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Seals are an important part of hydraulic valves and there are different types, precisely because they have to adapt to the chemical characteristics of the liquid being transported, the temperatures and the working pressure.
As a result, the most suitable material for the seal can be chosen on the basis of the different valve applications.
The Idrja and Small series of stainless steel valves are available with different types of seal that add their contribution to perfect product operation.
Given that the purpose of check or non-return valves is to allow the passage of fluid in only one direction, the material used to make the seal must essentially guarantee high sealing levels and, as a result, maximum safety.
Seal materials
The seals of our Idrja and Small check valves are made from these materials:
- NBR: nitrile rubber, very resistant to chemical agents but not suitable for high temperatures (-25 °C – +90 °C);
- EPDM (Ethylene-Propylene Diene Monomer): rubber with great elasticity and resistance to ageing, can be used at temperatures from -20 °C to +110 °C;
- FPM: a fluorocarbon elastomer, very resistant to high temperatures (-20 °C – +150 °C) and to many solvents and chemical agents;
- PTFE (Polytetrafluoroethylene or Teflon): a polymer that guarantees an optimal combination of temperature resistance (20 °C – +200 °C) and chemical properties;
- FEP (Fluorinated ethylene propylene): a polymer with an optimal temperature resistance (20 °C – +200 °C), very elastic and resistant to aggressive chemical substances.
How to identify the valve seal type
Have you bought an Idrja or Small check valve and want to verify the seal type, just to check or because you want to order the same product again? If you haven’t kept the packaging where all the necessary information is given, here are some indications on how to proceed.
If you have an Idrja series check valve, look inside the delivery side where you can see the shutter mechanism. Light up the inside, and if necessary use a magnifying glass to see the seal through the spaces left free by the flow control disc.
What colour is the seal? If it’s green, it’s made of FPM, if white it’s made of PTFE, if red then it’s made of FEP, if grey then it’s made of EPDM and if it’s black, the seal is made of NBR.
You must be careful when distinguishing between NBR or EPDM seals because the colour difference is minimum. A suggestion could be to observe the outside of the valve: if electropolished, the seal is EPDM, while if mirror polished, the seal is NBR.
With Small series valves, you should look through the inlet side, namely opposite the side from where you can see the internal mechanism.
If you illuminate the inside well and use a magnifying glass – necessary above all for ¼” valves – you should be able to see the seal between the end of the threaded outlet and the flap of the flow control disc.
The different materials of the Idrja series are of the same colour.
A final note regarding FEP seals: given their application in specific industrial contexts they are installed in Idrja 2”, 2½”, 3” and 4” check valves, but not in the Small series valves.
