Cleaning Q&A: Electrical Immersion Heater Issues

Protecting heaters from crystal build-up.

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Q. One of my phosphating process uses electrical resistance heaters to warm the solution. After time, crystals from this solution form on the heaters, decreasing efficiency and causing damage. Is there a way to protect these heaters?

A. Although they are less expensive and relatively easy to install and control, electrical resistant heaters in a process tank prone to sludging (due to expected precipitation of chemicals in the bath) can be problematic because of the very high heat density at the surface of these heaters. Other heating methods, such as a gas fired burner tube or a steam plate heat exchanger, have a lower heat density on their surface and result in a lower precipitation of the bath at that location. A steam-heated plate heat exchanger may be placed vertically at the back of the tank to mitigate the amount of surface build up. One potential solution would be ensure the heaters are not at the very bottom of the tank. You can minimize the buildup of the phosphating chemical if the heat exchanger is slightly off the bottom. Install safety measures on the tank to make sure the power to the heater is shut off in the event of a low fluid level situation.

Originally published in the January 2016 issue.

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