Horse Power (H.P.) Selection: Calculation of Discharge Rate of Bore well, Water Level, Friction Loss in Pipes, Valves & Fittings, H.P. Selection for Submersible Pump Sets, Unit Conversion

UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPALCalculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets The discharge during drilling or after completion of drilling is required, which is necessary for choosing appropriate pump. Taking the values of discharge and total head, the HP of pump set will be selected. The pump set should be selected which is efficient and consumes less power. Moreover the drawdown is another factor for correctly choosing the pump. Obviously deeper you install a pump, less water it pumps. Please note that higher the HP you use does not mean that more water you get. Ideally, a pump should extract only that much water as much as the yield rate of the aquifer permits so as to maintain a steady state in the pumping water level. Also a pump lifts water depending on the speed, diameter and stages of the impellers which again the pump manufacturers decide. For a given discharge capacity, one needs more stages (counted by the number of rings in the pump body) as one goes deeper. Ideally a bore well should be tested for its optimal yield before selecting a pump. Such test is known as “Step Drawdown Test”. In this test a submersible pump is lowered at a suitable depth and the pump is run for a fixed time (say 1 hr.) in steps. In each step the pump is made to lift water at very low, low, medium and high discharge rates using a Glove Valve in the delivery pipe to maintain a constant discharge for the particular step. The drawdown (fall in the pumping water level) is measured during and at the end of each step (1 hr.). The discharge drawdown curve gives the optimum discharges of the well. Lowering the pump at a suitable depth with sufficient submergence is important as the pumping water level usually falls depending upon the discharge rate of the pump and aquifer yielding capacity (permeability). Ideally a pump should extract water at such a rate so that the water level in the well stabilizes after some times and do not fall further. A pump running dry with lowering water level can burn out easily. To prevent this, you are advised to install a 1.0”-1.25” flexible PVC pipe in the bore well till the pump depth so that you can monitor the pumping water level using an electrical water level recorder at any time. The PVC guide pipe needs to the clamped at the top securely to prevent it from falling in to the bore hole. To decide about the correct size of submersible pump set, the details regarding Discharge (LPS) Total Head i.e. pumped water level (Static water head + Drawdown) in metres to discharge point on ground level required. Discharge data of winter season and pumped water level date of summer season is necessary as these are the maximum values based on which we can calculate H.P of pump set. Other option is, take the data of discharge and total head of your bore well to pump dealer. By using pump curves, the dealer can suggest you the correct size of pump set. You have to select the pump set which consumes less power. As per V-Notch method (at 90 degrees) at 2" the discharge is about 1LPS and 45 degrees the yield is still less. As per Drillers assumption 2" means about 2 LPS. As no pump set is installed in bore well, I suggest you collect the discharge and total head (winter and summer respectively) data of your neighbouring bore wells having same depth and approach the pump dealer for correct size of submersible pump set. However, correct details regarding discharge and pumped water level data can obtain by carrying out step-draw-down test by trained professionals. In addition, the existing voltage conditions, variable discharge and Totaleasons causes under loading and overloading of motor which leads to more 1 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets consumption of power and low power factor. In such conditions installation of L.T. Capacitor is necessary to safe guard your pump set. Capacity of the pump to be chosen depends on the depth at which the pump/foot valve is to be installed and the desired discharge. Based on the total depth of the bore well, the depth at which the pump is to be installed (usually 10-25 feet above total depth of pumps) is decided. The total head is determined using the depth of pump, overhead tank level and friction loss expected in the suction and delivery pipes. In the absence of above, the discharge and total head data of neighbouring wells having same depth and rock formations may be utilized for the selection of pump set. We should insist the pump dealer to suggest the pump set based on discharge and total head and pump should have BIS standard. Well reputed brands may be purchased having BIS standard. If the capacity of the pump set is more and pump setting is in low depth, after few minutes of pumping the water level may go below the pump setting. If the pump setting is quite deep the discharge may be very low. Hence correct details regarding discharge and total head are necessary to select the correct size (HP) of pump set and pump setting in the bore well. Then how to get the details of discharge and total head before actually installing pump set in a bore well. To conduct the yield test or step draw-down test to arrive at correct discharge, total head and specific capacity etc. How to determine yield of a bore well while drilling? Usually V-Notches (a metal plate/wooden board with V shaped slot on top) are used by bore well drillers for determining yield of a bore well during the bore well drilling process. To measure the flow, water coming out of the bore well during drilling process is allowed to flow through an earthen barrier created around the site is fixed with a V-notch temporarily. Drillers won’t be inclined to do so as this is an additional task they have to do. Based on their experience, they tell the rough yield which may not www.indiawaterportal.org be always correct. Yield of a bore well is usually referred in inches (i.e. depth of water flowing over the notch). How yield of an existing bore well can be determined? Yield of a bore well can be determined by conducting a step drawdown test, in which water is pumped at different rates (that is, so many litres per hour) by keeping the submersible pump at different depths to know the actual quantum of water that could be safely pumped and the resulting lowering of water level or drawdown. The test helps to know whether the bore well can meet the water requirements. Usually, reputed pump dealers can conduct such tests at a fee before deciding to purchase a pump. Such tests are necessary for large settlements like apartments to arrive at very suitable pumps which can provide huge quantities of water needed. Checking water resource capability of unused bore well In a pumping test or step drawdown test, water is pumped at different rates (that is, so many litres per hour) by keeping the submersible pump at different depths to know the actual quantum of water that could be safely pumped and the resulting lowering of water level or drawdown. The test helps to know whether the bore well can meet the water requirements of the land to be irrigated and the types of crops that could be grown with the available water. 2 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets Calculating Discharge Rate by Using the Horizontal Open Discharge Method The most reliable method of measuring flow is to use a flow meter. When a flow meter is not available, however, it is possible to estimate the discharge capacity by constructing an “L” shaped measuring stick similar to that shown in Figure 8-V. With the water flowing from the pipe, place the long end of the “L” on top of the pipe. Position the “L” so that the end of the short 4-inch side just touches the stream of water as the stream slants downward. Note the horizontal distance “X” from this point to the open end of the discharge pipe. With the value “X” and the nominal inside diameter of the pipe, use Table 8-X to find the discharge rate in gallons per minute. EXAMPLE: Horizontal distance”X” is measured to be 12 inches. The size of the pipe is known to be 11⁄2" (nominal diameter). Find 12 inches in the left hand column of the chart and move across to the 11⁄2" pipe size column. Table 8-X indicates that the discharge rate is 40.0 gallons per minute. FIGURE 8-V TABLE 8-X: Discharge Rate in Gallons per Minute (GPM) for Large Capacity Systems Horiz. Nominal Pipe Size (in Inches) Dist.(X) 1” 1.25” 1.5” 2” 2.5” 3” 4” 5” 6” 8” Inches Discharge Rate in Gallons Per Minute (GPM) 4 5.7 9.8 13.3 22 31 48 83 5 7.1 12.2 16.6 27.5 39 61 104 163 6 8.5 14.7 20 33 47 73 125 195 285 7 10 17.1 23.2 38.5 55 85 146 228 334 380 8 11.3 19.6 26.5 44 62 97 166 260 380 665 9 12.8 22 29.8 49.5 70 110 187 293 430 750 10 14.2 24.5 33.2 55.5 78 122 208 326 476 830 11 15.6 27 36.5 60.5 86 134 229 360 525 915 12 17 29 40 66 94 146 250 390 570 1000 13 18.5 31.5 43 71.5 102 168 270 425 620 1080 14 20 34 46.5 77 100 170 292 456 670 1160 15 21.3 36.3 50 82.5 117 183 312 490 710 1250 16 22.7 39 63 88 125 196 334 520 760 1330 17 41.5 56.5 93 133 207 355 550 810 1410 18 60 99 144 220 375 590 860 1500 19 100 148 232 395 620 910 1580 20 156 244 415 650 950 1660 21 256 435 685 1000 1750 3 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets Calculating Low Capacity Outlets: A simple procedure for measuring low capacity outlets such as small pump outlets, hose spigots, and faucets is to record the amount of time it takes to fill a container of known size. EXAMPLE: Select a container of known size such as a 5-gallon paint bucket. With a watch, measure, in seconds, the amount of time it takes to fill the bucket. If it takes 30 seconds to fill a 5-gallon bucket, Table 8-W indicates that the flow is 10.0 gallons per minute. To obtain gallons per hour (gph) multiply 10.0 x 60 to obtain 600 GPH. NOTE: Multiply gallons per minute (GPM) by 60 to obtain gallons per hour (GPH). TABLE 8-W: Discharge Rate in Gallons Per Minute (GPM) for Low Capacity Systems Capacity of Time (in seconds) to Fill Container Container 10 15 20 30 45 60 90 120 (Gallons) Discharge Rate in Gallons Per Minute (GPM) 1 6 4 3 2 1.3 1 0.7 0.5 3 18 12 9 6 4 3 2 1.5 5 30 20 15 10 6.7 5 3.3 2.5 10 60 40 30 20 13.3 10 6.7 5 How to measure depth of water and total depth of existing bore well? We can find the water level in a bore well from the ground by time calculating the time taken for a very small stone (0.5 inch) to strike the water surface. All you need is a watch and a very small stone. Drop the stone and note the time taken for it to strike the water surface. Multiplying with 9.8 (i.e. an object free falling near the earth surface would travel 9m/sec due to gravity) to the time taken for the stone to strike the water surface measured in seconds, we can get the water level depth in meters (Ex: for a 10 seconds time, depth to water is – 9.8 x 10 = 98 meters) . Repeat the exercise few times to get the correct depth. A thin nylon rope longer than the depth of bore well firmly attached to a small sized stone (2 inches) or metal ring (a small automobile bearing is ideal for this purpose) in one end is used for finding both the water level and total depth of the bore well. While leaving the stone/metal block attached to the rope into the bore well, when reduction in the weight of the stone is felt due to buoyancy of water after it strikes water surface, mark the point on the rope and remove the entire portion of rope let inside the bore well to measure for the water level from the ground. Similarly, when you feel that the rope is not freely moving downwards from your hand once the stone strikes bottom of the bore well, mark the point and measure for the total depth of the bore well after removing the rope. Calculating Distance to Water Level Install 1⁄8" or 1⁄4" pipe or tubing into the well so that the end of the tubing extends 10 to 20 feet below the lowest possible pumping water level. Be sure that all joints in the tubing are airtight. As the tubing is lowered into the well measure its length. Record the measurement. Once the tubing is fixed in a stationary position at the top of the well, connect an air-line and pressure gauge. With a tire pump or other air supply, pump air into the line until the pressure gauge reaches a point where it doesn't read any higher. Record the pressure gauge reading at this point. 4 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets Figure 8-Y illustrates a typical method for measuring distance to water level: X = Distance to water level (in feet). This figure to be determined. Y = Total length of air line (in feet). Z = Length of submerged air-line. This value is obtained from the pressure gauge reading which reads in pounds per square inch (psi). Multiply the pressure gauge reading by 2.31 to obtain the length of the submerged air-line in feet. Distance to water level (X) = (Y) - (Z) = The total length of the air line (Y) minus the length of the submerged portion of the air line (Z). Example: Assume that the air line is 100 feet long and the pressure gauge reads 8 psi. Calculate the distance to water level (X). 8 psi x 2.31 = 18.5 feet (X) = 100 feet (Y) - 18.5 feet (Z) = 81.5 feet = distance to water level Figure 8-Y: Calculating the distance to water level. FRICTION LOSS TABLES: Friction Loss Table – SCH 40 STEEL PIPE (Friction Loss in Feet of Head Per 100 Feet of Pipe) GPM ½” ¾” 1” 1 ¼” 1 ½” 2” 2 ½” 2 3 4 5 6 7 8 9 10 12 14 16 20 25 30 35 40 ID 0.622" 4.8 10 17.1 25.8 36.5 48.7 62.7 78.3 95.9 5 |12 P a g e ID 0.824" 2.5 4.2 6.3 8.9 11.8 15 18.8 23 32.6 43.5 56.3 86.1 ID 1.049" ID 1.380" ID 1.610" ID 2.067" ID 2.469" 1.9 2.7 3.6 4.5 5.7 6.9 9.6 12.8 16.5 25.1 38.7 54.6 73.3 95 1.8 2.5 3.3 4.2 6.3 9.6 13.6 18.2 23.5 1.2 1.5 2 2.9 4.5 6.3 8.4 10.8 1.3 1.8 2.4 3.1 1.3 3” 4” ID 3.068" ID 4.026" Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets 45 50 60 70 80 90 100 120 140 160 200 260 300 29.4 36 51 68.8 89.2 13.5 16.4 23.2 31.3 40.5 51 62.5 3.9 4.7 6.6 8.9 11.4 14.2 17.4 24.7 33.2 43 66.3 1.6 1.9 2.7 3.6 4.6 5.8 7.1 10.1 13.5 17.5 27 45 59.6 1.2 1.6 2 2.4 3.4 4.5 5.8 8.9 14.8 19.5 1.2 1.5 2.3 3.7 4.9 Friction Loss Table – VALVES and FITTINGS (Friction Loss in Equivalent Number of Feet of Straight Pipe) Type of Fitting and Pipe and NOMINAL SIZE OF FITTING AND PIPE Application Fitting ½” ¾” 1” 1 ¼” 1 ½” 2” 2 ½” EQUIVALENT LENGTH OF PIPE (IN FEET) Insert Coupling Plastic 3 3 3 3 3 3 3 Threaded Adapter Plastic 3 3 3 3 3 3 3 (Plastic to Thread) 900 Standard Elbow Steel 2 2 3 4 4 5 6 Plastic 2 2 3 4 4 5 6 Standard Tee Steel 1 2 2 3 3 4 4 (Flow Through Run) Plastic 1 2 2 3 3 4 4 Standard Tee Steel 4 5 6 7 8 11 13 (Flow Through Side) Plastic 4 5 6 7 8 11 13 Gate Valve1 Steel 1 1 1 1 2 2 2 Swing Check Valve1 Steel 5 7 9 12 13 17 21 NOTES: Based on schedule 40 steel and plastic fittings. Figures given are friction losses in terms of Equivalent Lengths of straight pipe. (1) Friction loss figures are for screwed valves and are based on equivalent lengths of steel pipe. Head and Pressure Head and pressure are related in a very simple and direct manner. Since water has known weight, we know that a 231 foot long, one inch square pipe holds 100 pounds of water. At the bottom of the oneinch square pipe we refer to the pressure as 100 pounds per square inch (psi). For any diameter pipe 231 feet high, the pressure will always be 100 psi at the bottom. Head is usually expressed in feet and refers to the height, or elevation, of the column of water. In a column of water 231 feet high creates a pressure reading of 100 psi. That same column of water is referred to as having 231 feet of head. Thus, for water, 231 feet of head is equivalent to 100 psi. Or, 2.31 feet of head equals 1 psi. 6 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets It should be noted that head and pressure readings for non-flowing water depend on the elevation of the water and not on the volume of water nor the size or length of piping. 7 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets Horse Power (HP) of Submersible Pump-Set Selection procedure Requirements: General Information Number of Submersible Pump-Sets: 02 Bore Well No.: 04 & 07 Location: West Side of New Guest House (Near Boundary Wall) & West Side of Administrative Block, RGPV Campus Bhopal. Bore Well Diameter: 7.5” (Inside dia.) Total Depth of Bore Well: 400 Feet Static Water Level in Bore Well: 150 Feet Drawdown: 50 Feet Total Pumping Head (H): 311 Feet (94.83 Feet) Pumping Liquid: Fresh Water Power Supply: 3 Phase / 50 Hertz / 380 Volts 1. [A] Capacity/Discharge Rate (Q) of Bore-well: 10 LPS (36 m3/hr. = 158.5GPM) [The Yield of a bore well while drilling is measured by driller using by V-notch Method and the yield of an existing bore well is measured by using the Horizontal Open Discharge Method or Step Drawdown Test by well owner/professional). As per V-Notch method (at 90 degrees) at 2" the discharge is about 2 LPS and 45 degrees the yield is still less. As per Drillers assumption - 2" means about 2 LPS. [B] Total Dynamic Head: (TDH) = Pumping Level + Head required + Drop pipe (Rising Pipe) friction loss + Check Valve(s) Friction (i) Static Water Level in Bore Well…………………………………..= 150 Feet (ii) Drawdown…………………………………………………………..= 50 Feet (iii) Pumping Water Level or Lift……………………… = 150 + 50 = 200 Feet (iv) Friction Losses in the Bore Well: Friction losses caused by the drop pipe/rising pipe and fittings between the pump and the top of the bore well. Submersible pumps frequently require smaller drop pipe since the full area of the pipe is used to deliver water to the surface. Minimum velocity in drop pipe should not be less than 3.5Ft./Sec. We recommend drop pipe size be selected to limit the maximum friction loss to 5’ per 100’ of pipe. (a) 1/2” drop pipe (or rising pipe) friction head for 2 LPS is 2.2 feet per 100 feet. 200 feet of new 1 1/2” drop pipe has a total loss of…………. = 2.2 x 2.0 = 4.4 Feet (b) Friction head loss in one 1 1/2” check valve =.....................................= 2.2 Feet (Where total head exceeds 200’, the use of a drop pipe check valve is recommended. Check valve should be located approximately 20’ above the bowl assembly. For settings over 600’, the use of two check valves are recommended, with the first valve approximately 100’ above bowl unit and the second located approximately 60% of the distance between the first valve and the surface plate.) (v) Total Lift in the Well…………………………………. = 200+6.6=206.60 (vi) Static Discharge Head………………………………..= 100 Feet (It is the elevation of the highest water level above the top of the well) (vii) Friction Losses in the Discharge System…………. = 4.40 Feet (Friction losses caused by piping, valve and fittings between the top of the well and the point of discharge) (viii) Total Discharge Head……………………………..= 100+4.40= 104.40 Feet (ix) Total Pumping Head………………………………. = 206.60+104.40=311 Feet [C] Submersible Pump Level in the Well: 8 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets (i) Setting of Pump……………………………………. = (The vertical distance from the top of the bore well to the top of the pump.) (ii) Overall Length………………………………………. = 375 Feet (The vertical distance from the top of the bore well to the bottom of the pump. Based on the total depth of the bore well, the depth at which the pump is to be installed (usually 10-25 feet above total depth of bore-well from bottom of well) is decided. (iii) Submergence………………………………………. = (2) Impeller Selection: Since no speed was specified, use 3450 RPM. The S9XHC shows 76% efficiency, full diameter. (i) Number of stages required = TDH/ (Head/Stage) = 311/125 = 2.48, USE 3 stages, 75.5%. (ii) Total Pump Thrust = TDH x Impeller Thrust Factor x Specific Gravity + (Rotor Weight per Stage x Number of Stages) = (311 x 4.9 x 1) + (10.6 x 3) = 1554.80 (iii) Water Horse Power (WHP) = GPM x TDH x Sp. Gr. = 158.5 x 311 x 1 = 12.45 3960 3960 (iii) Bowl Horsepower (Break Horse Power) = GPM x TDH x Sp. Gr. = 158.5 x 311 x 1 = 16.48 BHP 3960x Bowl (Pump) Efficiency 3960 x 75.5% (iv) Pump Efficiency = GPM x TDH x Sp. Gr. = 158.5 x 311 x 1 = = 75.53% 3960 x Bowl H.P. 3960 x 16.48 (3) Motor Selection: (i) Bowl Horsepower = 16.48 (b) Pump Operating Speed = 3450 RPM (c) Total Pump Thrust = 1554.80 (d) 3-Phase, 50 Hertz, 380/415 Volts (nameplate) (e) Thrust Bearing Loss = 0.10 x Total Pump Thrust = 0.10 x 1554.80 = 0.155 H.P. 1000 (f) Horsepower Loss in Cable: Select cable length equal to length of setting plus an additional 10’ or more to connect to starter at the surface, plus 1 additional foot for each 50’ of length in the well to compensate for unavoidable slack in the installation. Total Cable Length = 200 feet + 10 + 4 = 214 feet Select #00 cable from Selection Chart 16.48 H.P. motor current = Horsepower loss in #00 cable = H.P. loss per 100’ x Total Cable Length 100 (g) Total Horsepower: = [Bowl horsepower + Thrust HP loss + Cable horsepower loss] = H.P. (H.P. motor OK to use.) (4) Cable Selection: (a) Determine total cable length. Total Cable Length = Pumping Level + Surface Length + Slack = 200 + 10 + 4 = 214 feet (b) Per Cable Selection Chart @ 415 volts horsepower, use #00 cable. 9 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets (5) Surface Plate: Use 8” surface plate. (6) Check Valve: One 8” check valve required. (7) Calculation of Field Performance: To determine field head and overall pump efficiency: (a) Field Head = laboratory head minus total friction loss. (1) Total friction loss = loss in drop pipe + check valve(s) (b) Overall Pump Efficiency = Water HP x (motor eff. % - cable loss %) Laboratory H.P. (c) Water Horsepower = GPM x Head 3960 (d) Laboratory Horsepower = GPM x Head x Sp. Gr. 3960 x Pump Eff. Calculations for other values of power consumption can be carried out per equations noted below: (e) Wire to Water Efficiency - same as Overall Efficiency. (f) Input Horsepower = Pump Brake Horsepower Motor Efficiency - Cable Loss (g) Wire to Water Horsepower = Same as Input Horsepower (h) Kilowatt Hours per 100 Gallons = Field head x .00314 Overall Efficiency (i) Kilowatts Input = Input Horsepower x 0.746 (j) Gallons per Kilowatt Hour = Overall Efficiency x 1000 Field Head x .00314 FORMULA/UNIT MEASUREMENT: WORK, POWER, AND EFFICIENCY: 1 HP = 33,000 ft.-lb./minute = 550 ft.-lb./second Electrical power is measured in watts (w) or kilowatts(kw), and: 1,000 w = 1 kw = 1.34 hp, or 1 HP = 745 w = 0.746 kw WATER HORSEPOWER (WHP): Water horsepower is the power required to raise water at a specified rate against a specified head, assuming 100% efficiency. WHP = GPM x Total Pumping Head/3,960 BRAKE HORSEPOWER (BHP): Brake horsepower is based on test data and can be either the horsepower developed at the motor shaft (motor output) or that absorbed at the pump shaft (pump input). Pump BHP = WHP x 100/Pump Efficiency (%) 10 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets = GPM x Total Pumping Head x 100/3,960 x Pump Efficiency (%) Motor BHP = Power input x Motor Efficiency (%)/100 = 1.34 x kw input x Motor Efficiency (%)/100 PUMP EFFICIENCY: Pumps and motors, like all machines, are not 100% efficient. Not all of the energy supplied to them is converted into useful work. Pump efficiency is the ratio of power output to power input, or: Efficiency (%) = Power Output x 100/Power Input Pump Eff. (%) = WHP x 100/ Pump BHP (Input) = GPM x Total Pumping Head x 100/ 3960 x Pump BHP (Input) Motor Eff. (%) = Motor BHP (Output) x 100/ 1.34 x kw input Plant Eff. (%) = GPM x Total Pumping Head x 100/ 5,300 x kw Input ELECTRIC POWER (AC): E = Electrical pressure (volts). Similar to hydraulic head. I = Electrical current (amps). Similar to rate of flow. W = Electrical power (watts) = E x I x PF kw = Kilowatt (1,000 watts) kw-hr. = Kilowatt-hour = 1,000 watts for one hour Apparent Power = E x I = volt-amperes PF = Power Factor = Useful Power ÷ Apparent Power Power Calculations for Single-Phase Power W (Watts) = E x I x PF NOTE: When measuring single-phase power use a single-phase wattmeter. Input HP to motor = W ÷ 746 = 1.34 x kw Power Calculations for Three-Phase Power W (Watts) = 1.73 x E x I x PF Where: E = effective (RMS) voltage between phases I = average current in each phase NOTE: When measuring three-phase power use either (1) three phase wattmeter, (2) single-phase watt meters, or the power company’s revolving disc wattmeter. When calculating power with a revolving disc wattmeter use the following formula: kw input = K x R x 3.60/ t Input HP (to motor) = K x R x 3,600/ 746 x t = K x R x 4.83/ t Motor BHP (output) = Input HP x Motor Eff. (%)/ 100 11 |12 P a g e Prepared by Santosh Kumar Kharole UNIVERSITY INSTITUTE OF TECHNOLOGY, RAJIVGANDHI PROUDYOGIKI VISHWAVIDYALAYA BHOPAL Calculation of Discharge (Yield) of Bore-well, Water Level, Friction Loss in Pipes, Valves & Fittings, Cable Selection for Submersible Pump Sets Where K = Meter constant = watts per revolution of revolving disc (value of K is marked on the meter nameplate or on the revolving disc). Where current transformers are used, multiply meter constant by current transformer ratio. R = Number of disc revolutions counted. t = Time in seconds for R revolutions. CALCULATING OPERATING COSTS OF PUMPS: Costs in Cents per 1,000 Gallons: Cost (¢) = kw Input x r x 1,000/ GPH Cost in Cents per Acre-Inch Cost (¢) = kw Input x r x 452.6/ GPM Where: r = cost of power in cents per kw-hr. UNITS OF VOLUME AND WEIGHT: Weight equivalent basis water at 60°F. 1 U.S. GALLON = 3.785 LITERS = 0.003785 m3 = 8.34 POUNDS = 0.833 IMPERIAL GALLON UNITS OF FLOW: Discharge Rate 1 U.S. GALLON PER MINUTE (GPM) = 0.2271 m3/hr. = 0.0631 LITERS/SECOND (LPS) UNITS OF PRESSURE AND HEAD: NOTES: (1) Equivalent units are based on density of fresh water at 68°F. (2) Equivalent units are based on density of mercury at 32°F. (3) Each 1,000 feet of ascent decreases pressure about 1⁄2 pound per square inch. 1 LBS. PER SQUARE INCH = 2.31 x FEET OF WATER 12 |12 P a g e Prepared by Santosh Kumar Kharole