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Hot oil filters play a crucial role in maintaining the efficiency and reliability of your heat transfer systems. Filter packages are designed to remove contaminants and impurities from heat transfer fluid, ensuring optimal heat exchange performance and extending the lifespan of the fluid and your heat transfer system itself.

HEAT’s HTFF Series Filtration Packages are side-stream filtration systems designed for a hot oil system operating up to 650°F and 150 PSIG. HTFF Series filters can be connected in series or in parallel to any existing heat transfer system for continuous particulate filtration of your heat transfer fluid. They use spun-wound, glass fiber elements, which are compatible with nearly every heat transfer fluid and operating condition.

Continuous, side-stream filtration of thermal fluid has many advantages over the life span of your process:

  • Reduced wear of seals, pumps, valves, etc.
  • Reduced fouling of heat transfer surfaces
  • Reduced risk of unscheduled downtime
  • Improved heat transfer efficiency
  • Improved production yields
  • Improved system longevity

Follow along as we delve into the key steps and best practices for using hot oil filters, unlocking the secrets to maximizing the safe, reliable performance of your heat transfer system. This guide is intended to be a companion to the HTFF Series Operation Manual. Read and obey all Safe Work Procedures and Safety Data Sheets for the fluid being filtered. It is always critical to keep safety in mind whenever hot fluid is present – SAFETY RELIES ON YOU.  


  • Make sure you have the recommended Personal Protective Equipment (PPE):
    • Face shield
    • Safety glasses
    • Fire-resistant clothing
    • High-temperature chemical-resistant gloves
    • Proper footwear
  • Gather all necessary tools:
    • Correctly sized wrenches or drivers
    • Long-handled pliers
    • Metal drip pan
    • Catch basin
    • Spill kit
    • Fire extinguisher

Read and familiarize yourself with the Safety Data Sheets (SDS) and the Safe Work Procedures for the HTFF Series.

Read the entire Operations Manual before proceeding. Only individuals who have been properly trained should operate the HTFF Series filters. Be sure your workspace has proper ventilation and is free of unnecessary obstructions.

Watch: HOW TO Safely Use Hot Oil Filters


Make sure that all valves on the HTFF package are completely closed before proceeding.


  1. Consult the connection diagrams to determine the appropriate installation method (parallel or series). A globe style throttling valve is necessary in the series installation for encouraging flow through the filter.
  2. Use high-temperature insulated hoses to connect the HTFF Package to the heat transfer system.
  3. Make sure all connections are tight and properly made. Consult the flange bolt torque value table in the manual for the necessary torque values for the connecting flanges.
  4. Install spray shields on all flanges to prevent thermal spray if a leak occurs.

Inserting The Filter Element:

  1. Close all valves completely.
  2. Remove the top flange on the filter housing.
  3. Place the new filter element(s) inside, ensuring the guiding spring goes into the top of each filter element for secure fastening.
  4. Re-tighten the top flange onto the filter housing, ensuring the gasket is properly seated. Refer to the table for flange bolt torque values and apply the appropriate torque, depending on your model of HTFF Series Package.
  5. Open the valves on both sides of the inlet hose to let the hot fluid into the filter package. Check for leaks and address any leaks as necessary.

Venting the HTFF Package:

  1. Place a metal drip pan under the tube of the HTFF's vent line.
  2. Slowly open the vent valve on the top of the filter housing to release the trapped air.
  3. Once all vapor has been released, thermal fluid will come out of the vent tube in a steady stream. Caution: this fluid will be HOT.
  4. Completely close the vent valve.

Circulating fluid through the filter:

  1. Slowly open the valves on the outlet side of the filter and to the system connection. All valves to and from the HTFF Package should now be open.
  2. Monitor the differential pressure (dp) gauge. Once the gauge reads 25 psig, the filter has captured enough particulate and needs to be replaced.



  1. Prepare an area with spill pads to lay down the spent filter element once removed.
  2. Make sure there is a clear and unobstructed path between the filter housing and this designated area.

Isolation and draining:

  1. Close the isolation gate valves on both the HTFF Package and the system to isolate the filter housing. All valves to and from the filter should be closed.
  2. Place a metal containment pan under the discharge of the vent line. Slowly open the vent valve to release any pressure contained within the filter housing. Keep this vent valve open during the draining process.
  3. Place a large metal catch basin under the drain port. Make sure the catch basin has enough volume to collect the hot oil inside your filter package.
  4. Open the isolation drain valve to allow fluid to drain from the housing into the metal catch basin. Exercise caution as the fluid within the housing can be extremely hot.
  5. Once the filter housing is drained, close the drain valve fully.

Removing the filter element:

  1. Carefully remove the top flange of the filter housing.
  2. Use a pair of long-handled pliers to remove the spent filter element(s) from the housing. Place the spent filter(s) onto the prepared area or into a catch bucket. The filter(s) will be HOT.

Replacing the filter element:

  1. Place the new filter element(s) into the housing, ensuring it is properly positioned.
  2. Repeat the steps for tightening the flange, ensuring the gasket is properly seated.
  3. Open the inlet valves to let hot fluid back into the filter package.
  4. Vent the HTFF package following the same venting procedure as before.
  5. Again, slowly open the outlet valves to allow fluid to circulate through the filter housing.

Monitoring and replacement:

  1. Continuously monitor the dp gauge.
  2. Replace the filter element as needed when the gauge reads 25 psig or greater.