The dual seal convection tank is not convecting. The convection tank is running backwards. The dual seal barrier or buffer fluid has been shut off. The quench has failed. The product has a low specific heat and poor conductivity.
Oil is a good example of such a product.
The seal faces were over-compressed during the installation process. A wrong installation measurement was used. The mechanic did not read, or understand the print dimension. The pump sleeve moved as the impeller was tightened on the shaft. The measurement was taken at the wrong place.