Socket weld flange

INTRO

Our socket weld flanges offer a reliable and robust solution for connecting pipes in high-pressure and high-temperature systems.

Designed for superior sealing and strength, these flanges are ideal for use in demanding industries such as petroleum, chemical processing, natural gas, and power stations.

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

Socket Weld Flanges are used for small-size and high-pressure piping that do not transfer highly corrosive fluids.This due to the fact that these flange types are subject to corrosion in the gap area between the end of the pipe and the shoulder of the socket.

Manufacturer Intro

Longan Flange manufactures stainless steel socket weld flanges designed for small-bore, high-pressure piping applications. Our socket weld flanges cover DN10 to DN80, available in PN10 through PN100 per DIN/HG standards, and Class 150 through Class 1500 (PN20–PN260) per ASME B16.5. Available in SS304, 304L, 316L, duplex 2205, and super duplex 2507. The recessed socket allows the pipe to be inserted before fillet welding, providing strong joints without the need for beveling. All flanges forged and machined in-house. ISO 9001 & PED certified. Quote within 24 hours.

Socket Weld Flange Pressure Classes at a Glance

Longan Flange supplies socket weld flanges across both DIN/HG PN ratings and ASME Class ratings, covering DN10 to DN80. Complete dimensions for every rating below are listed in the tables further down this page.

Standard	Pressure Rating	DN Range	Reference Standard No.
DIN / HGEurope	PN10	DN10 – DN50	HG/T20597-2009(SW)
DIN / HGEurope	PN16	DN10 – DN50	HG/T20597-2009(SW)
DIN / HGEurope	PN25	DN10 – DN50	HG/T20597-2009(SW)
DIN / HGEurope	PN40	DN10 – DN50	HG/T20597-2009(SW)
DIN / HGEurope	PN63	DN10 – DN50	HG/T20597-2009(SW)
DIN / HGEurope	PN100	DN10 – DN50	HG/T20597-2009(SW)
ASMEAmericas	Class 150 (≈ PN20)	DN15 – DN80	HG/T20619-2009(SW)
ASMEAmericas	Class 300 (≈ PN50)	DN15 – DN80	HG/T20619-2009(SW)
ASMEAmericas	Class 600 (≈ PN110)	DN15 – DN80	HG/T20619-2009(SW)
ASMEAmericas	Class 900 (≈ PN150)	DN15 – DN65	HG/T20619-2009(SW)
ASMEAmericas	Class 1500 (≈ PN260)	DN15 – DN65	HG/T20619-2009(SW)

PN-to-Class equivalence shown above (e.g. Class 150 ≈ PN20) reflects the manufacturer’s catalog labeling convention and is approximate, not an exact regulatory conversion — please confirm the exact standard required for your project at the RFQ stage.

Socket Weld vs. Slip-On Flange: Which One Do You Need?

Socket weld flanges are best suited to small-bore (≤DN80), high-pressure piping where a strong, leak-resistant joint is critical — the pipe is recessed into the socket before fillet welding, providing better fatigue resistance than a slip-on connection. Slip-on flanges, by contrast, are easier and more affordable to install and cover a wider size range, but with lower joint strength, making them better suited to Class 150–300 services. See our Slip-On Flanges page for full details if your application falls in that range.

Quality Control for Precise Socket Fit

Material Testing

Spectral detection for composition

Forging

Solid forged, no cast components

CNC Machining

Socket bore & depth precision

Final Inspection

Dimensional check & material traceability

📦

MOQ from 1 Piece

Standard sizes and ratings available from a single piece.

⚡

Quote Within 24 Hours

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

📜

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.

A Note on Application: Not for Highly Corrosive Media

Socket weld flanges are best suited to small-size, high-pressure piping that does not carry highly corrosive fluids. This is because the gap between the pipe end and the socket shoulder can be a site for crevice corrosion over time. For corrosive media, please consult our engineers about weld neck flange options instead.

FAQ

What sizes are available for socket weld flanges?

Our stainless steel socket weld flanges are available from DN10 to DN80, covering PN10 through PN100 as well as ASME Class 150 through Class 1500 (PN20–PN260). Dimensions for each pressure rating are listed in the tables above.

When should I choose a socket weld flange over a slip-on flange?

Socket weld flanges are preferred for small-bore (≤DN100), high-pressure piping where strong, leak-resistant joints are critical. They provide better fatigue resistance than slip-on flanges because the pipe is recessed into the socket before welding.

What is the lead time and MOQ?

MOQ starts from 1 piece.

###CLASS 150###

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1		Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)				B2		U
15	1/2	21.3	90	88.9	60.3	16	15.7	4	9.6	15.5	15.7	22.5	22.4	10	30	14	0.42
20	3/4	26.9	100	98.6	69.9	16	15.7	4	11.2	21	20.8	27.5	27.7	11	38	14	0.59
25	1	33.7	110	108	79.4	16	15.7	4	12.7	27	26.7	34.5	34.5	13	49	16	0.81
32	1 1/4	42.4	115	117.3	88.9	16	15.7	4	14.3	35	35.1	43.5	43.2	14	59	19	1.07
40	1 1/2	48.3	125	127	98.4	16	15.7	4	15.9	41	40.9	49.5	49.5	16	65	21	1.36
50	2	60.3	150	152.4	120.7	18	19.1	4	17.5	52	52.6	61.5	62	17	78	24	2.1
65	2 1/2	76.1	180	177.8	139.7	18	19.1	4	20.7	66	62.7	77.6	74.7	19	90	27	3.33
80	3	88.9	190	190.5	152.4	18	19.1	4	22.3	77.5	78	90.5	90.7	21	108	29	3.9

###CLASS 300###

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1		Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)				B2		U
15	½	21.3	95	88.9	66.7	16	15.7	4	12.7	15.5	15.7	22.5	22.4	10	38	21	0.66
20	¾	26.9	115	98.6	82.6	18	15.7	4	14.3	21	20.8	27.5	27.7	11	48	24	1.15
25	1	33.7	125	108	88.9	18	15.7	4	15.9	27	26.7	34.5	34.5	13	54	25	1.4
32	1 ¼	42.4	135	117.3	98.4	18	15.7	4	17.5	35	35.1	43.5	43.2	14	64	25	1.75
40	1 ½	48.3	155	127	114.3	22	15.7	4	19.1	41	40.9	49.5	49.5	16	70	29	2.55
50	2	60.3	165	152.4	127	18	19.1	8	20.7	52	52.6	61.5	62	17	84	32	2.93
65	2 ½	76.1	190	177.8	149.2	22	19.1	8	23.9	66	62.7	77.6	74.7	19	100	37	4.4
80	3	88.9	210	190.5	168.3	22	19.1	8	27	77.5	78	90.5	90.7	21	117	41	5.92

###CLASS 600###

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1	Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)			B2		U
15	1/2	21.3	95	88.9	66.7	16	15.7	4	14.3	–	22.5	22.4	10	38	22	0.76
20	3/4	26.9	115	98.6	82.6	18	15.7	4	15.9	–	27.5	27.7	11	48	25	1.29
25	1	33.7	125	108	88.9	18	15.7	4	17.5	–	34.5	34.5	13	54	27	1.55
32	1 1/4	424	135	117.3	98.4	18	15.7	4	20.7	–	43.5	43.2	14	64	29	2.06
40	1 1/2	48.3	155	127	114.3	22	15.7	4	22.3	–	49.5	49.5	16	70	32	3.00
50	2	60.3	165	152.4	127	18	19.1	8	25.4	–	61.5	62	17	84	37	3.67
65	2 1/2	76.1	190	177.8	149.2	22	19.1	8	28.6	–	77.6	74.7	19	100	41	5.35
80	3	88.9	210	190.5	168.3	22	19.1	8	31.8	–	90.5	90.7	21	117	46	7.06

###CLASS 900###

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1	Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)			B2		U
15	½	21.3	120	120.6	82.6	22	22.3	4	22.3	–	22.5	22.4	10	38	32	1.8
20	¾	26.9	130	130	88.9	22	22.3	4	25.4	–	27.5	27.7	11	44	35	2.41
25	1	33.7	150	149.3	101.6	26	25.4	4	28.6	–	34.5	34.5	13	52	41	3.55
32	1¼	42.4	160	158.7	111.1	26	25.4	4	28.6	–	43.5	43.2	14	64	41	4.02
40	1½	48.3	180	177.8	123.8	30	28.4	4	31.8	–	49.5	49.5	16	70	44	5.45
50	2	60.3	215	215.9	165.1	26	25.4	8	38.1	–	61.5	62	17	105	57	10.2
65	2½	76.1	245	244.3	190.5	30	28.4	8	41.3	–	77.6	74.7	19	124	64	13.9

Frequently Asked Questions (FAQs)

What are the ideal applications for socket weld flanges?

Socket weld flanges are best suited for small-size, high-pressure piping systems that do not handle highly corrosive fluids due to potential corrosion in the gap area.

How does the static and fatigue strength of socket weld flanges compare to other flanges?

Socket weld flanges offer similar static strength to slip-on flanges but have higher fatigue strength due to the single fillet weld, which enhances durability under fluctuating loads.

What materials are available for socket weld flanges?

Our socket weld flanges come in a variety of materials, including 304, 304L, 316L stainless steels, and high-strength alloys like 2507 and 2205, catering to diverse application needs.