WN (welding neck)
SOP (slip-on welding, plate flange)Nominal pressure 5K, 10K, 10K thinThe pipe is slipped in and fillet welded. It is a flat plate with no hub and is the cheapest type. It is used for general low-pressure piping.SOH (slip-on welding, hub flange)Nominal pressure 5K, 10K, 10K thin, 16K, 20K, 30KA plate flange with a hub added to lower the stress at the root. Choose it where SOP does not stand the pressure or the repeated loading.SW (socket welding flange)Nominal pressure 5K, 10K, 16K, 20KThe pipe is pushed to the bottom of the socket and welded on the outside only. It is used for small-bore piping, 10A to 80A.WN (welding neck flange)All nominal pressures 5K to 63KIt is butt welded to the pipe. The joint is the strongest of all, and it is used for piping under high pressure, high temperature or repeated loading.LJ (lapped flange)Nominal pressure 5K, 10K, 16K, 20KIt is not fixed to the pipe but bears on the collar of a stub end. The flange turns freely, so lining up the holes is easy, and it can be a different material from the pipe.TR (threaded flange)Nominal pressure 5K, 10K, 16K, 20KThe pipe is screwed in with a taper pipe thread. It is used on sites where welding is not possible, and on lines where welding is unwanted. Only 10A to 150A are covered.IT (integral flange)Nominal pressure 5K, 10K, 16K, 20K, 30KA flange made in one piece with the body of a valve or a machine. It is not a separate part, so the table is consulted to match the joint dimensions to the mating side.BL (blind flange)All nominal pressures 5K to 63KA plate with no bore that closes the pipe end. It is used to stop a line off for testing, or for a branch to be added later.
Butt welded to the pipe. There is no abrupt change of section at the joint, which makes it the strongest form of flange, so it is used on high-pressure and high-temperature lines and where cyclic loading or thermal stress applies. Available in every nominal pressure from 5K to 63K.
Welding neck flange dimensions
Notes
- References
- JIS B 2220:2012 steel pipe flanges (Table 14, Table 15, Table 17, Table 18, Table 19, Table 20, Table 21, Annex F)
- The source has one table per nominal pressure. Here they are combined into a single table, with a rule where the nominal pressure changes. A dash means the dimension is not specified for that pressure. Selecting a single nominal pressure above drops the columns that do not apply, giving the same column layout as the source.
- The small end of the hub a equals the outside diameter of the pipe it joins (Annex B, Table B.1). Because the joint is butt welded, it has to match the pipe.
- The alternative sizes are the flange thickness t and the hub taper x, which may be adopted by agreement between the parties to the contract. They exist only for 700A and above at 5K, and 500A and above at 10K.
- A welding neck flange can take a raised face (RF) at any nominal pressure. At 5K, 10K and 16K a full face (FF) is also available; at 20K and above only the raised face (Table 8). For that reason g and f are listed at every nominal pressure.
- Inside diameter d is adjusted to suit the inside diameter of the pipe it joins.
- The calculated mass is for reference. It assumes a steel density of 7.85 g/cm3.