Reasons for Valve Sealing Surface Damage

Seals play a crucial role in valve passages, performing functions such as cutting off and connecting, regulating and distributing, separating and mixing media. Consequently, the sealing surfaces are frequently subjected to corrosion, erosion, and wear from the media, making them prone to damage.

Seal face damage is caused by two types: human-induced and natural damage. Human-induced damage is a result of poor design, inadequate manufacturing, improper material selection, incorrect installation, poor usage, and insufficient maintenance.

Natural damage refers to wear that occurs under the normal working conditions of the smoke door, caused by the inevitable corrosion and erosion of the medium on the sealing surface.

Reasons for the damage to the sealing surface can be summarized into the following categories:

 Poor quality of sealing surface processingDefects on the sealing surface, such as patterned grooves, air holes, and solid inclusions, are due to improper stacking and heat treatment machine washing, as well as incomplete operation during the stacking and heat treatment process.

Over-hardening of the sealing surface is caused by incorrect material selection or improper heat treatment, resulting in uneven hardness of the surface, poor corrosion resistance. This is primarily due to the bottom metal being blown onto the surface during the surfacing process.

The dilution of the alloy composition in the sealing surface is the cause. Of course, there are also design issues involved.

Improper selection and poor operation resulting in damage:Primarily, it is manifested in not selecting valves according to working conditions, using shut-off valves as throttle valves, which leads to excessive closing pressure, rapid closure, or incomplete closure.

Erosion and wear on the sealing surface occur. Incorrect installation and inadequate maintenance lead to abnormal operation of the sealing surface, causing the valve to run with defects and prematurely damage the sealing surface.

3. Chemical Corrosion of the MediumMedia surrounding the sealing surface directly chemically reacts with the sealing surface without generating an electric current, leading to corrosion of the sealing surface. Electrochemical corrosion occurs when sealing surfaces come into contact with each other,

Due to factors such as contact between the sealing surface and the closure body, as well as the concentration difference of the medium and oxygen concentration, potential differences are generated, leading to electrochemical corrosion. This results in the corrosion of the sealing surface on the anode side.

4. Erosion of the medium:It is the result of wear on the sealing surface due to medium flow, impingement, and air velocity. At certain speeds, fine particles in the medium collide with the sealing surface, causing localized damage.

Direct flushing of the sealing surface by high-speed medium leads to local damage. During mixing and partial vaporization of the medium, bubbles burst against the surface, causing local damage. The combined action of erosion from the medium and alternating chemical corrosion contributes to the damage.

Severe immersion sealing.

 5. Mechanical Damage:Sealing surfaces can sustain damage such as wear, scratch, and tear during opening and closing. Between the two sealing surfaces, under the influence of high temperature and pressure, atomic bonding and penetration occur, leading to adhesion phenomena.

As the two valve covers move past each other, the adhesive layer tends to pull away. The higher the surface contact between the covers, the more likely this phenomenon is to occur. During the closing process of the valve, the valve disc may be damaged and crushed against the sealing surface during the return-to-seat process.

Locally wear the sealing surface or cause indentation.

6. Fatigue DamageSeals may experience fatigue on their sealing surfaces over time, particularly under the influence of alternating loads, leading to cracks and delamination. Rubber and plastic materials tend to age more easily with prolonged use.

The analysis of the above causes of seal face damage shows that to improve the quality and service life of valve seal faces, it is essential to select appropriate seal face materials, reasonable seal structures, and processing methods.