1. 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
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.
2. In which of these treatment systems diaphragm valves are preferred?
a) Moving Bed Bioreactor(MBBR)
b) Desalination
c) Ultrafiltration
d) Demineralisation systems
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.
3. 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
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.
4.Which of these are used as throttling valves?
a) Butterfly valve
b) Check valve
c) Gate valve
d) Sluice valve
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.
5. 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
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.
6. Which valve is most commonly used in house hold applications?
a) Globe valve
b) Gate valve
c) Butterfly valve
d) Check valve
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.
7. 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
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
8. Which of these are usually not preferred for frequent operation?
a) Ball valve
b) Plug valve
c) Gate valve
d) Butterfly valve
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.
9. Which type of valve is preferred for vacuum applications?
a) Diaphragm valve
b) Butterfly valve
c) Globe valve
d) Sluice valve
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.
10. 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
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.