o c i t y of the piston (m/s) g = g r a v i t a t i o n a l constant = 9.81 m/s2 For stage two, the completion of the upstroke, the piston must produce s u f f i c i e n t suction to overcome the minor losses, accelerate the water column and maintain s u f f i c i e n t unbalanced head to produce flow from the water table to the pump. This suction, expressed i n meters of water, i s refe r r e d to a suction head (H). The force applied to the piston also includes the force required to l i f t and accelerate the unbalanced t r e a l e lever mass, and i s calculated using the equation: F = (H*Ap*w) + F f + ((M+Mt)*ap) (3) 32 where Ap = cross-sectional piston area (m2) and H = - WT - h - h a *1 r r (4) 1 d g g where H = suction head (m) AH = atmospheric head (m) WT = depth to water table (m) h-^  = t o t a l minor head losses h H = t o t a l head loss from drag = head required to accelerate the water g column a *1 — E _ - head required to accelerate water i n the g cylinder In the t h i r d stage, from the end of the upstroke to the closure of the foot-valve, the forces acting on the piston include the f r i c t i o n force of the seal against the cylinder and the drag force, from water escaping through the cl o s i n g foot valve, at the same rate as the piston downward movement. The force acting on the piston i s a r e s u l t of gravity acting upon the unbalanced mass of the treadle lever raised i n stage one and two. In the fourth stage, the piston continues downward a f t e r the c l o s i n g of the foot-valve. The forces from the s l i d i n g f r i c t i o n and the drag of the piston through the water are 33 calculated using the sum of the constant f r i c t i o n force and the drag force from equation (2), with the piston v e l o c i t y substituted f o r the r i s e r flow v e l o c i t y . This force i s also supplied by the unbalanced treadle lever mass. As stated, the forces i n stages three and four are not exerted by the operator but rather by gravity acting on the mass of the unbalanced portion of the treadle lever, the piston and the connecting pin. The unbalanced mass of the second treadle i s simultaneously being l i f t e d by the operator when the f i r s t i s exerting downward force. I t was included i n the force c a l c u l a t i o n s f o r the upward portion of the stroke where the force i s exerted but because the force transducer was located at the piston rod and measured the force exerted at the piston, not the force exerted by the operator to the treadle levers. The force exerted to r a i s e the unbalanced mass of the treadle lever was included i n the force and power input measurements by measuring the force exerted on the downward portion of the stroke by the unbalanced treadle mass. This was added into the power ca l c u l a t i o n s to account f o r the l i f t i n g force not measured on the upward stroke. The method of adding the e f f o r t exerted by unbalanced treadle lever mass on the downward stroke does not take into account the force differences between the upward and downward lever acceleration. I t was assumed that i f the pump i s properly i n s t a l l e d , the difference between the two i s minimal. From the above equations, cal c u l a t i o n s f o r the forces at d i f f e r e n t piston positions, based on one tenth of a second measurement increments, were conducted with the r e s u l t s shown i n figure 9. A water table depth of 3.34 meters, an abrupt i n l e t , 6.37 meters of uPVC r i s e r pipe with a f r i c t i o n c o - e f f i c i e n t of f=0.0005, a box type junction and the two plate standard piston loss c h a r a c t e r i s t i c s and the motion parameters taken from laboratory t e s t s were used i n the c a l c u l a t i o n s . 400 300 5TN0 CONFIGURATION : DEPTH TO VT=3.34 M 200 -150 -100 -PISTON POSTION ccentimeterS3 Figure 10: An example of calculated force r e s u l t s with laboratory measured input parameters. 5 LABORATORY TESTING 5.1 APPARATUS DESIGN CONSIDERATIONS The laboratory apparatus design required a c a r e f u l mix of strength and s e n s i t i v i t y to balance the imprecise c h a r a c t e r i s t i c s of the Treadle pump, r e s u l t i n g from manufacture and design for operation i n Bangladesh, and the pr e c i s i o n required for accurate measurement of performance c h a r a c t e r i s t i c s . Obtaining a measurement accuracy of twenty newtons, without the destruction of the s e n s i t i v e measuring apparatus by the large force and displacement fluctuations inherent i n the pump, involved the design of a s p e c i a l i z e d force transducer. This was achieved through repeated design and t e s t i n g of alternate designs over a period of three months to obtain the correct balance between s e n s i t i v i t y and d u r a b i l i t y . The addition of sign a l amplification and conditioning f i n a l l y enabled the t e s t i n g to be conducted within the required parameters. In addition, the use of a highly stable superstructure and wide range input transducers f o r l i n e a r motion measurement was also necessary to ensure accuracy and a high degree of s e n s i t i v i t y . The modified s t e e l superstructure, pump attachment and well structure increased s t a b i l i t y compared to the bamboo 35 commonly used i n Bangladesh. Used i n conjunction with pumps, seals and pistons unaltered from manufacture i n Bangladesh, the force and displacement fluctuations were minimized without compromising the operating c h a r a c t e r i s t i c s of the pump. Force inputs to the pump v i a the pistons were measured using a tubular s t r a i n gauge force transducer with reduced Figure 11: Instrumentation for the laboratory t e s t s . wall thickness to obtain maximum s e n s i t i v i t y mounted as part of the piston rod as shown i n figure 11. The tubular transducer was machined from aluminum, providing maximum s t a b i l i t y against bending and buckling from large loads but reta i n i n g the s e n s i t i v i t y required to accurately read the small force changes occurring during the pump cycle. Two dia m e t r i c a l l y opposed s t r a i n gauges were a f f i x e d to the transducer and connected i n opposite arms of the wheatstone bridge c i r c u i t . This cancelled the bending forces r e s u l t i n g from the often eccentric nature of the piston to cylind e r s l i d i n g forces, the roughness of the hook pin connection of the piston to the treadle and the arced motion of the c e n t r a l l y pivoted treadle lever which resulted i n angular displacement of the piston through the pump cycle. The force transducer was also temperature compensated using two 12 0 ohm r e s i s t o r s mounted beside the transducer on the pump frame and connected to adjacent arms of the bridge c i r c u i t from the s t r a i n gauges. The bridge c i r u i t was balanced by the use of a va r i a b l e resistance c i r c u i t connected i n serie s with one of the temperature compensating r e s i s t o r s . The stroke p o s i t i o n was instrumented using a l i n e a r v a r i a b l e distance transducer (LVDT) mounted between the ri g h t hand side (from the operator) piston pin and the v e r t i c a l upright posts of the pump structure. I t was 38 Figure 12: Laboratory apparatus. mounted with pivot connections at both ends to prevent bending of the transducer due to the arc of the treadle lever throughout the stroke. The LVDT was supplied with a ten v o l t e x c i t a t i o n voltage from a regulated d i r e c t current power supply. The data from the transducers was conditioned using an am p l i f i e r to boost the force transducer sig n a l 1000 times, to a l e v e l usable by the analog to d i g i t a l converter. The analog to d i g i t a l converter allowed for data c o l l e c t i o n and storage by a personal computer. Using a Basic language computer program, data input timing was c o n t r o l l e d and data 39 was c o l l e c t e d from the analog to d i g i t a l conversion board into the computer memory at a rate of 10 readings per second. The use of a high c o l l e c t i o n rate enabled the force peaks and delays at the p i s t i o n to be detected and analyzed but resulted i n very large data sets. Analysis of the data using spreadsheet based programs became very time consuming and was somewhat li m i t e d due to the large s i z e of each of the 64 data sets. The duration of each t e s t was l i m i t e d to f i v e minutes, at the ten hertz c o l l e c t i o n rate, by the amount of in t e r n a l memory availa b l e i n the personal computer and by the storage media where the data was stored f o r l a t e r processing. The Basic language program was also used to convert the data from raw converter readings to data sui t a b l e output f o r l a t e r analysis u t i l i z i n g previously measured c a l i b r a t i o n factors. The o v e r a l l t e s t i n g structure i s shown i n figure 12. Using free weights and a measuring scale, the force and distance instrumentation was i n i t i a l l y c a l i b r a t e d and the c a l i b r a t i o n factors re-checked a f t e r every four t e s t s . 5.2 TESTING PROCEDURE The f i v e steps of the procedure for the laboratory tests were: 40 1) Inspection of pump components and t r i a l pump operation to check f o r worn out components, any problems such as leakage and to obtain uniform pump operation. 2) The computer data c o l l e c t i o n channels were zeroed where appropriate and the i n i t i a l l e v e l of water i n the discharge c o l l e c t i o n tank was read and recorded. 3) With data c o l l e c t i o n started, the zero readings f o r the force and p o s i t i o n transducers were recorded followed by priming of the pump. Af t e r a pause, to indicate the beginning of discharge i n the c o l l e c t e d data set, the pump was operated f o r between 4 and 6 minutes, during which time the data was c o l l e c t e d from the force transducer, the LVDT, the LVDT and s t r a i n gauge voltage supplies and the computer timer at a rate of ten readings per second. 4) On completion of pumping, the data c o l l e c t i o n program was stopped and the data down loaded to a data f i l e on floppy disk f o r conversion from raw readings and analysis using a spreadsheet based program. 5) The water l e v e l i n the discharge c o l l e c t i o n tank was read and recorded along with the number of readings taken by the data c o l l e c t i o n system and the elapsed r e a l time f o r comparison and error checking of the computer c o l l e c t e d data. The t o t a l time that data could be c o l l e c t e d i n one te s t was constrained by the in t e r n a l memory l i m i t s of the computer used and by the si z e of data f i l e storable on a 41 single data storage diskette and readable by the spreadsheet program used f o r data analysis. C o l l e c t i o n times longer than f i v e minutes were found to exceed these constraints. 5.3 DATA REDUCTION AND ANALYSIS The data f i l e s r e s u l t i n g from the data c o l l e c t i o n computer program were transferred to a spreadsheet program using floppy disks. Using the spreadsheet functions, the data was imported, reduced and analyzed using the following steps: 1) The f i r s t portion of c o l l e c t e d data, taken with the pump at rest , was averaged to obtain a raw data reading equating to the zero point f o r each c o l l e c t e d v a r i a b l e . These i n i t i a l zero readings were also used to check for deviations i n data caused by va r i a t i o n s i n e x c i t a t i o n voltage supply or c i r c u i t r y voltage v a r i a t i o n . I f the average of the data c o l l e c t e d with the pump at re s t varied more than 10% from the average of the complete data set, normalized to the average supply voltage, then the t e s t was repeated. Usually only the i n i t i a l t e s t i n a given series was prone to large supply voltage and subsequent data v a r i a t i o n s due to c i r c u i t r y heating within the voltage supply, force transducer amplifier and s t r a i n gauge bridge c i r c u i t s . Small v a r i a t i o n s i n the data set about the average were permitted, as the area under the force-displacement curve remained constant. The small p o s i t i v e 42 and negative v a r i a t i o n s cancel each other out i n the c a l c u l a t i o n of the o v e r a l l area encompassed by the curve. 2) I f the data was within the acceptable l i m i t s f o r v a r i a t i o n , then the zero readings were recorded and the data c o l l e c t e d during zeroing, priming and between the completion of pumping and the stopping of data c o l l e c t i o n , was removed. 3) The force and p o s i t i o n data was then converted to appropriate units from the raw data readings, using the c a l i b r a t i o n factors and zero point data. 4) Calculations f o r work and power were then calculated on a time incremental basis from the piston p o s i t i o n , time and force inputs. The c a l c u l a t i o n of power used to l i f t the unbalanced treadle lever mass during the piston upstroke, l a t e r providing the force for the downstroke, was calculated from the force measured at the piston during the downstroke and added to that calculated for the upstroke. The stroke rate, t o t a l swept volume and average stroke length was calculated using the e n t i r e data set. Using the discharge data, calculated from the readings taken on the c a l i b r a t e d discharge c o l l e c t i o n tank, the piston p o s i t i o n and timing values, the volumetric e f f i c i e n c y , power output and, using the average of the calculated power values, power e f f i c i e n c y r e s u l t s were calculated. 6 FIELD TESTING 6.1 APPARATUS DESIGN CONSIDERATIONS The apparatus design for the f i e l d t e s t s was constrained by four factors. F i r s t l y , the l i m i t e d a c c e s s i b i l i t y of the t e s t s i t e s . A l l equipment and personnel reached the s i t e s by a combination of r i v e r boats, motorcycles and walking. Secondly, the u n a v a i l a b i l i t y and u n s u i t a b i l i t y of sophisticated t e s t equipment such as that used i n the laboratory due to extreme environmental conditions and the lack of t r a n s p o r t a b i l i t y , repair, component f a b r i c a t i o n f a c i l i t i e s and power a v a i l a b i l i t y . T h i r d l y , the v a r i a b i l i t y of pump i n s t a l l a t i o n s i n terms of o v e r a l l condition, set-up dimensions and operation parameters and fourthly, the l i m i t to disruption of pumping a c t i v i t i e s f o r t e s t i n g i n terms of both time and a l t e r a t i o n of the pump f i e l d s i t u a t i o n . Any undue disruption could have had the e f f e c t of minor crop damage due to non-i r r i g a t i o n , loss of income f o r the hired labour operating the pump i f hired labour was used, and undue expenditure by l o c a l farmers f o r food and drinks i n t h e i r e f f o r t s to befriend and impress the te s t e r s . 43 44 The r e s u l t i n g apparatus design u t i l i z e d two, t h i r t y l i t r e measurement pans, an e l e c t r i c a l water l e v e l sensor c i r c u i t attached to a tape measure, a two hole o f f s e t clamp to attach a pen to the piston rod, a clipboard/paper holder and four a d d i t i o n a l personnel. As i n the laboratory t e s t s , parameters for discharge, stroke length, stroke number and t e s t time needed to be measured. Discharge was measured by alternate f i l l i n g and dumping of the two measuring pans, stroke length was measured by repeatedly s l i d i n g the clipboard held paper along the holder and measuring the r e s u l t i n g traces from a pen or marker mounted to the piston rod. This method for measured stroke length was altered somewhat from pump to pump depending upon the ground surface surrounding the pump, the pump i n s t a l l a t i o n , the a p p l i c a b i l i t y of using the clipboard holder and the d i f f i c u l t i e s i n a f f i x i n g the pen or marker to the piston rod. In a few cases, the stroke length was measured by observation of the stroke against a measuring tape as the i n s t a l l a t i o n d i d not allow f o r a f f i x i n g a marker to the piston rod without i t s rapid destruction. Stroke number was counted by one of the additio n a l personnel and the te s t was timed from s t a r t to stop by a stop watch. The apparatus was simple i n design and was found to be very adaptable to var i a t i o n s i n t e s t s i t u a t i o n s and e a s i l y understood by the t e s t personnel. The apparatus was labour 45 intensive, by North American standards, but was appropriate for use i n Bangladesh, where labour i s r e a d i l y a v a i l a b l e and less expensive than the cost with increased apparatus complexity. Given the conditions f o r the t e s t i n g , the apparatus was found to be appropriate. 6.2 TEST LOCATIONS AND PROCEDURE Forty-one Treadle pumps were tested i n the f i e l d t e s t s , ten i n the Jamalpur and Sherpur regions i n north central Bangladesh, and t h i r t y - t h r e e i n the Kushtia and Pabna regions i n western Bangladesh as shown i n figure 11. Research into pump design and alt e r n a t i v e s was conducted i n the Kurigram region i n Northern Bangladesh and i n the Shonargoan region j u s t south of Dhaka. The t e s t procedure varied somewhat from s i t e to s i t e depending upon how the pump was situated and set up i n the f i e l d and the degree of co-operation from the farmer owner-operator or hired operator. In general, the procedure was as follows: 1) With permission from the owner and operator, s o i l below the pump spout was removed, i f necessary, to permit placement and removal of the discharge measurement pans below the discharge spout. 46 Partchagarti ,ni*,' iNiiphama. Scale l'= 80 Miles REFERENCES . InternoHonal Boundary . . District Boundary RaiJwoy Rivei-Air Port vlhet Moulvi bazar \VManikgonj\D|}al"i'i. \ ?/, rf Brahmanbaria 'Munshigani IMeherpur^r-r. ••.17 ^huadanga f tA Faridpur •jfJhenaidah J Magura 1 \ [ _ , , ^ ^ Jessore ' Narailc X\. x Gopalgan, \/7^ J t A . ^ N ^ j £_Perojpur v. 1 ( ' "» tSatkhira Figure 13: Location of f i e l d tests, 47 2) The owner of the pump was asked about the age of the pump, dates of most recent component replacements, depth and type of r i s e r and f i l t e r , and i f any problems had been encountered with the pump. The pump operator, often the owner, was asked h i s or her age, weight and number of hours the pump was operated per day during the dry season to gain i n s i g h t into operators t y p i c a l l y using the pump. The responses were recorded to provide information to a s s i s t i n design a l t e r a t i o n considerations and to sign a l any s i g n i f i c a n t deviations from t y p i c a l pump usage which might a f f e c t the data c o l l e c t e d . 3) The pump cylinders, pistons, cup seals and foot-valves were inspected f o r signs of undue wear and improper operation. I f the components were i n such poor condition as to be non-representative of normally used and maintained pumps, then the t e s t was abandoned and the t e s t moved to the next s i t e . 4) A f t e r f i v e to ten minutes of pumping to obtain as normal a sustainable pumping rate as possible, the depth to water table was measured using the e l e c t r i c a l measuring tape lowered into the r i s i n g main through the foot-valve and junction box. The measuring of the water table depth a f t e r the i n i t i a l pumping and draw down resulted a depth that would be consistent with sustained pump operation. 5) The clamping mechanism that attached the pen or marker to the piston rod was attached on the upper portion of the 48 piston, so as not to i n t e r f e r e with pump operation, and a pen was also attached at r i g h t angles to the piston. 6) The operator was instructed to pump as i f the t e s t was four hours i n duration, to obtain usual sustainable pumping rates. A f t e r f i v e minutes of pumping or when the stroke rate slowed and became consistent, the timing and stroke counting was started and the discharge measuring pan was placed under the spout. 7) At l e a s t four traces of the stroke motion were made, spaced at about one minute i n t e r v a l s , the discharge measuring pans were removed and emptied when f u l l with as l i t t l e s p i l l a g e as possible and the timing and stroke counting were continued. The minimum t e s t duration was four minutes and the maximum was ten minutes. 8) I f the stroke rate and length were consistent over the f i r s t four minutes of te s t i n g , then the data c o l l e c t i o n was stopped at the next f u l l measuring pan. I f not, then the t e s t was continued for as long as 10 minutes with incremental data values recorded to obtain the data for the most consistent pumping. 9) Following completion of the t e s t , the data was recorded on data c o l l e c t i o n sheets f o r future analysis. I f the pump was mounted on an uPVC r i s e r and f i l t e r , then the tes t s were repeated using the author as the operator f o r comparison to the laboratory data. 49 10) Upon completion of the t e s t i n g , the owner was advised of any repairs or maintenance required on the pump to improve performance and the pump set up was returned to as near i t s o r i g i n a l configuration as possible, unless asked to do otherwise, before leaving the t e s t l o c a t i o n . 6.3 DATA ANALYSIS The data from the f i e l d t e s t s had large v a r i a t i o n s due to differences i n pump condition, operator s i z e and motivation and turnover i n c o l l e c t i o n personnel. In analyzing the data, only severe o u t - l i e r s , those not p h y s i c a l l y possible, were removed. The stroke lengths were measured using the v e r t i c a l distance from the trough to the peak on the trace. The multiple traces for each t e s t were averaged to obtain the stroke length used i n calcu l a t i o n s to determine the t o t a l swept volume necessary f o r c a l c u l a t i n g the volumetric e f f i c i e n c y of the pump. The discharge volume was calculated from the number of discharge pans f i l l e d and the respective volumes of the pans. The pan volume was adjusted based on observation of how f u l l the pans were f i l l e d during the t e s t and on how much unmeasured discharge occurred on the switching of the pans. T y p i c a l l y t h i s adjustment ranged from a seven to twenty percent reduction i n the measured discharge, as the 50 pans were r a r e l y completely f u l l on removal and l i t t l e water was l o s t during the switching of the pans. The v a r i a t i o n i n adjustment was dependent upon the performance of the personal removing and replacing the pans during a p a r t i c u l a r t e s t , which was recorded for each t e s t . The volumetric e f f i c i e n c y was calculated using the r a t i o of the t o t a l swept volume, calculated from the number of strokes and the stroke lengths to the measured discharge. Using the depth to water table and the discharge data c o l l e c t e d , the input power to the pump was estimated based on the depth-discharge-power output r e s u l t s from the laboratory t e s t s . 7 RESULTS 7.1 PUMP FORCES The force displacement curves, generated from the laboratory t e s t s , are useful f o r measuring the changes i n forces applied to the piston throughout the four stages of the piston stroke. These changes are a r e s u l t of variatio n s i n f r i c t i o n , acceleration of the water column i n the r i s e r pipe, formation of the unbalanced head, and the use of the pot e n t i a l energy stored i n the raised treadle lever mass to provide the energy for the downward piston stroke. Pump configuration, piston and foot-valve design also cause force v a r i a t i o n s that are of p a r t i c u l a r i n t e r e s t i n pump design. Taking a de t a i l e d look at the i n i t i a l portion of the force curves, the large forces at the s t a r t of the upstroke, evident i n figures 14 and 15, r e s u l t from the large forces required to accelerate the water column i n the r i s e r pipe and the water above the piston from rest, or nearly so, to equal the v e l o c i t y of the piston at that same point i n the stroke. In comparing t e s t s using the standard two plate piston and the No.6 piston, shown i n figures 14 and 15 respectively, two differences i n acceleration forces are evident. 51 52 WATER TABLE DEPTH: 3.36 meters 400 2.3 3.3 4.5 3.3 6.5 PISTON POST I ON ccentlmeters} Figure 14: Force-displacement loop using the two-plate type piston. F i r s t l y , the peak accelerating force occurs much more ra p i d l y a f t e r the valve c l o s i n g i n the standard two-plate piston compared to the smaller slope following valve closure with the No. 6 piston. However, the maximum forces r e s u l t i n g from acceleration of the water columns are close to equal, given operator v a r i a t i o n s , and also occur at the same p o s i t i o n i n the stroke. The difference i n the slopes i n the i n i t i a l portion of the curves i s a r e s u l t of the combined e f f e c t of the fast e r valve c l o s i n g time of the No.6 400 330 WATER TABLE DEPTH : 5.34 meters <J 200 -130 100 _ 5 ° "1 1 1 1 1 1 1 1 1 r 2.6 3 3.4 3.B 4.2 4.6 PISTON POSITION ccentlmetere} ~ i 1 1 1 1 r— 5 5.4 5.B 5.2 Figure 15: Force-displacement loop using the No.6 type pistons. piston, indicated by the rapid increase i n piston force e a r l i e r i n the stroke, and the e f f e c t of greater i n i t i a l leakage through and by the No. 6 piston, which i s indicated by the f l a t t e r slope of the force curve f o r the No. 6 piston. The equivelent maximum forces indicates that the two pistons seal equally by the end of the stroke. Secondly, the standard piston shows a sharp decrease i n force of 100 to 150 newtons at mid-upstroke followed by an 54 increase i n force of 50 to 100 newtons at the completion of the upstroke. This i s not evident with the No. 6 piston, which has a more constant force throughout the stroke. Two explanations of t h i s force v a r i a t i o n are: 1) That the water column and piston rod exhib i t e l a s t i c properties r e s u l t i n g from the rapid valve closure and r e s u l t i n g shock forces. This e l a s t i c e f f e c t i s much l i k e a stretching and subsequent rebounding. The e l a s t i c e f f e c t s of a manual pump water column was documented, to explain s i m i l a r force v a r i a t i o n behavior, i n the t e s t i n g of deep set hand-pumps (Yau 1985). Although the documented force v a r i a t i o n i s s i m i l a r to that measured on the Treadle pump, the much shorter piston rod of the Treadle pump and the r e s u l t i n g e l a s t i c e f f e c t of the pump rod i s n e g l i g i b l e , compared to the ten meter rod used i n the analysis by Yau. The r e s u l t s are s t i l l useful however. The report (Yau 1985) concluded that the magnitude of the large force increase was required for the design of pump components to withstand the shock loading, but that the o v e r a l l area under the force displacement curve did not to change. S i m i l a r l y f o r the analysis of the Treadle pump force displacement curves, the reductions i n piston forces were found to be e f f e c t i v e l y cancelled by the increases, measured over the en t i r e stroke length, r e s u l t i n g i n a consistent work input measurement. 55 2) The force v a r i a t i o n could also be caused by the deformation of the piston seal i n the two plate standard piston. This would cause binding of the seal against the c y l i n d e r wall as the piston cup seal would deform under the maximum combined forces of head loss, head requirements and acceleration. The unrestricted piston seal i s able to rotate about i t s leading edge, the upper circumference, from the combined moment created by the downward forces of f r i c t i o n , unbalanced suction head and acceleration forces acting on the outer edge of the seal and the upward l i f t i n g motion of the piston acting on the inward edge. The large and sudden acceleration force, evident with the standard two plate piston, i s followed by a sudden reduction i n force, caused by poor sealing and loss of suction from seal deformation. The increase i n force a few centimeters l a t e r i n the stroke could be caused by the cup seal re-sealing against the c y l i n d e r and regaining the suction forces. The re- s e a l i n g occurs as the downward deforming forces on the seal are reduced and the shape memory inherent with temperature set p l a s t i c s , such as pPVC, return the seal to i t s o r i g i n a l un-deformed shape. In comparison, deformation of the seal by r o t a t i o n about i t s circumference edge i s not possible with the No. 6 piston as the seal i s s o l i d l y fixed between two threaded f i t t i n g s . Given that the force reductions and increases through the stroke are not constant with the fixed r i s e r length used i n 56 the laboratory t e s t s , and that the No. 6 piston d i d not show t h i s c h a r a c t e r i s t i c curve when maximum sealing and steep acceleration force curves occurred i n some t e s t s , the second explanation, that of the deformation of the piston seal, i s the most probable. This i s not conclusively provable with the t e s t apparatus and r e s u l t s of t h i s t h e s i s . More importantly, to the improvement of the pump design, the force curve when using the No.6 piston i s smoother with le s s shock loading on the piston than with two-plate design, due to shorter valve c l o s i n g times and probably l e s s seal deformation. The smoother force t r a n s i t i o n s also lessen the sudden loads on the pump superstructure, extending the working l i f e and improving structure s t a b i l i t y . 7.2 VALVE CLOSURE DELAYS The opening and c l o s i n g of the piston and foot valves are evident from the tension or compression forces measured at the piston rod. Examination of the time and distance t r a v e l l e d by the piston from the beginning of a stroke stage to the beginning of associated forces, indicates the delays i n valve opening and c l o s i n g . This i s useful i n analyzing the proportion of volumetric losses a t t r i b u t a b l e to valve delays as opposed to leakage past the piston s e a l . The piston valve closure delay, shown by the more hori z o n t a l portion of the force curve at the beginning of the stroke, i s about two times greater with the two-plate 57 piston than with the No. 6 piston. The average 1.0 cm stroke length delay of the two-plate piston valve e f f e c t i v e l y reduces the stroke length used f o r pumping by 25% i n the laboratory t e s t s and an estimated 8% i n the f i e l d t e s t s . The difference between the laboratory and f i e l d t e s t s i s a r e s u l t of the longer stroke lengths of the Bangladeshi operators i n the f i e l d t e s t s . The proportion of the stroke used for valve closure becomes smaller with the longer stroke. In eithe r case, the valve delay r e s u l t s i n reduced discharge and lower volumetric e f f i c i e n c y . The 0.5 cm delay with the No.6 piston reduces the useable stroke length by 12.5 percent and an estimated 4 percent i n the laboratory and f i e l d t e sts respectively. F i e l d Tests Standard Piston No. 6 Piston Lab. Tests Standard Piston No. 6 Piston Piston Foot-valve Total 8 25 12.5 13 13 40 40 21 17 65 52.5 Table I I : Percent loss from piston and foot-valve delays. 58 I t should also be noted that the looseness of the piston to treadle lever connection often r e s u l t s i n a longer treadle lever stroke length than piston stroke length. As such, the strokes seemed longer to the operator than those measured. Delays i n foot-valve c l o s i n g are indicated by the downward distance t r a v e l l e d by the piston before compressive forces which indicate movement of water through the piston rather than through the foot-valve, are exerted'on the piston. As seen i n figures 14 and 15, the delay i n foot-valve c l o s i n g i s large, taking up as much as 1.6 cm of stroke length. This delay represents an average of 40% of the stroke length i n the laboratory t e s t s and an estimated average of 13% i n the f i e l d t e s t s . The cumulative e f f e c t s of valve closure delays are given i n Table I I . As previously mentioned, the differences i n operating s t y l e s i n the f i e l d t e s t s r e s u l t i n the v a r i a t i o n between the losses calculated from the laboratory and averaged f i e l d t e s t values. The primary cause for the difference i s the three times longer average stroke length of 13 cm for the Bangladeshi operated f i e l d t e s ts as opposed to the 4 cm length f o r the author operated laboratory t e s t s . The longer stroke lengths used by the Bangladeshi farmers i n the f i e l d t e s t s reduces the o v e r a l l e f f e c t of valve closure delays. Although the percentage losses are not as great i n the f i e l d 59 t e s t s , the closure delays s t i l l represent a major loss i n the short strokes as compared to the f u l l c y l i n d e r length strokes of the o r i g i n a l rope and pulley system shown i n figure 3. The s h i f t to the "dheki" operating system that has resulted i n the shorter stroke lengths was i n i t i a t e d by Bangladeshi farmers to increase operator comfort. They found that the weight s h i f t i n g , non-knee bending s t y l e of operating the "dheki" system was more comfortable than the stepping action of the rope and pulley system. In e i t h e r system, the operator w i l l move towards or away from the pump to achieve the most comfortable stroke length and power input requirement. With the non-knee bending s t y l e of the "dheki" operation, the changes i n stroke length are l i m i t e d by the hip j o i n t motion and as such the range of stroke length i s small. For the analysis of the pump, i t was assumed that the stroke length i s u n l i k e l y to increase beyond the extremes measured i n the f i e l d . For the most part, the longer stroke lengths i n the f i e l d t e s t s over the laboratory t e s t s are a r e s u l t of many hours of pumping experience by the Bangladeshi operators. The laboratory operator, operating pumps i n Bangladesh, consistently had shorter stroke lengths, further i n d i c a t i n g that the difference l i e s with the operator rather than the pump i n s t a l l a t i o n . 60 7.3 THE EFFECT OF WATER TABLE DEPTH ON APPLIED FORCE As the force applied to the piston i s the sum of providing the unbalanced head to provide water flow, overcoming losses, accelerating the water column and increasing the pot e n t i a l energy of the treadle lever, an increase i n water table depth with no increase i n o v e r a l l r i s e r length, a f f e c t s only the force required to create the unbalanced head needed fo r water flow. The increase i n force, as shown i n figure 16, from 230 to 350 newtons, a differe n c e of 120 newtons, with an increase from 3.44 to 5.36 meters respectively, i s , for a l l intents and purposes, equal to the t h e o r e t i c a l difference of 123 newtons calculated using equation 1 and 2 from section 4.3, for the same depth increase. This shows that the acceleration and head losses are dependent upon r i s e r length and not the water table depth. As the area under the force displacement loop equals the work done, the increase i n force with an increase i n water table depth, increases the work done provided the stroke length and stroke rate are constant. 7.4 THE EFFECT OF WATER TABLE DEPTH ON DISCHARGE AND VOLUMETRIC EFFICIENCY The e f f e c t of water table depth on volumetric e f f i c i e n c y was found to be a reduction of volumetric 61 e f f i c i e n c y with increasing depth, as shown i n figure 17. This indicates that valve and seal leakage, responsible for poor volumetric e f f i c i e n c y , i s a function of water table depth and thus the magnitude of the suction below the piston. The curves presented f o r the f i e l d t e s t s represent averaged volumetric e f f i c i e n c i e s from the raw t e s t r e s u l t s . The values vary from 35 to 73 percent, with averages of 55% percent over a range of water table depths from 2.05 to 4.13 meters. The wide v a r i a t i o n was a r e s u l t of a wide range of 62 Figure 17: The e f f e c t of water table depth on volumetric e f f i c i e n c y . pump conditions, operational stroke lengths and cylinder conditions, r e s u l t i n g i n va r i a t i o n s i n foot valve and piston seal leakage. The laboratory r e s u l t s for the same configuration of pump as used i n the f i e l d , but tested over a greater range of water table depths, indicated volumetric e f f i c i e n c i e s ranging from 55 to 41 percent at 1.51 to 6.22 meters respectively. The small reduction i n volumetric e f f i c i e n c y through the t e s t range was primarily due to increased 63 leakage and piston and foot-valve delays, as seen by the force-displacement curves. This indicates that the volumetric e f f i c i e n c y c h a r a c t e r i s t i c s of the pump are more dependent on the motion c h a r a c t e r i s t i c s of the piston rather than an increase i n water table depth. The longer average stroke i n the f i e l d t e s t s produced reduced losses due to valve closure delays. The v a r i a t i o n i n stroke length between operators also caused increased data spread as the longer strokes decreased the proportion of the stroke taken up by valve opening and closings. This e f f e c t i v e l y increased the volumetric e f f i c i e n c y of the pump. The s i m i l a r i t y of the volumetric e f f i c i e n c i e s i n the laboratory and f i e l d t e s t s indicated much greater losses past the piston buckets i n the f i e l d t e s ts as the proportion of losses due to valve opening and cl o s i n g were les s with the longer stroke length. 7.5 POWER INPUT REQUIREMENTS The power for the Treadle pump, being supplied by human operators, varies with the condition and surroundings of both the pump and operator. The laboratory t e s t s , using the same pump configuration as tested i n the f i e l d , were conducted using shorter strokes at roughly the same stroke rate, r e s u l t i n g i n lower discharges. The shorter stroke length used i n the laboratory was a r e s u l t of the pump operation being c o n t r o l l e d according to operator comfort, as 65 POWER INPUT (watts) 1.51 2.57 3.34 3.62 4.09 5.36 DEPTH TO WATER TABLE (meters) ^ LAB. RESULTS ••+•- EST. FIELD RESULTS Figure 18: Laboratory and estimated f i e l d power input requirements. The laboratory measured and estimated f i e l d t e s t power requirements both indicate that there i s an upper maximum power output a b i l i t y f o r operators of the Treadle pump. This value was measured as 50 watts at the pump head with some v a r i a t i o n with operator and pump i n s t a l l a t i o n . Adding the losses r e s u l t i n g from f r i c t i o n i n the superstucture not measured by the laboratory instrumentation, the actual l i m i t f o r power input i s closer to 55 watts. Although i t i s possible to produce much more power than t h i s over a short period of time, the often malnourished Bangladeshi operator, 64 i s done by the Bangladeshi farmer. The difference between what was comfortable to the North American laboratory operator and the Bangladeshi farmer operators was the cause of the differences i n stroke length. Assuming the losses remained constant between the laboratory t e s t s and the f i e l d t e s t s , the power input should be proportional to the discharge i n both t e s t s . Using the laboratory discharge and power input measurements, including the power required to ra i s e the treadle lever estimated by the amount of work done by the lever during the piston downstoke, estimates were made f o r the power input from the f i e l d t e s t s , shown i n figure 18, using the f i e l d discharge measurements. The estimates do not f u l l y take into account the i n e f f i c i e n c i e s of the superstructure, which include the f r i c t i o n at the central axle pivot and at the piston to treadle lever connection, occurring between the operator and the pistons where the data was c o l l e c t e d . As with the measured laboratory data, the f i e l d power inputs r i s e sharply with an increase i n depth to the water table, as a r e s u l t of the increased force required create the unbalanced head required for.water flow from the water table. Corresponding to t h i s increasing power requirement, the pump discharge decreases due to increased losses from pipe f r i c t i o n and leakage through the valves and piston seals as described i n section 7.4. pumping fo r periods of at le a s t 30 minutes duration and a t o t a l d a i l y pumping requirement often between 8 and 10 hours per day, w i l l not exceed t h i s value. The t e s t i n g by EPC (EPC 1988), which measured power input using operator metabolic measurments, states maximum power operator output values as 69.73 and 51.7 watts for pumping durations of 20 and 30 minutes respectively, c l o s e l y agrees with the res u l t s obtained by c a l c u l a t i o n from the laboratory and f i e l d t e s t s . This l i m i t of power has implications to area i r r i g a b l e from a given depth. The area must remain above the minumum found by Orr (Orr and Islam 1988) to be the minimum fo r economic v i a b i l i t y and yet remain within the power c a p a b i l i t i e s of the operator. For example, the minimum discharge required to supply an average farmer's 0.24 Ha (0.65 acre) crop, with a consumptive use of 6 mm/day, using one pump and a maximum pumping time of 8 hours per day, i s 28 1/min. The maximum depth to water table s t i l l able to meet the i r r i g a t i o n requirements would be 3.8 meters and would require a constant power input of 40 watts, using the laboratory based f i e l d estimates of input power requirements and f i e l d discharge r e s u l t s . Regions where marketing of the pump has been less successful have water table depths of 4 meters and greater. The d i f f i c u l t y i n maintaining the 28 litre/minute i r r i g a t i o n requirement without exceeding the power input l i m i t of 55 67 watts at these depths, i s for the most part, the cause for the poor sales. 7.6 PUMP AGE EFFECTS ON DISCHARGE AND VOLUMETRIC EFFICIENCY The age of the treadle pumps f i e l d tested i n Bangladesh had l i t t l e e f f e c t on the discharge and volumetric e f f i c i e n c y c h a r a c t e r i s t i c s measured as shown i n figure 19. VOLUMETRIC EFFICIENCY DISCHARGE (L/min) 10 20 30 PUMP AGE (months) 40 • DISCHARGE - f - BEST FIT DISCH.CURVE * VOL. EFFICIENCY - B - BEST FIT V.E. CURVE Figure 19: E f f e c t of pump age on volumetric e f f i c i e n c y and discharge from f i e l d t e s t s . 68 The large v a r i a t i o n s i n owner maintenance and care of the pumps observed and tested, overshadowed any long term e f f e c t s from age as can be seen by the large degree of scatter i n the data. Variations of component wear were widely observed, with some pumps requiring replacement piston buckets and foot-valve flaps a f t e r two or three months and others not u n t i l a f t e r 2 or 3 years. Major wear i n the s t e e l pump body was comparatively minimal by v i s u a l inspection compared to the obvious wear of the cup seals and valves. 7.7 EFFECTS OF PUMP BODY CONFIGURATION ON VOLUMETRIC EFFICIENCY, POWER REQUIREMENTS AND DISCHARGES E f f e c t s from alternate pump configurations, the combinations of the two piston and two pump body types, were most evident i n the laboratory r e s u l t s f o r force inputs, volumetric e f f i c i e n c i e s , discharges and input power requirements as shown i n figure 20. The volumetric e f f i c i e n c y i s much lower when the No. 6 piston i s used as compared to the standard two plate piston, with e i t h e r pump body at the same water table depth. This i s a t t r i b u t a b l e to poor sealing of the poppet valve i n the No. 6 piston. The r e s u l t of t h i s leakage i s a loss of suction c a p a b i l i t y and the p a r t i a l l y the lower discharges indicated i n figure 20. 69 1 0.9 0.8 --0.7 --0.6 0.5 --0.4 --0.3 --0.2 --D.l --0 VOLUMETRIC EFF'Y 0. DISCHARGE (L/mln) T 30 -- 25 + + 2 3 4 5 WATER TABLE DEPTH (maters) 20 15 -- 10 -- 5 — - BOX:5 HOX:S BOX; 6 -0-- BOX: 6 YiSTND "A- YiSTND "B - Y:N0.6 -X- Y:N0.6 Figure 20: E f f e c t of pump configuration on laboratory measured volumetric e f f i c i e n c y and discharge. The e f f e c t s of pump body type are s i m i l a r to those of the pistons, but the reasons f o r the poorer performance of the Y-style pump are less obvious. As shown i n figure 20, the volumetric e f f i c i e n c i e s and discharges f o r the Y-style pump are a l l lower than f o r a s i m i l a r l y configured box manifold pump. The lower volumetric e f f i c i e n c y when using the same set of pistons i n each configuration, gives a clear i n d i c a t i o n that the foot-valve on the Y-style pump tested i n the laboratory was operating poorly, as no other change was 70 made which could a f f e c t leakage losses. As a r e s u l t , l i t t l e can be said about the e f f e c t s of the Y-style Treadle pump, except that any increases i n performance a t t r i b u t a b l e to the manifold design, e i t h e r Y-style or box, must be minimal to be overshadowed by va r i a t i o n s i n foot-valve performance. The alternate pump configurations were not f i e l d tested so no comparison i s possible to the performance the pumps would have i n Bangladesh. Given the poor laboratory t e s t r e s u l t s , an assumption of s i m i l a r f i e l d performance would be reasonable given the close agreement i n laboratory and f i e l d r e s u l t s of the configuration widely used i n Bangladesh, the box manifold and two-plate piston. 8 DISCUSSION 8.1 VALIDATION OF THEORETICAL MODEL BY LABORATORY TESTS The governing equations presented i n section 4.3 produced a force displacement curve that compares c l o s e l y with the laboratory r e s u l t s as shown i n figure 21, Figure 21: Comparison of calculated and laboratory r e s u l t s . which i s for a model with the box-type manifold Treadle pump using the standard two-plate piston. Values for mechanical f r i c t i o n and piston motion c h a r a c t e r i s t i c s used i n the cal c u l a t i o n s where taken from the laboratory t e s t data, not from the derived motion equations. The close agreement of the laboratory and calculated force curves shown i n figure 21 i s l a r g e l y due to using measured piston motion rather than the t h e o r e t i c a l values. This i s because the measured values account for i r r e g u l a r i t i e s present i n the laboratory t e s t s that would not be accounted for i n the t h e o r e t i c a l motion values. The laboratory and t h e o r e t i c a l r e s u l t s f o r the other three pump configurations are also i n close agreement. This i s to be expected because the a l t e r a t i o n s from the standard configuration are primarily i n valve delay and leakage parameters, which were derived from the laboratory data. 8.2 COMPARISON OF LABORATORY AND FIELD TEST RESULTS The inconsistency of f i e l d operators and pumps made the comparison between laboratory and f i e l d t e s t r e s u l t s d i f f i c u l t . Averaged f i e l d r e s u l t s , used for comparison at 0.2 meter increments of water table depth, showed that the shorter stroke lengths and the equal or slower stroke rates used i n the laboratory, as an estimation of how a Bangladeshi farmer would operate the pump over long durations, produced lower discharge than f o r s i m i l a r f i e l d configurations. The shorter stroke lengths used i n the laboratory t e s t s were a r e s u l t of what was comfortable for the operator. The Bangladeshi farmers are more comfortable with the s l i g h t l y longer stroke length but they s t i l l prefer the much shorter stroke of the "dheki" s t y l e superstructure to the f u l l length strokes of the rope-pulley superstructure. The f i e l d t e s t operators pumped with longer strokes and often a faster stroke rates than were assumed for the laboratory t e s t s , but tended to pump fo r shorter durations, about 1/2 hour rather than continuous pumping, as they reached the l i m i t of t h e i r power output c a p a b i l i t i e s . The shorter pumping duration, the motivation of i r r i g a t i n g the sole source of income f o r the family group, and a v a i l a b i l i t y and a f f o r d a b i l i t y of food and medicine may r e s u l t i n higher power inputs than anticipated from the laboratory t e s t s . The volumetric e f f i c i e n c y r e s u l t s were widely spread i n the f i e l d data but the averaged r e s u l t s agreed c l o s e l y with the laboratory data. This close agreement i n volumetric e f f i c i e n c y and thus losses, allowed for the c a l c u l a t i o n of input power for the f i e l d t e s t s to be scaled from the discharge measurements from the laboratory t e s t s . The close agreement between the t h e o r e t i c a l c a l c u l a t i o n s and the laboratory r e s u l t s , and the s i m i l a r values f o r volumetric e f f i c i e n c y i n the laboratory and f i e l d 74 r e s u l t s , provide a basis for design a l t e r a t i o n s v a l i d for f i e l d a p p l i c a t i o n based on the t h e o r e t i c a l and laboratory r e s u l t s . 8.3 IMPLICATIONS OF THE RESULTS ON PUMP RE-DESIGN Over the past few years, since the s t a r t of the rapid increase i n popularity and sales of the Treadle pump, many suggestions have been made to a l t e r the pump design. Part of the purpose of t e s t i n g the Treadle pump was to form a basis f o r evaluating these suggestions. Some of pump re-design suggestions have included changes to: 1. Pump body materials, including PVC, concrete, f i b e r g l a s s , juteglass and cast iron. 2. Piston configurations, including r e t a i n i n g the standard two-plate piston or using the No.6 piston tested. 3. Cylinder s i z e , with 76 mm (3 inch), 64 mm (2 1/2 inch) and 51 mm (2 inch) diameters suggested. 4. Cylinder length, such as a 203 mm (8 inch) or 254 mm (10 inch) c y l i n d e r to replace the current 356 mm (14 inch) length. 5. The s t y l e of pump to r i s e r junction, with the o r i g i n a l box-style and the Y-style suggested. The t e s t r e s u l t s have indicated that, i n the case of a l t e r i n g pump material, the f r i c t i o n force of the seal against the cylinder would change marginally with a cylinder material change, as the pressure of the seal against the 75 cylinde r would remain constant and the c o e f f i c i e n t of f r i c t i o n between the seal and any of the materials l i s t e d does not vary greatly. With the marginal scope f o r improvement from a hydraulics view, the reasoning f o r a change i n pump materials must rather be based upon economic or manufacturing benefits. In b r i e f , given the current development strategy to promote small scale decentralized manufacturing of treadle pumps i n Bangladesh and the more pragmatic reasons including the a v a i l a b i l i t y of machine tools f o r working with s t e e l and the a v a i l a b i l i t y , wide acceptance and re-sale value of s t e e l products throughout Bangladesh, the use of s t e e l for the treadle pump provides the best solu t i o n i n terms of the development and economic c r i t e r i o n at the present time. The use of s t e e l also reduces the rel i a n c e on new, more expensive imported materials, products and cent r a l i z e d production technology required f o r many of the alternate materials. In the case of piston design a l t e r a t i o n , both of the two piston configurations tested, the two-plate piston and the No. 6 piston, have advantages. The two-plate piston i s more widely used, e a s i l y f i x e d and provides better piston valve sealing than the No. 6 piston, which benefits from wide a v a i l a b i l i t y , shorter valve delays and a non-rusting pPVC construction. Optimally, a combination of the small c l o s i n g time of the No.6 and p o s i t i v e sealing of the two plate design should be used. 76 In the case of the cyli n d e r s i z e , discharge and power input requirements are primarily affected by any a l t e r a t i o n . A decrease i n cyli n d e r diameter would reduce the discharge i n comparison to the present 89 mm (3.5 inch) design. This would allow use of the pump to a greater depth without exceeding a power input l i m i t a t i o n of 55 watts, which corresponds to a hydraulic output of 25.3 watts, i n normal use. As a r u l e of thumb, an increase i n water table depth a c c e s s i b i l i t y of 1.4 meters per 13 mm (1/2 inch) reduction i n c y l i n d e r diameter. The 13 mm reduction i n diameter i s accompanied by a 27% decrease i n discharge, assuming losses are the same as those occurring i n the current pump design, with the 55 watt input l i m i t a t i o n . For example, using a discharge requirement of 25 L/min as the minimum to meet i r r i g a t i o n requirements, the maximum depth of a p p l i c a t i o n for a 102 mm (4 inch) c y l i n d e r diameter Treadle pump would be 3.86 meters, l i m i t e d by power input. The 89 mm (3.5 inch) treadle was found to have a maximum water table depth application of 4.09 meters, l i m i t e d by discharge below the requirement and near the l i m i t of power input. A 76 mm (3 inch) Treadle pump would have a maximum app l i c a t i o n depth of 5.88 meters, l i m i t e d by discharge below the i r r i g a t i o n requirement. A 64 mm (2.5 inch) Treadle would have a maximum of 4.3 meters, l i m i t e d by discharge below the requirement. 77 From these c a l c u l a t i o n s , the optimum cy l i n d e r diameter, assuming operating losses, power inputs and pumping operating parameters remain unchanged from those measured i n the f i e l d and laboratory t e s t i n g , i s 76 mm (3 inches). This s i z e would allow Treadle pump usage to a maximum water table depth and remain within the l i m i t s of power input and i r r i g a t i o n requirements. Any increase i n e f f i c i e n c y would increase the power output for the 55 watt l i m i t of power input and increase the optimum cylin d e r s i z e within the 6 meter water table l i m i t . In the case of cylind e r length, a reduction would reduce the pump cost by about 8 Taka (0.32 CAD) per centimetre. Although on average only 140 mm of the 356 mm (14 inch) c y l i n d e r i s used during the pump stroke, the portion of cylind e r used varies between i n s t a l l a t i o n s . F i e l d t r i a l s conducted by IDE with the 305 mm (12 inch) c y l i n d e r pump, found that the reduction i n length required greater accuracy of superstructure placement at i n s t a l l a t i o n . This reduced pump popularity due to the l i m i t of i n s t a l l a t i o n v a r i a t i o n possible. In the case of the junction s t y l e , from the calculated r e s u l t s , i t was determined that the power losses r e s u l t i n g from turbulence through the manifold account for l e s s than 12% of the t o t a l head losses, not including valve delay and leakage losses, at maximum water v e l o c i t y i n the piston and r i s e r , at a head of 3.34 meters. The a l t e r a t i o n i n type of 78 junction manifold from the box-style to the Y-style suffers from increased manufacturing complexity and cost with l i t t l e or no savings from reduced losses. The benefit from the smoother junction would reduce suction head requirements by 0.03 meters at maximum flow. This represents a 6.4% reduction i n hydraulic losses but i s only 1% of the t o t a l head losses i n the whole system, including valve and leakage losses, and i s not worth the increase i n cost and manufacturing d i f f i c u l t y . 10 CONCLUSION In conclusion, the Treadle pump performance can be best improved by design a l t e r a t i o n s to the piston and foot-valves as indicated by the low discharges and volumetric e f f i c i e n c i e s measured i n the laboratory and f i e l d t e s t s , and by a reduction i n cylind e r diameter to permit pump use i n areas with greater water table depths. The comparatively small losses caused by turbulence and f r i c t i o n indicate that a l t e r a t i o n s to the pump material and configuration, as shown i n the laboratory and t h e o r e t i c a l r e s u l t s , are not warranted on the basis of improved pump performance, but must be decided from economic and development strategy benefits. The primary problems i d e n t i f i e d from the laboratory and f i e l d t e s t i n g of the "dheki" s t y l e Treadle pump i n s t a l l a t i o n s were the leakage through the piston and foot-valves and the large valve closure delay times. Although the longer stroke lengths of the f i e l d t e s t s reduced the e f f e c t of the valve delays, even at the maximum comfortable stroke lengths recorded the minimum loss r e s u l t i n g from valve delays i s 17%. For example, i f both the piston and foot-valve closure delay times where halved, the decrease i n leakage represents a pot e n t i a l increase i n volumetric 79 80 e f f i c i e n c y of 46%, r e s u l t i n g i n increased discharge and use to greater water table depths. The water table depth to which the Treadle pump i s usable i s l i m i t e d by eithe r i n s u f f i c i e n t discharge or large input power requirements, depending upon cy l i n d e r s i z e and depth to water table. The current 89 mm (3.5 inch) cylinder diameter pump i s li m i t e d to a water table depth of 4 meters, due to the sustainable power input l i m i t of 55 watts indicated by the f i e l d and laboratory r e s u l t s . The d i f f i c u l t y of s e l l i n g the pumps i n regions with water table depths deeper than 4 meters and the EPC t e s t r e s u l t s also indicate a water table depth l i m i t of 4 meters. A reduction i n c y l i n d e r s i z e to 76 mm (3 inch) would increase the water table depths accessible to the Treadle pump within the l i m i t a t i o n s of power input and maintain enough discharge to meet i r r i g a t i o n requirements. The 76 mm pump would be most suita b l e f o r water table depths i n the 4 to 5.5 meter range, to assure that the power input required does not exceed 55 watts. Any further reduction i n diameter past 76 mm would reduce the discharge below the i r r i g a t i o n requirements f o r the 0.24 Ha (0.6 acre) minimum i r r i g a t e d area required for pump repayment. The use of the widely a v a i l a b l e 89 mm (3.5 inch) pPVC piston cup seal, manufactured f o r use i n the ubiquitous No.6 pump, and the poor a v a i l a b i l i t y of the 76 mm (3 inch) pPVC seal reduces the d e s i r a b i l i t y of the 76 mm 81 pump at the present time, but more work i n manufacturing a l t e r n a t i v e s may y i e l d more options. Overall, the study of the piston force c h a r a c t e r i s t i c s and the use of va r i a t i o n s between f i e l d and laboratory r e s u l t s to analyze the pump design, c l e a r l y shows the benefits of the combined use of laboratory, a n a l y t i c a l and f i e l d r e s u l t s as the basis for design a l t e r a t i o n s . The study also indicated the strength of the design and the innovation by the aid workers who o r i g i n a l l y developed the Treadle pump, as very l i t t l e a l t e r a t i o n i s required to optimize the operation of the Treadle pump. LIST OF REFERENCES A l l i s o n , Stephen V. 1986. Handpump I r r i g a t i o n i n Bangladesh. Vancouver: International Development Enterprises Barnes, Gunnar. 1985. The Development of a Manual I r r i g a t i o n Device: The Twin Treadle Pump, Manilla, P h i l i p p i n e s : International Rice Research I n s t i t u t e . Photocopied. Barnes, Gunnar. 1981. Low Cost I r r i g a t i o n ( A g r i c u l t u r a l Programme of RDRS). Association of Development Agencies i n  Bangladesh News. March/April. Baumann, E r i c h and Richard J . F u l l e r . 1984. Manual  I r r i g a t i o n i n Bangladesh. Dhaka: Swiss Development Cooperation. Bos, M.G., ed. 1976. Discharge Measurement Structures. New Delhi: Oxford & IBH Publishing Co. Bureau of Research Testing and Consultation. 1986. Laboratory Testing of Treadle Pump. Dhaka: Bangladesh Unive r s i t y of Engineering and Technology Consumers' Association Testing and Research Laboratories, Rural Water Supply Handpumps Project. Laboratory Testing of  Handpumps fo r Developing Countries. World Bank Technical Report No. 19. Engineering and Planning Consultants Ltd. 1988. Testing of  Handpumps under IDA Assisted HTW Project (Credit 1140-BD). Dhaka: Bangladesh Rural Development Board Gibson, A.H. 1925. Hydraulics and i t s Applications. 4th ed. New York: D. Van Nostrand Company Inc. G i s s e l q u i s t , David, ed. 1985. Report on BARC Sponsored  Course on: Manual and Animal Powered Pumps for I r r i g a t i o n . Dhaka: Bangladesh A g r i c u l t u r a l Research Council. Hahn, Robert. 1984. Handpump Testing and Development. Part 4, The F i r s t Year - Results of Completed and Ongoing Tests. Stockholm: Lund I n s t i t u t e of Technology. 82 83 Hyde, Charlotte. 1987. A Mathematical Modelling Simulation of Rower Pump Performance. B.A.Sc. th e s i s , University of B r i t i s h Columbia. International Development Enterprises. 1988. Annual Report. Dhaka: International Development Enterprises. . 1988. Pump sales figures. Dhaka: International Development Enterprises. Typewritten. K r i s t a l , Frank A. and F.A. Annett. 1940. Pumps: Types.  Selection, Operation, and Maintenance. New York: McGraw-Hill Book Company Inc. Manual Pump Group. 1987. Long-range Strategic Issues. Dhaka: Manual Pump Group. Typewritten. . 1988. Annual Report. 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Dhaka: Mennonite Central Committee. 84 Stickney, R.E., C. Abrina, R.L. Bacalocos, J.A. Damian, R. Domingo, B.C. Gonzalo, V.N. Piamonte, Q. deSagun and I. Ventura. 1987. Human-Powered Pump for Lo w - l i f t I r r i g a t i o n . Manila: International Rice Research I n s t i t u t e . The World Bank. 1981. Bangladesh Hand Tubewells Project S t a f f Appraisal Report. 3280-BD. The World Health Organization International Reference Centre for Community Water Supply. 1977. Handpumps fo r use i n  Drinking Water Supplies i n Developing Countries. The Hague: The World Health Organization. Todd, David K. 1959. Ground Water Hydrology. New York: John Wiley and Sons Inc. United Nations. United Nations Development Programme. 1982. Ground Water Survey - The Hydrogeologic Conditions of  Bangladesh. U.S. Bureau of Reclamation. 1975. Water Measurement Manual. 2nd ed. Denver. WHO. 1977. See The World Health Organization International Reference Center for Community Water Supply. 1977. Yaw, Goh Sing. 1985. Laboratory and F i e l d Testing of  Handpumps. Ottawa: International Development Research Council. IDRC-TS51e. APPENDIX 1: AVERAGED FIELD TEST DATA TESTS CONDUCTED IN THE JAMALPUR AND KUSHTIA REGIONS OF BANGLADESH OPERATOR PUMP W. T. STROKE VOL. STROKE POWER :ST AGE WEIGHT AGE DEPTH LENGTH DISCHARGE EFF'Y RATE OUTPUT # (yrs) (lbs) (yrs) (m> (cm) (1/min) (/mi n) (watts) 21 27 125 1 2.05 12.32 39. 22 0.66 39.02 13. 14 42 40 110 1 2.20 16.06 33. 12 0.35 47.51 11.91 11 28 130 1 2.23 9.57 36.59 0.73 42.26 13.34 16 18 90 12 2.29 13.75 30. 30 0.44 40. 61 11. 35 17 25 150 12 2.29 9.02 23.32 0. 63 32.95 8. 73 19 30 150 12 2.37 11.11 35. 35 0.72 35.76 13.70 18 25 95 12 2.47 15.62 27.27 0.38 36. 55 11.01 22 31 100 12 2.59 9.79 37. 15 0.63 48.48 15. 73 39 25 100 2 2.73 14.85 43.83 0.54 44. 42 19.56 32 18 95 24 2. 78 15. 73 41.93 0.52 41.55 19.06 41 18 90 2 2.79 12.98 45.00 0.61 46.00 20.53 13 22 120 12 2.86 12.54 40. 82 0.60 43.67 19. 09 40 40 130 1 2.88 18.92 22.52 0. 36 26.31 10.61 43 37 125 3 2.97 11.99 39.22 0.55 28.04 19.04 35 50 120 12 3. 13 11.66 29.51 0.62 33.05 15. 10 9 40 125 2 3. 25 15.73 60.89 0.51 61.33 32. 35 10 25 150 __. 2 3. 25 8.47 32.97 0.67 46.81 17.52 36 18 100 2 3. 56 13.97 39.60 0.57 39.80 23.05 37 30 120 2 3. 61 13.64 46.23 0.58 46.85 27.29 27 28 126 12 3. 73 6.27 23.96 0.57 54.25 14.61 29 14 80 24 3. 83 12.76 28.57 0.45 40.00 17.89 33 25 130 12 3. 85 10. 12 27.86 0.51 43. 10 17.54 31 35 125 36 3. 97 9. 13 36.92 0.70 46.34 23.97 28 23 115 36 4. 01 6.82 27. 19 0.46 70.33 17.83 23 24 110 36 4. 13 16. 28 43.23 0.54 39. 77 29. 19 24 25 150 36 4. 13 9.24 25. 17 0.51 43.09 16.99 25 45 110 3 4. 28 5.94 24. 19 0.86 38. 13 16. 93 26 25 150 3 4. 28 5.72 22.73 0.89 36. 06 15.90 85 APPENDIX 2: AVERAGED LABORATORY DATA -TESTS CONDUCTED AT THE UNIVERSITY DF BRITISH COLUMBIA, CANADA NOTE: THE FIRST TWO DIGITS OF THE TEST CODE INDICATE CONFIGURATION 01:BOX MANIFOLD, 2-PLATE PISTON 02:BOX MANIFOLD, NO. 6 PISTON 03:Y-MANIFOLD, 2-PLATE PISTON 04:Y-MANIFOLD, NO. 6 PISTON TEST STROKE VOL. POWER POWER POWER CODE HEAD LENGTH DISCHARGE EFF' Y RATE OUTPUT INPUT EPF' Y (m) (cm) ( l/iiiin) (/mi n) (watts) (watts) TO1021 1. 51 4. 04 25. 06 0.68 73.41 6. 11 26.55 0. 23 TO1022 1. 51 3.35 25. 04 0. 41 73.72 6. 15 23.64 0.26 TO1041 3. 34 3.56 24.07 0. 60 45.52 13. 15 50.56 0.26 TO1042 3. 34 4.24 12.36 0. 41 57. 07 6.69 31.88 0.21 TO1061 5. 36 3. 30 16.63 0. 58 70. 20 14.58 64.80 0.23 TO1062 5. 36 1.91 6.27 0. 30 87. 94 5.49 35.44 0. 16 TO1081 6. 22 4.32 34.54 0. 55 60. 00 34. 51 95.85 0.36 TO1082 6. 22 4.84 20.85 0.41 41.81 21. 17 81.44 0.26 T02021 1. 51 4.08 42.60 1.08 77.99 10. 56 45.92 0.23 T02022 1. 51 2.78 28.44 0. 49 91.72 7.57 37.85 0.20 T02041 3. 34 3.28 24.53 0.43 69.30 13.50 42. 19 0.32 T02042 3. 34 2. 94 15.13 0. 33 63.84 8.28 30. 68 0.27 T02061 5. 36 2.79 16. 14 0.34 67. 73 13.92 51.57 0.27 T02062 5. 36 3. 02 9.03 0.23 53.50 8.00 40. 00 0. 20 T02081 6. 22 4.69 28.70 0.33 74.00 30. 16 115.99 0.26 T02082 6. 22 3.61 12.21 0. 23 58.30 12. 13 86.63 0. 14 T03021 1. 51 4.57 35.54 0. 54 58. 17 8.75 29. 18 0.30 T03041 3. 34 3.68 15.77 0. 28 61.81 8.71 39.60 0.22 T03061 5. 36 1.88 12.97 0.23 60. 08 11.44 54.46 0.21 T03081 6. 22 4.21 9. 72 0. 17 54.56 9.94 99.44 0. 10 T04021 1. 51 4.94 25.84 0. 33 63. 55 6.53 40.84 0. 16 T04022 1. 51 3.72 27. 19 0. 41 72. 13 6.87 42.92 0. 16 T04041 3. 34 4.49 15.67 0. 21 65. 66 8.71 67.01 0. 13 T04042 3. 34 4. 11 19. 10 0.27 68.35 10.55 70.35 0. 15 T04061 5. 36 6.71 17. 15 0. 18 56. 14 15.51 129.28 0. 12 T04062 5. 36 4.31 11.44 0. 17 63. 17 9.53 105.87 0.09 T04081 6. 22 7.65 5.80 0. 10 39. 20 5.61 93.58 0.06 T04082 6. 22 4.77 11. 03 0. 17 55.88 10.91 121.21 0.09 86 

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