Valve body and valve cover leakage :
1.High quality cast iron castings, valve body and valve cover blisters, loose organization, slag and other defects on the body
2.Cold cracking;
3.Bad welding, there is a slag, not welded, stress crack and other defects
4.Cast iron valve damage after heavy impact
Fill in the leakage (external leakage of the valve, the proportion of filler accounted for the largest:
1.Filler selection is wrong, the media is not resistant to corrosion, the valve is not resistant to high pressure or vacuum, high temperature or low temperature;
2.Filler installed wrong, there is a small generation of big, bad spiral coil connector, under the tight loose defects;
3.Filler over the use of the period, has been aging, loss of elasticity
4.Valve stem is not high, there are bending, corrosion, wear and other defects
5.Less than of the number of no compression gland packing ring;
6.Damaged gland, bolts, and other components, so no compression gland;
7.Improper operation, excessive force, etc.;
8.Gland skew, gap between the gland and the stem is too small or too large, resulting in stem wear, packing damage.
Leakage of sealing surface :
1.Sealing surface grinding uneven, can not form a close line;
2.The stem and the closure of the connection between the top of the heart is left hanging, not right or wear;
3.Stem bending or assembly is not, so that the closure of a skew or not;
4.Sealing surface material quality selection is improper or not according to the working conditions of the selection valve
Leakage at the junction of the sealing ring :
1.Seal ring rolling is not strict
2.Sealing ring and body welding, welding quality is poor;
3.Sealing ring connection screw, screw, pressure ring loose;
4.Sealing ring connection and corrosion
Off pieces off to produce leakage :
1.Poor operation, the closure member stuck on dead center or more, damage to fracture junction;
2.Pieces of connection is not firmly closed, slack off;
3.Choose the material of the connection piece is wrong, can not afford the media of corrosion and mechanical wear
