Selecting Materials for Diaphragm Valves

Diaphragm Valve Materials

A stainless steel, electrically actuated diaphragm valve

Figure 1: A stainless steel, electrically actuated diaphragm valve

Diaphragm valves are suitable for various applications, making proper material selection critical to ensure the chosen valve suits the specific application. For example, a diaphragm valve with a neoprene diaphragm can be suitable for wastewater applications but not oil and gas applications. This article provides guidance primarily on selecting materials for the diaphragm and the valve body, as these are the only valve components that contact the media flowing through the valve.

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Diaphragm materials

When selecting material for the diaphragm valve's diaphragm, consider the following criteria:

  • Temperature rating: Different materials can have vastly different temperature ratings. If the diaphragm is frequently exposed to temperatures outside its rating, it will quickly wear down.
  • Flexibility: Diaphragm flexibility ranges from highly flexible to relatively stiff. For guidance on choosing this value, see the next section (Diaphragm flexibility—why it matters).
  • Application/System media: As seen in Table 1, some diaphragm materials are well suited for particular applications or system media and not well suited for others. The media running through the system can likely decide which material to select for the diaphragm.

Table 1: Diaphragm valve selection criteria for the diaphragm

Material Temperature Rating Flexibility Applications
EPDM -29 °C to 110 °C (-20 °F to 230 °F) High Handling acids, alkalis, alcohols, ozone resistance, steam sterilization
PTFE (Teflon) -184 °C to 149 °C (-300 °F to 300 °F) Low due to stiffness Strong acids, alkalis, solvents, high sealing force applications
Neoprene -29 °C to 93 °C (-20 °F to 200 °F) Moderate to High Wastewater pipelines, fluids with oils, acids, alkalis, petroleum, explosives, fertilizers
Butyl rubber -20 °C to 120 °C (-4 °F to 248 °F) High Gaseous media, steam sterilization, acids, alkalis
Nitrile rubber -26 °C to 57 °C (-14 °F to 134 °F) High Gasses, fuels, fats, oils, alcohols, petroleum (not with acetones, ketones, ozone)
Natural rubber -40 °C to 57 °C (-40 °F to 134 °F) Very High Abrasives, dilute mineral acids, brewing
Viton -29 °C to 149 °C (-20 °F to 300 °F) Moderate Most chemicals, solvents, oils (not ammonia, polar solvents)

Note: The values for flexibility (e.g., high or moderate) indicate the material's flexibility relative to the other materials in the table. Learn more about each material's chemical resistances in our chemical resistance of materials guide.

Diaphragm flexibility - why it matters

If the system parameters (e.g., temperature and media) allow for different diaphragm materials, selecting flexibility may be the next step toward choosing the most suitable material.

  • High flexibility advantages: Highly flexible diaphragms are more responsive to low pressures, open and close faster, and provide tighter seals because they can better take the shape of the valve seat.
  • Lower flexibility advantages: Diaphragms with lower flexibility typically have higher temperature and pressure resistance and are usually less porous, making them suitable for applications for which leak prevention is a top priority.

Diaphragm valve body materials

A diaphragm valve can be metal or plastic, indicating the material used for its body. Table 2 describes the most common material types and each material's most important properties.

Table 2: Diaphragm valve body material types

Body material Pressure rating (bar [psi]) Temperature rating Primary advantages
Stainless steel diaphragm valve 10.3 - 413 (150 - 6,000) -157 to 427 °C (-250 to 800 °F) Corrosion resistance, durability, cleanliness
PVC diaphragm valve 1.4 - 31 (20 - 450) Up to 60 °C (Up to 140 °F) Chemical resistance, lightweight, cost-effective
Carbon steel diaphragm valve 10.3 - 172 (150 - 2,500) -29 to 427 °C (-20 to 800 °F) Strength, toughness, shock resistance
Cast iron diaphragm valve 8.6 - 17.2 (125 - 250) Up to 232 °C (Up to 450 °F) Durability, cost-effectiveness, good vibration dampening

Other component materials

The two other primary components for a diaphragm valve are its stem and bonnet. The stem is typically made of stainless steel or plastic and the bonnet will likely be made of the same material as the valve body. Selecting the material is not as critical because the system's media will not interact with the bonnet or stem. When choosing between stainless steel or plastic for the stem, select stainless steel if the temperature around the stem will be 60 °C (140 °F) or higher.

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