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Double-type Safety Valve-regulating Valve In Fire Protection In Chemical Enterprises
Dec 20, 2018

Double-type safety valve-regulating valve in fire protection in chemical enterprises

Valve leakage: Under the normal working pressure of the equipment, leakage occurs above the allowable degree at the sealing surface of the valve disc and the seat. The leakage of the regulating valve will not only cause media loss. In addition, the continuous leakage of the medium will also damage the hard sealing material. However, the sealing surface of the commonly used regulating valve is metal material to metal material. Although it is required to be smooth and flat, it should be done under the condition of medium pressure. It is also very difficult to never miss. Therefore, for a regulating valve that is a flammable or flammable medium, if a professional test tool is used at a specified pressure value, if the specification is permitted, the sealing performance is considered to be acceptable. There are three main reasons for the leakage of the valve:

First, the debris falls on the sealing surface, and the sealing surface is padded, causing a gap between the valve core and the valve seat, so that the valve leaks. The way to eliminate this kind of fault is to remove the debris falling on the sealing surface. Generally, when the pressure vessel is ready for maintenance, the pressure vessel safety door running test is first performed. When the leak is found, the pressure vessel is stopped and the valve is inspected. The sealing surface is flushed.

The second is damage to the sealing surface. The main reasons for the damage of the sealing surface are as follows: First, the sealing surface material is poor. Due to years of use, the sealing surface of the valve plug and the valve seat has been generally studied very low, so that the hardness of the sealing surface is also greatly reduced, resulting in a decrease in sealing performance. The best way to eliminate this phenomenon is to turn the original sealing surface. Continue, and then re-weld according to the drawings to improve the surface hardness of the sealing surface. Note that the processing quality must be guaranteed during the processing. For example, cracks, trachoma and other defects on the sealing surface must be turned and reworked. Newly processed spool seats must meet the drawing requirements. Second, the quality of the inspection is poor, and the valve seat is not up to the quality standard. The method to eliminate the failure is to repair the sealing surface or reinstall the new regulating valve according to the degree of damage by grinding or turning.

Third, another cause of leakage of the regulating valve is due to improper assembly or improper size of the parts. During the assembly process, the valve seat is not completely aligned or the joint surface is transparent, or the sealing surface of the valve seat is too wide to seal. The elimination method is to check the size and uniformity of the matching clearance around the valve core, and ensure that the top hole of the valve core and the sealing surface are the same degree. Check the gap of each part, it is not allowed to lift the valve core, and the width of the sealing surface is appropriately reduced according to the drawing requirements to achieve effective sealing. .

Fourth, the valve core and valve seat are deformed and leaked. The main cause of leakage of the valve core and seat is the corrosion enhancement due to casting or forging defects in the production process of the regulating valve. The passage of the corrosive medium and the flushing of the fluid medium can also cause leakage of the regulating valve. Corrosion mainly exists in the form of erosion or cavitation. When the corrosive medium passes through the regulating valve, it will cause erosion and impact on the valve core and the valve seat material to make the valve core and the valve seat elliptical or other shapes. The passage of time causes the valve core and the valve seat to be unsupported, there is a gap, and the leakage is not tight. The key to the solution is to select the quality of the valve core and valve seat, and to close the quality. Choose corrosion-resistant materials and resolutely eliminate defects in products such as pitting and trachoma. If the valve core and the valve seat are not too deformed, they can be ground through fine sandpaper to eliminate the marks and improve the sealing finish to improve the sealing performance. If the damage is serious, replace the valve with a new one.