The basic material of a diaphragm valve is always something that is highly resistant to chemical contamination and corrosion. The body is made of either plastic (like PVC and CPVC) or metal (like cast iron, copper, ductile iron, brass and stainless steel).
However, since stainless steel is more acid and corrosion resistant than others, sanitary diaphragm valves are almost exclusively made of this. More specifically, the AISI 316 and 316L stainless steel. AISI, which stands for the American Standard, is the most used standard measure for categorizing steel build. Both of these are austenitic steel with face-centered cubic atomic structure, which makes the material extremely durable.
Some companies, like SIMPLE VALVES, also add molybdenum in the structure to make the material more resistant to chloride. The only actual difference between the 316 and 316L alloys is their carbon levels. 316L’s carbon level never passes past 0.03% whereas 316’s is always around the medium. This is why the former is more resistant to corrosion when used in a welded structure.
The diaphragm itself is made of some flexible elastomers like Ethylene Propylene (EPDM) and Polytetrafluoroethylene (PTFE). The most common variants of these materials that are used in making the diaphragm are EPDM+Teflon (PTFE), silicon and Viton (FPM).
PTFE is a hydrophobic fluorocarbon solid, which means it’s resistant against all kinds of water and water-based wetness. Its coefficient of friction is one of the lowest displayed by any solid.
Silicon is an extremely temperature resistant material that can withstand anything between -80 degrees Fahrenheit and +450 degrees Fahrenheit. However, while it’s highly resistant to ozone and most corrosive elements, undiluted lye and steam can actually destroy a silicon-based diaphragm.
Viton is pretty similar to silicon when it comes to ozone and temperature resistance. Vulnerable to acid, lye, alcohol and steam corrosion, Viton can stand up to a temperature of 400 degrees Fahrenheit. FPM is mostly used as a substitute for silicon when the latter cannot be used for technical reasons.
As a manufacturer of stainless steel sanitary valves, SIMPLE VALVES aims to arm its potential customers with information that would help them in making an informed decision.
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