Sharon Spielman touches on thermal fluid changeout safety.

Though data refers to scalding by hot water, it shows just how sensitive skin can be to temperature. When performing changeouts of heat transfer fluids, consider the potential for workers to be exposed to the hot fluid.
Wouldn't it be convenient if you could pull your thermal fluid heaters into a bay to have the oil changed, and 10 minutes later they would be up and running again? Unfortunately, it's not as simple as that. Changing the heat transfer fluid in a thermal fluid heater can be a dangerous task. This “Safety Zone” series focuses on the safest ways to change the fluid in your thermal fluid heaters.

According to David Dowlen, assistant service manager at Heatec Inc., Chattanooga, Tenn., the key to a successful thermal fluid install or change lies in the job being performed by a trained technician, engineer or project manager.

“These individuals would, or should, know to check for percent fluid expansion, system volume requirements, expansion tank volume, etc.,” says Dowlen, who has more than 22 years experience in servicing heaters that use heat transfer oil.

First and foremost, Dowlen says, the customer should acquire a copy of the material safety data sheet (MSDS) for the fluid that is being used in the system.

The MSDS will cover the following:

  • Product and company identification.
  • Composition/information on ingredients.
  • Hazards identification.
  • First aid measures.
  • Fire-fighting measures.
  • Accidental release measures.
  • Handling and storage.
  • Exposure control and personal protection.
  • Physical and chemical properties.
  • Stability and reactivity.
  • Toxicological data.
  • Ecological information.
  • Transport and disposal information.
  • Regulatory information.

The MSDS must be readily available to any employee. Dowlen explains that it is up to the individual company or end user to develop a standard for any employee that would be involved to ensure the safe handling of any heat transfer fluid, whether it is petroleum, glycol or synthetic based.

Doug Irvine, engineering manager, thermal fluids, at Petro-Canada Lubricants, Mississauga, Ontario, says that an additional consideration is thermal protection in case the fluid is still hot enough to cause burns. “That might not be obvious because MSDSs are written considering the fluid is at room temperature when handled,” Irvine says.

Jim Oetinger, sales director and chief chemical engineer at Paratherm Corp., Conshohocken, Pa., says that the employee should wear gloves that resist heat as well as oil and chemicals. “Draining fluid cold is better from a safety standpoint, but you will leave more residue. The maximum recommended draining temperature for mineral oil is 200oF [(93oC)],” he says.

According to Irvine, the heat source should be shut down and de-energized (see “Safety Zone” lockout/tagout series, March to November 2003). The fluid should be circulated continuously until it has reached a safe temperature for draining from the system. Irvine says that what constitutes a safe temperature depends on whether or not there is a potential for workers to be exposed to the hot fluid. “If there is a significant potential for exposure of workers, then temperatures as low as 120oF [(49oC)] may be necessary.” As a guide to show just how sensitive skin can be to temperature, Irvine provides data on scalding by hot water in table 1.

Irvine also says that care should be taken to ensure that spill containment and cleanup kits are available and that personnel are familiar with their use and company procedures with respect to spills.

Oetinger says to have lots of Oil-dri Nu-Pig oil mats and rags on hand. Both Oetinger and Irvine maintain that appropriate fire extinguishers should be available and in good working order.

Next month (click here to go to Part 2), I will cover the vapor pressure curve, a nitrogen purge system, draining the system, taking advantage of maintenance during changeout and filling the system.

Editor's Note: Neither Process Heating nor any of the sources contributing to this article are liable for the suggestions or recommendations made. As with any engineering project, you need to consider the specifics of your applications as well as local codes and restrictions.