First of all, do you know some mechanical seal basics ? Such as what is a mechanical seal, the definition of mechanical seal ? Thinking about classification of mechanical seal, we can figure out to do it by different types of mechanical seals for pumps. We will show you some different mechanical seal types in this blog. For example, pusher seals, cartridge seals , Non pusher seals and bellow types. Also, you will find some different images of seals in the blog from our companies. You still want to know some basics about design and material selection.

Definition Of Mechanical Seal

Seals intend to prevent media( water or oil ) used by machine leaking to external enviroment. That is the reason that mechanical seals can help to stop enviroment contamination. And save power through efficient operation.

A seal is simply a method of containing, such as pumps or agitators. Where rotate shaft pass through pump housing, by occasionally.

Mechanical Seal Types

There are multiple design structure to choose for mechanical seal configuration. Knowing mechanical seal basics and working principle will assist user to select proper seal type for application.

Pusher seals

Pusher seals contain secondary seals, which move axially along shaft or sleeve to accommodate wear and assist in misalignment of shaft by spring compression, to keep contact of seal faces.

The advantages are those mechanical seal are cheap and have a wide range of sizes and configuration.

M3N o ring pusher seal
M3N o ring pusher seal

Non pusher seals and Bellow types

No pusher seals have no secondary seal, must move along shaft or sleeve to keep seal faces contact. In non pusher seals, secondary seals are in static state, even pumps on running. The secondary seal is not required to make up travel, when rotary seal and stationary seal wear. Primary seal faces are accommodated by elastomer bellows or welded metal. That move can assist in compression of rotary to static seal faces.

Elastomer bellow seals
Elastomer bellow seals

Advantages: It doesn’t need secondary seal, and it can also handle high temperature and low temperature application. Elastomer bellows are commonly used for water.

Disadvantages: The cost of metal bellow seals is very expensive.

Cartridge seals

Mechanical seals can be premounted on sleeve. Those are installed onto shaft or sleeve. It can provide single, double, tandem configuration. The best pump user will fully consider cartridge mechanical seals.

Cartridge seals
Cartridge seals

Advantages: The seal configuration eliminates requirements of sealing setting measurement. Setting a cartridge seals will be easier. Lower maintaince cost and less seal setting errors.

Disadvantage: It is the higher cost, plus in some cases they will not fit into existing stuffing box/seal housings.

Design & Material Seleciton

Design and material is very important for mechanical seal basics.

Design

A basic mechanical seal contains 3 sealing point. Static part of sealing is fitted onto pump houising through static seal. This can be sealed by o ring or gasket clamp between pump housing.

Rotary part of sealing is typically fitted onto shaft by o ring. The sealing point can be regard as static, because the part of sealing rotate with shaft.

Material

The selection of primary sealing material can also have effect on seal life. Chemical and process is just a consideration. Harder material is more resist abrasive.

Thermal conductivity of material can dissipate heat away from seal face. Then it can promote seal life. Material roughness can also be a primary role in mechanical seal life.

Pls note that many seal failure result from exceed chemical compatibility, temperature limits, pressure, failed secondary seal. Metal parts must be compatible to avoid corrosion. And spring and other hardware must hold up in operation.

 

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