Damage to the steam valve seal is the main cause of internal leakage of the valve. There are many reasons for the failure of the valve seal, among which the failure of the sealing pair composed of the valve core and the seat is the main reason.
There are many reasons for the damage of valve sealing surface, including mechanical wear and high-speed erosion caused by incorrect selection, cavitation of media, various corrosion, jamming of impurities, selection of valve core and seat material and heat treatment process , deformation of the sealing pair caused by water hammer, etc. Electrochemical erosion, the contact of the sealing surfaces with each other, the contact between the sealing surface and the sealing body and the valve body, and the concentration difference of the medium, the oxygen concentration difference, etc., will generate a potential difference, electrochemical corrosion will occur, and the sealing surface on the anode side will be eroded. Chemical erosion of the medium, the medium near the sealing surface will directly act chemically with the sealing surface without generating current, eroding the sealing surface.
Erosion and cavitation of the medium, which is the result of wear, flushing and cavitation of the sealing surface when the medium is active. When the medium is at a certain speed, the floating fine particles in the medium collide with the sealing surface, causing local damage, and the high-speed moving medium directly washes the sealing surface, causing local damage. Impact the sealing surface, causing local damage. The erosion of the medium and the alternating action of chemical erosion will strongly erode the sealing surface. Damage caused by improper selection and poor manipulation. It is mainly manifested in that the valve is not selected according to the working conditions, and the shut-off valve is used as a throttle valve, which leads to excessive closing pressure and fast closing or poor closing, which causes the sealing surface to be eroded and worn.
The processing quality of the sealing surface is not good, mainly manifested in defects such as cracks, pores and ballast on the sealing surface, which are caused by improper selection of surfacing and heat treatment specifications and poor manipulation during surfacing and heat treatment, and the sealing surface is too hard. If it is too low, it is caused by the wrong material selection or improper heat treatment. The hardness of the sealing surface is uneven and it is not resistant to corrosion. of. Improper installation and poor maintenance lead to a lot of abnormal operation of the sealing surface, and the valve operates in a diseased manner, which prematurely damages the sealing surface. Sometimes brutal operation and excessive closing force are also the reasons for the failure of the sealing surface, but it is often not easy to find and judge.
The jam of impurities is a common problem, because the welding slag and excess gasket material that are not cleaned in the welding of steam pipes, and the scaling and falling off of the steam system are the root causes of impurities. If the 100 mesh steam filter is not installed in front of the control valve, it is very easy to damage the sealing surface caused by the jam. It can be seen that the reasons for the damage to the sealing surface can be summarized as man-made damage and application damage. Man-made damage is caused by factors such as poor design, poor manufacturing, improper material selection, improper installation, poor use and poor maintenance. Application damage is the wear and tear of the valve under normal working conditions, and it is the damage caused by the inevitable erosion and erosion of the sealing surface by the medium. Damage prevention can reduce losses and prolong service life. No matter what kind of damage, select the appropriate steam valve correctly, install, configure and debug in strict accordance with the installation manual. Regular maintenance is to prolong the life of the valve and reduce the leakage caused by damage to the sealing surface.
Post time: Oct-28-2022