When people choose a mechanical seal, the choice of wear face material depends on factors such as the reliability and safety of the material, the complete lifecycle cost of the mechanical seal, and its usage and wear.
Also, the selection depends on the sealed or pumped fluid How much is the resistance to erosion and corrosion. How much is the lubricity of the wear face material? Check the capability of producing a smooth and flat surface when lapped.
Finally, the temperature, pump speed, and pressure are also important points of consideration. It is important to use high-quality material for longer service life.
How is the face material chosen?
If you compare different face materials, then you will find that most materials show poor wear behavior when they are sliding in contact with another surface fabricated from the same material.
It is the reason two dissimilar materials are used in a combination. While choosing the materials, one is always softer than the other.
Only in extremely abrasive or corrosive environments, two hard materials are used. It is because the softer material will wear rapidly in this condition.
In extensively corrosive or abrasive environments, combination like Tungsten-Carbide and Silicon-Carbide are used.
In applications where high pressure is used and the diameters are large, two faces fabricated are used so that the face deformation caused by the pressure force gets minimized.
In such an arrangement, it is extremely important to keep the lubrication level high. In case of reduced or lost lubrication, the faces will get damaged or worn out faster.
Tungsten and Silicon Carbide- the two most preferred face materials
In widespread applications, Tungsten and Silicon Carbide are used popularly. The cost of these is higher than pure oxide ceramic and metallic type face materials. However, their higher wear resistance brings high levels of reliability and long service life.
Also, these materials can work well in harsh lubricating environments, high speeds, and temperatures, and so on.
In clean fluids, they are paired with softer materials such as carbon and graphite. In dirty fluids or fluids that contain abrasive particles, they are paired or matched against the surface of the same material.
Looking at their properties and capabilities of giving a great performance in varied applications, these two materials are used commonly. The developments in products and industry standards in the past decade have shown the trend towards more use of silicon carbide.
It is important to consult experts while picking the best combination of wear face materials.
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