Common quality problems of valves
1. The casting quality of iron castings is not high, and there are defects such as blisters, loose structure and slag inclusion on the valve body and the valve cover.
2. Day freeze cracking;
3. Poor welding, there are defects such as slag inclusion, non-welding, stress cracks, etc.
4. The cast iron valve is damaged after being hit by a heavy object
Leakage at the packing (external leakage of the valve, the proportion of the packing is the largest)
1. Wrong selection of packing, not resistant to medium corrosion, not resistant to valve high pressure or vacuum, high temperature or low temperature use
2. The packing is installed incorrectly, there are defects such as replacing the big with the small, the screw-wound joint is not good, and the tightening and loosening are present;
3. The filler has exceeded its service life, has aged and lost its elasticity
4. The valve stem is not high in precision, and has defects such as bending, corrosion, and abrasion.
5. The number of packing circles is insufficient, and the gland is not tightly pressed;
6. The gland, bolts, and other parts are damaged, making it impossible to compress the gland;
7. Improper operation, excessive force, etc.;
8. The gland is skewed, and the gap between the gland and the valve stem is too small or too large, causing the valve stem to wear and the packing to damage
Leakage of sealing surface
1. The sealing surface is unevenly ground and cannot form a tight line;
2. the top center of the connection between the valve stem and the closing part is suspended, incorrect or worn;
3. The valve stem is bent or improperly assembled, which makes the closing member skewed or misaligned;
4. The quality of the sealing surface material is not selected properly or the valve is not selected according to the working conditions
Leakage at the joint of the sealing ring
1. The sealing ring is not tightly rolled
2. The sealing ring is welded to the body, and the surfacing quality is poor;
3. the sealing ring connection thread, screw and pressure ring are loose;