Its limit is determined by the type and grade of material being used. Some grades of carbon and most coated, or plated hard faces have severe temperature limits. The pumping fluid can be altered if subjected to high heat. It can crystallize, solidify, vaporize, coke etc. This will restrict the free movement of the seal components.
Corrosion always increases with heat.
Stuffing box or seal environmental controls are necessary a great deal of the time. With the exception of split seals most applications require a large seal chamber with a stuffing box recirculation line connected to the suction side of the pump. The temperature of the fluid in the sealing chamber should be kept within certain limits. These limits are determined by the specific gravity. The pressure in the sealing chamber can be controlled to prevent vaporization of the product or vaporization of the solvent carrying the product.