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If plastic valves operation only one pressure direction should be in the external body with the arrow mark, symmetrical design of plastic valves two-way operation shall be suitable for the fluid flow and isolation. Sealing parts by stem drive plastic valves operation should be in the end, or any intermediate position by friction or device to perform positioning, fluid pressure will not change its position. The body according to EN736-3, the smallest hole should meet the following two points: for any size valves medium circulation, should be no less than 90% of the valve DN value; Need to narrow the medium circulation aperture in the structure of the valve, the manufacturer shall specify the actual minimum hole. Seal between the valve stem and valve body in accordance with the EN736-3, plastic valves operation should be without fault. In plastic valves operation wear-resisting performance, the design of the valve should consider the service life of wear parts, or producer should be indicated in the operating instruction to replace the whole electric actuators . All plastic valves operation device should reach the applicable velocity of 3 m/s. Look from the top of the valve, the valve handle or handwheel should close the valve clockwise.
The performance of the purchased raw materials should be consistent with the raw material manufacturer’s instructions, and conform to the requirements of the product standards. Plastic valves operation should be highlighted, the body should be marked materials PN code, sizes available DN, nominal pressure; the body should identify the producer name or trademark; the body should identify the production date or code; the valve body shall be marked producers code of different production site.
Short-term performance belongs to the factory inspection items in the product standard, mainly do the seat sealing test with the valve body sealing test, used to check the plastic valves operation of sealing performance, requirements within the plastic valve cannot have leakage phenomenon of leakage (seat), also cannot have outside leakage phenomenon of leakage (the body). Seat plastic valves operation of sealing test is to validate the valve isolation performance of pipeline system, the valve body sealing experiment is to verify the valve stem seal and valve connection end seal leakage.
Plastic valves operation should be done according to the ISO1167 with thermoplastic fluid conveying pipe resistance to internal pressure test method "regulation. Seat sealing experiment when the valve is in close state; Do when the valve seal test, should make the valve is in full open position or half open position (such as ball valve), half should be able to make fluid into the position of the valve stem seal. For one-way seal valves, do only one direction of seat tightness test; And two-way sealed valve, two directions of seat tightness test needs to be done. Test of plastic valves operation requires net sample of air valve, increased testing pressure, meet the pressure in the 30s. That should be paid attention to test plastic valves in the process of operation test apparatus cannot generate additional stress of valve. If with air as medium, in view of the compressed gas safety measures must be taken.
Body test and overall performance test for a long time in pneumatic actuators belongs to the type of inspection items, in the product standard body test is used to verify the strength of the valve body, the whole valve long-term performance testing is used to verify the plastic valves the overall reliability of the operation. Test and the overall long-term performance of valve body in the process of the test, the sample no leakage or rupture phenomenon, which test. Leakage or rupture occurs before the end of the test sample, the determination test is unqualified. If the problems of the joint determination test are invalid, you need to take a sample test.