Gas mechanical seals and gas supply systems
Seals lubricated by gas are known for their efficiency, reliability and environmental friendliness.
They are used in almost any industry and for any purpose. Until recently gas seals were associated mainly with compressors, but today they can be used to seal the most diverse equipment:
- pumps for pumping liquids, including those containing solids or having poor lubricating properties such as, for example, hydrocarbons;
- as additional emergency seal;
- for slowly rotating shaft mixers and reactors, chemical and pharmaceutical industries, which use sterile techniques should be excluded from entering or barrier fluid leaks into the product (dry working).
Gas seals meet the stringent international requirements, and seals are the so-called "zero" discharge of harmful substances.
Besides, they are very economical, on the one hand, lower capital costs, and on the other - an increased service life and low operating costs.
The operating principle of the gas seal:
The construction and operation of a gas seal in general, correspond to the conventional mechanical seal with the only difference that the sliding surface had wider, and they are not lubricated with liquid and gas. This is achieved through the special geometry of the V- and U-shaped grooves in the sliding surface.
Through the V-shaped groove gas is supplied between the sliding surfaces during rotation. This increases the pressure that leads to the sealing surfaces of the joint disclosed and transition to the contactless mode. Seals with V-shaped grooves are designed for one-way rotation.
U-shaped grooves on the sliding surface act on the same principle as V-shaped, with the important difference that the seal can be rotated in any direction.
Even at the minimum speed of rotation in the sealing gap occurs stable gas film, which prevents the contact between sliding surfaces and provides a non-contact and wear-free movement, and the power consumption is minimal and it is approximately 95% smaller than for liquid lubricated seals.
For lubrication and cooling multi-seal does not require expensive installations supplying sealing liquid. Barrier gas pressure exceeding the pressure of the product to about 5-10%, prevents leakage of working fluid. A small gap height (about 3 micron) between sliding surfaces of the closure to minimize gas consumption, which largely depends on the pressure, rotational speed and the diameter of the seal.
Gas supply systems
Gas supply systems are specially designed for gas lubricated mechanical seals, running in non-contact mode. The gas stream (e.g. air or nitrogen) coming from the supply line into the seal, is controlled or regulated by the system in accordance with the specified parameters. According to the rules of safety in the gas supply system provided flow alarms and emergency shutdown. At the user's request can be installed a centralized control system. In principle, this system is designed for each individual case, taking into account the respective operating conditions. This applies in particular to the gas supply system for the operation of the seals in the compressors.
Functions in the gas supply system seal:
- filtering gate and purge gas;
- control and pressure regulation;
- gas flow control;
- control and removal of leaks;
- supply gas to the double gate seals;
- purge gas single seals;
- gas at a tandem arrangement.