Materials and Resistance Charts
One of the main criteria when selecting a solenoid valve will be according to the media being controlled. This is easy when using mains water, compressed air, vacuum or any other inert liquid or gas at Ambient temperature, as a general purpose solenoid valve in Brass with NBR seals will suit well. Useful note for vacuum applications use NBR seals, FKM and EPDM have a tendency to stick in dry applications but are fine for other compatible liquids and gases.
But what happens when you are using a slightly aggressive media such as pure water on an RO system? A maintenance engineering company you might not know that even a general purpose stainless steel or plastic solenoid valve will have copper in the core tube, even a Brass solenoid valve will cause problems.
How about dilute or even concentrated Sulphuric Acid or Hydrochloric Acid? You might guess that PVC is OK but where can you check?
Well we have over the years of experience and have formulated a quite extensive list of chemicals and material compatibility charts that may prove helpful. We would always recommend that you contact the suppliers Technical Team for chemical compatibility assistance.
Helpful Hint: Ask your chemical supplier what materials are compatible with their supplied chemical as Branded Chemical names can be very challenging to determine the chemical make up. Try solenoid valves designed for very aggressive media, these remove the issues with media coming into contact with the armature and core tube as these have various grades of 302,304 and 430F stainless steel so you can focus only on body and seal material.
For seriously aggressive and concentrated acids it is wise to use PTFE solenoid valves with PTFE seals and what we call isolated diaphragm or dry armature designed tubes so the media only comes into contact with PTFE.
If in doubt always ask before you buy. When buying solenoid valves for slightly aggressive media and you know that all grades of stainless steel are compatible the you need only choose a compatible sealing material. Typical choices are NBR, EPDM, FKM or PTFE, however remember that PTFE is not a soft elastomer seal and may not offer the positive sealing characteristics of NBR, EPDM and FKM. See our article on materials of construction.
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