how to prevent leakage of breathing valve correctly?

                In the respiration valve design or use experience, elevating the respiration valve packing for asbestos packing ptfe or graphite packing or v-shaped packing, but these packing are subject to the limit the number of the valve opening and closing, is with the increase of valve opening and closing times, packing will wear and clearance increases gradually, to a certain number of times (according to the statistics, but not more than 2000 times) the valve will be leaked from the packing.After leakage the packing gland will need to be repressed.This scheme is suitable for valve opening and closing times are not many occasions.If the valve is opened and closed frequently (such as 100,000 to 300,000 times a year), this undoubtedly increases the use and maintenance costs of the breathing valve.

                 One method is to add a washer under the packing and a spring under the packing (spring preload needs to be calculated). When the packing wears out, the spring will re-press the packing to seal it.This method can only reach 500,000-1 million times without leakage after passing the use inspection at present. When the user needs to repress the packing gland during the annual overhaul, it can only reduce the usual maintenance.

                 Another way, is to choose hydraulic, pneumatic seal technology, change the original valve design idea, use oil cylinder seal slip ring in the packing place, increase type 0 seal ring (need to calculate friction, seal specific pressure, to determine the number of slip ring and type 0 seal ring).This method can achieve 2 million times of opening and closing without leakage, but the type 0 sealing ring should be aged, the service time is only 5 years, and the cost is higher.

                 The packing box of breathing valve is composed of packing box, packing, packing pad and packing pressure mechanism.The packing box is placed on the valve body or bonnet to accommodate the packing.The packing pad is placed at the bottom of the packing box to support the packing.Packing sub - soft sealing packing and molding packing two kinds.Molding filler to elastic material as raw materials, using molding or turning processing made of various ring sealing ring, in contrast, molding filler structure compact, good sealing performance, more applicability.Media leakage in the sealing packing, the reason is loose packing gland, sealing packing is not tight, packing variety or quality does not meet the requirements, packing aging or wear by the stem.Cause of leakage at body joint seal means the seal between body and bonnet.

                 Under normal circumstances for the flange connection seal, when the adjustment valve nominal diameter is small for the threaded connection seal.Gasket type, material or size do not meet the requirements, flange sealing surface processing quality is poor, connection bolt fastening improper, due to the unreasonable configuration of the pipeline and the connection of the excessive additional load, can cause leakage valve body connection parts.The key to eliminate the leakage of the breathing valve is to optimize the design of the structure of the breathing valve, according to different technological conditions to choose the reasonable material of the valve, improve the quality control level of the valve in the production process, and according to the process operating system to optimize the selection of the valve.With the progress of science and technology, especially the appearance of new materials, some new structure adjustable breathing valves have been put into use.