Internationally, the types of plastic valves mainly include plastic ball valves(https://www.chinavalvefittings.com/product/valve-series/pvc-compact-ball-valve/), plastic butterfly valves(https://www.chinavalvefittings.com/product/valve-series/butterfly-valve/), plastic check valves, plastic diaphragm valves, and plastic globe valves. The main structural forms are two-way, plastic three-way and multi-way valves. The raw materials are mainly ABS, PVC- U, PVC-C, PB, PE, PP and PVDF etc. In the international standards of plastic valve products, the first requirement is the raw materials used in the production of valves. The manufacturer of the raw materials must have a creep failure curve that meets the standards of plastic pipe products. At the same time, the sealing test, valve body test, and overall The long-term performance test, fatigue strength test and operating torque of the valve have all been stipulated, and the design service life of the plastic valve used for industrial transportation of fluid is 25 years.
Plastic valves meet the following standards:
1. Raw material requirements: The materials of the valve body, bonnet and bonnet should be selected in accordance with ISO15493:2003 "Industrial Plastic Piping Systems—ABS, PVC-U and PVC-C—Pipe and Fitting System Specifications—Part 1: Metric Series" And ISO15494:2003 "Industrial plastic piping systems-PB, PE and PP-pipes and fittings system specifications-Part 1: Metric series".
2. Design requirements: If the valve has only one pressure bearing direction, it should be marked with an arrow on the outside of the valve body. The valve with symmetrical design should be suitable for two-way fluid flow and isolation. The sealing component is driven by the valve stem to open and close the valve. It should be positioned at the end or any position in the middle by friction or actuators, and fluid pressure cannot change its position.
The minimum through hole of the plastic valve should meet the following standards:
1. Any aperture through which the medium flows on the valve should not be less than 90% of the DN value of the valve;
2. For valves whose structure needs to reduce the diameter of the medium flow, the manufacturer should state the actual minimum through hole.
3. The seal between the valve stem and the valve body should comply with EN736-3.
4. In terms of the wear resistance of the valve, the design of the valve should consider the service life of the worn parts, or the manufacturer should indicate in the operating instructions a recommendation to replace the entire valve.
5. The applicable flow rate of all valve operating devices should reach 3m/s.
6. Seen from the top of the valve, the handle or handwheel of the valve should close the valve in a clockwise direction.
Due to the advantages of light weight, corrosion resistance, non-adsorption of scale, integrated connection with plastic pipes, and long service life of plastic valves, plastic valves are used in water supply (especially hot water and heating) and other industrial fluids. In the piping system, its application advantages are unmatched by other valves. At present, in the production and application of domestic plastic valves, there is no reliable method to control them, resulting in uneven quality of plastic valve products for water supply and other industrial fluids, causing lax closure and serious leakage in engineering applications. Formed a statement that plastic valves cannot be used, affecting the overall development of plastic pipe applications. China's national standards for plastic valves are in the process of being formulated, and its product standards and method standards are formulated in accordance with international standards.
