This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Different Types of Valves”.
1. What is the function of a butterfly valve?
a) On/ off control
b) Flow regulation
c) Pressure control
d) Hydraulic control
View Answer
Explanation: Butterfly valve is used for flow regulation in large diameter pipes. Spool valve is used for hydraulic control. Ball valve is used for on/ off control of pipes without pressure drop.
2. Which of the following valves is better for on/ off control?
a) Ball valve
b) Butterfly valve
c) Plug valve
d) Knife valve
View Answer
Explanation: Butterfly valve is for flow regulation. Plug valve involves pressure drop during on/ off control. Ball valve involves on/ off control without pressure drop. It has an ideal quick shut-off since a 90˚ turn offers complete shut-off angle.
3. Which of the following valves are used in high duty cycle applications?
a) Check valve
b) Clapper valve
c) Ceramic disc valve
d) Choke valve
View Answer
Explanation: Check valves are used where one directional flow is required. In clapper valves, two hose are used instead of one. Ceramic disc valves are used in heavy duty cycle applications or on abrasive fluids.
4. Check valve is also called as _________
a) Non-return valve
b) Gate valve
c) Knife valve
d) Choke valve
View Answer
Explanation: Check valve is also called as non-return valve because it allows flow in just one direction. Gate valve is used for on/ off control with low pressure drop. Knife valve is similar to gate valve.
5. What is the purpose of piston valve?
a) Regulate fluids
b) Regulate fluids carrying suspended solids
c) Regulates flow
d) Regulates pressure
View Answer
Explanation: Piston valves are used to regulate fluids carrying solid particles in suspension. Spool valves are used for hydraulic control. Needle valves are used for accurate flow control.
6. Poppet valves are used in piston engines.
a) True
b) False
View Answer
Explanation: Poppet valves are a type oh valves that are used in piston engines. Poppet valves are used to regulate the fuel mixture intake and exhaust. Thermal expansion valves are used in refrigerator and air conditioning systems.
7. Diaphragm valves are used to control flow by a movement of a diaphragm.
a) True
b) False
View Answer
Explanation: Diaphragm valves are used to control flow by a movement a diaphragm. Upstream pressure, downstream pressure, or an external source can be used to change the position of the diaphragm.
8. What is the other name for the plug valve?
a) Needle valve
b) Slim valve
c) Poppet valve
d) Spool valve
View Answer
Explanation: Plug valve is also called as slim valve and is used for on/ off control but with little pressure drop. Needle valve is used for accurate flow. Poppet valve is commonly used in piston engines.
9. What is the purpose of pinch valve/
a) Hydraulic control
b) Slurry flow regulation
c) Flow control
d) Regulate fluids
View Answer
Explanation: Pinch valve is used for slurry flow regulation and control. The piston valve is used for regulating fluids that carry solids in suspension. Spool valves are used for hydraulic control.
10. In globe valves, the flow rate control is determined by _______
a) Size of the opening
b) Lift of the valve plug
c) Pressure difference
d) Gravity
View Answer
Explanation: Size of the opening plays a major role in controlling the flow rate but in the globe valves, the flow rate is controlled by the lift of the valve plug and not by the size of the opening in the valve seat.
11. Of the below mentioned valves which of these are used to control the flow of liquid in a single direction?
a) Butterfly valve
b) Ball valve
c) Check valve
d) Plug valve
View Answer
Explanation: Check valves are designed to allow the flow of fluid in a single direction only. When the power is turned off, in order to prevent the backflow of liquid, check valves are used as the discharge valve of a pump. Check valves are also called non-return valves or reflux valves.
12. In which of these treatment systems diaphragm valves are preferred?
a) Moving Bed Bioreactor(MBBR)
b) Desalination
c) Ultrafiltration
d) Demineralisation systems
View Answer
Explanation: In a demineralization plant diaphragm valves are preferred. This is because the diaphragm protects the inner parts of the valve from the corrosive ions present in the water which is to be treated by this system. If diaphragm valves are used it is not necessary to select SS body parts for a Demineralisation system as the diaphragm acts as a boundary between the water to be treated and the seat of the valve.
13. Which Material of construction is preferred when the valves are going to be fitted for a desalination plant?
a) SS316 L
b) SS304
c) Duplex
d) SS 316
View Answer
Explanation: Duplex is the preferred material. This is because desalination plants treat water with very high total dissolved solids. In order to prevent corrosion of the valve’s inner parts duplex should be used as the material of construction.
14. Which of these are used as throttling valves?
a) Butterfly valve
b) Check valve
c) Gate valve
d) Sluice valve
View Answer
Explanation: Butterfly valves are suitable for throttling. They can be used to control the flow of water. Butterfly valves are used to control the flowing water in either direction.
15. Which valve is used when a straight line of fluid and minimum restriction is required?
a) Gate valve
b) Lift check valve
c) Butterfly valve
d) Plug valve
View Answer
Explanation: Gate valves are used when a straight line of fluid and minimum restriction is required. Gate valves cannot be used for throttling. Due to their design, they can be either used for completely closing or for completely opening.
16. Which valve is most commonly used in house hold applications?
a) Globe valve
b) Gate valve
c) Butterfly valve
d) Check valve
View Answer
Explanation: Globe valves are commonly used in household applications. These are used for water faucets and for other house hold plumbing. These are preferred for applications that call for frequent opening and closing.
17. Though a needle valve is similar to a gate valve in design and operation it can be used as a throttling valve.
a) True
b) False
View Answer
Explanation: The needle valve is similar to a gate valve in construction and operation. The closing element is in the shape of a long tapering endpoint. The long tapering endpoint of the valve results in a smaller surface area of the seat when compared to that of a gate valve’s seat. This is more appropriate for throttling applications.
18. Which of these are usually not preferred for frequent operation?
a) Ball valve
b) Plug valve
c) Gate valve
d) Butterfly valve
View Answer
Explanation: Gate valves are not used in applications where-in frequent opening and closing is involved. This is because they require enormous time in opening and closing of the valves. They are appropriate for equipment which remain open or close for a long time.
19. Which type of valve is preferred for vacuum applications?
a) Diaphragm valve
b) Butterfly valve
c) Globe valve
d) Sluice valve
View Answer
Explanation: Diaphragm valves are used in vacuum applications. This is because these are well suited to service in application where tight closure is important. This tight closing feature makes them suitable for vacuum applications.
20. Which valve can be used in the service to handle fluids and gases and at the same time can be used for throttling as well?
a) Butterfly valve
b) Gate valve
c) Plug valve
d) Diaphragm valve
View Answer
Explanation: Plug valves can safely handle liquids and gases. These can be used in throttling applications also. These can be suited for moderate vacuum services as well.
Sanfoundry Global Education & Learning Series – Waste Water Engineering.
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