01 February 2016
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Schrader valves are commonly used on refrigeration & air conditioning because they are a simple, cost effective method of providing access to a system.
But they commonly leak. One cause of leakage is over or under tightening of the core. Most Schrader valve cores should be tightened to a torque of between 0.23 and 0.8 Nm.
Eliminating the guesswork which results in over or under tightening will reduce refrigerant leakage.
But they commonly leak. One cause of leakage is over or under tightening of the core. Most Schrader valve cores should be tightened to a torque of between 0.23 and 0.8 Nm.
Eliminating the guesswork which results in over or under tightening will reduce refrigerant leakage.
 Schrader valve torque tool | The photo shows an example of a simple torque tool. To use it simply tighten the core into the body until the tool clicks at its pre-set torque setting. The use of the torque tool also ensures that the Schrader core depressor is at the correct height, so it is not fouled or depressed when a cap is fitted, but is depressed only by the pin in the gauge line. A valve core comprises a machined component and a seal that screws into a separate valve body. The core seal is attached to a pin which is actuated when contacted by the depressor in your hose. An external seal on the core provides leak-free attachment between the core and body. |
Other ways of reducing leakage at Schrader valves include:
- Ensuring the correct core is used – one type does not suit all applications. You should select the core to suit the refrigerant, oil, pressure and temperature. Cores are colour coded and you should check compatibility against the manufacturer’s data sheets.
- Removing the core when brazing in the valve, and re fitting the core (using the torque tool) when the body has cooled to below 100OC as a large number of cores are damaged before refrigerant is even introduced to the system.
- Capping the valve with an appropriate cap (such as a hexagonal cap which can be carefully tightened using a spanner). The cap should be carefully selected for use with the particular Schrader core body.
Access points in the system should be minimised. If possible do not fit Schrader valves, especially during installation for pressure testing where they are left in inaccessible areas such as roof voids and service ducts. Locations of access points, including Schrader valves, should be marked clearly on isometric drawings for future reference.
For more information or to buy torque tools contact [email protected]
Real Zero has more information about leak reduction: www.ior.org.uk/real-zero
Real Zero has more information about leak reduction: www.ior.org.uk/real-zero
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