The correct selection of sealing gaskets is the key to ensuring no leakage of equipment. For the same working condition, there are generally several kinds of gaskets to choose from. Gaskets must be selected reasonably according to the physical properties, pressure, temperature and equipment size of the medium, operating conditions, and the length of the continuous operation cycle, so as to maximize the strengths and avoid weaknesses, and give full play to the characteristics of various gaskets.
When choosing gaskets, the following factors should be fully considered:
(1) It has good elasticity and recovery, and can adapt to pressure changes and temperature fluctuations;
(2) It has appropriate softness and can fit well with the contact surface;
(3) Does not pollute the process medium;
(4) It has sufficient toughness without causing damage to the ring due to pressure and tightening force;
(5) No hardening at low temperature, small shrinkage;
(6) Good processing performance, convenient installation and pressing;
(7) The sealing surface is not bonded, and the disassembly is easy;
(8) The price is cheap and the service life is long.
In the use of gaskets, pressure and temperature are mutually restrictive. With the increase of temperature, after the equipment runs for a period of time, the gasket material will soften, creep, stress relaxation, and the mechanical strength will also decrease. The pressure of the seal is reduced. vice versa. For example, the manual lists the high-pressure asbestos rubber sheet XB450 in water and steam medium, with a temperature of 450°C and a pressure of <6MPa (when the material is tested for sealing performance, the pressure is maintained in steam at 440°C~450°C and 12MPa for 30 minutes) . But in long-term practical use, if the temperature reaches 450℃, the pressure that can be sealed is only 0.3~0.4MPa. For the gas medium with strong permeability, it is only 0.1~0.2MPa.
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