General Classification of Mechanical Seals through Their Arrangement
A mechanical seal can be simply attributed as a method of containing fluid inside a vessel (usually pumps, mixers) in which a rotating shaft passes through the stationary housing and sometimes the shaft is around where the housing rotates.
The most notable aspect is to take care at the time of sealing a centrifugal pump, there’s a challenge to permit a rotating shaft to make their entry into the wet area of the pump and not allowing the large volumes of pressurized fluids to escape.
To address the same issue, a seal is needed between the shaft and the pump housing which can withstand the pressure of the process that is being pumped and the friction that is caused by the rotation of the shaft.
Conventional Technique
Talking about the conventional techniques, one of the most widely used methods is gland packing. It is attributed as a braided; a material like rope is usually packed around the shaft physically filling the space between the shaft and pump housing. Though the technique of gland packing is one of the widely adopted techniques but is now replaced by the introduction of mechanical seals because of its sealing point, great design and the fluid film. Let’s have a brief view at the arrangement of a mechanical seal.
Design
If we look at the design and structure of a basic mechanical seal, it usually contains three sealing points. Stationary part of the same is attached to the housing with a static seal (sealed with an O-ring or gasket) fixed between the stationary part and the pump housing. The mechanical seal itself acts as an interface between the static and rotary segments of the seal.
Sealing Points
At the time, when two of the sealing points under the design are simple static seals, the seal that is fitted between the rotating and stationary members requires due consideration as the primary seal is the basis of every seal design and is considered extremely essential for its effectiveness.
Fluid Film
In general most mechanical seals, there is lubrication of the faces with the help of a thin film of fluid between the faces of the seal. This film can either be directed from the process fluid that is being pumped or from an external source.
The main attribution of mechanical seal engineering to increase the long lastingness of the seal faces by ensuring a good quality of the fluid for lubrication and by choosing the adequate seal face materials for the procedure being pumped.