NON-RETURN/CHECK VALVES

 

 

Non-Return Valve (NRV) or Check Valve allows a medium to flow in only one direction. A NRV/Check Valve is fitted to ensure that a medium flows through a pipe in the right direction, where pressure conditions may otherwise cause reversed flow.

 

NRV’s/Check Valves can be fitted to ensure that a medium flows through a pipe in the right direction, where pressure conditions may otherwise cause reversed flow. A NRV/Check Valve allows a medium to flow in only one direction. The flow through the non-return valve causes a relatively large pressure drop, which has to be taken into account when designing the system.

 

There are different types of NRV/Check Valves, such as spring-loaded, swing type, and clapper type valves.

Popular Manufacturers:

Non Return Valves

  • Vitas
  • Heaton
  • Schroeder
  • Velan
  • Triangle
  • LVF
  • TT
  • Bonney Forge
  • Gestra
  • John Mills

  • Neway
  • Mokveld
  • Shaw
  • Trent
  • Kitz
  • Yarway
  • Glenfield
  • Langley
  • PV
  • Peter Smith

  • HNH
  • Orion
  • Firsa
  • Hopkinsons
  • Taylor
  • Shaw
  • Blakeborough
  • Crane
  • Vitas
  • Pacific

  • Mission
  • Alco
  • Tocina
  • Adams
  • Klinger
  • Valvo Sider
  • Chapman
  • Sella
  • Shipham
  • Raimondi

Leak Rates for Valves

 

All valves are designed to meet a designated internal permissible leak rate standard (FCI/ANSI).  There are six (6) permissible leak rates or Classes numbered 1 through VI. The higher the leak rate number, the lower permissible internal leak rate.

  • Class I valves will have the highest internal leak rate and usually the lowest cost.
  • Class VI valves will have the lowest permissible internal leak rate therefore cost will increase.

Identifying the permissible internal leak rate for a valve has to be one of the top priorities when choosing the correct valve.  A valve with a high leak rate, will cause excessive wear. The valves with a high leak rate will internally pass more medium and result in premature valve failure.

There are six different seat leakage classifications as defined by ANSI FCI 70-2.

  • Class I: is also known as dust tight and can refer to metal or resilient seated valves.
  • Class IV: is also known as metal to metal. It is the kind of leakage rate you can expect from a valve with a metal shut-off disc and metal seat.
  • Class Vl: is known as a soft seat classification. Soft Seat Valves are those where the seat or shut-off disc or both are made from some kind of resilient material such as Teflon.

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