Pumps
Lesson 9 Pumps
Key Concepts
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Pressure – 1 foot of water height = 0.43 psi gage pressure
•
Head – The vertical distance between start and finish water level in feet
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Work – Work can be expressed as lifting a weight a certain vertical distance
(Units are usually ft-lbs)
Work = Weight, lb x Height, ft
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Power – Power is the rate of doing work (Units are usually ft-lb/min)
Power = Work, ft-lb
Time, min.
•
Horse Power – A unit of power defined as 33,000 ft-lb/min.
HP =
Power, ft-lb/min
33,0000 ft-lb/min/HP
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Water Horse Power – The amount of power required to lift water
•
Water HP = (Flow, gpm) x (Head, ft)
3960 gpm-ft/HP
Break Horse Power – Takes into account that pumps are not 100% efficient
Break HP = (Flow, gpm) x (Head, ft)
3960 gpm –ft/HP x Ep
•
Motor Horse Power – Takes both pump and motor efficiency into account
Motor HP = (Flow, gpm) x (Head, ft)
3960 gpm-ft/HP x Ep x Em
•
1 Horse Power is equal to 0.746 Kw
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Example 1:
Calculate the Motor horse power required to pump water at a flow rate of 300 gpm
against 25 ft of head. Pump efficiency is 65% and motor efficiency is 90%.
Example 2:
Calculate the daily electrical cost to operate the pump in example 1 if the cost of
electricity is $0.12 per Kw-hr.
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Pumps
Solve the following for Water Horse Power
Water HP = (Flow, gpm) x (Head, ft.)
3,960 gpm-ft/HP
1. A flow of 300 gpm is pumped against a head of 70 feet. What is the Water HP?
2. A flow of 450 gpm is pumped against a head of 120 feet. What is the Water HP?
3. A flow of 150 gpm is pumped against a head of 60 feet. What is the Water HP?
4. A flow of 250 gpm is pumped against a head of 75 feet. What is the Water HP?
5. A flow of 600 gpm is pumped against a head of 85 feet. What is the Water HP?
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Solve for Brake Horsepower:
Break HP = (Flow, gpm) x (Head, ft.)
(3,960 gpm-ft/HP) x (Ep)
6. A flow of 200 gpm is pumped against a head of 25 feet by a pump that is 75% efficient.
What is the Break HP?
7. A flow of 300 gpm is pumped against a head of 75 feet by a pump that is 70% efficient.
What is the Break HP?
8. A flow of 500 gpm is pumped against a head of 50 feet by a pump that is 77% efficient.
What is the Break HP?
9. A flow of 450 gpm is pumped against a head of 65 feet by a pump that is 80% efficient.
What is the Break HP?
10. A flow of 125 gpm is pumped against a head of 85 feet by a pump that is 65%
efficient. What is the Break HP?
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Pumps
Solve for Motor Horsepower:
Motor HP = (Flow, gpm) x (Head, ft)
(3,960 gpm-ft/HP) x (Ep) x (Em)
11. A flow of 225 gpm is pumped against a head of 75 feet. The pump is 70% efficient and
the motor is 80% efficient. What is the Motor HP?
12. A flow of 125 gpm is pumped against a head of 100 feet. The pump is 65% efficient
and the motor is 89% efficient. What is the Motor HP?
13. A flow of 75 gpm is pumped against a head of 125 feet. The pump is 72% efficient and
the motor is 95% efficient. What is the Motor HP?
14. A flow of 300 gpm is pumped against a head of 75 feet. The pump is 80% efficient and
the motor is 85% efficient. What is the Motor HP?
15. A flow of 475 gpm is pumped against a head of 85 feet. The pump is 75% efficient and
the motor is 87% efficient. What is the Motor HP?
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Calculate the electrical cost for the following:
1 HP = .746 Kw
16. Energy cost is $0.11 per Kw-hr. Pump HP is 17. What is the daily cost to operate this
pump?
17. A pump is to pump 300 gpm against a head of 30 feet. Electricity cost $0.10 per Kw-hr.
What will be the daily cost to operate this pump?
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Pumps
18. A 65% efficient pump is pumping 200 gpm against a head of 100 ft. If electricity cost
$0.13 per Kw-hr, what will be the annual cost to operate this pump? Assume continuous
operation.
19. A pump that is 70% efficient is pumping 100 gpm against a head of 160 feet. If electricity
cost $0.12 per Kw-hr, what is the annual cost to operate this pump? Assume continuous
operation.
20. A 75% efficient pump is pumping 500 gpm against a head of 70 feet. If electricity cost
$0.14 per Kw-hr, what is the annual cost to operate this pump? Assume continuous
operation.
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