Тест по Pumps and Pumping Operations (CES v5.0)

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Правильні відповіді:
1

A pump is to be used to pump fresh water at a temperature, where the vapour pressure of the water is equivalent to the pressure caused by 0,2 m head of fresh water, and atmospheric pressure is equivalent to 10,6 m head of fresh water. The maximum suction lift is 6,0 m, and the pipeline losses on the suction side are equivalent to a head of 3,0 m. What will the pump NPSH available be?

Ваша відповідь правильна:

1,4 m.
2

Cavitation of the fluid in a centrifugal pump is caused by:

Ваша відповідь правильна:

The vapour pressure in the suction pipe falls below the vapour pressure of the liquid at a given temperature.
3

If NPSHA is too small, how can it be increased? Select the ONE correct answer:

Ваша відповідь правильна:

Reduce the length of the suction side pipe work.
4

If a pump had available NPSH of 0,5 m would a NPSH requirement of 0,48 be suitable for this purpose?

Ваша відповідь правильна:

No.
5

If a pump has a NPSH requirement of 0,5 m, would an available NPSH of 0,45 m be suitable?

Ваша відповідь правильна:

No.
6

Is the following statement True or False? No types of positive displacement pump can change their delivery rate, unless the speed of the drive motor is changed.

Ваша відповідь правильна:

False.
7

Is the following statement True or False? When operating pumps in parallel, if we use three pumps we will get three times the flow.

Ваша відповідь правильна:

False.
8

Is the following statement True or False? In centrifugal pump series operation, the flow through all of the pumps is equal.

Ваша відповідь правильна:

True.
9

Is the following statement True or False? When operating pumps in parallel, if we double the number pumps the flow is also doubled.

Ваша відповідь правильна:

False.
10

In this pump a single acting pump or a double acting pump?

Ваша відповідь правильна:

Double acting.
11

Is this statement True or False? Positive displacement pumps can only vary their delivery rate by changing the speed of the drive motor.

Ваша відповідь правильна:

False.
12

Under what system conditions would operating pumps in parallel achieve very little benefit? Select the ONE best answer:

Ваша відповідь правильна:

If the piping system is undersized or some component in the system acts as a bottleneck.
13

What is the advantage of starting a centrifugal pump with the delivery valve closed? Select the ONE correct answer:

Ваша відповідь правильна:

The starting load on the motor will be minimum.
14

What is the main advantage of a double entry centrifugal pump? Select the ONE best answer:

Ваша відповідь правильна:

It has a lower NPSH required characteristic, giving an advantage in poor suction conditions.
15

What is the main advantage of starting a centrifugal pump with the delivery valve closed? Select the ONE best answer:

Ваша відповідь правильна:

The starting load in the motor will be minimum.
16

What is the main cause of cavitation of the fluid in a centrifugal pump? Select the ONE best answer:

Ваша відповідь правильна:

The vapour pressure in the suction pipe falls below the vapour pressure of the liquid at a given temperature.
17

What is the main reason for operating pumps in parallel? Select the ONE best answer:

Ваша відповідь правильна:

It allows a larger range of flow than for a single arrangement.
18

What is the main reason for operating pumps in series? Select the ONE best answer:

Ваша відповідь правильна:

So that commercially available pumps (i. e. small) can be used and to avoid extremely high discharge pressures which would be necessary with only one pump.
19

What operating principle do positive displacement pumps rely on? Select the ONE best answer:

Ваша відповідь правильна:

Changes of volume of the pump chambers.
20

What will happen if the NPSHA is less than the NPSHR? Select the ONE best answer:

Ваша відповідь правильна:

The pump will suffer cavitation damage.
21

Which ONE of the following does NOT affect the efficiency of a pump?

Ваша відповідь правильна:

NPSHA.
22

Which ONE of the following statements is correct?

Правильну відповідь:

Positive displacement pumps can require priming.

Ваша відповідь:

Positive displacement pumps are always self-priming.
23

Which ONE of the following statements is correct?

Ваша відповідь правильна:

Centrifugal pumps cover the lower ranges of specific speeds, axial flow the higher, and mixed flow the intermediate values.
24

Which ONE of these statements best describes the energy transformation within a centrifugal pump?

Ваша відповідь правильна:

The impeller increases the liquid velocity, an increase in velocity means an increase in kinetic energy, the increased kinetic energy is converted into pressure by reducing the velocity in the volute casing.
25

Which one of the following does not directly affect the efficiency of a pump? Select the ONE best answer:

Ваша відповідь правильна:

NPSHA.
26

Which one of the following statements best describes the energy transformation within a centrifugal pump? Select the ONE best answer:

Ваша відповідь правильна:

The impeller increases the liquid velocity, increase the fluid’s kinetic energy. This kinetic energy is then converted into pressure by reducing the velocity in the volute casing.
27

Which one of these options is NOT a cause of excessive vibration in centrifugal pumps? Select the ONE correct answer:

Ваша відповідь правильна:

Discharge valve partly closed.
28

Why are positive displacement pumps ideal for fuel transfer duties? Select the ONE best answer:

Ваша відповідь правильна:

They are usually self-priming.
29

Why are positive displacement pumps well suited for fuel transfer duties? Select the ONE best answer:

Ваша відповідь правильна:

They are self-priming and can handle some amount of vapours and gases.
30

Why do centrifugal pumps need priming? Select the ONE correct answer:

Ваша відповідь правильна:

It is the movement of the liquid from the eye of the impeller to the discharge that causes a low-pressure region at the suction. If the pump is started full of air this movement of liquid does not occur therefore no suction pressure is created.
31

Why do positive displacement pumps require a relief valve? Select the ONE best answer:

Ваша відповідь правильна:

Because the pump will always try and displace a constant volume of fluid, it can generate dangerously high pressures against a closed discharge valve.
32

Why is the axial flow pump ideal for trimming and heeling duties? Select the ONE best answer:

Ваша відповідь правильна:

It is reversible and has a high capacity flow.
33

Why should positive displacement pumps not have their delivery restricted? Select the ONE best answer:

Ваша відповідь правильна:

Because a constant volume is displaced, very high pressures would be created.
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