The five leakage problems of the valve can be easily solved

1、 Leakage of valve body and bonnet

reason:

1. The casting quality of iron castings is not high, and there are sand holes, loose structure, slag inclusion and other defects on the valve body and bonnet body;

2. Cold weather and frost crack;

3. Poor welding, slag inclusion, non welding, stress crack and other defects;

4. The cast iron valve was damaged after being hit by heavy objects.

Maintenance method:

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

2. Valves with air temperature of 0 ℃ and below shall be insulated or heated, and valves out of service shall be drained of ponding;

3. The welds of valve body and bonnet composed of welding shall be carried out according to relevant welding operation procedures, and flaw detection and strength test shall be carried out after welding;

4. It is forbidden to push or put heavy objects on the valve. It is not allowed to hit cast iron and non-metallic valves with a hammer. Large diameter valves shall be installed with supports.

2、 Leakage at packing

The packing accounts for the largest proportion of the external leakage of the valve.

reason:

1. The packing is not selected correctly, which is not resistant to medium corrosion, high pressure or vacuum, high temperature or low temperature of the valve;

2. The packing is not installed correctly, and there are defects such as replacing large with small, poor spiral winding joint, tightening and loosening;

3. The filler has expired, aged and lost elasticity;

4. The precision of the valve rod is not high, with defects such as bending, corrosion and wear;

5. The number of packing rings is insufficient and the gland is not compressed;

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

7. Improper operation, excessive force, etc;

8. The gland is skewed, and the gap between the gland and the valve rod is too small or too large, resulting in the wear of the valve rod and the damage of the packing.

Maintenance method:

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

2. The packing shall be installed correctly according to relevant regulations, the packing shall be placed and pressed one by one, and the joint shall be 30 ℃ or 45 ℃;

3. The filler with long service life, aging and damage shall be replaced in time;

4. The valve rod shall be straightened and repaired after bending and wear, and the seriously damaged valve rod shall be replaced in time;

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

6. Damaged gland, bolts and other parts shall be repaired or replaced in time;

7. The operating procedures shall be followed. Except for the impact handwheel, it shall be operated with constant speed and normal force;

8. The gland bolts shall be tightened evenly and symmetrically. If the clearance between the gland and the valve rod is too small, the clearance shall be appropriately increased; The clearance between gland and valve rod is too large and should be replaced.

3、 Leakage of sealing surface

reason:

1. The sealing surface is unevenly ground and cannot form a sealing line;

2. The top center of the connection between the valve stem and the closing part is suspended, incorrect or worn;

3. The valve rod is bent or improperly assembled, so that the closing part is skewed or out of alignment;

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

Maintenance method:

1. Correctly select the material and type of bump gasket according to the working conditions;

2. Careful adjustment and stable operation;

3. The bolts shall be tightened evenly and symmetrically. If necessary, a torque wrench shall be used. The preload shall meet the requirements and shall not be too large or small. There shall be a certain pre tightening clearance at the flange and threaded connection;

4. The gasket assembly shall be aligned and stressed evenly. Overlapping and double gaskets are not allowed;

5. If the static sealing surface is corroded, damaged and the processing quality is not high, it shall be repaired, grinded and checked for coloring to make the static sealing surface meet the relevant requirements;

6. Pay attention to cleaning when installing the gasket. The sealing surface shall be cleaned with kerosene, and the gasket shall not fall to the ground.

4、 Leakage at seal ring connection

reason:

1. The sealing ring is not rolled tightly;

2. The sealing ring is welded with the body, and the surfacing quality is poor;

3. The connecting thread, screw and pressure ring of the sealing ring are loose;

4. Corrosion of sealing ring connection

Maintenance method:

1. The leakage at the sealing rolling position shall be filled with adhesive and then rolled and fixed;

2. The sealing ring shall be re welded according to the welding specification. If repair welding is not possible at the surfacing position, the original surfacing and processing shall be removed;

3. Remove the screw and pressure ring, clean, replace the damaged parts, grind the sealing surface between the seal and the connecting seat, and reassemble. The parts with large corrosion damage can be repaired by welding, bonding and other methods;

4. If the connecting surface of the sealing ring is corroded, it can be repaired by grinding, bonding and other methods. If it cannot be repaired, replace the sealing ring.

5、 Leakage due to falling off of closing parts

reason:

1. The closing part is stuck or exceeds the top dead center due to poor operation, and the connection is damaged and broken;

2. The closing parts are not firmly connected, loose and fall off;

3. The material of the selected connector is incorrect and can not withstand medium corrosion and mechanical wear.

Maintenance method:

1. Operate correctly. Do not use excessive force to close the valve, and do not open the valve beyond the top dead center. After the valve is fully opened, the handwheel should be reversed a little;

2. The connection between the closing part and the valve rod shall be firm, and the threaded connection shall have a non-return part;

3. The fasteners used for connecting the closing part and the valve rod shall withstand the corrosion of the medium and have certain mechanical strength and wear resistance.

11 --- material list of electric stop valve parts in pound power station

Structural characteristics of electric stop valve in pound power station

1. Low fluid resistance. The medium channel inside the valve body of the gate valve is straight through, and the medium flows through the channel. When the medium flows through the gate valve, it does not change the direction, so the flow resistance is small.

2. The opening and closing is labor-saving. When opening and closing, the ram is transported vertically, so it is labor-saving.

3. The medium flow direction is generally unrestricted. The medium can flow through the gate valve in any direction, which can achieve the purpose of connection or disconnection.

4. The end connection adopts welding, which is used in occasions with high sealing requirements.

5. The valve body and bonnet are connected by self sealing, with good sealing performance.

6. The ends are connected by butt welding and sealed reliably.

Technical parameters of electric stop valve in pound power station

Nominal pressure: 900lb ~ 1500Lb;

Caliber range: 4 "~ 16";

Applicable temperature: - 29-540 ℃;

Applicable media: water, gas, oil, etc;

Driving form: electric device.

Technical standard for electric stop valve of pound power station

1. Design and manufacture: ASME. 16.34;

2. Structure length: ASME B16.10;

3. Connecting flange: ASME B16.5;

4. Pressure and temperature: ASME B16.34;

5. Inspection and test: API 598.