A growing number of modern refining or manufacturing processes require the use of highly corrosive materials, or the ability to operate at very high or very low temperatures. In most cases, standard pressure and temperature measuring instruments cannot be used for these applications as these sensitive devices literally can’t take the heat (or extreme cold) for long periods of time.
Extremely hot, cold, or corrosive processes require specialized measuring instruments, typically including a protective diaphragm seal. In extreme temperature cases, the diaphragm seal should be constructed of a corrosion-resistant material, such as Stainless Steel 316 series or several Hastelloy grades, Monel alloys or tantalum to name a few.
Common Specialty Materials for Diaphragm Seals
WIKA customers can order custom diaphragm seals made from over 25 specialty materials, and our experienced engineers will help you to identify suitable material for your specific application. Given that the customer has the final word materials such as Hastelloy C276, Hastelloy C22, Monel 400, and tantalum are materials commonly used in diaphragm seals for chemical and petrochemical applications.
In some cases, the entire diaphragm seal is constructed of the special material. For a more economical alternative, a layer of a corrosion-resistant material is attached to the surface of a steel diaphragm seal with a metallic bonding process.
Hastelloy C22 and C276 alloys are frequently used for wetted parts in chemical process technology and equipment. These alloys have excellent corrosion resistance against acids at high temperatures, various solvents, chlorine-based media, formic and acetic acid, or brine/salt solutions, and can be used in a broad range of applications.
Diaphragm seals and other equipment made of Monel 400 are also relatively common in the chemical industry. This alloy is highly resistant to organic and inorganic acids, caustic alkali solutions, and salts in a variety of operating conditions. Monel 400 offers better protection from reduction reactions than it does from oxidation reactions.
Tantalum is highly resistant to corrosion, roughly equivalent to glass or platinum, but it is quite expensive. Very few organic or inorganic materials will corrode this rare metal at room temperature. The reason tantalum is so resistant to corrosion is that a layer of tough tantalum pentoxide that inhibits chemical reactions forms quickly on surfaces exposed to air.
WIKA Technical Director of Diaphragm Seals Raimund Weissner emphasizes the goal with specialty material diaphragm seals is to help the customer select the most economical material for the seal to get the job done. For example, there’s probably no need to pay for an expensive tantalum diaphragm seal if a relatively inexpensive Hastelloy C276 seal will work just as well.
Let the pressure measurement experts at WIKA help you figure out the ideal material for your diaphragm seals so you can give your valuable instruments maximum protection at reasonable cost. Give WIKA a call today, and we’ll get a conversation started about what specialty materials are the best fit for your applications.
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