# Environmental Engineering Questions and Answers – Selection of Pumping Units

This set of Environmental Engineering Questions and Answers for Aptitude test focuses on “Selection of Pumping Units”.

1. The plot of total dynamic head and discharge of a pump is called ____________
c) Pump curve
d) Discharge curve

Explanation: The plot of total dynamic head and discharge of a pump is called system head curve and each point on it denotes the head which consists of total static head, head loss in suction and delivery pipe.

2. _______ is the point of intersection of system head curve with the characteristic curve of the pump.
a) Discharge point
b) Operating point
d) Pumping point

Explanation: The operating point is the point of intersection of system head curve with the head – discharge characteristic curve of the pump. It is also called as operating range.

3. Which of the following is not included in the friction head?
a) Head Loss in entire length of piping
c) Head Loss in bend tees

Explanation: The friction head is the sum of head Loss in the entire length of piping, head Loss in bend tees and head Loss in valves.

4. When the pumps are in parallel operation?
a) H = H1 + H2
b) 1/H = 1/H1 +1/ H2
c) Q = Q1 + Q2
d) 1/Q = 1/Q1 + 1/Q2

Explanation: When the pumps are in parallel operation, then the total discharge is equal to the sum of the discharges by each pump i.e Q = Q1 + Q2.

5. When the pumps are in series operation?
a) H = H1 + H2
b) 1/H = 1/H1 +1/ H2
c) Q = Q1 + Q2
d) 1/Q = 1/Q1 + 1/Q2

Explanation: When the pumps are in series operation, then at a given discharge, total head is equal to the sum of heads added by each pump i.e H = H1 + H2.
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6. The efficiency of the pump at half load is ____________
a) 50%
b) 70%
c) 80%
d) 100%

Explanation: The efficiency of a pump depends on the amount of load. At half load, the efficiency of the pump is 70%.

7. The efficiency of the pump at quarter load is ____________
a) 50%
b) 70%
c) 80%
d) 100%

Explanation: The efficiency of the pump at quarter load is 50% and at full load, the efficiency of the pump is 80%.

8. The installed capacity of the pump does not depend on which of the following?
a) The maximum rate of hourly demand
b) Balancing storage
c) Power of pump
d) Operation schedule

Explanation: The installed capacity of the pump depends on three factors, namely- balancing storage, the maximum rate of hourly demand and the operation schedule. The installed capacity of the pump is kept larger than the maximum rate of demand.

9. If the diameter of pumping mains decreases, then the total dynamic head will increase.
a) True
b) False

Explanation: If the diameter of pumping mains decreases, then the velocity of flow will increase for a given fixed discharge resulting in the increase of friction head loss and velocity head and ultimately increases the total dynamic head.

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