ASME B16.5 · ASME B16.47
Slip-On Flange Manufacturer — ASME B16.5, Class 150–2500
Slip-on flanges slide over the pipe and are fillet-welded on both sides. They are the most economical B16.5 flange for low-pressure, low-temperature lines where alignment matters more than fatigue life.
Standard
ASME B16.5 / EN 1092-1 / DIN
Size range
1/2″–24″ (DN15–DN600)
Pressure class
150 / 300 / 600 / 900 / 1500 / 2500
Materials
A105, A350 LF2, 304/316L, F11/F22
Faces
RF, FF
Weld
Fillet weld, both sides
A slip-on flange (SO) is positioned by sliding the bore over the pipe until the hub face sits at the correct stand-out, then welded with a fillet on both the inside and outside. The double fillet gives a robust joint and the generous bore makes field alignment simple, which is why slip-on flanges dominate utility water, HVAC, fire protection and low-pressure process lines.
The trade-off is mechanical: the pipe does not pass through a tapered hub, so the flange is weaker in fatigue and cannot be radiographed like a butt weld. We therefore recommend slip-on flanges for Class 150 and 300 service at moderate temperature, and weld neck flanges for cyclic, high-pressure or severe-service duties. Slip-on flanges are machined to B16.5 in A105, A350 LF2, 304/304L, 316/316L and F11/F22, with RF or FF faces and a 125–250 AARH finish.
ASME B16.5 dimensions — Class 150 and 300
All values in millimetres (inch equivalent in brackets). Wall thickness, bore and hub are machined to the ordered standard. Size-specific pages include the full dimensional record for that size and class.
Class 150 slip-on flange
| Size | OD | Thickness | RF Ø | Bolt circle | Bolts | Approx. weight | |
|---|---|---|---|---|---|---|---|
| 2″ / DN50 | 150 mm (5.91″) | 17.5 mm (0.69″) | 92.1 mm (3.63″) | 120.7 mm (4.75″) | 4 × Ø19 mm | 2.3 kg (5.1 lb) | Details → |
| 4″ / DN100 | 230 mm (9.06″) | 22.3 mm (0.88″) | 157.2 mm (6.19″) | 190.5 mm (7.5″) | 8 × Ø19 mm | 5.9 kg (13 lb) | Details → |
| 6″ / DN150 | 280 mm (11.02″) | 23.9 mm (0.94″) | 215.9 mm (8.5″) | 241.3 mm (9.5″) | 8 × Ø22.2 mm | 8.6 kg (19 lb) | Details → |
| 8″ / DN200 | 345 mm (13.58″) | 27 mm (1.06″) | 269.9 mm (10.63″) | 298.5 mm (11.75″) | 8 × Ø22.2 mm | 13.7 kg (30.2 lb) | Details → |
| 12″ / DN300 | 485 mm (19.09″) | 30.2 mm (1.19″) | 381 mm (15″) | 431.8 mm (17″) | 12 × Ø25.4 mm | 29 kg (63.9 lb) | Details → |
Class 300 slip-on flange
| Size | OD | Thickness | RF Ø | Bolt circle | Bolts | Approx. weight | |
|---|---|---|---|---|---|---|---|
| 2″ / DN50 | 165 mm (6.5″) | 20.7 mm (0.81″) | 92.1 mm (3.63″) | 127 mm (5″) | 8 × Ø19 mm | 3.2 kg (7.1 lb) | Details → |
| 4″ / DN100 | 255 mm (10.04″) | 30.2 mm (1.19″) | 157.2 mm (6.19″) | 200 mm (7.87″) | 8 × Ø22.2 mm | 10 kg (22 lb) | Details → |
| 6″ / DN150 | 320 mm (12.6″) | 35 mm (1.38″) | 215.9 mm (8.5″) | 269.9 mm (10.63″) | 12 × Ø22.2 mm | 17.7 kg (39 lb) | Details → |
| 8″ / DN200 | 380 mm (14.96″) | 39.7 mm (1.56″) | 269.9 mm (10.63″) | 330.2 mm (13″) | 12 × Ø25.4 mm | 26 kg (57.3 lb) | Details → |
| 12″ / DN300 | 520 mm (20.47″) | 49.3 mm (1.94″) | 381 mm (15″) | 450.8 mm (17.75″) | 16 × Ø31.8 mm | 52 kg (114.6 lb) | Details → |
Need Class 600–2500, RTJ faces or sizes above 12″? Send the size and class and we will return a dimensioned drawing and price the same day.
Key features
Easy field alignment
The clearance bore lets the flange be rotated and positioned on the pipe before welding, which reduces fit-up time on site and in fabrication shops.
Lower unit cost
Less material and simpler machining than a weld neck flange — the right choice when the line is not fatigue- or pressure-critical.
Both-side fillet weld
The hub is machined with a defined stand-out so the welder can run a consistent fillet inside and outside without burning through the pipe wall.
Standard and custom bores
Bores are machined to the mating pipe OD; for thin-wall or lined pipe we adjust the bore and hub to keep the weld sound.
Typical applications
- Utility water, cooling water and fire-protection lines
- HVAC and building services piping
- Low-pressure chemical and food-grade lines
- Compressed air and inert gas distribution
- Tank and vessel connections
- Retrofit and maintenance work where alignment is difficult
Quality control & documentation
- Dimensional inspection to B16.5 tables, recorded per lot
- Visual and PMI check on stainless and alloy heats
- MTC 3.1 per heat with chemical and mechanical results
- Face flatness and surface finish checked before packing
Material certificates to EN 10204 3.1 are issued with every shipment; third-party inspection (SGS, BV, TÜV) can be arranged on request.
Frequently asked questions
Where should a slip-on flange not be used?
Avoid slip-on flanges in cyclic or high-pressure service, in lines that will be radiographed, and where crevice corrosion is a risk — the gap between pipe and bore can trap process fluid. Use weld neck flanges in those cases.
How far should the pipe sit inside the flange?
Set the pipe end flush with the flange face minus the weld preparation, so the pipe does not protrude into the gasket area. We can mark the stand-out on the hub on request.
Do you supply slip-on flanges to DIN or EN?
Yes — DIN 2632/2633 and EN 1092-1 Type 12/13 are available alongside ASME B16.5. Send the standard and pressure rating (PN or class) and we will confirm dimensions.
Request a quotation
Send your slip-on flange specification
Include the standard, size, pressure class, material, face type and quantity. Drawings are welcome — we will confirm feasibility, lead time and price within one business day.
- ★ Reply within 24 hours on business days
- ★ MTC 3.1 and dimensional report with every order
- ★ FOB, CIF and DDP terms available
Send an Inquiry
Send drawings, dimensions or a standard reference. Our sales engineers reply within 24 hours on business days.