How to solve the regulator leakage problem?
Cast Iron Check Valve Supplier shares that regulating valves are the main type of actuators that change fluid flow through dynamic operation by receiving control signals from the regulating control unit. Control valves are generally composed of actuators and valves. If according to its matching actuator power, control valve can be divided into pneumatic, electric, hydraulic three. Below we say the control valve several common faults and solutions.
In the modern factory automation control system, the control valve, as the terminal actuator of the automatic control system, receives the control signal to realize the adjustment of chemical process. Its motion sensitivity is directly related to the quality of the regulating system. According to the actual statistics on the scene about 70% of the fault from the control valve. Therefore, the factors and countermeasures affecting the safe operation of control valve are summarized and analyzed in daily maintenance.
The following analysis of several common leakage fault phenomenon, put forward countermeasures.
Leaks in the valve
Uncomfortable stem length. Open valve, stem too long stem up (or down) distance is not enough, resulting in a gap between the valve core and the seat, not enough contact, resulting in lax closure and leakage. The same air off valve stem is too short, resulting in a gap between the valve core and the seat, not enough contact, resulting in lax closure and leakage.
Solutions:
Should shorten (or extend) the control valve stem to make the control valve length appropriate, so that it is no longer internal leakage.
Packing leakage
After the packing is loaded into the packing box, axial pressure is applied to it through the gland. The packing is plastic, causing radial force and close contact with the stem, but this contact is not very uniform. Some parts are loose, some parts are tight, and some parts are not touching at all. Control valve in the use of the process, there is a relative movement between the stem and packing, this movement is called axial movement. In the process of use High Temperature Ball Valves China, with the high temperature, high pressure and strong permeability of the fluid medium, the control valve packing box is also the location of leakage phenomenon more. The main cause of packing leakage is interfacial leakage, and there will be leakage for textile packing (pressure media leak outward along the tiny gap between packing fibers). The interface leakage between the stem and the packing is caused by the gradual attenuation of the contact pressure of the packing, the packing itself aging and other reasons, at this time the pressure medium will leak outward along the contact gap between the packing and the stem.
Solutions:
In order to facilitate packing loading, a metal protective ring with small erosion resistance clearance is placed at the bottom of packing box to prevent packing from being pushed out by medium pressure. Stuffing box each part and the packing contact part of the metal surface to finish processing, in order to improve the surface finish, reduce the packing wear. Flexible graphite packing is chosen, because of its good air tightness, friction small, use for a long time after the change is small, the wear loss is small, easy maintenance, gland bolts to tighten, do't change after the friction pressure resistance and heat resistance, good internal media, contact with the valve stem and gland internal metal corrosion pitting or not. In this way, effectively protect the valve stem packing box seal, and ensure the reliability and long-term packing seal.
Spool, valve seat deformation leakage
The main cause of spool and seat leakage is the strengthening of corrosion caused by casting or forging defects in the production of control valves. And corrosive medium through, fluid medium erosion can also cause the leakage of the control valve. Corrosion mainly exists in the form of erosion or cavitation. When the corrosive medium through the control valve, it will produce erosion and impact on the valve core, valve seat material into an oval or other shape, as time goes by, leading to the valve core, valve seat is not matched, there is a gap, close lax leakage.
Solutions:
The key to the valve core, valve seat material selection, quality. Choose corrosion - resistant materials, pitting point, trachoma and other defects of the product resolutely removed. If the valve core, valve seat deformation is not too serious, can be ground by fine sandpaper, eliminate traces, improve the sealing smoothness, in order to improve the sealing performance. If the damage is serious, it should be replaced with a new valve.