Slip-On Flanges
Giriraj Impex is a manufacturer, stockist, supplier and exporter of slip-on flanges to ASME B16.5 from ½" to 24" NB in Class 150, 300, 400, 600, 900 and 1500, to ASME B16.47 for larger sizes on request, and to EN 1092-1 Types 01 and 12. We manufacture slip-on flanges in stainless steel, carbon steel, alloy steel, duplex and super duplex steel and nickel alloys, with raised face and flat face, with mill test certificates.
A slip-on flange slides over the pipe and is fillet welded inside and outside. It is easy to align and economical, and is widely used for water, air, cooling water, firewater and low-pressure process lines.
What is a slip-on flange?
The slip-on (SO) flange has a bore slightly larger than the pipe's outside diameter, so the pipe slides into it. The flange is attached by two fillet welds: one at the hub outside, and one at the pipe end inside the bore, set back from the flange face. Because the pipe position can be adjusted before welding, slip-on flanges are easy to align, and they need less accurate cutting of the pipe length than weld neck flanges. They have a short hub and are lighter and cheaper than weld neck flanges.
Specifications
| Item | Details |
|---|---|
| Dimensional standards | ASME B16.5; ASME B16.47 on request; EN 1092-1 Type 01 (plate) and Type 12 (hubbed); MSS SP-44 |
| Sizes | ½" to 24" NB (B16.5) |
| Classes | 150, 300, 400, 600, 900, 1500; PN ratings to EN 1092-1 |
| Facings | Raised face (RF), flat face (FF) |
| Bore | To suit pipe outside diameter |
| Coating (carbon steel) | Black paint, yellow paint, rust-preventive oil, hot-dip galvanised |
| Documents | Mill test certificate (MTC); third-party inspection on request |
Slip-on flange materials
- Stainless steel flanges – ASTM A182 F304/304L, F316/316L, F321, F347.
- Carbon steel flanges – ASTM A105, A350 LF2, A694 F42–F70.
- Alloy steel flanges – ASTM A182 F5, F9, F11, F22, F91.
- Duplex steel flanges – ASTM A182 F51, F60.
- Super duplex flanges – ASTM A182 F53, F55.
- Inconel flanges – ASTM B564 alloys 600 and 625, and other nickel alloys.
All flange materials are on the flanges page.
ASME B16.5 Class 150 dimensions
| NPS | Outside diameter | Min. thickness | Bolt circle | No. of bolts | Bolt hole |
|---|---|---|---|---|---|
| ½ | 90 | 9.6 | 60.3 | 4 | 16 |
| ¾ | 100 | 11.2 | 69.9 | 4 | 16 |
| 1 | 110 | 12.7 | 79.4 | 4 | 16 |
| 1¼ | 115 | 14.3 | 88.9 | 4 | 16 |
| 1½ | 125 | 15.9 | 98.4 | 4 | 16 |
| 2 | 150 | 17.5 | 120.7 | 4 | 19 |
| 2½ | 180 | 20.7 | 139.7 | 4 | 19 |
| 3 | 190 | 22.3 | 152.4 | 4 | 19 |
| 4 | 230 | 22.3 | 190.5 | 8 | 19 |
| 5 | 255 | 22.3 | 215.9 | 8 | 22 |
| 6 | 280 | 23.9 | 241.3 | 8 | 22 |
| 8 | 345 | 27.0 | 298.5 | 8 | 22 |
| 10 | 405 | 28.6 | 362.0 | 12 | 25 |
| 12 | 485 | 30.2 | 431.8 | 12 | 25 |
| 14 | 535 | 33.4 | 476.3 | 12 | 29 |
| 16 | 595 | 35.0 | 539.8 | 16 | 29 |
| 18 | 635 | 38.1 | 577.9 | 16 | 32 |
| 20 | 700 | 41.3 | 635.0 | 20 | 32 |
| 24 | 815 | 46.1 | 749.3 | 20 | 35 |
Dimensions are from ASME B16.5 (2013 and later editions) and are given for guidance. Minimum thickness excludes the raised face for Class 400 and above. Always check the current edition of the standard and the project specification. More classes and dimensions are in the flange dimensions chart.
Slip-on vs weld neck flanges
| Feature | Slip-on | Weld neck |
|---|---|---|
| Attachment | Two fillet welds | One butt weld |
| Alignment | Easy, pipe slides in | Pipe must be cut and fitted accurately |
| Strength under pressure | About two-thirds of a weld neck flange | Highest |
| Fatigue life | Roughly one-third of a weld neck flange | Highest |
| Weld inspection | Fillet welds – surface tests only | Butt weld – can be radiographed |
| Cost | Lower | Higher |
| Typical service | Water, air, utilities, low pressure | High pressure and temperature, cyclic, critical |
Many piping specifications limit slip-on flanges to Class 150 and 300 and to non-cyclic, non-hazardous service, and use weld neck flanges elsewhere.
How we manufacture slip-on flanges
We manufacture slip-on flanges from forged blanks or, for plate-type flanges to EN 1092-1 Type 01, from plate of certified material. Machining covers the bore to suit the pipe, the facing and face finish, the hub and the bolt holes. Every flange is marked with material, size, class, facing and heat number and inspected before dispatch. Carbon steel slip-on flanges for water and firewater lines are often supplied hot-dip galvanised.
Ordering slip-on flanges
Please give the material, size, class, facing, pipe outside diameter if not standard, coating, quantity and any testing or third-party inspection. Flanges are packed in wooden boxes or on pallets.
Frequently Asked Questions
A slip-on flange slides over the pipe and is attached with fillet welds inside and outside. It is easy to align and economical for low-pressure service.
A slip-on flange is fillet welded and costs less; a weld neck flange is butt welded through a tapered hub and gives higher strength and fatigue life.
Slip-on flanges are used for water, cooling water, air, firewater and low-pressure process lines, often limited to Class 150 and 300.
ASME B16.5 covers slip-on flanges from ½" to 24" NB; EN 1092-1 Types 01 and 12 cover metric slip-on flanges.
With two fillet welds: one on the outside at the hub and one inside the bore at the pipe end, set back from the flange face.
Yes. Carbon steel slip-on flanges are supplied hot-dip galvanised for water and firewater service.
Request a Quote for Slip-On Flanges
Tell us the product, grade, size, standard, quantity and delivery location, and our sales team will reply with a quotation.
Inconel® is a trademark of Special Metals Corporation.