The diaphragm is a key component of these valves and is usually made of a flexible material such as plastic or rubber.
When deciding which diaphragm type to use, the following factors need to be considered:
* Chemical nature of the media
* Temperature of the media
* Pressure to be used
Here we introduce several common diaphragm materials and the characteristics of each material.
Nitrile Rubber (NBR / Buna-N)
Nitrile rubber is often referred to as NBR or Buna-N. NBR is probably the most common solenoid valve sealing material and many people consider it to be the standard material for neutral fluids. NBR is also the standard material for O-rings.
NBR can withstand operating temperatures from -10°C to about 80°C continuously and higher temperatures intermittently. NBR can resist aging caused by heat very well. NBR has poor sunlight resistance, but very good wear and tear resistance.
NBR seals are suitable for most media, such as water, air, fuel, oil, gas.
EPDM Rubber
EPDM stands for Ethylene Propylene Diene Monomer Rubber. EPDM solenoid valve seals are ideal for hot water and steam because EPDM has excellent heat resistance. The operating temperature of EPDM is approximately -10 °C to +140 °C. EPDM is not suitable for most oils and fuels and is most commonly used for cold water, Freon, air, steam, hot water.
Viton (FKM)
Viton (FKM) is known for its excellent heat resistance and is suitable for oils, combustible gases, fuels, solvents. The operating temperature range is -10°C to + 150 °C. FKM seals are most commonly used for hot water, acids, alkalis, oils, hydrocarbons, salt solutions.
PTFE - Polytetrafluoroethylene
PTFE is polytetrafluoroethylene. PTFE is resistant to almost all fluids. PTFE is non-elastic, which limits its use in certain applications. PTFE is particularly suitable for media with very high temperatures (usually up to 230°C).
Table 1: Selection criteria for diaphragms
| Material | Temperature | Flexibility | Media |
| Nitrile Rubber | -10 to +80℃ | High | water, air, fuel, oil, gas |
| EPDM | -10 to 140℃ | High | cold water, Freon, air, steam, hot water |
| Viton (FKM) | -10 to 150℃ | Moderate | hot water, acids, alkalis, oils, hydrocarbons, salt solutions |
| PTFE | -180 to 150℃ | Low due to Stiffness | Strong acids, alkalis, solvents, high sealing force applications |
To enhance the life of the diaphragm, a layer of engineered fabric material is utilized as part of the diaphragm construction. This fabric allows for great design flexibility.
Fabrics are made of polyester, nylon and silk and are commonly used in most applications, such as those exposed to high temperatures, or where extreme strength is required.
Advantages of fabric reinforced diaphragms:
* No leaks * No lubrication required * No separation force
* No friction * Wide pressure range * High strength
* Low cost * Simple design * Versatility
DOTEC is not responsible for the above information and is for reference only.