Brief Description about Double Mechanical Seal
Amongst the several types of mechanical seals, double seals are preferred for maximum sealing safety. The seals reduce the possibility of leakage of gas or fluid being handled in mixers or pumps to almost zero.
Hence, in the applications that need zero emission compliance or 100% safety guarantee, the double seals are the best choice.
When properly installed and maintained, they offer a complete service guarantee.
Since the double seals give the total control over the fluid film over the seal faces and the operating environment, they serve for quite a long time as compared to the single seals.
The working mechanism of a double mechanical seal
The double seal uses a couple of primary seals and a buffer fluid area or barrier in between the two layers. Each primary seal has two parts; a soft and narrow stationary face and a hard and wide rotating face.
The soft seal shows wear and tear whereas the hard part maintains the integrity of the seal when it is operational.
Applications that use double seals
- To stop a pollutant or hazardous material reaching the surroundings
- To prevent leakage of some precious process fluid product
- To extend the life of the seal by controlling the type of fluid film on the faces of the seal
- To keep the mechanical seal secure from the atmospheric conditions
- To avoid contamination of the process media even if one seal fails
- In the situation of inboard seal failure or scheduled equipment repair, double seal acts backup seal
- In the applications where no reliable and stable lubrication of the seal face is offered by the process fluid, it works as an alternative. The examples are non-settling slurries, viscous fluids or gaseous media
To extend the life of the seal; it is essential to control the fluid film that gets into the contact of the seal face. By this, ideal pressure, temperature and lubrication are achieved.
When the double seal is installed, it must contain the environmental support and control system. It is nothing but a buffer or barrier fluid. It is stored in a separate tank and supplied to the seal faces. It keeps the faces cool and lubricated.
The level of the fluid and pressure is crucial for the safety of the system and the environment. It can manage the operating temperature, lubrication and isolate the seal from external conditions.
Double seals are used in various situations when safety is the prime concern.
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