Fluid Power Journal

Oil-heater Problems with a Hydraulic Power Unit (HPU) Located in an Unheated Shed

figure it outA metal fabrication shop has a 30-year-old bending press that can bend wide flange beams to a semi-circular shape. The machine was up-graded to bend larger beams and required additional floor space. The contractor located the HPU just outside the building in an unheated shed. The contractor told the customer that the unheated shed would not cause problems because the contractor added a Chromalox brand electric heater to the reservoir, and there was a 230-volt 3-phase electrical supply close buy.

Within a month, a fork truck damaged the heater where it projected from the tank. The customer could read most of the part number and ordered another 230-volt unit. During the upcoming winter months in the Chicago area, when they started up the pump that was mounted on top of the unit, the pump started to cavitate badly. They determined the Chromalox heater was not heating the oil. They confirmed that the heater was getting 230 AC volts to the heater connection so they un-screwed the heater and had difficulty getting it out. The unit looked like a 4 to 5-inch lead pencil from the threads to the tip of the elements. The black coating was brittle and broke off into chunks that an old timer said looked like chunks of coal.  They checked the name tag, and everything seemed to be connected properly, as before.

Any idea what went wrong?

By Robert Sheaf, CFPAI/AJPP, CFPE, CFPS, CFPECS, CFPMT, CFPMIP, CFPMMH, CFPMIH, CFPMM, CFC Industrial Training

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