Lap Joint Flange

Size Range: DN15-DN600 (1/2″- 24″)
Pressure Class: PN20-PN150 (Class 150 – Class 900)
Sealing Faces: RF, FF, MFM, TG, RJ
Standards: ASME B16.5, ASME B16.47 Series A/B, EN1092-1, HG/T20592, HG/T20615, HG/T20623, JIS B2220
Materials: 20#, A105, LF2, F11/F22, 304, 316L, 2205, 2507, Alloy20, Hastelloy C, TA2
Media: Steam, oil, gas, acid/alkali, seawater, organic solvent, cryogenic medium
Temperature: -196℃ ~ 1000℃
Application: Oil&gas, petrochemical, power plant, marine, municipal water, metallurgy, environmental protection

Product details

Lap Joint Flange, commonly abbreviated as LJ Flange, is also known as a Loose Flange or Loose Backing Flange. It is a detachable flange assembly widely used in piping systems requiring frequent disassembly, alignment flexibility, and corrosion resistance.

A complete Lap Joint Flange assembly consists of two separate components: Loose Flange Ring (Backing Flange) ， Stub End (Lap Joint Stub End / Welding Ring)

The flange ring does not come into direct contact with the process medium and can rotate freely around the pipe. Only the Stub End is welded to the pipe and exposed to the fluid, providing the pressure boundary and corrosion-resistant contact surface.

Working logic: Weld the stub end to the pipe; pre-install the loose flange for free rotation and bolt hole alignment. Bolt fastening compresses the gasket for sealing. Maintenance only needs bolt loosening, with no need to touch pipe welds

Product Specifications

Note: The flange inner diameter (B) is determined by the wall thickness of the steel pipe and shall be specified by the user at the time of ordering.（Unit: mm）

LJ-150LB-900LB

DN	NPS	Type/Class	Part No	A	D	K	L	Th	n	C	B	N	H	R1	h	d1
15	0.5	LJ-150LB-SFT	XLXLJ150SFT05	21.3	90	60.3	16	M14	4	11.2	22.9	30	16	3	51	35.1
20	0.75	LJ-150LB-SFT	XLXLJ150SFT075	26.9	100	69.9	16	M14	4	12.7	28.2	38	16	3	51	42.9
25	1	LJ-150LB-SFT	XLXLJ150SFT1	33.7	110	79.4	16	M14	4	14.3	34.9	49	17	3	51	50.8
32	1.25	LJ-150LB-SFT	XLXLJ150SFT125	42.4	115	88.9	16	M14	4	15.9	43.7	59	21	5	51	63.5
40	1.5	LJ-150LB-SFT	XLXLJ150SFT15	48.3	125	98.4	16	M14	4	17.5	50.0	65	22	6	51	73.0
50	2	LJ-150LB-SFT	XLXLJ150SFT2	60.3	150	120.7	18	M16	4	19.1	62.5	78	25	8	64	91.9
65	2.5	LJ-150LB-SFT	XLXLJ150SFT25	76.1	180	139.7	18	M16	4	22.3	78.5	90	29	8	64	104.6
80	3	LJ-150LB-SFT	XLXLJ150SFT3	88.9	190	152.4	18	M16	4	23.9	91.4	108	30	10	64	127.0
100	4	LJ-150LB-SFT	XLXLJ150SFT4	114.3	230	190.5	18	M16	8	23.9	116.8	135	33	11	76	157.2
125	5	LJ-150LB-SFT	XLXLJ150SFT5	139.7	255	215.9	22	M20	8	23.9	144.4	164	36	11	76	185.7
150	6	LJ-150LB-SFT	XLXLJ150SFT6	168.3	280	241.3	22	M20	8	25.4	171.4	192	40	13	89	215.9
200	8	LJ-150LB-SFT	XLXLJ150SFT8	219.1	345	298.58	22	M20	8	28.6	222.2	246	44	13	102	269.7
250	10	LJ-150LB-SFT	XLXLJ150SFT10	273	405	362.0	26	M24	12	30.2	277.4	305	49	13	127	323.8
300	12	LJ-150LB-SFT	XLXLJ150SFT12	323.9	485	431.8	26	M24	12	31.8	328.2	365	56	13	152	381.0
350	14	LJ-150LB-SFT	XLXLJ150SFT14	355.6	535	476.3	30	M27	12	35.0	360.2	400	79	13	152	412.8
400	16	LJ-150LB-SFT	XLXLJ150SFT16	406.4	595	539.8	30	M27	16	36.6	411.2	457	87	13	152	469.9
450	18	LJ-150LB-SFT	XLXLJ150SFT18	457	635	577.9	33	M30	16	39.7	462.3	505	97	13	152	533.4
500	20	LJ-150LB-SFT	XLXLJ150SFT20	508	700	635.0	33	M30	20	42.9	514.4	559	103	13	152	584.2
600	24	LJ-150LB-SFT	XLXLJ150SFT24	610	815	749.3	36	M33	20	47.7	616.0	663	111	13	152	692.2
15	0.5	LJ-300LB-SFT	XLXLJ300SFT05	21.3	95	66.7	16	M14	4	14.3	22.9	38	22	3	51	35.1
20	0.75	LJ-300LB-SFT	XLXLJ300SFT075	26.9	115	82.6	18	M16	4	15.9	28.2	48	25	3	51	42.9
25	1	LJ-300LB-SFT	XLXLJ300SFT1	33.7	125	88.9	18	M16	4	17.5	34.9	54	27	3	51	50.8
32	1.25	LJ-300LB-SFT	XLXLJ300SFT125	42.4	135	98.4	18	M16	4	19.1	43.7	64	27	5	51	63.5
40	1.5	LJ-300LB-SFT	XLXLJ300SFT15	48.3	155	114.3	22	M20	4	20.7	50.0	70	30	6	51	73.0
50	2	LJ-300LB-SFT	XLXLJ300SFT2	60.3	165	127.0	18	M16	8	22.3	62.5	84	33	8	64	91.9
65	2.5	LJ-300LB-SFT	XLXLJ300SFT25	76.1	190	149.2	22	M20	8	25.4	78.5	100	38	8	64	104.6
80	3	LJ-300LB-SFT	XLXLJ300SFT3	88.9	210	168.3	22	M20	8	28.6	91.4	117	43	10	64	127.0
100	4	LJ-300LB-SFT	XLXLJ300SFT4	114.3	255	200.0	22	M20	8	31.8	116.8	146	48	11	76	157.2
125	5	LJ-300LB-SFT	XLXLJ300SFT5	139.7	280	235.0	22	M20	8	35.0	144.4	178	51	11	76	185.7
150	6	LJ-300LB-SFT	XLXLJ300SFT6	168.3	320	269.9	22	M20	12	36.6	171.4	206	52	13	89	215.9
200	8	LJ-300LB-SFT	XLXLJ300SFT8	219.1	380	330.2	26	M24	12	41.3	222.2	260	62	13	102	269.7
250	10	LJ-300LB-SFT	XLXLJ300SFT10	273	445	387.4	30	M27	16	47.7	277.4	321	95	13	254	323.8
300	12	LJ-300LB-SFT	XLXLJ300SFT12	323.9	520	450.8	33	M30	16	50.8	328.2	375	102	13	254	381.0
350	14	LJ-300LB-SFT	XLXLJ300SFT14	355.6	585	514.4	33	M30	20	54.0	360.2	425	111	13	305	412.8
400	16	LJ-300LB-SFT	XLXLJ300SFT16	406.4	650	571.5	36	M33	20	57.2	411.2	483	121	13	305	469.9
450	18	LJ-300LB-SFT	XLXLJ300SFT18	457	710	628.6	36	M33	24	60.4	462.3	533	130	13	305	533.4
500	20	LJ-300LB-SFT	XLXLJ300SFT20	508	775	685.8	36	M33	24	63.5	514.4	587	140	13	305	584.2
600	24	LJ-300LB-SFT	XLXLJ300SFT24	610	915	812.8	42	M39×3	24	69.9	616.0	702	152	13	305	692.2
15	0.5	LJ-600LB-SFT	XLXLJ600SFT05	21.3	95	66.7	16	M14	4	14.3	22.9	38	22	3	76	35.1
20	0.75	LJ-600LB-SFT	XLXLJ600SFT075	26.9	115	82.6	18	M16	4	15.9	28.2	48	25	3	76	42.9
25	1	LJ-600LB-SFT	XLXLJ600SFT1	33.7	125	88.9	18	M16	4	17.5	34.9	54	27	3	102	50.8
32	1.25	LJ-600LB-SFT	XLXLJ600SFT125	42.4	135	98.4	18	M16	4	20.7	43.7	64	29	5	102	63.5
40	1.5	LJ-600LB-SFT	XLXLJ600SFT15	48.3	155	114.3	22	M20	4	22.3	50.0	70	32	6	102	73.0
50	2	LJ-600LB-SFT	XLXLJ600SFT2	60.3	165	127.0	18	M16	8	25.4	62.5	84	37	8	152	91.9
65	2.5	LJ-600LB-SFT	XLXLJ600SFT25	76.1	190	149.2	22	M20	8	28.6	78.5	100	41	8	152	104.6
80	3	LJ-600LB-SFT	XLXLJ600SFT3	88.9	210	168.3	22	M20	8	31.8	91.4	117	46	10	152	127.0
100	4	LJ-600LB-SFT	XLXLJ600SFT4	114.3	275	215.9	26	M24	8	38.1	116.8	152	54	11	152	157.2
125	5	LJ-600LB-SFT	XLXLJ600SFT5	139.7	330	266.7	30	M27	8	44.5	144.4	189	60	11	203	185.7
150	6	LJ-600LB-SFT	XLXLJ600SFT6	168.3	355	292.1	30	M27	12	47.7	171.4	222	67	13	203	215.9
200	8	LJ-600LB-SFT	XLXLJ600SFT8	219.1	420	349.2	33	M30	12	55.6	222.2	273	76	13	203	269.7
250	10	LJ-600LB-SFT	XLXLJ600SFT10	273	510	431.8	36	M33	16	63.5	277.4	343	111	13	254	323.8
300	12	LJ-600LB-SFT	XLXLJ600SFT12	323.9	560	489.0	36	M33	20	66.7	328.2	400	117	13	254	381.0
350	14	LJ-600LB-SFT	XLXLJ600SFT14	355.6	605	527.0	39	M36×3	20	69.9	360.2	432	127	13	305	412.8
400	16	LJ-600LB-SFT	XLXLJ600SFT16	406.4	685	603.2	42	M39×3	20	76.2	411.2	495	140	13	305	469.9
450	18	LJ-600LB-SFT	XLXLJ600SFT18	457	745	654.0	45	M42×3	20	82.6	462.3	546	152	13	305	533.4
500	20	LJ-600LB-SFT	XLXLJ600SFT20	508	815	723.9	45	M42×3	24	88.9	514.4	610	165	13	305	584.2
600	24	LJ-600LB-SFT	XLXLJ600SFT24	610	940	838.2	51	M48×3	24	101.6	616.0	718	184	13	305	692.2

Easy bolt hole alignment: The freely rotating flange ring allows convenient positioning during installation.

Cost saving on expensive materials: Only the Stub End requires corrosion-resistant alloy material, reducing overall material costs.

Easy assembly and repeated disassembly: Suitable for piping systems requiring frequent maintenance or inspection.

Excellent corrosion resistance: Ideal for applications involving corrosive media and special alloy piping systems.

The flange connection is completed by tightening bolts between the Lap Joint Flange and the mating flange, compressing the gasket to achieve reliable face sealing performance.

Lap Joint Flange

Product details

Product Specifications

LJ-150LB-900LB

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