Correct Answer - Option 4 : Reflux valves
Explanation:
Gate valve or Sluice valve:
(i) These valves are used to regulate the flow of water through the pies.
(ii) They are generally located along the large pipe line at intervals of about 3 to 5 km to divide the pipe into different sections.
(iii) These valves are placed at the summits of the pressure conduits.
Scour valve or Blow off valve or Drain valve:
(i) These valves are also known as wash-out valves.
(ii) To remove the entire water from pipe after closing the supply, small gate valves are provided at low point.
(iii) These valves, are necessary at low level points for completely emptying the pipe for inspection, repair etc.
Check valve or Reflux valve:
(i) These valves are also known as non-return valves or reflux valves.
(ii) They allow the water to flow in one direction only.
(iii) They may be installed on the delivery side of the pumping set so as to prevent the backflow of stored or pumped water when the pump is stopped.
(iv) When the pump is operated, the valve is opened, but when the pump is suddenly stopped the valve is automatically closed. This prevents the backward flow of water to the pump.
Air Relief Valve:
it is a type of safety valve used to control or limit the pressure in a system, pressure might otherwise build up and create a process upset, instrument or equipment failure, or fire. The pressure is relieved by allowing the pressurized fluid to flow from an auxiliary passage out of the system.
