JIS B2220 · Standard reference
JIS B2220 flange types and gasket faces
JIS B2220:2012 classifies flanges by shape and gives each type a short designation. Table 1 defines eight of them: the plate flange (SOP), the hubbed slip-on (SOH), socket welding (SW), welding neck (WN), lap joint (LJ), threaded (TR), integral (IT) and blank (BL). Table 2 splits the SOH type used at 20K and 30K into Types A, B and C.
Gasket faces are classified separately in Table 3. There are four families — full face (FF), raised face (RF), male-female (MF) and tongue and groove (TG) — and the last two are supplied as a seat pair, MF-M with MF-F and TG-T with TG-G. The face you specify fixes the gasket and the surface finish: Table 9 gives the Ra limits and Table 10 links them to turning conditions.
- Standard
- JIS B2220:2012
- Flange types
- 8 (Table 1)
- SOH types
- A, B, C at 20K and 30K
- Gasket faces
- 4 families, 6 designations
- Face finish
- Ra 3.2–6.3 μm (FF/RF)
- Coating
- Black / white (ZN)
Flange types and designations (Table 1)
Table 1 groups the shaped flanges under a parent classification and assigns the two- or three-letter designation. SOP, SOH, SW and WN are all welding flanges; LJ, TR, IT and BL stand alone.
- Table 2 covers only 20K and 30K: it divides the SOH into Type A, Type B and Type C. The type letter is part of the designation and is marked after the nominal pressure.
- Designation example: JIS B 2220 SOH RF 20K A 50A SUS F316L is an SOH flange, raised face, 20K, Type A, 50A, in SUS F316L (clause 19, Example 7).
- Zinc coating has its own designations: flanges without zinc coating are black flanges, and flanges with hot-dip or electroplated zinc coating are white flanges (ZN) (Table 4).
JIS B2220 · JIS B2220:2012
| Classification | Designation | Description |
|---|---|---|
| Welding flange — slip-on welding flange (plate flange) | SOP | Plate flange with a plain bore, fillet-welded to the pipe on both sides; the common low-pressure JIS slip-on. |
| Welding flange — slip-on welding flange (hubbed flange) | SOH | Slip-on with a hub; the 20K and 30K versions are split into Types A, B and C by Table 2. |
| Welding flange — socket welding flange | SW | Socket-type flange for small-bore socket-welded piping. |
| Welding flange — welding neck flange | WN | Butt-weld flange with a tapered hub for higher pressure and cyclic service. |
| Lap joint flange | LJ | Loose flange used with a stub end; the LJ itself has no gasket face. |
| Threaded flange | TR | Screwed flange; the thread is made to JIS B 0203. |
| Integral flange | IT | Flange integral with the pipe, forging or nozzle. |
| Blank flange | BL | Solid disc used to blank off a line end or opening; sold as a blind flange in many catalogues. |
Gasket faces and surface finish (Tables 3, 9 and 10)
Table 3 defines the face designations. FF and RF are single faces; MF and TG are pairs, so the seat has to be stated: MF-M with MF-F, or TG-T with TG-G.
- Table 9 finishing: Ra 3.2 to 6.3 μm for full-face and raised-face flanges, and Ra 3.2 μm or under for male-female and tongue-and-groove seats. Ra is defined in JIS B 0601.
- Table 10 turning conditions: with a 0.8 mm blade edge radius the serration pitch is 0.25 to 0.30 mm for Ra 3.2 μm and 0.35 to 0.42 mm for Ra 6.3 μm; with a 1.6 mm radius it is 0.36 to 0.42 mm and 0.52 to 0.60 mm respectively.
JIS B2220 · JIS B2220:2012
| Gasket face | Seat | Designation | Description |
|---|---|---|---|
| Full face (FF) | — | FF | Gasket face covering the whole flange face; takes a full-face gasket. |
| Raised face (RF) | — | RF | Raised ring around the bore; the usual face for general steel-pipe flanges. |
| Male-female face (MF) | Male seat | MF-M | Male seat; specified as a pair with the female seat MF-F. |
| Male-female face (MF) | Female seat | MF-F | Female seat; together with MF-M it forms the MF pair. |
| Tongue and groove (TG) | Tongue seat | TG-T | Tongue seat; specified as a pair with the groove seat TG-G. |
| Tongue and groove (TG) | Groove seat | TG-G | Groove seat; together with TG-T it forms the TG pair. |
JIS B2220 flange types — questions
What is the difference between SOP and SOH?
Both are slip-on welding flanges. SOP is the plate flange: a flat plate with a bore, fillet-welded to the pipe on both sides. SOH has a hub and is split into Types A, B and C at 20K and 30K by Table 2. SOP is the common low-pressure JIS slip-on.
Which gasket face should I specify for a JIS flange?
RF (raised face) is the usual choice for general steel piping. FF (full face) is used where the gasket must cover the whole flange face, including low-pressure plate and blank flanges. MF and TG locate the gasket in a seat pair and need matching male/female or tongue/groove flanges — state the seat, MF-M/MF-F or TG-T/TG-G.
What surface finish does JIS B2220 require on the gasket face?
Ra 3.2 to 6.3 μm for FF and RF faces, and Ra 3.2 μm or under for MF and TG seats (Table 9). Table 10 correlates the Ra value with turning conditions — blade edge radius and serration pitch.
Does JIS B2220 include blind and lap joint flanges?
Yes. Table 1 includes the blank flange (BL) and the lap joint flange (LJ). The LJ has no gasket face of its own; the sealing face is on the stub end it holds (Note 7 to clause 19).