Non-Return Valves

Pneumatic non-return valves are used where a normal non-return valve would be ineffective. This is for example where there is a risk of flood water entering a site but an equal risk of pollution or a chemical spills leaving a site and polluting the environment. Pneumatic non-return valves are installed below ground and can be used to pneumatically lock the non-return valve closed thus containing a site in the event of a spill. It is common practice to lock sites using pneumatic non-return valves during the loading or transferring of chemicals or hazardous waste. Pneumatic non-return valves have a longer service life when compared to pneumatic bladder systems.

non return valve can be stated as one way root.no return back to pump. In this case the fluid coming from delivery of pump press the plate inside the non return valve along with screw. When the fluid generates back pressure the screw comes down and the return way is blocked by the plate that is how "screw down non-return valve works.