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Treatment of Valve Leakage(Part 1)

Jul. 03, 2020

Marine valve exporter shares with you.

Leakage of valve body and bonnet

the reason:

1. The casting quality of the cast iron parts is not high, and there are defects such as sand holes, loose structure and slag inclusion on the valve body and valve cover body;

2. Freeze cracking;

3. Poor welding, there are defects such as slag inclusion, unwelded, stress cracks;

4. The cast iron valve is damaged after being hit by a heavy object.

Maintenance method:

1. Improve the casting quality, and perform the strength test in strict accordance with the regulations before installation;

2. For valves with air temperature below 0℃ and below 0℃, heat preservation or heat mixing shall be carried out, and the valves which are out of service shall exclude accumulated water;

3. The welding seam of the valve body and valve cover composed of welding shall be carried out in accordance with the relevant welding operation regulations, and the flaw detection and strength test shall be carried out after welding;

4. It is forbidden to push or release heavy objects on the valve, and it is not allowed to hit the cast iron and non-metallic valves with a hammer. The installation of large-diameter valves should have a bracket.

Leakage at the packing

The leakage of the valve is the largest in the packing.

the reason:

1. Wrong choice of filler, not resistant to the corrosion of the medium, not resistant to the use of high pressure or vacuum, high temperature or low temperature of the valve;

2. The packing is not installed properly, and there are defects such as small-to-large, bad spiral coiled joints, loose tightening, etc.;

3. The filler exceeds the service period, has aged, and has lost its elasticity

4. The precision of the valve stem is not high, and there are defects such as bending, corrosion and wear;

5. The number of packing circles is insufficient, and the gland is not pressed tightly;

6. The gland, bolts, and other parts are damaged, so that the gland cannot be compressed;

7. Improper operation, excessive force, etc.;

8. The gland is skewed, and the gap between the gland and the stem is too small or too large, causing the stem to wear out and the packing to be damaged.

Self Contained Check Valves

Maintenance method:

1. The material and type of filler should be selected according to the working conditions;

2. Install the packing correctly according to the relevant regulations, the packing should be placed and tightened circle by circle, and the joint should be 30℃ or 45℃;

3. Packing that is too long, aging or damaged should be replaced in time;

4. The valve stem should be straightened and repaired after bending and wear, and it should be replaced in time for serious damage;

5. The packing should be installed according to the specified number of turns, the gland should be tightened symmetrically and evenly, and the pressure sleeve should have a pre-tightening gap of more than 5mm;

6. The damaged gland, bolt and other parts should be repaired or replaced in time;

7. Observe the operating regulations, except for the impact handwheel, operate with normal speed and normal force;

8. The gland bolts should be tightened evenly and symmetrically. The gap between the gland and the stem is too small, and the gap should be increased appropriately; the gap between the gland and the stem is too large and should be replaced.

The above information is provided by self contained check valves.


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