How much do you know about valves?

How much do you know about valves?

Introduction: through the international standards of plastic valve products and test methods of raw material requirements, design requirements and manufacturing requirements, performance requirements, test method, system application requirements and the use of pressure and temperature, etc, the relationship between can understand the need of plastic valve seal test, torque test and fatigue strength test and so on basic quality control requirements. The requirements of valve seat seal test, valve body seal test, valve body strength test, valve long term test, fatigue strength test and operating torque are summarized in the form of tables. Through the discussion of several problems in international standards, the producers and users of plastic valves are concerned. With the increasing proportion of plastic pipeline in cold and hot water supply and industrial pipeline engineering, the quality control of plastic valve in plastic pipeline system becomes more and more important. Because the plastic valve has the advantages of light weight, corrosion resistance, no adsorption scale, and plastic pipeline integration connection and long service life, plastic valve in water supply (especially hot water and heating) and industrial use of other fluids in the plastic pipeline system, its application advantages are other valves can not be compared. At present in domestic production and application of plastic valves, its control is no reliable way, water supplies and other fluid plastic valves used in industry product quality is uneven, the engineering application of closed lax and leakage phenomenon is serious, the formation of a plastic valve cannot use, affect the overall development of plastic pipe application. The national standard of plastic valve in Our country is in the process of making, its product standard and method standard are made according to the international standard. International plastic valve types are mainly ball valve, butterfly valve, check valve, diaphragm valve and globe valve, the structure of the main form of two, three and multi-way valve, the main raw materials are ABS, PVC-U, PVC-C, PB, PE, PP and PVDF and so on. In the international standard of plastic valve products, first of all, the raw materials used in the production of valves are required. The manufacturers of the raw materials must have creep failure curves in line with the standard of plastic pipe products. At the same time, the sealing test, valve body test, long-term performance test, fatigue strength test and operating torque of the whole valve are stipulated, and the design service life of the plastic valve used for industrial fluid transportation is 25 years. ISO 15493:2003 Plastics Piping Systems for Industrial use — ABS, PVC-U and PVC-Pipe and fitting Systems — Specification for pipe and fitting systems — Specification for the first part of the valve body, bonnet and bonnet shall be in accordance with ISO 15493:2003 Plastics Piping Systems for Industrial use — ABS, PVC-U and PVC-C — Pipe and fitting Systems — Specification for the first part of the valve body, bonnet and bonnet shall be in accordance with ISO 15493:2003 Plastics Piping Systems for Industrial use — ABS, PVC-U and PVC-C — Pipe and fitting Systems Metric series and ISO 15494:2003 Plastics Piping Systems for Industrial use — PB, PE and PP — Pipes and Fittings Systems specification — *** Part: Metric Series. A) If the valve * has a bearing direction, it shall be marked with an arrow on the outside of the valve body. Valves of symmetrical design shall be suitable for two-way flow and isolation. B) The sealing part is driven by the valve stem to open and close the valve. It should be positioned at the end point or any middle position by friction or actuator, and the fluid pressure cannot change its position. C) According to EN736-3, the smallest through hole in the valve cavity should conform to the following two points: – for any aperture of the valve medium flow, it should not be less than 90% of the valve DN value; For valves that are structurally required to reduce the medium flow aperture, the manufacturer shall state the actual minimum through hole. D) Seal between stem and body shall be in accordance with EN736-3. E) With regard to the wear resistance of valves, the design of valves shall take into account the service life of worn parts, or the manufacturer shall indicate in the operating instructions suggestions for replacing the entire valve. F) all valve operating devices shall have a flow rate of 3m/s. G) When viewed from above the valve, the valve handle or handwheel shall close the valve clockwise. 3 Manufacturing requirements a) The performance of the purchased raw materials shall conform to the specifications of the raw material manufacturer and meet the product standards. B) The raw material code, diameter DN and nominal pressure PN shall be marked on the valve body. C) The valve body shall be marked with the manufacturer’s name or trademark. D) The valve body shall be marked with date of manufacture or code number. E) The valve body shall be marked with the code of the manufacturer’s different locations. 4 short-term performance requirements short-term performance in the product standard is a factory inspection items, mainly to do the sealing test of the valve seat and valve body sealing test, used to check the sealing performance of plastic valves, plastic valves that can not have internal leakage (valve seat leakage) phenomenon, also can not have external leakage (valve leakage) phenomenon. The valve seat sealing test is to verify the performance of the valve isolation piping system; The valve body seal test is to verify the leakage of the valve stem seal and the valve joint seal. The plastic valve and pipeline system are connected by welding connection: the outer diameter of the valve connection part is equal to the outer diameter of the pipe, and the end face of the valve connection part is welded relative to the end face of the pipe; Socket bonding connection: the connecting part of the valve is in the form of socket, which is bonded with the pipe fittings; Electric fusion socket connection: the valve connection part is the socket form with electric heating wire in the inner diameter, and is electrically fused with the pipe; Socket hot melt connection: the valve connection part is the socket form, and the pipe is connected with the hot melt socket; Socket bonding connection: the valve connection part is in the form of socket, and the pipe is bonded socket connection; Bearing rubber sealing ring connection: the valve connection part is the bearing form of inlaid rubber sealing ring, and the pipe is connected with the socket; Flange connection: the valve connection part is in the form of flange, connected with the flange on the pipe; Thread connection: the valve connection part is in the form of thread, connected with the thread on the pipe or pipe fittings; Live connection: the connection part of the valve is in the form of live connection, and the pipe or pipe fittings are connected. Different connections can be made simultaneously on the same valve. With the increase of temperature, the service life of plastic valves should be shortened. To maintain the same service life, you need to reduce the service pressure.
How much do you know about valves?
Pipe flanges mainly include integral (IF), plate flat welding (PL), neck flat welding (SO), neck butt welding (WN), socket welding (SW), screw (Th), butt welding ring loose sleeve (PJ/SE)/(LF/SE), flat welding ring loose sleeve (PJ/RJ) and flange cover (BL), etc.
The valve base
1, the main way of valve connection are: flange, thread, welding, clamping
2, the valve basic function: cut off the medium, adjust the flow, change the flow direction
3, the basic parameters of the valve are: nominal pressure PN, nominal diameter DN
4, valve pressure – temperature grade: different materials, different working temperature, allow no impact working pressure is different
5, pipe flange standards mainly have two systems: European system and American system.
To distinguish suitable by pressure grade:
European system is PN0.25, 0.6, 1.0, 1.6, 2.5, 4.0, 6.3, 10.0, 16.0, 25.0, 32.0, 40.0MPa;
The American system is PN1.0(CIass75), 2.0(CIass150), 5.0(CIass300), 11.0(CIass600), 15.0(CIass900), 26.0(CIass1500), 42.0(CIass2500)MPa.
Common (universal) valves
1, valve type code Z, J, L, Q, D, G, X, H, A, Y, S respectively: gate valve, globe valve, throttle valve, ball valve, butterfly valve, diaphragm valve, plug valve, check valve, safety valve, pressure reducing valve, trap valve
2, valve connection code 1, 2, 4, 6, 7 respectively: 1 – internal thread, 2 – external thread, 4 – flange, 6 – welding, 7 – clamp
3, the valve transmission mode code 9, 6, 3 respectively: 9 – electric, 6 – pneumatic, 3 – turbo worm
4, valve body material code Z, K, Q, T, C, P, R, V respectively: gray cast iron, malleable cast iron, ductile cast iron, copper and alloy, carbon steel, chromium nickel stainless steel, chromium nickel molybdenum stainless steel, chromium molybdenum vanadium steel
5, seat sealing or lining code R, T, X, S, N, F, H, Y, J, M, W respectively: austenitic stainless steel, copper alloy, rubber, plastic, nylon plastic, fluorine plastic, Cr stainless steel, hard alloy, rubber lining, Monel alloy, valve body material
6, cast iron valve body is not suitable for the occasion: flammable and explosive fluid; Where the ambient temperature is below -20℃; Compressed gas; Water vapor or wet gas containing a lot of water.
Flange sealing surface type mainly includes: full plane (FF), protrusive surface (RF), concave (FM) convex surface (M), tenon (T) groove (G) surface, ring connection surface (RJ), etc.