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Dowtherm™ and High Temperature Seals

Seal Stability & DOWTHERM™

Daniel Cohen 
Sr. Market Developer - Dow Glycol Heat Transfer Fluids 

Dowtherm™ & High Temperature Systems  

The last few years have been challenging and unpredictable; however, heat transfer and thermal equipment have been consistent performers amidst the volatility. As companies navigate the difficult economy and conduct maintenance on their thermal heating systems, it quickly becomes apparent that some system components need to be replaced, such as O-rings and seals, which can degrade and shrink, leading to undesired leakage.
This type of issue can occur when a high-temperature heating system is accustomed to running continuously and the components are subjected to an abrupt cooldown period, which has happened since the pandemic. When restarting thermal heating systems, it is critical to ensure there is enough safety stock of DOWTHERM™ heat transfer fluid on hand for start-up to fulfill system requirements.
There is no shelf life for DOWTHERM™ synthetic heat transfer fluids, but the risk of running out is highly probable if a pipe or seal unexpectedly leaks. Maintaining an adequate backup supply of heat transfer fluids and chemicals for your applications and systems can prevent shutdowns or material replacement. In addition, DOWTHERM™ synthetic heat transfer fluids are formulated to have high compatibility and operate well in extreme temperature applications and single-fluid process heating and cooling. Dow has formulated its synthetic DOWTHERM™ O-ring chemical fluids to have excellent thermal stability, providing a long-standing and higher-performing heat transfer fluid. All grades of this have a vapor pressure lower than standard steam, which can translate into more efficient thermal transfer and system flexibility.  

Seal Thermal Ranges  

O-rings and seals are used in a wide range of applications and industries to help tightly seal connection pipes, tubes, and other elements of complex hydraulic heating systems. When evaluating O-rings, seals, and elastomers, there is a wide variety of materials to choose from. Using the proper material at their preferred organic temperatures is important for ideal thermal stability. Some materials have a better high-temperature leeway, while others have a lower thermal tolerance. The chart below highlights the recommended materials and their optimum service temperature ranges. 


-100°F to 350°F
-73°C to 177°C

Perfluoro Rubber

5°F to 500°F
-15°C to 260°C

Tetrafluoroethylene-Propylene (AFLAS®)

23°F to 338°F
-5°C to 170°C

Expanded PTFE (Gore-Tex®)

-450°F to 550°F
-268°C to 288°C

Graphite (Grafoil®)

-400°F to 1600°F
-200°C to 870°C

Fluorocarbon Rubber (Viton®)

-20°F to 450°F
-29°C to 232°C

To avoid shrinking and hardening, avoid using incorrect elastomers. Understanding the compatibility between these products and their heating capabilities and thermal stability is critical. Seals can harden due to plasticizer leaching or disintegrating at high temperatures. To avoid the needless costs incurred from leaking a premium synthetic heat transfer fluid like DOWTHERM™ thermal fluid, ensure a proper seal, O-ring, or elastomer is selected. It is also critical to ensure appropriate fluid chemical compatibility with elastomers.

DOWTHERM™ product line has seven specialty grades of high-temperature synthetic O-ring fluids. DOWTHERM™ thermal fluids have a lower-than-standard steam vapor pressure and are ideal for requirements in high-temperature applications and single-fluid process heating and cooling. Dow has formulated its synthetic DOWTHERM™ thermal fluids to have extraordinary thermal stability, providing a lasting, higher-performance fluid. With extensive knowledge of thermal compatibility and heat transfer fluids, ChemPoint can provide guidance and assistance in selecting the best fluid for your application. When you need DOWTHERM™ synthetic heat transfer fluids, call ChemPoint! 

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