Heat check occurs on hard faces in a mechanical seal and can cause seal failure. Heat check is not one of the most common forms of seal failure but it is important to recognize because it will tell you a lot about what is happening inside the seal. Heat check is very recognizable, it shows up as radial crack marks along the seal face. Heat check is caused from excessive heat on the hard seal face. The excessive heat will cause the face to crack in many places and the material will pull up slightly. This will cause the face to act as a grinding wheel which will wear down the opposite face much faster than what should be expected. The grinding action will cause even more heat in the seal and can damage other parts in the seal, including the other face, elastomers, springs, metal parts, etc. Because of the depth of heat check the seal face is typically un-repairable.
The causes of heat check can come from one or more of the following scenarios:
Application Temperature: If the application fluid is pumped at excessive heat beyond the face’s tolerance then this can cause it heat check.
Solution: Double check to make sure the seal materials are compatible with the process fluid temperatures.
Over Compression: If the dynamic part of the seal is over compressed then this can cause excessive pressure between the faces which will reduce seal face lubrication. The heat generated from between the faces can cause the face to heat check.
Solution: Check to make sure the compression on the seal faces is adequate to allow fluid between the faces.
Improper Lubrication: If the seal is not properly flushed and lubricated this will of course create too much heat within the seal and cause heat check.
Solution: Check to make sure there is enough flush into the seal and that the correct barrier fluid is selected.
Dry Running: This occurs when there is not enough lubrication fluid between the seal faces which will cause the faces to heat check.
Solution: Check the seal is properly flushed and the flush ports are open before starting the equipment.
Inadequate Cooling: If the seal chamber is too hot then this can cause Heat Checking.
Solution: Adjusting the flush system or changing face material can help with the inadequate cooling.