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Practical knowledge of valves

  • Author:Cassie
  • Release on :2019-01-09


Valve foundation



1. The basic parameters of the valve are: nominal pressure PN, nominal diameter DN.

2. the basic function of the valve: cut off the medium, adjust the flow, change the flow direction.
3. the main way of valve connection: flange, thread, welding, butt.
4. the pressure of the valve - temperature grade means: different materials, different working temperatures, the maximum allowable non-impact working pressure is different.

5. There are two main systems for pipe flange standards: the European system and the American system.
The pipe flange connections of the two systems are completely different in size and cannot be matched.



It is most appropriate to distinguish by pressure level:



The 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, 40.0 MPa.


The US system is PN1.0 (CIass75), 2.0 (CIass150), 5.0 (CIass300), 11.0 (CIass600), 15.0 (CIass900), 26.0 (CIass1500), 42.0 (CIass2500) MPa.


The types of pipe flanges are: integral (IF), plate flat welding (PL), neck flat welding (SO), neck butt welding (WN), socket welding (SW), screw (Th), butt weld ring Loose sleeve (PJ/SE) / (LF / SE), flat welding ring loose (PJ / RJ) and flange cover (BL).


The flange sealing surface types mainly include: full plane (FF), convex surface (RF), concave (FM) convex (M) surface, tenon (T) groove (G) surface, ring connection surface (RJ), and the like.



Common (Universal) valve


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, stop Return valve, safety valve, pressure reducing valve, steam trap.


2, The valve connection code 1, 2, 4, 6, 7 respectively:

  1 - internal thread, 2 - external thread, 4 - flange, 6 - welding, 7 - clip.


3, The transmission mode of the valve code 9, 6, 3 respectively:

  9 - electric, 6 - pneumatic, 3 - worm.
4, Valve body material code Z, K, Q, T, C, P, R, V respectively:

  gray cast iron, malleable cast iron, ductile iron, copper and alloy, carbon steel, chrome-nickel stainless steel, chrome-nickel-molybdenum stainless steel, Chrome molybdenum vanadium steel.


5. Seat seal or lining code R, T, X, S, N, F, H, Y, J, M, W respectively:

  austenitic stainless steel, copper alloy, rubber, plastic, nylon plastic, fluoroplastic, Cr-based stainless steel, hard alloy, rubber, Monel, valve body material.


6. Where the cast iron valve body is not suitable for use:


  1) Water vapor or wet gas with a large water content.
  2) Flammable and explosive fluids.
  3) When the ambient temperature is lower than -20 °C.
  4) Compressed gas.