Regulator valve common fault solution

1, jam blocking valve often appears the problem is stuck, often appear in the new commissioning system and major repair and commissioning of the initial period, due to the welding slag, rust, etc. in the pipeline caused by the throttling mouth, leading to blocked media flow, Or over-tightening of the filler in the overhaul of the regulating valve, resulting in increased friction, resulting in a phenomenon that the small signal does not move and the large signal moves too much.

Solution: You can quickly open or close the secondary line or control valve so that dirt can be washed away from the secondary line or ball valve. Another method uses a pipe wrench to clamp the valve stem. When signal pressure is applied, the valve stem is forced to rotate forward and backward so that the spool flashes past the card. If not, increase the air pressure and increase the drive power by moving it up and down several times to solve the problem. If it still does not work, it needs to be disassembled.

2. Leakage 2.1 The valve leaks, and the length of the valve stem does not apply. Air opening valve, too long valve rod stem up (or down) distance, resulting in a gap between the valve plug and the butterfly valve seat, can not fully contact, resulting in lax and internal leakage. Also, the air valve stem is too short, resulting in a gap between the valve plug and the valve seat that cannot be fully contacted, resulting in lax shut-off and internal leakage.

Solution: The valve stem should be shortened (or lengthened) so that the length of the regulator valve is appropriate so that it is no longer leaking.

2.2 Leakage of packing. After the packing is installed in the stuffing box, axial pressure is applied to it by the glands. Due to the plasticity of the packing, it generates a radial force and is in close contact with the valve stem, but this contact is not very uniform. Some parts of the loose contact, some parts of the contact tight, and even some parts do not have contact. During the use of the gate valve, there is relative motion between the valve stem and the packing. This movement is called axial movement. In the process of use, with the influence of high temperature, high pressure and strong fluid medium, the valve packing box is also the site where more leakage occurs. The main cause of the leakage of the filler is the interface leakage, and leakage occurs to the textile filler (the pressure medium leaks outward along the tiny gap between the filler fibers). The interface leakage between the valve stem and the packing is caused by the gradual attenuation of the packing contact pressure and the aging of the packing itself. At this time, the pressure medium leaks outward along the contact gap between the packing and the valve stem.

Solution: In order to make the packing easy to install, chamfer at the top of the stuffing box, and place a metal ring with less erosion resistance at the bottom of the stuffing box (the contact surface between the stop valve and the packing cannot be beveled) to prevent the packing from being filled. The media pressure is pushed out. The metal surfaces of the parts of the stuffing box that are in contact with the filler must be finished to improve the surface finish and reduce filler wear. Filler is made of flexible graphite, because of its good airtightness, low friction, small changes after long-term use, small wear and tear on the wear, easy maintenance, no change in friction force after re-tightening gland bolts, pressure resistance and heat resistance Good, free from internal media, no pitting or corrosion of the metal in contact with the stem and stuffing box. In this way, the seal of the pressure-relief valve stem packing box is effectively protected, ensuring the reliability and long-term stability of the packing seal.

2.3 Spool, seat deformation leakage. The main reason for the leakage of cores and seats is due to the strengthening of corrosion due to casting or forging defects in the production of regulating valves. The passage of corrosive medium, the flushing of the fluid medium can also cause leakage of the regulating valve. Corrosion mainly occurs in the form of erosion or cavitation. When the corrosive medium passes through the regulating valve, erosion and impact on the valve core and the seat material are caused, so that the valve plug and the valve seat of the marine valve are formed into an elliptical shape or other shapes. Over time, the valve core and the valve are caused. The seat is not matched, there is a gap, and leaks do not occur.

Solution: The key to a good valve plug, valve seat material selection, quality off. Choose corrosion-resistant materials and strongly reject defective products such as pits and trachoma. If the valve core and the valve seat are not deformed seriously, they can be ground with fine sandpaper to eliminate the marks and improve the sealing finish to improve the sealing performance. If the damage is serious, the new valve should be replaced.