The cause of valve leakage

1, valve leakage, the valve stem length discomfort: valve leakage, gas regulator valve stem is too long and close the valve stem is too short, upward or downward from the stem is not enough, cause there is space between valve core and valve seat, not fully contact, causing the closed lax internal leakage. The solution is to shorten, Or longer) Regulating valve stem the stem length appropriate, so that it is no longer leak. 2, packing leakage: after packing into the stuffing box, the gland axial pressure on it. As a result of the packing shape, make its produce radial force, and closely contact with the valve stem, but the contact is not very uniform. Some parts of the contact tightly, some parts loose contact, even some parts not exposed to; Regulating valve in use process, there is relative motion between stem and packing, with high temperature, high pressure and the influence of the porous medium, the regulating valve stuffing box is prone to leaking. Countermeasures: (1) To make packing easy loading, at the top of the stuffing box chamfer, in the stuffing box placed at the bottom of the erosion resistance of gap smaller metal protection ring, in order to prevent the packing launched by medium pressure. 2) Each part of the stuffing box and packing contact part of the metal surface to finish machining, in order to improve the surface finish, reduce packing friction. 3) Flexible graphite packing is chosen, because of its good air tightness, friction small, use for a long time after change small, wear loss is small, easy maintenance, etc. Through the above points can guarantee the reliability of the packing seal and long-term. Deformation of 3, regulating valve, valve core, valve seat leakage. The main reason is because the regulator the strengthening of the casting defects in the process of production can lead to corrosion, and corrosion medium, fluid scouring can also cause a regulating valve leakage. Mainly in the form of the erosion and cavitation corrosion. When the corrosive medium by the regulator, will be on the valve core seat erosion, lead to deformation of valve core, valve seat or gap. Solution: the key to good seat valve core material selection, quality, can take charge of butt welding too alloy, strengthens the sealing surface hardness. 4, because of the impurity in the medium or new pipeline welding slag cut control valve sealing surface, the cause of leakage.