Valve stem breakage or deformation

Valve its pressure, temperature (high temperature), corrosion (a variety of materials, configuration), with two-way sealing function, resistance to wear and long life more and more widely used in various industrial systems to achieve the media on and off, for the system stability and control play an important role. valve stem break stem fracture generally occurs in the upper and lower thread roots, where the smallest cross-sectional area, and prone to excessive stress concentration phenomenon. Especially when the working conditions when a large deviation from the design parameters. If an electric power plant have been frequent DN150 valve stem is turned on at the ladder thread undercuts pull off the accident. The survey found that the valve nut tightening loose valve cover, valve cover shift, stem nut stuck, it is clearly Denso trip debugging bit to protect the accident caused by excessive torque. Another stem breakage occurred in the open moment. Performance of the gate is not out of the seat, or on the stem that is threaded under the root fracture. The reason is usually considered a gate stuck, this is actually part of the reason, or secondary causes.
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 An important reason is that after the closure of the valve body cavity abnormal boost, which is the valve closed, closed at the upstream and downstream sides of the sealing surface between the fluid pressure in the cavity is much higher than the pressure upstream of the phenomenon. There are two reasons for this phenomenon. One of the upstream fluid in the cavity fluid is heated warming swell, leading to severe pressure rise. The second gate closed off at the moment of the fluid chamber, unable to drain, in the stem cavity space is further squeezed, due to the compressibility of the liquid is very limited, the pressure will surge, this is especially likely to occur in plants The main water supply valve on the class Z962. At the same time, its unusual geometric step will generally increase, far exceeding the stem strength design limits.
valve stem stem bending deformation usually appears in the electric power valve was not installed debugging, such as closing torque is too big and has not established to protect or disorders such as stroke, the destruction of the valve is very large.