With feed water pumps in particular, the distribution of temperature throughout the medium enclosed in the shaft stuffing box during standstill can be so uneven that it results in unacceptable bending of the shaft and deformation of mechanical seal parts. It is essential, therefore, to prevent the formation of thermal layers. This is done by taking the following steps:

• providing intensive jacket cooling

• creating a forced-direction current in the stuffing box by means of a circulating pump or injection of an external medium.

• by extensively isolating the mechanical seal (interruption of the thermosyphon circuit) and switching off all cooling systems in the area of the mechanical seal (this is possible only when the temperature operating limit of the secondary seal materials is not exceeded).