How to determine whether the sealing surface of the three eccentric butterfly valve needs to be replaced

To determine whether the sealing surface of the three-eccentric butterfly valve needs to be replaced, it can be evaluated from various aspects such as appearance, performance and operating condition. The following is the specific method:

Visual inspection

Wear condition: Check whether there are obvious wear marks on the sealing surface, such as scratches, grooves, peeling, etc. Especially often open and close butterfly valve, valve plate and valve seat contact parts prone to wear, when the wear depth exceeds a certain limit, affecting the sealing performance, you need to consider replacing the sealing surface.

Corrosion: Observe whether there are corrosion spots, rust or corrosion pits on the sealing surface. If the corrosion is serious, resulting in uneven sealing surface or material performance degradation, the sealing effect will be worse, and the sealing surface should be replaced at this time.

Deformation: Check whether the sealing surface has deformation, such as distortion, warping, etc. Sealing surface deformation can cause a tight fit between the valve plate and the valve seat, causing leakage. Once significant deformation is found, it usually needs to be replaced.

Crack condition: carefully check the sealing surface for cracks, and use magnifying glass or non-destructive testing equipment to assist inspection. Cracks will seriously damage the integrity of the sealing surface, so that the sealing performance loss, cracks generally need to be replaced in time.

Performance testing

Leakage test

Bubble method: close the butterfly valve, fill the side of the valve cavity with a certain pressure of gas, and then immerse the butterfly valve in water or smear soapy water in the part that may leak, and observe whether there are bubbles. If there is a bubble, the sealing surface is leaking, and the leakage reaches a certain level, it needs to be replaced.

Pressure drop method: in the pipeline system, the butterfly valve is closed and the pressure change before and after the valve is measured. If the pressure drops significantly within a certain period of time and exceeds the normal allowable range, it indicates that the sealing surface may leak and needs to be further checked to determine whether to replace it.

Flow method: For the system with flow monitoring, observe whether there is abnormal flow through the butterfly valve in the closed state. If there is a significant non-allowable leakage flow, the sealing surface sealing performance is poor and may need to be replaced.

Seal pressure test: Carry out the seal pressure test on the butterfly valve, gradually increase the pressure to the rated working pressure or even slightly higher than the rated pressure, and observe the sealing surface. If the sealing surface leaks or cannot withstand the specified pressure during the test, the sealing surface can not meet the working requirements and should be replaced.

Health assessment

Operating torque change: if the operating torque is significantly increased when the butterfly valve is operated, it may be that the friction between the sealing surface increases, which may be caused by the wear, deformation or foreign body stuck on the sealing surface. When the torque increases to affect the normal operation or exceeds the allowable range of the equipment design, the sealing surface needs to be checked and considered for replacement.

Abnormal sound: in the process of butterfly valve opening and closing, if you hear abnormal friction sound, impact sound or other abnormal sound, there may be problems with the sealing surface, such as loose parts, uneven wear, etc., you need to further check to determine whether you need to replace the sealing surface.

Media leakage: In the process of system operation, observe whether there is media leakage around the butterfly valve. Even minor leaks that persist and cannot be resolved by simple repairs may mean that the sealing surface is damaged and needs to be replaced.