Ideally, facilities never need to clean their heat transfer systems. Should that time come, however, it is good to know the options, says the engineering team at Duratherm Heat Transfer Fluids in Lewiston, N.Y.

A cleaner for a thermal fluid heating system might be needed for a number of reasons. Four common reasons are:

• The fluid was in use for too long.
• The expansion tank was running hot.
• Air entered the system.
• A sudden stop in flow due to a power outage or emergency stop overheated the fluid.

Understanding fluid degradation will help extend the service life of thermal fluid and minimize the need for cleaning. The option a facility should choose will depend mostly on how badly fouled the system is.

Downtime is always at a premium, and if the system is not too badly fouled, system cleaners can be used without stopping production. One product from Duratherm can be used for preventive maintenance during production at temperatures up to 550°F (288°C). It can be left in the system for a complete oil cycle if needed, Duratherm says.

To use the Duratherm system cleaner, the operator should drain the current degraded fluid, fill with the cleaner, and run production for a typical oil cycle. If the system is heavily fouled, the system cleaner should be used with caution as it could knock deposits loose, causing blockages and disrupting production in systems with smaller lines and orifices. Food-grade system cleaners also are available.

Other system cleaners are additive style cleaners meant for larger systems where filling the entire system with cleaner is too costly. They can be used while running production as well. One such cleaner typically is used at concentrations up to 10 percent. It is designed to clean slowly and should be cycled for three to four weeks to ensure a thorough cleaning.