Configuring Valve Body and Seal Material

When configuring a Gems Sensors solenoid valve, it’s important to select the correct material for the body and the seals.  These are main components of the valve and it’s crucial that these are chemically compatible with the media traveling through the valve.

From the below image, you can see all the wetted components of a 2-Way Normally closed valve.

Selecting the Body Material:

The Body is the portion of the valve that accepts the plumbing connections and the seat for the plunger to seal on.  The body also receives the guide tube and flange via threads and is sealed by an O-ring.  Gems offers various types of body materials, depending on the type of the valve series you have selected.  Generally, the body materials can be Brass, Aluminum, 303SS, 304SS, 430FSS, and 316SS.  Below are some pros and cons of each. 

  • 316SS has the most chemical compatibly with different medias.  However, this is a premium material and a harder material to machine, so it costs more. 
  • Brass is one of the more softer metals, making it easier and quicker to machine but offers less chemical compatibility then stainless-steel.
  • Aluminum is another easy metal to machine but has similar chemical compatibility as Brass and sometimes requires plating to help prevent corrosion. It is typically the most cost-effective material when compared to Brass and all types of stainless steels. 
  • 303SS is the softest stainless-steel Gems offers making it easy to machine and thus cost effective.  It can also be just as cost effective as Brass in volume quantities which is one reason it is a standard selection on many Gems Solenoid series.
  • 304SS is harder than 303SS which makes it more difficult to machine and more costly.  It offers a little better chemical compatibility then 303SS.
  • 430FSS is a magnetic stainless steel which helps enforce the magnetic field around the coil.  It is typically offered for Cryogenic valves.

Selecting the Seal Material:

The O-ring is one component that makes up the seal material, and the plunger is the other portion.  The O-ring seals the connection between the guide tube flange and the body.  This prevents the media from escaping the valve which is known as an external leak.

The plunger seals the internal flow path of the valve, preventing media from flowing from the inlet to the outlet when the valve is in the closed position.  When media is able to flow when the valve is closed this is called an internal leak.

Gems offers numerous types of seal materials.  They can be elastomer (softer) seals or non-elastomer (harder).  Read “Elastomer Seals Vs. Non-Elastomer Seals in Solenoid Valves” to learn more about the difference.  The following are different seals (O-ring and plunger seal) that are offered on Gems solenoid valves.

Nitrile (Buna), Neoprene, EPR, Viton, Silicone, Hydrin, Perfluoroelastomer (FFKM), PTFE, and Rulon.  Typically, the softer the seal is, the better it will seal.  However, these seals can wear out more quickly.  Softer seals are more susceptible to swelling from being incompatible with the media.  Harder seals like PTFE and Rulon can last longer but don’t seal as well.  They are more inert and thus chemically compatible with most medias.  They perform well in extreme temperatures as they don’t expand or contract that much, so you will see them used on hot water and steam for use in coffee makers, and cryogenic valves for use on rocket engines.

It’s crucial to review each seal to see how chemically compatible it is to the media you will be using.  Especially for a plunger seal, because if the media causes this seal to swell, it can restrict and/or prevent any flow.  Below you will see some examples of where different seals are used.

  • Nitrile- Water and air applications
  • EPR- Water, and Hydrogen gas applications
  • Hydrin- Natural gas plunger lift applications
  • Viton- Inks for printing applications, hydrocarbons
  • Silicone- Water and air application
  • Perfluoroelastomer- Inks for printing applications or where the media is corrosive.  FFKM is the most expensive seal available.
  • PTFE- Hot water and steam, cryogenic applications like liquid carbon dioxide
  • Rulon- Cryogenic applications like liquid nitrogen    

Regardless of the above common applications per seal, it’s still recommended to review chemical compatibility websites to determine the rating of certain seals in your media.  In addition, even after reviewing the chemical compatibility rating its recommended to test your selected seal materials in your media.

Learn more about valves HERE.