Reference tables are transcribed from JIS B2220:2012; table numbers, printed page numbers and cell values keep the standard's original wording.
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.
StandardJIS B2220:2012
Flange types8 (Table 1)
SOH typesA, B, C at 20K and 30K
Gasket faces4 families, 6 designations
Face finishRa 3.2–6.3 μm (FF/RF)
CoatingBlack / 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).
Table 1 (p. 3) — classification of flanges and their designations
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.
Table 3 (p. 4) — classification of gasket faces and their designations
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.
FAQ
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).
Sources
JIS B2220:2012, clause 4 and Table 1 (PDF p. 8; printed p. 3)
JIS B2220:2012, clause 4 and Table 2 (PDF p. 9; printed p. 4)
JIS B2220:2012, clause 5 and Table 3 (PDF p. 9; printed p. 4)
JIS B2220:2012, clause 6 and Table 4 (PDF p. 9; printed p. 4)
JIS B2220:2012, clause 14.1 and Tables 9 and 10 (PDF p. 14; printed p. 9)