fundamentals of rotary mechanical seals

Fundamentals of rotary mechanical seals

The rotary joints manufacturers in India manufacture different types of mechanical seals. A mechanical seal is a method of containing fluid within a vessel mostly in the pumps and mixers, where a rotating shaft passes all the way through a stationary housing or sometimes, where the housing rotates about the shaft.

The rotary unions manufacturers in India are also used in numerous manufacturing processes. While sealing one of the kinds of a centrifugal pump, the major challenge is to have a rotating shaft to go into the required ‘wet’ area of the pump, without permitting large volumes of pressurized fluid to run off.

To overcome this challenge there requires a seal between the pump and the shaft that can contain the overall pressure of the process being pumped and resist the friction origin by having the shaft rotating.

Mechanical seal design

A basic mechanical seal contains 3 sealing points. The fixed part of the seal is attached to the pump housing with a still seal, sealed with an o-ring or gasket clamped connecting the fixed part and the required pump housing.

The rotary portion of the seal is sealed onto the shaft more often than not with an O ring. This sealing point can also be addressed as static as this part of the seal rotates along with the shaft.

Mechanical seal acts as the interface between static and the rotary portions of the seal.

The Sealing Points

Despite the fact that two of the sealing points in a seal design are highly simple static seals, the seal linking the stationary members and rotating require a little more concern. This primary seal is the foundation of all seal design and is vital to its usefulness.

The Fluid Film

In the majority of mechanical seals their faces are kept lubricated by having a thin film of fluid among the seal faces.  This film can come from process fluid pumped or from external source.

The Leakage

We are considering the visible leakage of the seal. Thin fluid films hold the 2 seal faces spaced out from each other. By having a micro gap a leak path is generated making it almost impossible for a mechanical seal to be entirely leak free. So the leakage on a mechanical seal should be lower which can be visually undetectable.


Modern cartridge seal designs do not harm the pump shaft. Daily maintenance turns less as seals have inboard springs which make them self regulated as the faces wear.

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