Page 277 - The Tribology Handbook

B24 Mechanical seals

TYPES OF MECHANICAL SEAL

Table 24.1 Standard types of mechanical seal

Maximum
Type of seal allowable sealed Remarks
pressure
UNBALANCED SEALS 10-14 bar Design is more simple than a
balanced seal. Can be fitted
CIRCULATION
CONNECTION directly to a constant diameter
shaft.
lbf/in2 Rubber bellows type is less
sensitive to build up of
contaminants on the shaft
surface

PRODUC

WIND UP OF SPRI~G COILS GRIPS
AND DRIVES METAL SEAL RING
BALANCED SEALS 70 bar Balanced design reduces load on
seal faces and enables higher
pressures to be sealed.
1000 lbf/in2 Design is more complex and shaft
QUENCH, COOLANT OR
LEAK OFF CONNECTIONS MULTIPLE SPRING ARRANGEMENT sleeve is essential
CIRCULATION ! ROTARY SEAL RING
CONNECTIOYS DRIVEN BY DIMPLES
\ AND SLOT:

PRODUC

PTFE WEDGE PACKING PROVIDES
SLIDING SEAL ON SHAFT SLEEVE

BACK TO BACK SEAL As above If fluid to be sealed is:
a gas,
SEALANT a liquid near its boiling point,
OUT SEALANT IN
4 abrasive,
UNBALANCEOS a poor lubricant,
this arrangement enables a
separate liquid sealant (such as
oil) to be used. It is, however,
rather complex.
Environmental awareness and
safety requirements make the
use of this seal more necessary.

B24.1