Pneumatic valve and pneumatic valve cover common leakage fault

. Cast iron casting quality is not high, pneumatic valve body and valve cover on the body has the defects such as sand holes, loose organization, slag
. Days freezing crack;
　　. Bad welding, there is a slag, no welding, stress crack defects such as
. Cast iron pneumatic valves are heavy impact damage after the leakage of
filler ( The packing place of pneumatic valve leakage, accounted for the proportion of largest) Choose wrong packing, no resistance to corrosion medium, not resistant to high pressure or vacuum pneumatic valve, the use of high and low temperatures; Packing installation is wrong, exist in small generation, spiral wound under joint, to tighten the loose defects such as; Insufficient packing laps, gland not compaction; Gland, bolts, and other components damaged, make gland cannot compress; Improper operation, too hard, etc. ; Gland askew, and pneumatic valve rod between the gap is too small or too large, the pneumatic valve stem wear and damage of packing leakage

seal face, sealing surface grinding, cannot form a closed line;
, pneumatic valve stem and shut down a joint centers are suspended, incorrect or wear;
, pneumatic valve rod bending or assembly is not straight, make close a skewed or do not meet;
, sealing surface material selection of quality or not according to the working condition of pneumatic valve
leakage of sealing ring linked area
, sealing ring rolling is lax
, sealing and welding of ontology, welding quality is poor;