In recent years, with the continuous improvement of process parameters in petroleum, chemical, petrochemical, and other industrial sectors, the requirements for mechanical seals and their auxiliary measures operating in high-pressure, high-temperature, volatile, corrosive, and solid-containing media are also increasing. high.
High-temperature fluid mechanical seal In the mechanical seal, due to the continuous increase of the fluid temperature, the wear and corrosion of the seal will be accelerated, the sealing ring will be easily deformed, the rubber will be aged, and the joint ring will be loose, resulting in leakage. In petrochemical and oil refineries, medium and high-pressure hot water pumps and boiler feed pumps have gradually adopted the mechanical seal of the pump.
Mechanical seals for pumps used in special working conditions: The dynamic and static ring seats of the mechanical seal are made of titanium metal, with a small linear expansion coefficient, similar to tungsten carbide, and easy to fix dynamic and static rings. The PTFE V-shaped sealing ring is used to ensure the followability of the auxiliary sealing ring and the dynamic and static rings at the working temperature. The outlet liquid cooler is used, and the cooled high-pressure liquid is sent to the shaft seal box for flushing. Simple structure and self-flushing. Due to the use of a flushing liquid cooler, the auxiliary seal is guaranteed to be within the allowable working temperature range of PTFE, and the problem of the high-temperature auxiliary seal is solved.
In petrochemical and oil refining equipment, it is used as plasticizer carrier and oil for high-temperature media such as tower bottom heat transfer oil pump, heat carrier pump, oil slurry pump, residual oil pump, wax oil pump, asphalt pump, molten sulfur, hot oil, heat, etc. pulp. Chemical pumps also use the mechanical seal of the pump.
In the high-temperature oil pump, the mechanical seal problem of the low-pressure vacuum tower bottom thermal oil pump containing solid particles can be solved by using a hard seal pair. When the temperature exceeds 250℃, the welded metal bellows are used for mechanical seals. Sealing materials require heat treatment to maintain stability. Adequate cooling and rinsing are required with single-sided sealing. External barrier fluid is required to use double seals. In order to improve the service life of the auxiliary sealing ring, a cooling jacket is provided on the seal on the side in contact with the medium. The single spring rotary mechanical seal is adopted, the carbon graphite static ring is changed to tungsten carbide, and the sealing pair of tungsten carbide and tungsten carbide is used, and the effect is very good. This kind of seal adopts metal bellows mechanical seal instead of a spring and auxiliary sealing ring, which doubles as an elastic element and auxiliary sealing element, which solves the problem of auxiliary sealing at high temperature and ensures stable sealing operation. The bellows seal itself is a partially balanced seal with flushing fluid at low (negative) pressure. The bellows mechanical seal has the ability to withstand negative pressure and evacuation; under high pressure, the bellows mechanical seal can work normally within the pressure limit, so it has a wide range of applications. The steam back-cooling measure is used to preheat the machine before starting the machine, and it is cooled in normal time to reduce the sudden temperature change and temperature difference. At the same time, it can flush the sediment in the dynamic and static rings, flush the condensed water, and prevent fire when the leakage is serious. . The static structure can avoid heating of high-viscosity liquids due to high-speed stirring. Adopt bimetal bellows. It can maintain a low elastic constant and can withstand high pressure. At low pressure, the outer layer wears off, while the inner layer still functions. It adopts a double-layer metal bellows mechanical seal with good elasticity. When in use, care must be taken that the bellows mechanical seal will fail due to deposits or coking around the bellows due to changes in operating conditions. And the inner layer still works. Using double-layer metal bellows, good elasticity.
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