Pumps 1. A double suction centrifugal pump delivers 70 ft 3/sec of water at a head of 12 m and running at 1250 rpm. What is the specific speed of the pump? Solution: √
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2. The pump centerline of a centrifugal pump is located 2.5 m above from the high tide level. The sea water varies two meters from high tide to low tide level. If friction loss at the suction is 0.8 m, determine the total suction head. Solution:
3. A centrifugal pump requires 40 ft head to deliver water from low level to higher level. If pump speed is 1600 rpm, determine the impeller diameter of the centrifugal pump. Solution: Solve for velocity, v: √
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Solve for diameter of the impeller, D:
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4. The suction pressure of a pump reads 2 in of mercury vacuum and discharge pressure reads 130psi is use to deliver 100 gpm of water with specific volume of 0.0163 ft3/lb. Determine the pump work. Solution:
Solve for density of fluid, w:
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Solve for pressure head, h:
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Solve for pump work, P:
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5. A pump is to deliver 150gpm of water at a head of 120 m. If pump efficiency is 70%, what is the horsepower rating of motor required to drive the pump? Solution: Solve for water power, Pw:
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Solve for Brake Power, BP:
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6. A motor is used to drive a pump having an efficiency of 85% and 70% respectively. What is the combined efficiency of pump and motor? Solution:
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7. In a boiler feed pump, the enthalpy at the entrance is 765 kJ/kg. If pump has a head of 900 m, what is the exit enthalpy of the pump? Solution: (
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8. A submersible pump delivers 350 gpm of water to a height of 50 ft from the ground. The pump were installed 120 ft below the ground level and a draw down of 8 ft during the operation. If water level is 25 ft above the pump, determine the pump power. Solution: Solve for head, h: (
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Solve for water power, Pw:
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9. Determine the number of stages needed for a centrifugal pump if it is used to deliver 400 gpm of water and pump power of 15 Hp. Each impeller develops a head of 38 ft. Solution:
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Solve for number of stages:
10. A boiler feed pump receives 50 li/sec of water with specific volume of 0.00112 m 3/kg at a head of 750 m. What is the power output of driving motor if pump efficiency is 65%?
Solution: Solve for water power, Pw:
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Solve for Brake Power, BP:
11. What power can a boiler feed pump can deliver a mass of 35 kg/s water at a head of 500 m? Solution:
12. A pump running at 100 rpm delivers water against a head at 30 m. If pump speed will increased to 120 rpm, what is the increase in head? Solution: (
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13. A pump is used to deliver 50 li/sec of sea water at a speed of 120 rpm. If speed will increased to 135 rpm, determine the increased in pump capacity. Solution:
14. A 15 kW motor running at 350 rpm is used to drive a pump. If speed will changed to 370 rpm, what is the increased in power? Solution: (
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15. A pump delivers 500 gpm of water against a total head of 200 ft and operating at 1770 rpm. Changes have increased the total head to 375 ft. at what rpm should the pump be operated to achieve the new head at the same efficiency? Solution: (
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16. A centrifugal pump delivers 80 liters per second of water on test. Suction gage reads 10 mm Hg vacuum and 1.2 meters below pump centerline. Power input is 70 kW. Find the total dynamic head in meters. Solution:
Using the typical pump efficiency of 74%
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17. A vacuum pump is used to drain a flooded mine shaft of 20°C water. The pump pressure of water at this temperature is 2.34 kPa. The pump is incapable of lifting the water higher than 10.16 m. What is the atmospheric pressure? Solution: Using Bernoulli’s Theorem
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18. It is desired to deliver 5 gpm at a head of 640 m in a single pump having specific speed not to exceed 40. If the speed is not to exceed 1352 rpm, how many stages are required? Solution: √
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19. A pump driven by an electric motor moves 25 gpm of water from reservoir A to reservoir B, lifting the water to a total of 245 feet. The efficiency of the pump and motor are 64% and 84% respectively. What size of motor (HP) is required? Solution: Solve for water power, Pw:
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Solve for size of motor:
Therefore, use 3 Hp motor 20. A fuel pump is delivering 10 gpm of oil with a specific gravity of 0.83. The total head is 9.14 m, find how much energy does the pump consumes in kJ per hour. Solution:
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