The Fill Fluid Selection Process in Detail
Selecting fill fluids for diaphragm seals may seem complicated, but it doesn’t have to be a challenge. There are several factors to consider when deciding which fill fluid to use.
First, the pressure and temperature of your process should be considered. Fluids react differently when under extreme temperature or when under vacuum.
Secondly, you must take the regulations and requirements of the process under consideration. For example, food and pharmaceutical applications are subject to FDA review and fill fluids used in these applications must be approved by the FDA.
Third, determine if your process has frequent pressure changes and needs to react quickly or your process has steady pressure and seeing the fluctuations immediately is not as important.
Finally, you need to consider the reactivity of the medium to other substances. While the fill fluid is separated from the process medium by the diaphragm seal, it is important to be sure that the fluid will not react violently with the process medium in the event of seal failure.
Fill Fluid Types
Once you feel confident that you know how to select diaphragm seal fill fluids, you’ll need to make your choice from a range of options. The following is a list of commonly used fill fluids and descriptions of their applications and temperature ranges. For additional information, please feel free to reach out to us at ESP.
FDA-Approved White Oil, Fluid Number LRS1:
This fill fluid is used with all standard devices and in food and pharmaceutical applications when FDA approval is needed. Its operating temperature range is -15-150 °C.
Silicone DC510-100, Fluid Number LRS2:
Use this fluid in low-temperature applications. Its operating temperature range is -60-150 °C.
Silicone DC550-100, Fluid Number LRS3:
This fluid should be used in high-temperature applications. Its operating temperature range is -20-300 °C.
Fluorolube, Fluid Number LRS4:
Fluorolube should be used in oxygen or chlorinated circuit applications (maximum 160 bar pressure). Its operating temperature range is -15-150 °C.
Silicone DC200-10, Fluid Number LSR5:
Silicone DC200-10 should be used when a quick response time is needed. Its operating temperature range is -40-150 °C.
Glycerin and Water, Fluid Number LRS7:
Glycerin and water are appropriate for paint applications (not to be used with vacuum). Its operating temperature range is -20-80 °C.
Silicone DC704, Fluid Number LRS8:
This fill fluid should be used for vacuum and absolute pressure applications. Its operating temperature range is -10-200 °C.
Slytherm 800, Fluid Number LRS9:
Slytherm 800 is perfect for process measurement transmitters, high-temperature applications, and applications where a quick response time is needed. Its operating temperature range is -40-400 °C.
FDA-Approved Paraffin Oil, Fluid Number LRS10:
This fill fluid is a good option for applications where FDA approval is needed. Its operating temperature range is -20-225 °C.
Low-Temperature Silicone, Fluid Number LRS12:
Choose low-temperature silicone for very low-temperature applications. Its operating temperature range is -100-150 °C.
Feel Confident in Your Decision
Armed with in-depth knowledge about the applications and requirements of various fill fluids, you can make an informed decision about your fill fluid selection. We at ESP always want to ensure that our clients are confident in their pressure gauges and ensure that the fill fluids are exactly what they need. Please feel free to reach out to us at ESP if you have any more questions or need assistance in selecting the right products for your needs.