Resilient seated gate valve manufactures’ valve pressure plugging technology
Resilient seated gate valve leakage often occurs on the packing, flange seal and valve body. Long-term valve leakage can cause erosion of the valve stem and flange sealing surface, and eventually the valve will be scrapped. In addition to the loss of medium and fluid, the power plant will consume Increase, cost rises, and economic benefits decline. If the medium fluid is toxic, flammable, explosive, corrosive, etc., it is prone to accidents such as poisoning, fire, explosion and other casualties, and accelerates the corrosion rate of plant equipment, shortens its service life, pollutes the surrounding environment, and destroys electricity Production harms people’s health. The existence of leakage is a serious threat to safety in production, increasing unplanned shutdown accidents. The following introduces some of the reasons for valve leakage, plugging methods, and valve repair and maintenance methods for reference.
Leakage and causes of valve packing
During the operation of the resilient seated gate valve, there is relative movement between the valve stem and the packing, which includes rotation and axial movement. As the number of switches increases, the number of relative movements also increases. There are also effects of temperature, pressure and the characteristics of the fluid medium. The valve packing is the most prone to leakage. It is caused by the gradual weakening of the contact pressure of the filler, the aging of the filler itself, and the loss of elasticity. At this time, the pressure medium will leak outward along the contact gap between the packing and the valve stem, which will blow away part of the packing and flush the valve stem out of the groove for a long time, thereby expanding the leakage.
The flange sealing of the resilient seated gate valve mainly relies on the pre-tightening force of the connecting bolts, and the gasket achieves sufficient sealing specific pressure to prevent the leakage of the sealed pressure fluid medium. There are many reasons for its leakage. The pressure of the gasket is insufficient, the roughness of the joint surface does not meet the requirements, gasket deformation and mechanical vibration, etc. will cause the sealing gasket and the flange joint surface to leak tightly. . In addition, deformation or elongation of bolts, aging of gaskets, drop in resilience, cracks, etc. will also cause leakage of flange surface due to loose sealing. There are also human factors that cannot be ignored in flange leakage, such as the offset of the sealing gasket, which makes the partial sealing pressure insufficient and excessive tightening force, exceeding the design limit of the sealing gasket, and uneven force or two methods in the flange tightening process Leakage is prone to occur due to the deviation of the center line of the orchid, causing false tightening.
Leakage of the valve body and its cause
The main leakage of the valve body is caused by casting or forging defects in the resilient seated gate valve production process, such as sand holes, pores, cracks, etc., and the erosion and cavitation of the fluid medium are also common factors that cause valve body leakage.
Principle of leak plugging under pressure
The principle of plugging under pressure is based on the sealing mechanism of solid sealing materials under dynamic conditions of liquid media. The method is to install special equipment at the leaking part, use the cavity formed between the sealed part and the special equipment, and use a special high-pressure glue injection tool to inject the sealant into the chamber, and fill the entire chamber space to make the sealant squeeze The force is balanced with the pressure of the leaking medium, and a new sealing structure is established to block the channels of the leaking pore and block the leakage of the medium.
Advantages of leak plugging under pressure
(1) There is no need to shut down or isolate the system.
(2) There is no need to depressurize the system.
(3) Save a lot of energy and manpower.
(4) Greatly reduce the power loss caused by equipment isolation or shutdown.
(5) Reduced social and economic losses.
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