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Safe Sampling of Heat-Transfer Fluids

| By Chemical Engineering

Collecting representative samples of heat-transfer fluid for routine quality checks falls short of the goal if safety or the environment is compromised. While users should consider their systems’ unique design features in consultation with their safety and health experts, incorporating the tips below can help to avoid common potential safety concerns associated with sampling these fluids, which may be at extreme temperatures. Understanding these safety issues is the first step in planning a safely conducted task.


Safe access to heat-transfer-fluid sample ports is a key part of an ergonomically designed station. Important aspects of a well-designed sampling station include the following:

• Clear standing area with unobstructed path of egress

• Height of sample port below chest-high, to avoid upper body splash

• Limited extent of reach required to avoid body strain

• Space beneath sample port to allow hands-free placement of a properly labelled flush bucket

• Non-slip, solid floor surfaces to prevent drips to a lower level

• Globe valves in sample port are preferred for the best control of flowrate


Extreme temperatures

Representative samples are best collected during operation, when the fluid is uniformly mixed throughout the system. Heat-transfer fluids routinely reach temperatures that can present thermal burn hazards. The following tips are for sampling hot streams:

• Review safety data sheets (SDS) for the personal protective equipment (PPE) that is required for the fluid being sampled, as well as its physical and chemical properties, and hazard information

• Use a sample cooler to reduce fluid temperature to below 93ºC (200ºF) to protect sample composition integrity

• Wear gloves that provide chemical and thermal protection, as well as a splash apron, eye goggles and a face shield

• Inspect the port area for uninsulated contact points to avoid

• Avoid drips which may occur before, during or after collection

• Do not remove PPE until the port and sample bottle are secured


Splashes and spray

Even with the proper PPE in use, initiating flow from the sample port is a transient operation that can result in splatter or spray, and efforts should be made to limit the splash potential. Since the fluid may be hot, it is important to take precautions against accidental hot-fluid contact to avoid thermal burns. Thermal burns are the single greatest safety concern to personnel working with high-temperature fluids and equipment. Use of a globe valve can provide better flow control when opening the sample port.

Think ahead to plan what actions will be taken in the event of an unexpected spray. Anticipate pressure on the line when opening the port valve, and open the valve gradually. Stand to the side so that any spray will be directed away from potential physical contact. One technique to better control the sample stream is to install a short length of small-diameter tubing on the sample valve outlet, which steadies the stream and also permits easy insertion into the neck of sample bottles.

When flushing the sample port prior to collecting the “good” sample, direct the stream into a dry bucket. Any moisture in the flush bucket can result in violent splatter of the hot heat-transfer fluid into the vicinity, if the sample stream is above the boiling point of water.

Take the time needed to sample the fluid safely. Rushing to perform this task can pose unnecessary safety risks for those collecting the fluid samples.


By expecting the unexpected, we can prepare adequately to avoid potential spills and their consequences, or minimize their extent and impact. A well-placed sample port will be at ground level with little exposure to sewers or floor drains. A small, curbed area can help keep small releases contained. Above all, efforts should be taken to keep potential releases of organic heat-transfer fluids from drains and waterways. If a storm drain is in the area, it should be adequately covered or otherwise blocked during sample collection.

High-temperature heat-transfer fluids are commonly organic liquids, and suitable dry, absorbent media should be available in the area for response to stabilize and aid in clean-up. These fluids are also likely to be combustible, and clean-up should be performed promptly.

Some heat-transfer fluids may have unique spill clean-up and disposal methods that are directed by their manufacturers, so refer to the product SDS for specific guidance.

Finally, any fluid residues will also create a hazard by making walking surfaces, handrails, or coated structures slippery. To avoid slips and falls, and to avoid fueling a fire, these residues should also be cleaned. Oil-absorbent cloths and socks can also be used to help keep the areas clean. Additional clean-up may be done with appropriate detergents or chemical cleaners.


Each heat-transfer fluid chemistry can be different, so learn about the unique requirements of each one from the supplier’s literature. Key concepts to avoid unnecessary exposure to fluid vapors are the following:

• Cooler fluid has lower vapor pressure, and provides less exposure

• Stand upwind of the sample port during flushing and sampling

• Place a lid over the sample port flush bucket when finished

• Promptly cap and seal the sample bottle once filled

For products containing components that have established airborne-exposure limits, consult with an industrial hygiene technician about the need for respiratory protection. In many cases, proper job planning and sample cooling may eliminate the need for respiratory protection.

Finishing the job well

Now that the sample has been collected, it is ready for packaging and shipment to the laboratory for analysis. While most organic heat-transfer fluids are not regulated for transport by the U.S. Dept. of Transportation (Washington, D.C.; for sample quantities, the bottle should be packed properly so that it remains leak- and damage-free until it arrives at its destination.

Bottles should be protected against breakage. Metal containers offer the greatest resistance, and glass containers will require adequate packing materials. Precautions against container leakage can include the following actions:

• Ensure all seals are properly in place in the neck and mouth of the bottle

• Do not use substitute parts for liquid seals

• Apply tape to the outside of the tightly-sealed container cap

• Place the bottle within a chemically compatible bag, which is then closed to prevent liquid escape into the outer package

• Foam packing (pre-formed, or “peanuts”) can be placed around the sample container to protect it against sharp blows

• Properly dispose of fluid collected in the sample-port flush bucket



1. “Therminol Information Bulletin #2: In-Use Testing of Therminol Heat Transfer Fluids. Pub. #7239112C, Solutia Inc., a subsidiary of Eastman Chemical Co.

2. “Liquid Phase Design Guide” Pub. #TF-04, 5/14, Eastman Chemical Co.


Editor’s note: The content for this column was provided by Eastman Chemical Co. (Kingsport, Tenn.; Eastman and Therminol are trademarks of Eastman Chemical Co. or its subsidiaries.

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