Before researching pump mechanical seal parts functions. It is very necessary to know the other method of forming the seal. Which one is widely used called gland packing seal.
Conventional method of fluid seal
Gland packing is a soft rope material, that is packed around the shaft. Stuffing gap between pump housing and spinning shaft. Gland packing is still widely used in much application. More and more user select mechanical seal for following reasons.
- Friction of shaft means package also need to flush with many volume of water. Which will keep seal and shaft cool.
- As over time, rotary shaft wear away at the packing because of friction. This will lead to increased leakage until to adjust packing or repack it.
- Packing need to press on the shaft very closing to reduce leakage rate. That mean motor need more power to drive shaft rotate.
- Packing need to contact shaft, thus it will eventually wear a groove onto it. Repairing will cost much.
Basic pump mechanical seal parts design
The rotary portion of seal is generally sealed onto shaft with an o ring. When its component of seal rotate with shaft. It can be also considered as static.
The stationary pump mechanical seal parts is fitted into pump housing by static seal. Which might be o ring or rubber gasket between stationary part and pump housing.
One portion of seal is always spring loaded or resiliently mounted to adapt any tiny shaft diversion, shaft movement because of bearing tolerance and not accurate mechanical seal measurement during manufacturing.
Mechanical seal basics
mechanical seal itself is interface between static seal and rotation portion. A mechanical seal is a simple method of contain fluid in vessel.
When seal centrifugal, the challenge is to allow pump shaft contact wet area. But not allow much fluid outside under increase pressure.
What is important seal point ?
Although two seal point in a seal design is a simple static seal. But the seal between stationary seal and rotary seal need a little more consideration. Such a primary seal is basics for all seal design. It is crucial for its effectiveness.
A primary seal is basically spring loaded vertical bearing. That is consist of two flat face. Using combination of spring of seal design and hydraulic pressure from seal fluid , in order to press face seal together.
Any function for fluid film？
In most mechanical seal, faces keep itself lubricate by maintain thin film between faces. The films can come from barrier fluid or media.
Need fluid film between faces that present a challenge. Allowing enough lubricating to flow between faces. On the other hand, without seal leak an unexpected volume of fluid.
That is how to achieve by keeping precise gap between faces. The gap can’t too large to allow contaminants get into. Ether it can’t too small enough to allow clean lubricating into faces.
The leakage of pump seal
When we talk about leakage, we are referring to a visible leakage. As it is, very thin film keep two faces apart. By keeping micro-gap, cause leakage path. So, mechanical seal can’t be totally no leakage. But different from packing, leakage is very low on a mechanical seal. That make it difficult to be detected , visually.
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