What is a gas non-return valve?

Non-return valves are a means of preventing a reverse flow and must be fitted (Gas Act 1972) in the gas line where air at higher pressure is mixed with fuel gas prior to combustion and many types of industrial burners.

Where are non-return valves used?

Non-return valves are for example used with mixing loops in heating and cooling systems to ensure proper operation, and with domestic water systems to prevent backflow.

Which valve can be known as a non-return valve?

Check valves
Check valves, also known as non-return, reflux or one-way valves are automatic valve types that do not require any manual or electrical intervention to open and close. Check valves are used to allow flow in one direction only and prevent the reversal of flow.

How many types of NRV are there?

There are two types of wafer check valve designs available. Single plate wafer check valve. Dual plate wafer check valve.

Why NRV is used in pump?

Consequent upon power trip off to a pump-motor pump discharge decelerates and sets up a down surge in a pumping system. A non-return-valve (NRV) restricts flow reversal in the system and ultimately keeps water hammer at a lower magnitude. …

Do non-return valves restrict flow?

Do non-return valves restrict flow? Most non-return valves do restrict flow but the amount depends on the type of non-return valve. Swing type wafer non-return valves have a reduced bore, so these will restrict the flow somewhat.

How does a non-return valve work?

Non-return valves work by allowing media to flow through them in only one direction. These valves have two openings in the body, one for media to enter and the other for media to leave. The main seat of ball NRVs is conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow.

What is difference between check valve and NRV?

A check valve is the simplest type of directional control valve used in hydraulic systems. Check valves stop the flow of fluid in one direction and allow free flow in the opposite direction. They are also known as non-return valves. This is called a line rupture valve.

How do non return valves work?

Non-return valves work by allowing media to flow through them in only one direction. These valves have two openings in the body, one for media to enter and the other for media to leave. Non-return valves work automatically, which means that most are not controlled by a person or an external control.

Do non return valves restrict flow?