Agriculture:- Model Bankable Projects in India | Minor Irrigation : Pumpsets Part - 1 --- www.nabard.org

Agriculture:- Model Bankable Projects in India

Minor Irrigation : Pumpsets Part 1

Pumpsets

Field studies by NABARD and other agencies like Indian Pump Manufacturers' Association, Indian Diesel Engine Manufacturers' Association, Petroleum Conservation and Research Association, Rural Electrification Corporation, Institute of Co-operative Management, have revealed that most of the agricultural pumpsets selected and installed operate at much lower efficiency than desired. This is because of improper selection and installation of pumpsets by farmers who are often guided by the dealers and village mechanics. The financing institutions and other agencies who advance loans for pumpsets are expected to help farmers in proper selection and installation. Improper selection of pump, prime mover and accessories results in wastage of energy and fuel causing financial burden to farmers and the nation. The Bureau of Indian Standards (BIS) has already brought out a standard IS-10804 (1994) for selection of efficient pumpsets. NABARD has conducted workshops to educate bank officials and farmers in proper selection and installation of agricultural pumpsets. This document on "Selection and Financing of Agricultural Pumpsets" is an endeavour to help bank officers, farmers and other agencies in selecting an energy efficient pumping system and would serve as a ready reckoner. The criteria for selection mentioned in the document are for guidance only. This document is also available on www.nabard.org. Any suggestion for further improvement is welcome. CONTENTS FIELD STAFF GUIDE Introduction Minor Irrigation Units Existing Well Practices Suggested Well Dimensions Agricultural Pumpsets Selection of Centrifugal Pump Selection of Electric Motor Selection of Diesel Engine Selection of Suction and Delivery Pipes Selection of Foot Valve Farmers' Guide for Selection of Agricultural Pumpsets FINANCING OF AGRICULTURAL PUMPSETS Cost of Pumping System Loan for Pumping System Repayment Period Economics Subsidy Rate of Interest Maintenance And Repairs of Centrifugal Pumpsets Further Guidance ANNEXURES Matrix for Selection of Agricultural Pumpsets - with RPVC Pipes Matrix for Selection of Agricultural Pumpsets - with G.I. Pipes National Bank Circular on Quality Control of Agricultural Pumpsets Average Unit Cost of Complete Pumping System National Bank Circular on Unit Cost under Schematic Lending Economic Analysis of Financing of Agricultural Pumpset Introduction The necessity of having simple field oriented guidelines for selection of proper agricultural pumpset and its accessories arises out of the fact that studies so far conducted by various agencies in the country indicate that even at present majority of pumpsets are improperly selected, incorrectly installed and have deficiencies in selection of not only the major components of a pumpset namely, pump and motor but also in selecting proper size of suction and delivery pipes and foot valve. Studies have indicated that a farmer can save over his present expenses for pumpset operation if his pumping system is properly selected compared to an improper selection and installation. Such correct selection would not only salvage the farmer from his avoidable yearly financial loss but would also save the nation power by way of savings in diesel oil consumption and electric power input to the large number of pumpsets used in agricultural operations. Minor Irrigation Units A farmer generally draws water either from a dugwell or a shallow tubewell fitted with a pumpset. In both cases a horizontal centrifugal pumpset is mostly used. In all future references in this document such a unit would be called as 'well and a pumpset'. When a farmer decides to construct a well his first worry is to make an estimate about the volume of water he can expect from the well. The most convenient way to have an idea about this is to go to a nearby similar working well and find out the discharge that is being obtained from it. This type of field survey would also give an idea about the depth to water below ground level from where it has to be lifted. In an unexplored area where no ground water pumpage structures exist, the expected yield from well requires certain hydrogeological estimates for which guidance from the State Ground Water Department could be taken. Criteria recommended in this document  are in conformity with IS-10804 (1994) for selection of a complete pumping system (Fig.1) by Bureau of Indian Standards. This not only gives norms for estimation of head and discharge on a farmer's well but also indicates the steps that are required for proper selection of a pumpset and its accessories in accordance with the head and discharge conditions at a well. Selection of Electric Motor 1.   Monobloc pumpset should be preferred over coupled pumpsets. 2.   The BHP of the pump should match power output of the prime mover. However, for practical considerations the BHP of the prime mover is always kept about 10 percent more than what is theoretically required for the pump. 3.  The efficiency of the motor as declared by the manufacturer should be considered. IS-10804 (1994) has provided the range of the following minimum efficiency ratings (Table V). TABLE I Range of yield and Size of Existing Dugwells in India Sr. No. Well Size Saturated thickness of formation (m) Discharge (liters /sec) States where encountered Diameter (m) Depth (m) I. HARD ROCK AREAS 1 3 to 4 20 to 25 6 to 8 4 to 6 Rajasthan, Gujarat 2 4 to 6 10 to 15 4 to 5 4 to 6 UP, MP, Orissa, Bihar, Kerala 3 5 to 7 10 to 20 4 to 5 4 to 6 MP, AP, Tamil Nadu, Karnataka, Maharashtra II. ALLUVIAL AREAS 4 2 to 3 20 to 50 6 to 8 5 to 6 Rajasthan, Gujarat 5 2 to 3 15 to 30 4 to 5 6 to 10 UP, Bihar, Orissa TABLE II Range of yield and Size of Existing Shallow Tubewells in Alluvial Formations in India Sr. No. Well Size Saturated thickness of aquifer tapped (m) Discharge (liters/sec) States where encountered Diameter (m) Depth (m) 1 80 to 100 30 to 45 10 to 15 8 to 12 Punjab, Haryana, Western UP 2 80 to 100 30 to 45 10 to 15 8 to 10 Eastern UP, Orissa, Bihar, Assam 3 80 to 100 30 to 50 10 to 15 8 to 10 West Bengal Suggested Well Dimensions Along with the existing type of irrigation wells, it would be desirable to indicate the well dimensions that would be appropriate for a given set of conditions existing in an area. For this purpose the most important consideration is the type of water yielding strata encountered in a well. This is also called an aquifer. For design purpose these water yielding strata have been grouped here into three categories as below. 1. Excellent 2. Very Good 3. Good The recommended design of irrigation wells for the above three categories of aquifers are given in Tables III and IV both for Dugwells and Shallow Tubewells/Borewells. TABLE III Expected Yield and Size of Dugwells in Hard Rock and Alluvial Areas Sr. No. Type of Aquifer HydraulicConducti-vity (m/day) Well size Thickness of Aquifer required (m) Average Discharge (liters /sec) Diameter (m) Depth (m) I. HARD ROCK AREAS Excellent 20 3 10 to 15 5 5 15 4 12 to 15 5 5 Very Good 12 5 10 to 15 5 5 10 6 15 to 18 5 5 Good 8 6 12 to 20 5 4 II. ALLUVIAL AREAS Excellent 40 2.5 10 to 15 4 8 Very Good 30 2.5 to 3 10 to 15 4 7 Good 20 3.5 to 5 15 to 20 4 6 TABLE IV Expected Yield and Size of Shallow Tubewells/Borewells in Alluvial and Hard Rock Areas Sr. No. Type of Aquifer Hydraulic Condu- ctivity (m/day) Size of Well Thickness of Aquifer required (m) Average Discharge (liters /sec) Diameter (mm) Depth (m) I. ALLUVIAL AREAS Excellent 40 80 to 100 30 10 8 to 12 Very Good 30 80 to 100 40 12 8 to 10 Good 20 80 to 100 50 12 8 to 10 II. HARD ROCK AREAS Excellent 20 80 to 100 45 10 to 15 6 Very Good 12 100 to 150 45 20 to 25 5 Good 8 100 to 150 50 20 to 25 4 Agricultural Pumpsets A complete pumping system for lifting water for irrigation comprises of the following main components. 1. Centrifugal Pump (coupled or monobloc) 2. Prime Mover - Electric Motor or Spark Ignition Diesel Engine 3. Piping System - Suction and Delivery pipes 4. Foot Valve, Reflux Valve 5. Pipe Fittings (Bends and other Fittings) All the above components constitute a pumping system. Each of the above components has to be properly selected to match the field requirement. If any component is wrongly selected, it makes the system inefficient. Thus, an efficient pumping system aims at maximum output at minimum capital and operating cost. Proper selection of an agricultural pumpset requires estimation of discharge and head over which water is to be lifted. The discharge required depends on peak irrigation requirement of crops grown in the command area of the well. Hydrogeological conditions should be such that this discharge is available from the well. The total head comprises of maximum depth to water in the well, depression in the water level during pumping and friction losses in the piping system and allied fittings, valves, etc. Having estimated the maximum discharge and head over which water is to be lifted, a right pumping system should be selected so that it works efficiently with minimum operating cost. Guidelines given below would be helpful in selecting a centrifugal pumpset for agricultural purposes. Centrifugal pumpsets normally operate at 440 volts 3 phase power supply and at an RPM of about 1500. These guidelines are meant for guidance of technical staff in the banks and other extension workers for selecting a proper pumping system for a farmer. Selection of Centrifugal Pump The following are the main guidelines for selection of Centrifugal Pumps. The Brake Horse Power (BHP) required for a pump can be calculated from the following formula : BHP = ( Q x H ) / ( 75 x e ) Where Q = Discharge in liters per second H = Total Head in meters (including friction losses) e = Efficiency of the pump, as percentage For belt drive pumps the BHP may be increased by about 10 percent. 2.      The pump should be selected so as to have a maximum efficiency at the operating head likely to be obtained during peak demand period. For example, if the duty condition of the system is for a discharge of about 8 litres/sec at a total head of approximately 11.4 m then the centrifugal pump for which the characteristic curves have been given in Fig. 2 will be ideally suited as the same will have efficiency nearly at optimum level at the operating conditions. If, however, the duty condition of the system demands a discharge of about 12 litres/sec at a total head of about 11 m, this particular pump will not be suitable for the purpose as the pump will not give the requisite discharge at that head and also its efficiency will be much lower than optimum. In that case another suitable pump will have to be selected which will operate at optimum or near optimum efficiency at the required duty condition of total head and discharge. 3.      For the site conditions of head and discharge the centrifugal pump should have the minimum efficiency of 43 percent as per the efficiency curves provided by Bureau of Indian Standards (BIS) under IS-10804 (1994). 4.      On practical considerations the vertical distance between the deepest water level at which the pump would be required to operate and centre line of the pump should not be more than 5 metres. 5.      The pump should have BIS certification conforming to IS - 6595 or IS - 9079 or IS-11501. 6.      The pump which has a maximum efficiency for the head and discharge required at site should be selected from a range of BIS marked pumps available in market. This criteria should over-ride cost considerations. 7.      Only those pumps for which genuine spare parts are readily available should be preferred. 8.      Only those pumps for which after sales service is easily and effectively available should be preferred. 9.      The pumps which have reputation of giving efficient and trouble free service should be preferred. Selection of Electric Motor 1.      Monobloc pumpset should be preferred over coupled pumpsets. 2.      The BHP of the pump should match power output of the prime mover. However, for practical considerations the BHP of the prime mover is always kept about 10 percent more than what is theoretically required for the pump. 3.      The efficiency of the motor as declared by the manufacturer should be considered. IS-10804 (1994) has provided the range of the following minimum efficiency ratings (Table V).

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