TP80-40/4 Shaft Seals Manual

14
Shaft seals in general
Shaft seals
Metal bellows shaft seals
In an ordinary mechanical seal, the spring produces the
closing force required to close the seal faces. In a metal
bellows mechanical seal the spring has been replaced
by a metal bellows with a similar force.
Metal bellows act both as a dynamic seal between the
rotating ring and the shaft and as a spring.
The stainless steel are corrugated to give the desired
spring force.
Fig. 17
Metal bellows shaft seal
Advantages and disadvantages
Advantages:
Not sensitive to deposits such as rust and lime on the
shaft.
Suitable in hot water and high-pressure applications.
Long life due to a low wear rate and a low balancing
rate (cost of ownership).
Disadvantages:
Fatigue failure of the shaft seal may occur if the pump
is not aligned correctly.
Fatigue failure may occur as a result of excessive tem-
peratures or pressures.
Cartridge shaft seals
Fig. 18 Cartridge shaft seal
In a cartridge shaft seal, all parts form a compact unit
on a shaft sleeve, ready to be installed between pump
shaft and motor shaft.
A cartridge seal offers many benefits compared to con-
ventional shaft seals:
• Easy and fast service
• The design protects the seal faces
• Preloaded spring
• Safe handling
• Balanced.
Grundfos offers O-ring and bellows seals in cartridge
design.
TM02 4279 0402
Metal bellows
TM02 7100 2603