What is a Non Return Valve?

What is a Non Return Valve?

Non return valves are an important component in air systems and can be found anywhere in a circuit. Their function is to open in order to allow air to flow in and to stop air further downstream leaking back. Small, and often simply designed, non return valves are lightweight components.


Also known as...

Non return valves are also referred to as NRVs, check valves or one-way valves.


How do non return valves work?

These types of valves are constructed with a ball or a diaphragm, and are sometimes spring assisted. The valve only opens when the inlet pressure exceeds the outlet pressure, otherwise known as the cracking pressure. The mechanism of the valve does not allow air to flow from outlet to inlet.


How do I select non return valves?

Depending on the application, there are a number of different non return valves available, which are broken down into heavy duty non return valves, and standard non return valves. More than one valve can be used in a system depending on what is required.

The sizes available range from 4mm o/d through to 12mm o/d with variable port sizing. Non return valves can be threaded or a push fit and are made from materials like brass, aluminium or composite.

When selecting non return valves, consider the following:

  • Pressure
  • Flow
  • Temperature
  • Cracking pressure
  • Connections


Types of non return valves

There are a number of different types of non return valves available depending on the size of the operation and the pressure required. In the IMI Norgren range, non return valves are broken down into heavy-duty and standard categories.

  • Heavy-duty non return valves: Made from brass, this type of non return valve is available in a range of sizes and can operate at high pressure, from 0,3 bar up to 16 bar (232 psi), with a cracking pressure of 0,1 bar (1 psi).
  • Non return valves: Generally made from aluminium, non return valves are available in a range of sizes, with operating pressure ranging from 0,1 up to 10 bar (1.4 through to 145 psi) and a cracking pressure of 0,05 bar (0,7 psi).
  • Pneufit C series: Non return valves with push in fittings have an outside diameter of 4mm-16mm and a maximum operating pressure of 10 bar (145 psi). They're also made from nickel-plated brass for corrosion resistance.


Typical applications of non return valves

Non return valves are used in any machine or process where back-flow could be a problem and needs to be avoided. They are found in many industrial automation and process applications.


Do I need anything else to make non return valves work?

Accessories used in conjunction with non return valves include fittings and tubing.

More information

Browse our range of non-return valves to find out more