What Is JIS B2220?

JIS B2220 is the Japanese Industrial Standard for steel pipe flanges. It defines dimensions, pressure ratings, materials, and marking requirements for flanges used in Japanese-designed plants and projects across Asia. JIS flanges use a “K” rating system (e.g., 5K, 10K, 16K, 20K, 30K, 40K, 63K) where the number roughly indicates the maximum working pressure in kgf/cm2 at ambient temperature. JIS B2220 flanges are dimensionally different from both ASME B16.5 and EN 1092-1 flanges.

JIS B2220 Pressure Ratings

JIS Rating	Working Pressure (kgf/cm2)	Working Pressure (barg)	Approximate ASME Equivalent
5K	5	4.9	Class 150 (low end)
10K	10	9.8	Class 150
16K	16	15.7	Class 150-300
20K	20	19.6	Class 150-300
30K	30	29.4	Class 300
40K	40	39.2	Class 300
63K	63	61.8	Class 600

Approximate equivalences only. JIS and ASME pressure-temperature derating methods differ.

JIS B2220 Flange Types

JIS Type	Description	ASME B16.5 Equivalent
SOH	Slip-on hubbed	Slip-on
WN	Welding neck	Weld neck
BL	Blind	Blind
TR	Threaded	Threaded
SW	Socket weld	Socket weld
LJ	Loose (lap joint)	Lap joint

Dimensional Example: DN 150 / 6B

Parameter	JIS B2220 10K	ASME B16.5 Class 150	EN 1092-1 PN 16
Flange OD	280 mm	279.4 mm	285 mm
Bolt circle	240 mm	241.3 mm	240 mm
Number of bolts	8	8	8
Bolt size	M20	3/4 in (19.05 mm)	M20
Bolt hole diameter	23 mm	22.4 mm	22 mm
Thickness	22 mm	22.4 mm	22 mm

Common Mistake

JIS 10K and ASME Class 150 flanges in size 150A/NPS 6 appear dimensionally close (OD within 1 mm, same bolt count). Some contractors attempt to bolt them together. This is not recommended—bolt hole diameters and threading (metric vs. UNC) differ, leading to misalignment and inconsistent gasket compression.

Materials

JIS Material	Type	ASTM Equivalent
SGP, STPG 370	Carbon steel pipe/plate	A36, A283
SFVC2A	Carbon steel forging	A105
SUS 304	Austenitic stainless	A182 F304
SUS 316	Austenitic stainless	A182 F316
SFVA F22	Alloy steel forging	A182 F22

Pro Tip

JIS B2220 uses “A” and “B” size designations: “A” refers to the pipe outer diameter in mm (e.g., 150A = 165.2 mm OD), and “B” refers to the nominal size in inches (e.g., 6B = NPS 6). Both designations refer to the same flange. When converting JIS to ASME sizes, 150A = 6B = NPS 6.

Read the full guide to flanges