A steel company was having problems with brush holders and brushes in their pickle line in the steel mill where hydrochloric acid (HCI) fumes are present. HCI is used in pickling of steel to remove rust or iron oxide scale from steel before subsequent processing. At this plant it was common to change brush holders as frequently as every month on the more problematic units. Helwig was called upon to develop a brush holder that could survive in this harsh environment.
GE DC motors are used in the pickle line. Horse powers range widely from 5 HP to 600 HP. Operating in a hydrochloric acid environment at temperatures up to 200°F
Hydrochloric acid is one of the most corrosive acids and is even more reactive at the reported temperatures. Only a few materials are able to hold up under these conditions. The holder and the mounting hardware all had to be able to withstand the HCl vapors at 200°F. The holders were coated with a custom protective coating which has excellent resistance to HCl and the mounting hardware was given special silver plating which also is resistant to HCl.
The Helwig custom coated boxes held up for over one year and the brushes were still able to slide freely in the boxes. The inspection frequency was one month. The customer reported significant reduction in frequency of brush and holder changes. The customer is in the process of changing the brush holders on all the motors for this pickle line to Helwig's Teflon coated boxes. 32 motors in all - over 300 brush holders. By working closely with the customer we were able to implement the solution to address the maintenance needs.
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