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Causes of Internal Leakage of Large Diameter Globe Valve

Update:31-08-2018
Summary:

Large-diameter globe valves are generally used in boile […]

Large-diameter globe valves are generally used in boiler outlets, main sub-cylinders, steam mains, etc. These locations have the following problems:

1.The general pressure difference of the boiler outlet is relatively large, so the steam flow rate is also larger, and the erosion damage to the sealing surface is also greater. In addition, the boiler combustion efficiency cannot be 100%, which will cause the steam at the outlet of the boiler to have a large water content, which is easy to cause cavitation and cavitation damage to the valve sealing surface.

2.For the shut-off valve near the boiler outlet and the sub-cylinder, intermittent steam overheating occurs from the steam coming out of the boiler. In the process of saturation, if the boiler water softening treatment is not too good, some acid will be precipitated. Alkali substances can cause corrosion and erosion on the sealing surface; some crystallizable substances may also adhere to the sealing surface of the valve to crystallize, resulting in the valve not being tightly sealed.

3.The inlet and outlet valves of the cylinders are caused by the steam consumption after the valve due to the production requirements, etc., and the steam consumption is large and small. When the flow rate changes greatly, the phenomenon of flashing and cavitation is easy to occur. The sealing surface of the valve causes erosion, cavitation and other damage.

4.Generally, when the large diameter pipeline is opened, the pipeline needs to be preheated, and the preheating process generally requires a small flow of steam to pass through, so that the pipeline is slowly and evenly heated to a certain extent, then the shutoff valve can be completely opened to avoid the pipeline rapidity. The temperature rises to cause excessive expansion, which damages part of the joint. However, in this process, the opening degree of the valve is often very small, so that the erosion rate is far greater than the normal use effect, and the service life of the valve sealing surface is seriously reduced.

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