Vacuum Furnace  Maintenance Tips

Moisture in Vacuum Pump Oil

The efficiency of a vacuum pumping system can be greatly reduced by moisture in the oil in the mechanical pump. The moisture content of the oil is generally ignored by most users until the pump's sight glass looks like it's full of chocolate milk. By then, the pump capacity has been seriously affected, and the pump's internals are probably not very happy.

A buildup of moisture can be avoided by simply cracking open the gas ballast valve on the pump and running it against a vacuum for a few hours or overnight. Doing so once a week or so will clean up the oil and keep the effect of water vapor to a minimum. In hot, humid weather, the frequency might be increased to twice as often, possibly every few furnace cycles.

When not in use, a vacuum furnace should be left with the door closed and under vacuum. There is usually no need to leave the vacuum pumps running, just pump down, and close the main vacuum valve. A furnace with a graphite hot zone, for example, left at atmosphere, especially with the door open even slightly will absorb a surprising amount of moisture that will at least lengthen the next pumping cycle, and much of the water will wind up in the oil.

The latest design, materials and equipment specifications should be obtained from the company before any reliance is placed on the enclosed since changes may occur due to product improvement.