Pneumatic control Valve Seal Material

[From:来自网络] [Author:admin] [Date:11-10-13] [Hit:]

Seal in the solenoid valve is referring to a part that joins body and plunger in such a way as to prevent leakage. It may also refer to seat of the solenoid valve since it directly in contact with the plunger at the disc area. See below picture to get clear understanding regarding seal of solenoid valve. The solenoid valve seal material usually made from NBR (nitrile), viton, etc. So what it should be the solenoid valve seal material that serve shutdown valve or control valve?

Choosing seal material is dependent on a number of different factors, but two of the most critical factors are the operating temperature range that seal are subjected to and the different chemicals they may be exposed to. But for shutdown valve application or control valve application, the seal will be exposed to instrument air or nitrogen only. The operating or design temperature of the instrument air usually not greater than 100 F. Therefore from this condition (instrument air chemical compatibility & its operating temperature) we can select the best suited seal material for solenoid valves.

Below is the general operating temperature of some rubber:

Material Typical Temperature Services Ranges
Buna N / Nitrile (NBR) -65 oF to +250 oF
Fluorocarbon (FKM) / Viton -10 oF to +400 oF

 Below is general chemical compatibility for instrument air (data taken from http://www.marcorubber.com).

Services Fluid Buna N / Nitrile (NBR) Fluorocarbon (FKM) / Viton
Nitrogen / Air Excellent Excellent

 From the table above, all rubber has compatibility with instrument air. Although like this, we should also consider the budget that we have. Below is the general cost of each rubber material (data taken from http://www.marcorubber.com).

  Buna N / Nitrile (NBR) Fluorocarbon (FKM) / Viton
Cost $ $$$

 In practical, many project specifications require Viton as a solenoid valve seal material. But usually as a standard, manufacture will give NBR as a default seal material. Both of it is ok for shutdown valve application which only operates with instrument air or nitrogen. But as default material if there were no any particular project specification, we can specify seal material as Viton (most used) in shutdown valve data sheet.

 

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