1. The casting quality of iron castings is Check Valve  not high, and there are defects such as blisters, loose tissues, slag inclusions on the valve body and the valve cover;

2. Day freeze cracking;

3. Poor welding, there are defects such as slag inclusion, non-welding, stress cracks, etc.;

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

► Maintenance method:

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

2. Valves whose temperature is below 0° and 0° should be kept warm or mixed with heat, and the valves that are out of service should be drained of stagnant water;

3. The welding seam of the valve body and bonnet 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 and put heavy objects on the valve, and it is not allowed to hit the cast iron and non-metal valves with a hand hammer. The installation of large-diameter valves should have brackets.

► Specific treatment methods for valve body leakage:

1. Bonding method

Taking advantage of the fast curing speed of the adhesive, fill the vicinity of the pin with the adhesive in time to form a new solid sealing structure to achieve the purpose of preventing leakage. It is a method of using the special function of the adhesive to plug leaks under pressure.

For pressure medium and blisters with small leakage, you can first polish the vicinity of the leakage point to give a metallic luster, and then use a tapered pin to aim at the leakage point and drive in with appropriate strength.

During operation, fix the top pressure mechanism on the side of the regulating valve, press the screw at high speed, make the axial direction of the top pressure screw face the leakage point, rotate the top pressure screw, and use the rivet at the end of the top pressure screw to firmly press against the leak. On the site, forcing the leak to cease.

2. Welding method

A) When the leakage medium pressure of the valve body is low and the leakage is small, a nut with an inner diameter more than twice the leakage point can be used to let the leakage medium flow out of the nut, and the nut is welded to the valve body. Fit a bolt with the same specification as the nut, place a rubber pad or asbestos pad at the bottom of the nut, and screw the top of the bolt with raw tape into the nut to prevent leakage.

For the valve body with high leakage medium pressure and large leakage, drainage welding method can be used. First, use an iron plate with a round hole in the middle, weld an isolation valve with a diameter commensurate with the round hole on the round hole of the iron plate, open the isolation valve, and align the central hole of the iron plate with the leakage point and attach it to the valve body. Let the leakage medium flow out through the central hole of the iron plate and the isolation valve.

B) The leakage medium in the valve body is high temperature and high pressure, but the adjustment valve has a larger shape and size and the leakage is not large. Welding can also be used.

First, directly weld all the gaps related to the leakage point on the valve body (not welding the leakage point), and then use a length of pipe that meets the working conditions (working temperature, pressure) depending on the site environment (usually about 200mm) , Its diameter should be larger than the leakage point. Weld an adjusting valve that is compatible with the pipe to one end of the pipe, and fully open the adjustment valve, then take the other end of the pipe to the leakage point and weld it, and then close the adjustment valve to stop it. leakage.

If the bonding surface is not good, you can place rubber or asbestos pads on the bonding surface, then weld the iron plate to the valve body, and then close the isolation valve to achieve the purpose of resealing.