Slip-On Flanges

INTRO

The Slip-On Flange is designed to accommodate lower pressure and temperature applications, featuring a central bore that matches the outside diameter of the pipe. This allows for easy pipe insertion and secure fillet welding on both the interior and exterior sides.

The absence of a weld bevel offers flexibility in adjusting pipe length relative to the flange's position.

Available in large sizes, Slip-On Flanges are ideal for connecting big-bore piping to storage tank nozzles. Typically forged with a hub, they can also be fabricated without one in a ring style for applications with limited space.

Standard：
GB/T9119-2010 HG/T20592-2009 HG/T20615-2009 DIN ASME BS JIS

Material：
304：F304 S30408 S30408II S30408III S30400
304L：S30403 S30403II 30403 30403II
316L：31603 31603II 31603III
2507（F53） 2205（F51） TP310S（06Cr5Ni20） TP321（06Cr18Ni11） S22053III=2205III T321-32168=321

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DESCRIPTION DOWNLOAD

Manufacturer Intro

Longan Flange manufactures stainless steel slip-on flanges for industrial piping systems worldwide. Our slip-on flanges range from DN15 to DN600, covering Class 150 through Class 1500 per ASME B16.5, as well as DIN and GOST standards. Materials include SS304, 304L, 316L, duplex 2205 (F51), and super duplex 2507 (F53). Forged with a raised hub for added strength, each flange is machined in-house for precise bore-to-pipe fit. Slip-on flange dimensions for all classes are available in the tables below. ISO 9001 & PED certified. Factory-direct pricing with quotes within 24 hours.

Quality Control for Precise Bore-to-Pipe Fit

Material Testing

Spectral detection for composition

Hub Forging

Raised hub for added strength

CNC Bore Machining

Precise bore-to-pipe fit accuracy

Final Inspection

Dimensional & bore diameter check

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MOQ from 1 Piece

Standard sizes and classes available from a single piece.

⚡

Quote Within 24 Hours

Factory-direct technical quotations delivered within 24 hours of your inquiry.

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ISO 9001 / ISO 14001 / ISO 45001 / CE / PED

Manufactured in a certified facility, compliant with ASME B16.5, DIN, and GOST standards. MTC per EN 10204 3.1 supplied with every order.

FAQ

What sizes of stainless steel slip-on flanges do you supply?

We supply stainless steel slip-on flanges from DN15 (NPS ½”) to DN600 (NPS 24″) in Class 150 through Class 1500. Custom large-diameter slip-on flanges up to DN4000 are available for tank nozzle connections.

What is the difference between a slip-on flange and a weld neck flange?

A slip-on flange slides over the pipe and is fillet-welded on both sides, making it easier to align and more affordable. A weld neck flange is butt-welded to the pipe, providing superior strength for high-pressure applications. Slip-on flanges are best suited for Class 150 and Class 300 services.

Can slip-on flanges be used in high-pressure systems?

Slip-on flanges are supplied from Class 150 through Class 1500 per ASME B16.5, covering a wide range of pressure requirements. Please confirm your specific class and operating conditions at the RFQ stage so we can recommend the right flange type for your application.

What is the lead time and MOQ?

MOQ starts from 1 piece.

###CLASS 150###

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	90	60.3	16	4	M14	9.6	22.5	30	14
20	3/4	26.9	100	69.9	16	4	M14	11.2	27.5	38	14
25	1	33.7	110	79.4	16	4	M14	12.7	34.5	49	16
32	1 1/4	42.4	115	88.9	16	4	M14	14.3	43.5	59	19
40	1 1/2	48.3	125	98.4	16	4	M14	15.9	49.5	65	21
50	2	60.3	150	120.7	18	4	M16	17.5	61.5	78	24
65	2 1/2	76.1	180	139.7	18	4	M16	20.7	77.6	90	27
80	3	88.9	190	152.4	18	4	M16	22.3	90.5	108	29
100	4	114.3	230	190.5	18	8	M16	22.3	116.0	135	32
125	5	139.7	255	215.9	22	8	M20	22.3	143.5	164	35
150	6	168.3	280	241.3	22	8	M20	23.9	170.5	192	38
200	8	219.1	345	298.5	22	8	M20	27.0	221.5	246	43
250	10	273.0	405	362	26	12	M24	28.6	276.5	305	48
300	12	323.9	485	431.8	26	12	M24	30.2	328.0	365	54
350	14	355.6	535	476.3	30	12	M27	33.4	360.0	400	56
400	16	406.4	595	539.8	30	16	M27	35.0	411.0	457	62
450	18	457	635	577.9	33	16	M30	38.1	462.0	505	67
500	20	508	700	635	33	20	M30	41.3	513.5	559	71
600	24	610	815	749.3	36	20	M33	46.1	616.5	663	81

###CLASS 300###

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	95	66.7	16	4	M14	12.7	22.5	38	21
20	3/4	26.9	115	82.6	18	4	M16	14.3	27.5	48	24
25	1	33.7	125	88.9	18	4	M16	15.9	34.5	54	25
32	1 1/4	42.4	135	98.4	18	4	M16	17.5	43.5	64	25
40	1 1/2	48.3	155	114.3	22	4	M20	19.1	49.5	70	29
50	2	60.3	165	127	18	8	M16	20.7	61.5	84	32
65	2 1/2	76.1	190	149.2	22	8	M20	23.9	77.6	100	37
80	3	88.9	210	168.3	22	8	M20	27	90.5	117	41
100	4	114.3	255	200	22	8	M20	30.2	116	146	46
125	5	139.7	280	235	22	8	M20	33.4	143.5	178	49
150	6	168.3	320	269.9	22	12	M20	35	170.5	206	51
200	8	219.1	380	330.2	26	12	M24	39.7	221.5	260	60
250	10	273	445	387.4	30	16	M27	46.1	276.5	321	65
300	12	323.9	520	450.8	33	16	M30	49.3	328	375	71
350	14	355.6	585	514.4	33	20	M30	52.4	360	425	75
400	16	406.4	650	571.5	36	20	M33	55.6	411	483	81
450	18	457	710	628.6	36	24	M33	58.8	462	533	87
500	20	508	775	685.8	36	24	M33	62	513.5	587	94
600	24	610	915	812.8	42	24	M39X3	68.3	616.5	702	105

###CLASS 600###

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	95	66.7	16	4	M14	14.3	22.5	38	22
20	3/4	26.9	115	82.6	18	4	M16	15.9	27.5	48	25
25	1	33.7	125	88.9	18	4	M16	17.5	34.5	54	27
32	1 1/4	42.4	135	88.4	18	4	M16	20.7	43.5	64	29
40	1 1/2	48.3	155	114.3	22	4	M20	22.3	49.5	70	32
50	2	60.3	165	127	18	8	M16	25.4	61.5	84	37
65	2 1/2	76.1	190	149.2	22	8	M20	28.6	77.6	100	41
80	3	88.9	210	168.3	22	8	M20	31.8	90.5	117	46
100	4	114.3	275	215.9	26	8	M24	38.1	116	152	54
125	5	139.7	330	266.7	30	8	M27	44.5	143.5	189	60
150	6	168.3	355	292.1	30	12	M27	47.7	170.5	222	67
200	8	219.1	420	349.2	33	12	M30	55.6	221.5	273	76
250	10	273	510	431.8	36	16	M33	63.5	276.5	343	86
300	12	323.9	560	489	36	20	M33	66.7	328	400	92
350	14	355.6	605	527	39	20	M36X3	69.9	360	432	94
400	16	406.4	685	603.2	42	20	M39X3	76.2	411	495	106
450	18	457	745	654	45	20	M42X3	82.6	462	546	117
500	20	508	815	723.9	45	24	M42X3	88.9	513.5	610	127
600	24	610	940	838.2	51	24	M48X3	101.6	616.5	718	140

###CLASS 900###

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	120	82.6	22	4	M20	22.3	22.5	38	32
20	3/4	26.9	130	88.9	22	4	M20	25.4	27.5	44	35
25	1	33.7	150	101.6	26	4	M24	28.6	34.5	52	41
32	1 1/4	42.4	160	111.1	26	4	M24	28.6	43.5	64	41
40	1 1/2	48.3	180	123.8	30	4	M27	31.8	49.5	70	44
50	2	60.3	215	165.1	26	8	M24	38.1	61.5	105	57
65	2 1/2	76.1	245	190.5	30	8	M27	41.3	77.6	124	64
80	3	88.9	240	190.5	26	8	M24	38.1	90.5	127	54
100	4	114.3	290	235	33	8	M30	44.5	116	159	70
125	5	139.7	350	279.4	36	8	M33	50.8	143.5	190	79
150	6	168.3	380	317.5	33	12	M30	55.6	170.5	235	86
200	8	219.1	470	393.7	39	12	M36X3	63.5	221.5	298	102
250	10	273	545	469.9	39	16	M36X3	69.9	276.5	368	108
300	12	323.9	610	533.4	39	20	M36X3	79.4	328	419	117
350	14	355.6	640	558.8	42	20	M39X3	85.8	360	451	130
400	16	406.4	705	616	45	20	M42X3	88.9	411	508	133
450	18	457	785	685.8	51	20	M48X3	101.6	462	565	152
500	20	508	855	749.3	55	20	M52X3	108	513.5	622	159
600	24	610	1040	901.7	68	20	M64X3	139.7	616.5	749	203

###CLASS 1500###

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	120	82.6	22	4	M20	22.3	22.5	38	32
20	3/4	26.9	130	88.9	22	4	M20	25.4	27.5	44	35
25	1	33.7	150	101.6	26	4	M24	28.6	34.5	52	41
32	1 1/4	42.4	160	111.1	26	4	M24	28.6	43.5	64	41
40	1 1/2	48.3	180	123.8	30	4	M27	31.8	49.5	70	44
50	2	60.3	215	165.1	26	8	M24	38.1	61.5	105	57
65	2 1/2	76.1	245	190.5	30	8	M27	41.3	77.6	124	64

Frequently Asked Questions (FAQs)

Are slip-on flanges appropriate for underground sewage systems?

Slip-on flanges are not recommended for underground sewage systems. This is due to the required welding process in such a context. According to experts, it is better to use flange adapters. Looking for other more suitable flanges may also work.

Is any specific surface preparation needed before welding slip-on flanges?

For better results, you may thoroughly clean slip-on flange surfaces. This practice ensures that the flange is free of debris or contaminants before welding.

Are slip-on flanges suitable for steam systems?

You may use slip-on flanges for steam piping systems. However, remember that their suitability still depends on the specific pressure and temperature conditions. Before buying slip-on flanges for steam systems, first, verify the application requirements. Consulting relevant standards may also help.

Do slip-on flanges provide a leak-proof connection?

When properly installed and welded, slip-on flanges can provide a secure connection that minimizes the risk of leaks.

What standards govern the use of slip-on flanges?

The installation and testing of slip-on flanges are governed by standards such as ASME B16.5 and ASME B31.3, which specify requirements for dimensions, materials, and pressure ratings