No.1 Leakage of Seal Face
● Reasons:
The top center of the valve stem is hanging, improper or worn at the joint of the valve stem and the closing piece;
Sealing surface material quality selection is not appropriate or not according to the operating conditions of valve selection.
Stem bending or assembly is not correct so that the closure of skew or misfit;
The Seal surface is abraded unevenly, can not form the close-fitting line;
● Maintenance methods:
According to the working condition, the gasket material and type should be selected correctly
The bolts should be evenly and symmetrically screwed. Torque wrenches should be used when necessary. The pre-tightening force should meet the requirements and not be too large or too small. The flange and the thread connection place should have certain pre-tight clearance;
Gasket Assembly should meet the right, the force is uniform, the gasket is not allowed to lap and use double gasket;
Static sealing surface corrosion, damage processing, processing quality is not high, should be repaired, grinding, coloring inspection, so that static sealing surface meet the relevant requirements;
Installation gasket should pay attention to cleaning, sealing surface should be used kerosene clean, gasket should not fall to the ground.
No. 2 Leakage Due To Break Off Of Closure Piece
● Reasons:
The operation is not good so that the closing piece is stuck or over the dead point, and the joint is damaged and broken;
The material of the connector is not right, it can not stand the corrosion of the medium and the wear of the machine.
The connection of the closing part is not firm, and it falls off because of loosing strength
● Maintenance methods:
The correct operation, close the valve can not force too large, open the valve cannot exceed the dead point, the valve open, the handwheel should be reversed a little;
The closing piece and the valve stem connection should be solid, the thread connection place should have the check back piece;
The fastener connecting the closure to the valve stem shall be resistant to media corrosion and shall have a certain mechanical strength and wear resistance.
No.3 Leak at Seal Ring Joint
● Reasons:
Seal Ring Rolling is not strict;
Seal ring connection thread, screw, pressure ring lose;
The sealing ring is connected and corroded.
Sealing ring and body welding, build-up welding quality is poor;
● Maintenance methods:
Sealing and rolling place leakage should be injection adhesive and then rolling fixed;
The sealing ring should be rewelded according to the welding specification. The original build-up welding and processing should be removed when the build-up welding place can not be repaired
Remove the screw, ring cleaning, replacement of damaged parts, grinding seal and connecting seat sealing surface, re-assembly. For the parts with large corrosion damage, it can be repaired by welding, bonding, etc.
Seal ring joint surface corrosion, available grinding, bonding and other methods to repair, cannot be repaired by replacing the seal ring.
No. 4 Body and Bonnet Leakage
● Reasons:
The cast iron casting quality is not high, the valve body and the valve cover body have the sand hole, the loose organization, the inclusion slag and so on flaw;
Days cold cracking;
The cast iron valve was damaged by the heavy impact.
Poor welding, there are slag inclusion, not welding, Stress Crack and other defects;
● Maintenance methods:
Improve casting quality, carry out strength test strictly according to regulation before installation;
On the temperature of 0 and below the valve, should be thermal insulation or mixing heat, stop the use of the valve should be excluded water;
The welds of Valve Body and valve cover made up of welding shall be carried out according to the relevant welding operation regulations, and after welding, flaw detection and strength test shall be carried out;
It is not allowed to push and put heavy objects on the valve, it is not allowed to hit the cast iron and non-metal valve with hand hammer, the installation of large diameter valve should have bracket.
Specific Treatment of Valve Body leakage:
● Bonding method
By using the fast curing speed of adhesive, a new solid sealing structure is formed by coating adhesive around the pin in time to stop leakage. It is to use the special function of the adhesive to plug the leak with pressure.
For the pressure medium and leakage of small sand hole location, can first leak point near the polished metal luster, and then use taper pin to leak point, the appropriate force into.
During operation, the jacking mechanism is fixed on one side of the regulating valve, and the high-speed jacking screw is used to make the axial direction of the jacking screw face the leakage point, and the jacking screw is rotated to press firmly on the leakage position by using the rivet at the end of the Jacking Screw To Stop the leak.
● Welding method
A) in the body of the leakage medium pressure is low, small leakage can use an inside diameter than the leakage point more than double nuts, let the leakage medium from the nut flow, nuts welded to the body, with a nut with the same specification of bolts, nuts placed on the bottom of a rubber pad or Asbestos Pad, bolts around the top of the raw tape screwed into the nut to prevent leakage purposes.
For leakage medium pressure is high, large leakage of the valve body can be used drainage welding method. First of all, a piece of iron plate with a circular hole in the middle, the diameter of a hole with a suitable diameter of the isolation valve welded to the circular hole in the Iron Plate, open the isolation valve, the central hole of the iron plate to the leakage point in the valve body, let the leakage media through the Iron Plate central hole and the isolation valve flow.
B) in the body of the leakage medium-high temperature and high pressure, but the control valve has a larger size, leakage is not the big case can also be used welding method.
First of all, directly on the valve body and leak-related gaps are welded to death (not welding leak point) , and then with a section in line with the operating conditions (working temperature, pressure) depending on the length of the field (generally about 200 mm) , its diameter should be greater than the leak point, weld a regulating valve suitable for the pipe to one end of the pipe and open the regulating valve completely. Then weld the other end of the pipe to the leaking spot. Close the regulating valve to stop the leakage.
If the joint is not good, can be placed in the joint of Rubber or Asbestos Pad, and then the iron plate near the body welded, and then closed isolation valve can achieve the goal of re-sealing.
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Post time: Jul-28-2021