Easy solution to valve leak problem

Leakage of valve body and bonnet

The reason:

1, cast iron casting quality is not high, the valve body and valve cover body has trachoma, loose organization, slag and other defects;

2, days frozen crack;

3, poor welding, there are slag, welding, stress cracks and other defects;

4, cast iron valve is damaged after heavy impact.

Maintenance method:

1, improve casting quality, before installation in strict accordance with the provisions of the strength test;

2, the temperature in 0℃ and 0℃ below the valve, should be thermal insulation or heat, stop using the valve should remove water;

3. The weld of valve body and valve cover composed of welding should be carried out according to the relevant welding operation rules, and the flaw detection and strength test should also be carried out after welding;

4, the valve is prohibited to push heavy objects, not allowed to use a hammer to impact cast iron and non-metal valves, the installation of large caliber valves should be supported.

Two, the leakage of sealing surface

The reason:

1, the sealing surface grinding uneven, can not form a tight line;

2, valve stem and closing parts of the joint center hanging, straight or wear;

3, the valve stem bending or assembly is not correct, so that the closing parts skewed or not in the middle;

4. Improper selection of sealing surface material quality or valve selection according to working conditions.

Maintenance method:

1, according to the working conditions of the correct selection of the material and type of the bump gasket;

2, carefully adjust, smooth operation;

3, bolts should be evenly and symmetrically screwed, torque wrench should be used when necessary, pretightening force should meet the requirements, not too large or small. Flange and thread joints should have a certain preload clearance;

4, gasket assembly should meet the center alignment, uniform force, gasket is not allowed to lap and use double gasket;

5, static sealing surface corrosion, damage processing, processing quality is not high, should be repaired, grinding, coloring inspection, make the static sealing surface meet the relevant requirements;

6, when installing gaskets, pay attention to cleaning, sealing surface should be clear with kerosene, gaskets should not fall to the ground.

Three, the leakage of filler

Valve leakage, the proportion of packing is larger.

The reason:

1, filler selection is not correct, not resistant to medium corrosion, not resistant to valve high pressure or vacuum, high temperature or low temperature use;

2, packing installation is not correct, there are small instead of large, spiral coiling joint is not good, tight under loose defects;

3, the filler exceeds the use period, has aging, loss of elasticity;

4, the valve stem accuracy is not high, bending, corrosion, wear and other defects;

5, the number of packing rings is insufficient, the gland is not pressed;

6, gland, bolts, and other parts damaged, so that the gland can not be pressed;

7, improper operation, excessive force, etc.;

8, the gland is skewed, the gap between the gland and the stem is too small or too large, resulting in stem wear, packing damage.