Page 400 - Centrifugal Pumps 2E
P. 400
Mechanical Seals 365
The temperature of the seal faces is a function of the heat generated by
the seal plus the heat gained or lost to the pumpage. The heat generated at
the faces from sliding contact is the mechanical power consumption of
the seal being transferred into heat. Therefore,
where Q s = heat input from the seal Btu/h
C t = 0,077
If the heat is removed at the same rate it is produced, the temperature
will not increase. If the amount of heat removed is less than mat gener-
ated, the seal face temperature will increase to a point where damage will
occur. Estimated values for heat input are given in Figure 17-6 and Fig-
ure .17-7.
Heat removal from a single seal is generally accomplished by a seal
flush. The seal flush is usually a bypass from the discharge line on the
pump or an injection from an external source. The flow rate for cooling
can be found by:
When handling liquids at elevated temperatures, the heat input from
the process must be considered in the calculation of coolant flow. Then
The heat load Q p from the process can be determined from Figure 17-8.
Example;
Determine the net heat input for a 3-ineh diameter balanced seal in wa-
2
ter at 3600 rpm. Pressure and temperature are 400 lb/in and 170°F.
From Figure 17-7.
Q s = (2750 Btu/h/1000 rpm) 3600 = 9900 Btu/h
