Page 204 - Know and Understand Centrifugal Pumps

Mechanical Seals

The single, balanced, external mechanical seal

Outside balanced seals permit sealing pressures up to about 150 psig.
They offer the other benefits of outside seals, which make them popular
in the food processing industry (Figure 13-7).
In the food production and OTC (Over the Counter) Drug industries,
like milk, soups, cough syrup, and juices, outside balanced seals are
quite popular. Their design permits easy cleaning of the equipment
without pump disassembly. These seals are prominent in the chemical
processing industry because all metal components in the seal are located
outside the fluid. This avoids problems of galvanic corrosion.

Advantages of 0-Rings

The majority of mechanical seal manufacturers make models that
incorporate O-rings as secondary seals. These O-rings offer advantages
over other forms of secondary elastomers.
1. The O-ring can flex and roll - There is no need for the shaft to
slide and rub under the O-ring while under an axial load.

2. Availability - It’s the only elastomeric seal form easily available in
most cities and towns.
3. Material of construction - Almost all elastomeric compounds are
available in the O-ring configuration.

Fiaure 13-7

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