Pump Theory II

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Question 1:
Calculate the volumetric efficiency, expressed as a percentage, for a reciprocating pump where the pump piston displaces 3.50 litres but only 3.36 litres are forced into the discharge.

C - 96%
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Question 2:

Water hammer is the result of a pressure wave that is created in a liquid by a sudden change in flow rate. The maximum intensity of the wave can be calculated by Joukowsky's Law. Of the values represented in the formula: Hwh = , all of the following are correct except:

A - c = velocity of sound in the liquid, m/s
B - g = acceleration due to gravity, 9.81 m/s2
C - v = instantaneous velocity change in liquid (m/s)
D - All of the above

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Question 3:

Calculate the slip, in litres/stroke, for a reciprocating pump where the pump piston displaces 1.75 litres but only 1.49 litres are forced into the discharge. D - 0.26

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Question 4:

To lessen the effects of water hammer, long pipelines are usually equipped with:

A - Surge dampening valves
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Question 5:

In a system where two pumps are used to draw water from a stream and pump it 8 km to a holding pond, the best way to avoid damage from water hammer would be to stage the pump start-ups so that water hammer from the first pump has subsided before the next pump is added.

A - True
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Question 6:
In a reciprocating pump, the volumetric efficiency is the ratio of the volume of liquid delivered to the:

A - Piston displacement

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Question 7:
A pump delivers water to a tank 50 metres above the pump. Assume that the water is at 15.6°C. Assume the speed of sound in water is 1469 m/s at 15.6 ºC.The power fails and the pump discharge check valve is jammed open for a few seconds and then finally slams shut. Before the check valve can close, water begins to flow backwards through the pump at a velocity of 20 metres per second, causing water hammer. Calculate the total head produced when the water hammer occurred.

D - 3045 m

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Question 8:

To calculate the work done upon the water being pumped, the correct formula is:

C - Pump power = m³/s x kg/m³ x total head (m) x 9.81 m/s²
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Question 9:

At 15.6 °C, the speed of sound through water is:

D - 1469 m/s
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Question 10:
With rotary pumps, the pump power varies:

A - Directly with the discharge pressure
B - With the pump speed

D - Both a and b