Needle Valve The sealing surface is damaged
As the needle valve seal on the channel plays a truncated and connected, adjust and distribution, separation and mixing media and other effects, so the sealing surface is often subject to the media corrosion, erosion, wear, easy to damage.
Needle valve seal surface damage is divided into two kinds of damage and natural damage. Man-made damage is due to poor design, manufacturing is not refined, improper selection, improper installation, poor use and poor maintenance and other factors caused. Natural damage is the normal work of the valve under the wear and tear, the media on the sealing surface is inevitable corrosion and erosion caused by damage.
The cause of damage to the sealing surface of the needle valve can be summarized as follows.
Sealing surface processing quality is not good, mainly in the sealing surface cracks, stomata and ballast and other defects, due to improper welding and heat treatment specifications improper selection and welding and heat treatment process caused by poor operation, the sealing surface hardness is too high or Too low, is due to improper selection or improper heat treatment caused by the uneven sealing surface hardness, intolerance, mainly due to the process of surfacing the bottom of the metal blowing to the above, dilute the sealing surface alloy composition caused. Of course, there is also a design problem.
Improper selection and damage caused by poor operation. Mainly in the absence of working conditions selected valve, the truncated valve when the throttle valve used to lead to close the pressure is too large and close too fast or closed lax, so that the sealing surface by erosion and wear.
Needle valve installation is not correct and poor maintenance caused the sealing surface is not working properly, the valve with disease operation, prematurely damaged the sealing surface.
The chemical corrosion of the medium, the sealing surface of the medium in the absence of current, the media directly with the sealing surface from the chemical effect, corrosion sealing surface.
Electrochemical corrosion, sealing surface contact with each other, the sealing surface and the closure of the body and the valve body contact and the media concentration difference, oxygen concentration and other reasons, will produce potential difference, the occurrence of electrochemical corrosion, resulting in the anode side of the sealing surface corrosion.
The erosion of the medium, it is the media flow on the sealing surface wear, erosion, cavitation results. The media at a certain speed, the medium of the planktonic particles hit the sealing surface, causing it to local damage, high-speed flow of the media directly flush the sealing surface, causing local damage, medium mixed flow and local vaporization, resulting in bubble blasting shock seal Surface surface, causing local damage. The erosion of the medium combined with chemical corrosion alternately, will be a strong erosion of the sealing surface.
Mechanical damage, sealing surface in the opening and closing we will produce scratches, bumps, crush and other damage. Between the two sealing surface, under the action of high temperature and high pressure atoms infiltration, resulting in adhesion phenomenon. When the two sealing surfaces move each other, the adhesive is easy to tear. The higher the surface roughness of the sealing surface, the more likely it is to occur. Needle valve in the closing process, the valve flap in the process of back to the bumps and crush the sealing surface, so that the sealing surface of local wear or indentation.