Diaphragm Valve Materials
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.
