What are the characteristics of ball valve damage?

When a ball valve is damaged, it usually shows the following characteristics, which can be judged by visual inspection, operation test, sealing verification and other methods. The specific damage characteristics are as follows:

1. External visible damage

Cracks or corrosion of the valve body: cracks, sand holes, severe rust or perforation on the valve body surface (especially in high pressure or corrosive media environment).

Valve stem deformation or leakage: the valve stem is bent, worn or rusted on the surface, resulting in difficulty in operation. The valve stem packing (seal) continues to leak the medium (even if the packing gland is tightened, it cannot be solved).

Leakage at the connection: leakage at the flange or threaded connection (may be due to aging of the gasket, loose bolts or damage to the sealing surface).

2. Abnormal operation

The switch is stuck or cannot be turned: the resistance of the handwheel or handle is too large when operating, or even completely stuck (commonly seen when there are impurities, rust or medium crystallization between the valve ball and the valve seat). Electric/pneumatic ball valves are slow to move or the motor is overloaded.

Incomplete stroke: the valve cannot be fully opened or closed (such as rotating only part of the 90° angle). The limit device fails, resulting in over-rotation (may damage the valve ball or seal ring).

3. Seal failure (internal or external leakage)

Internal leakage (not tightly closed): After the valve is closed, the medium continues to flow out from the downstream (the valve ball and valve seat sealing surface are worn, scratched or impurities are stuck). Use soapy water or a leak detector to detect bubbles or pressure drops at the valve outlet.

External leakage: medium leaks from the connection between the valve body and the valve cover, the valve stem seal or the middle flange (floating ball valve). Jet-like leakage may occur under high pressure conditions.

4. Internal component damage (need to be disassembled for inspection)

Valve ball damage: surface scratches, pits or corrosion (affecting sealing). The connection between the valve ball and the valve stem is loose or falls off (causing the valve ball to be unable to rotate with the valve stem).

Aging of the valve seat seal: PTFE (polytetrafluoroethylene) or other soft sealing materials are cracked, deformed or chemically corroded. Wear or erosion of the metal valve seat sealing surface (common in high temperature and high pressure conditions).

Valve cavity fouling or blockage: particles and scale in the medium accumulate in the valve cavity, hindering the movement of the valve ball.

5. Damage under special working conditions

High temperature deformation: the valve ball or valve seat softens and deforms due to high temperature (beyond the rated temperature range of the valve).

Low temperature brittle cracking: in a deep cold environment, the brittleness of the material increases, causing the valve body or seal to crack.

Corrosion perforation: the medium is incompatible with the valve material (such as stress corrosion of chloride ions on stainless steel).

Quick judgment method

1. Manual test: try to open and close the valve, feel whether the resistance is uniform, and observe whether it can be completely opened and closed.

2. Leakage check: close the valve and observe whether there is still medium flowing downstream. Apply soapy water to the seal and check for bubbles.

3. Listen to the sound: whether there is abnormal friction or impact sound when the valve is actuated (such as loose valve ball).

Handling suggestions

Minor damage: clean the valve ball and valve seat, lubricate the valve stem, replace the packing or seal ring.

Serious damage: replace the valve ball, valve seat or the entire valve (such as large-scale damage to the sealing surface or cracks in the valve body).

Precautions: regular maintenance, selection of valves suitable for the media material, installation of filters (to prevent impurities).

Notes

Safe operation: Valves with pressure or high temperature should be depressurized and cooled before inspection.

Professional tools: Special tools should be used to disassemble high-pressure valves to avoid violent operation.

If the valve is used in a critical process (such as chemical industry, gas), it is recommended to perform pressure tests and sealing tests regularly, and record maintenance history.