What causes a single seat pneumatic valve to leak?

The leakage of the single seat pneumatic control valve can be solved by compressing the packing or replacing the packing. For the case that the leakage must be strictly prevented, the upper valve cover of the bellows seal can be used, so that the problem of leakage can be basically solved. The internal leakage of the valve, the reason is more, first described as follows:

1, the valve leak, the length of the stem does not fit: the reasons for the valve leakage, air-seat single-seat pneumatic valve stem is too long and the gas valve seat single pneumatic valve stem too short, resulting in the valve stem up or down distance Insufficient, resulting in a gap between the valve plug and the valve seat, can not fully contact, resulting in lax and internal leakage. The solution is to shorten (or extend) the stem of the single-seat pneumatic regulator so that the length of the stem is appropriate so that it is no longer leaking.

2. Packing Leakage: After the packing is installed in the stuffing box, axial pressure is applied to the plug. Due to the shaping of the filler, it generates a radial force and is in close contact with the valve stem, but this contact is not very uniform. Some parts are in tight contact, some parts are loose in contact, and some parts are not in contact; in the use of a single seat pneumatic control valve, there is relative movement between the stem and the filler, with high temperature, high pressure and permeability. The influence of the medium, single-seat pneumatic valve packing box is prone to leakage. Solution: 1) In order to facilitate the packing, insert a chamfer at the top of the stuffing box and place a metal ring with a small erosion-resistant gap at the bottom of the packing box to prevent the packing from being pushed out by the medium pressure. 2) The metal surfaces of the parts of the stuffing box that are in contact with the filler must be finished to improve surface finish and reduce filler friction. 3) Filler is made of flexible graphite because of its good air-tightness, low friction, small change after long-term use, low wear and tear, and easy maintenance. Through the above points, the reliability and long-term stability of the packing seal can be ensured.

3, single-seat pneumatic valve spool, valve seat leakage. The main reason is that due to the casting defects in the production process of a single seat pneumatic valve, the corrosion can be strengthened, and the passage of corrosive medium and the flushing of the fluid medium can also cause the inner leakage of the single seat pneumatic control valve. Corrosion is mainly in the form of erosion or cavitation. When the corrosive medium passes through the single-seat pneumatic control valve, it will erode the valve seat seat, resulting in deformation of the valve plug and valve seat or a notch. Solution: The key to a good valve seat material selection, quality, can be welded to the company too alloy, strengthen the hardness of the sealing surface.

4, due to impurities in the media or new pipeline welding slag scratch single seat pneumatic control valve sealing surface, causing internal leakage. Solution: The new pipe must be purged or a filter installed in front of the single-seat pneumatic regulator. Once the inner leakage occurs, the single-seat pneumatic control valve can be disassembled, and the valve core and valve seat can be re-ground and assembled.