Main components of a water pump mechanical seal
Stationary seal and rotation seal are main parts for a water pump seals. And it also contain secondary seal, such as o ring and oil seal.
The more common end face and rotating face design mating faces as main seal components. The ring of carbon, ceramics, carbide composites of those materials is lapped on axial end faces, flatly. Those flat lapped face against each other. One rotate with shaft, the other one placed onto the pump housing. Spring compression will force both two seal run against each other.
Fluid imgrated between faces, and form stable fluid film. During shaft rotation, face materials heat up, quickly without any lubricating fluid films. Seal fluid make such a thin film.
For a lip type mechanical seal, seal fluid film also lubricate faces. Seal interfaces are not two flat faces, but composite material against hard material. Those material can be hard, coating, plating metal. One of those elements rotate with shaft, while the other one fit onto pump casting.
What is reason of pump shaft need to be sealed ?
In order to understand the reason of pump need seals. Let us back to some pump basics and review how centrifugal pump work.
Fluid enter centrifugal pump through suction nuzzle of center of rotary impeller. When impeller rotate, vanes full of fluid, then push it to pump casting. Where it leave away pump through discharge nuzzle.
Unluckily, discharge pressure will force fluid back to behind the impeller, where it attempt to exit through driving rotate shaft. Pump manufactures have tried to minimize the leakage by design. But leakage will never stop entirely. It must take some form of seal way to make leakage lower.
Why do we use water pump seals ?
No visble leakage, seal leak when fluid film on the faces reach atmospheric side of the seal faces.
Modern seal design will not damage pump shaft or sleeve.
Since seal have inside spring, as faces wear, Those can be self-adjusting, then maintance was reduced.
Seal have light load faces, use up less power than gland packing.
On normal operation, bearing contamination is reduced. Because lubricating was not effected by flush and leakage of a seal.
If seal contain in pumps, corrosion from factory equipment is less, too.
Less wasting will save money, even water is cherish resources. Reducing clean up that area is needed.
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