Question

Consider the following statements regarding valves in a pipe line:

1. In long pipe lines, air will accumulate in the low point of the line and will interfere with the flow.

2. Pressure relief valves are used in pipe lines where pressure may increase beyond the maximum permissible pressure.

3. Non-return valves prevent water flowing back i.e in the opposite direction.

Which of the above statements are correct?
1. 1 and 2 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3

Answer 1

Correct Answer - Option 2 : 2 and 3 only

Concept-

S. No	Types of valves	Significance
1.	Check Valve/Reflux valve/Non- returning valve	It allows the water to flow in one direction only.
2.	Sluice valve/Gate valve/Shut off valve	These valves are provided to regulate the flow of water through the pipe and are essential to divine the main line into several sections. These valves are usually placed at the summits of the pressure conduits where the pressure is low.
3.	Air valves/Air relief valves	It is provided at the summits to release the air pressure. At every summit of a pipeline and U/S of sluice vale, an air valve should be provided. They ensure gravity flow under atmospheric pressure.
4.	Scour valve/Blow off and Value/Drain	Similar to sluice valves, but their function is different. It is provided at the dead end of the pipeline. It’s function is to remove the sand, silt etc. from the pipeline.
5.	Butterfly valve	Butterfly valve are used to regulate and stop the flow especially in large sized conduits. Butterfly valves involve slightly higher head loss than sluice valves and valves and also are not suitable for continuous throttling.
6.	Relief valve/Safety valve/Pressure relief valves/Cut off valves	These valves protect the pipeline from bursting. When the pressure of the water suddenly exceeds the permissible pressure to water hammer phenomenon, then the valve is opened automatically and the excess pressure is released instantaneously.
7.	Ball valves/Bell float valves	It is used to maintain a constant level in a service reservoir or elevated tank.
8.	Needle & Cone valve	It is similar to sluice valve but are more expensive then sluice and butterfly valves. It is suitable for throttling flow.

 

In long pipe lines, air will accumulate in the highest point of the line and will interfere with the flow.so statement 1 is wrong.

Statement 2 & 3 are correct.