Page 429 - Centrifugal Pumps 2E

Mechanical Seals 393

Figure 17-29. Carbon primary ring with hydropad face design (courtesy of John
Crane).

types of seals are measured in parts per million. The seal illustrated in
Figure 17-30 has been successfully applied to sealing light hydrocarbon
at the following conditions:

• Liquid sealed: ethylene, ethane, or propane
• Stuffing box pressure: 500 to 1200 psig
• Temperature: 30 to 60°F
• Specific gravity: 0.3 to 0.9
• Speed: 1500 to 3480 rpm
• Seal size: 5.375 inches

Many installations have been made and thousands of hours of seal life
have been realized. The materials of construction for the seal faces are
carbon versus tungsten carbide.
Hydropads have also been successfully applied to high temperature ap-
plications requiring a metal bellows seal. The seal shown in Figure 17-31
is a typical installation that has been in service for more than three years.
This was a difficult application for the original seals that were specified.