A recent seminar was held that was focused on gear distortion. While the distortion aspect of the seminar was extremely interesting and very well presented, the impact on the writer was toward quenching and maintenance of quench oils.

With the ever-increasing price escalation of oil from the Middle East, there will be equally an ever-increasing price for quench oils. It behooves the heat-treatment operation to protect their quench-oil investment to better maintain the quenching system.

It is suggested to quench-oil users to follow a regular oil inspection through testing and analysis. The following is a suggestion of points of concern that one might consider in order to preserve the quality and effectiveness of the quench oil:
  • Regular inspection for particulates that can be present in the oil such as oxide scale fines, soot (particularly if carburizing).
  • Regular inspection of the oil for water contamination.
  • Regular inspection of pneumatic systems, particularly if the furnace is an integral quench furnace. Pneumatic door-lift cylinders (if not maintained) can leak air into the furnace. The air will generally have a moisture contamination from compressed air, high humidity levels in the shop air or both.
  • Regular inspection of the oil for contamination by decomposition, particularly if the quench oil is maintained at high operating temperatures for mar-quenching procedures.
  • Regular cleaning of the quench oil should also be seriously considered in order to maintain a high level of quench effectiveness.
  • Regular de-sludging of the quench tank of the furnace should be a standard operating procedure and part of the preventative maintenance plan.
  • Regular inspection of the quench-oil agitation system should be made. A simple thing to observe in the quench system would be to check that the agitation impellers are turning and have not fallen off the impeller driveshaft for whatever reason.
  • Regular inspection and cleaning of the filters that are present on the oil-quench piping system.
  • Regular inspection and cleaning of the external heat exchanger (especially if the system is a tube internal-cooling system).
  • Regular inspection of the external air-cooling system (if the water-cooled heat exchanger has been replaced and substituted with an air cooler).
  • If you are sending the quench oil out for cleaning, ensure that the oil drums that contain the potentially contaminated oil are appropriately marked for identification. This is most important because contaminated oil can be put back into the quench tank if the drum is not identified in a clear manner.
The cost of quench oil is likely to increase rather than decrease. Your operating investment in the quench oil can be protected with good and effective oil maintenance.

An alternative method to quench oil would most likely be the use of blended Poly Alkylene Glycols. This method of quenching can be a useful substitute to oil. Since the base material is water, it is an ecologically friendly quench medium. One singular major advantage of a Poly Alkylene Glycol system is that it is not a fire risk. It does, however, necessitate its own maintenance. The maintenance is generally done on a daily basis with a simple refractometer. A monthly maintenance would be to check the quench-medium viscosity.

The negative for this method of quenching is the potential for increase in the cost of water. This would be particularly problematical in dry geographic areas.