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How to Solve the Leakage Problem of Regulating Valves?

The external leakage of the regulating valves can be solved by pressing the packing or replacing the packing. For the working conditions that firmly need to eliminate the external leakage, the upper valve cover sealed by bellows can be used, which can basically solve the problem of external leakage. There are many reasons for the internal leakage of the regulating valves, which are described below.

Ⅰ. Internal leakage of regulating valves and improper length of valve rod

The reason for the internal leakage of the regulating valves is that the valve stem of the air on regulating valve is too long and the valve stem of the air off regulating valves are too short, resulting in insufficient upward or downward distance of the valve stem, and resulting in a gap between the valve core and the valve seat, which cannot be fully contacted, resulting in internal leakage due to lax closing. 

Solution: It is effective is to shorten or extend the regulating valves stem so that the length of the valve stem is appropriate and finally it will no longer leak.

Ⅱ. Packing leakage of regulating valves

After the packing is installed into the stuffing box, axial pressure is applied to it through the gland. Due to the shaping of the packing, it produces radial force and is in close contact with the valve stem, but this contact is not very uniform. Some parts are in tight contact, some parts are in loose contact, and even some parts are not in contact; During the use of the regulating valves, there is relative movement between the valve stem and the packing. With the influence of high temperature, high pressure and highly permeable medium, the stuffing box of the pressure regulating system is prone to leakage.

1. In order to make the packing easy to install, chamfer the top of the stuffing box, and place a metal protective ring with small erosion resistance gap at the bottom of the stuffing box to prevent the packing from being pushed out by the medium pressure.

2. The metal surface of each part of the stuffing box in contact with the stuffing shall be finished to improve the surface finish and reduce the friction of the stuffing.

3. Flexible graphite is selected as the filler used in the high quality valve, because it has the characteristics of good air tightness, small friction, small change after long-term use, small burning loss of wear and easy maintenance. The above points can ensure the reliability and long-term performance of the packing seal.

Ⅲ. The deformation of valve core and seat of the regulating valves

The main reason is that the casting defects in the production process of the control valve can lead to the strengthening of corrosion, and the passage of corrosive medium, the scouring of fluid medium can also cause the internal leakage of the control valve. Corrosion mainly exists in the form of erosion or cavitation. For example, valves used in sewage treatment plant will corrode. When the corrosive medium passes through the regulating valves, it will erode the valve core and valve seat, resulting in deformation or notch of the valve core and valve seat. 

Solution: The key is to control the selection and quality of valve core and valve seat materials. Stellite alloy can be butt welded to enhance the hardness of sealing surface.

Ⅳ. The impurities in the medium or the welding slag of the new pipeline scratch the sealing surface of the regulating valves

Solution: Worker should clean the new pipeline or install a filter in front of the regulating valves. In case of internal leakage, the regulating valves can be disassembled, the valve core and valve seat can be Regrind, and then assembled for use.

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