For a heat transfer system to operate reliably, its components must be constructed from materials that are compatible with the thermal fluid in use. Below is an overview of the most common components and key considerations for each.

Seals – gaskets, O-rings

Seals come in many different materials, so it’s important to work with your seal supplier to confirm they’re approved for the fluid you’re using*. A seal application guide is a helpful resource for checking which seal types are compatible with different fluids. When in doubt, your supplier should be able to confirm whether a given seal is suitable.

Beyond fluid type, seals must also be rated for your system’s operating temperatures. Always choose high-quality products from trusted sources.

Metal components

Some metals can impact the fluid, while others may be affected by it**. For instance, copper can act as a catalyst that accelerates oxidation and degrades the fluid. Aluminum doesn’t harm the fluid, but certain fluids may cause pitting or erosion in aluminum parts.

Your fluid supplier is usually the best source for verifying whether your chosen fluid is compatible with the system’s metal components.

Pumps

Pumps should also be evaluated to ensure they are designed for use with thermal fluids, especially in terms of temperature ratings. Keep in mind that pumps contain seals as well, so those must meet the same fluid and temperature requirements discussed above.

It’s equally important to account for viscosity. Since fluid viscosity increases as temperature decreases, you’ll need to ensure the pump can handle the fluid’s maximum viscosity at the lowest operating temperatures it might encounter.

Electric heaters

The critical factor for heaters is watt density. If the watt density is too high, the fluid can degrade thermally and burn onto the heater surface.

As a general guideline for Duratherm fluids, the recommended watt density is 20–22 watts per square inch for circulated systems and 10–12 watts per square inch for non-circulated systems. Staying within these limits helps prevent thermal degradation.

While often overlooked, ensuring compatibility between system materials and your thermal fluid is essential for smooth operation. If you have additional questions, we’re always here to help.

*Most Duratherm fluids are compatible with Buna-N or Viton seals. Seals rated for hydrocarbon or “oil and gas” service are also acceptable.
**Duratherm fluids are formulated with metal deactivators that neutralize potential reactions, ensuring compatibility with common steels, alloys, and even components containing copper.