IBR Approved · Buttweld Fittings
Lap Joint Stub End Manufacturer
Type A and Type B stub ends to ASME B16.9 / MSS SP-43 — used with lap joint backing flanges. In carbon, alloy, stainless and duplex steel, 1/2" to 24" NB. IBR approved with Form IV (Part D) (formerly Form III-C), EN 10204 3.1 / 3.2 traceable.
Overview
A stub end is buttwelded to the pipe and paired with a loose lap joint (backing) flange that slides over the barrel. Only the stub end contacts the fluid, so the backing flange can be a cheaper material and can rotate freely for bolt-hole alignment. This makes stub ends ideal for frequently dismantled joints and for expensive alloy piping, where only the stub end need be the alloy grade.
Every stub end is produced to the applicable material specification with full traceability, supplied with EN 10204 3.1 or 3.2 test certificates and, for boiler and steam service, IBR Form IV (Part D) certification.
Stub End Types & Standards
| Type | Barrel / Lap | Standard | Matches |
|---|---|---|---|
| Type A | Long barrel, radiused lap | ASME B16.9 | Slip-on / lap joint flanges |
| Type B | Short barrel, larger lap OD | MSS SP-43 | Lap joint flanges |
| Short / Long pattern | Per flange face | ASME B16.9 | To customer flange spec |
Available Material Grades
Stub ends are supplied in our full material range. Click a grade for full specification, chemistry and mechanical data:
Technical Specifications
| Parameter | Range |
|---|---|
| Size range | 1/2" to 24" NB (larger on enquiry) |
| Schedules | SCH 10, STD, XS, SCH 80, SCH 160, XXS |
| Dimensional standard | ASME B16.9 / MSS SP-43 |
| End preparation | Bevel end per ASME B16.25 |
| Certification | EN 10204 3.1 / 3.2 · IBR Form IV (Part D) |
| Testing | PMI, dimensional, DP / RT as specified |
Testing & Inspection
- ✓ Chemical and mechanical testing against the ordered ASTM / ASME material specification
- ✓ PMI (positive material identification) and visual and dimensional inspection to ASME B16.9
- ✓ NDT (DP / MPI, UT or RT) as your specification requires
- ✓ EN 10204 3.1 certificate as standard; 3.2 witnessed by Bureau Veritas, TÜV, Lloyd’s Register, SGS, DNV or your own inspector
- ✓ IBR Form IV (Part D) for Indian boiler piping
Export Documents & Packing
- ✓ Commercial invoice, packing list and certificate of origin
- ✓ Heat-number traceability on every piece
- ✓ Seaworthy wooden cases or pallets, bevel ends protected, marked to your instructions
- ✓ FOB, CFR or CIF terms — see how an export order works
Frequently Asked Questions
What is a lap joint stub end used for?
A stub end is buttwelded to the pipe and used with a loose lap joint (backing) flange that slides over it. The bolts pass through the backing flange while only the stub end contacts the fluid, so the flange can be a cheaper material and can rotate freely for easy bolt-hole alignment. Stub ends are ideal for frequently dismantled joints and for expensive alloy systems where only the stub end needs to be the alloy grade.
What is the difference between Type A and Type B stub ends?
Type A stub ends have a longer barrel and a machined radius at the back of the lap suited to ASME B16.5 slip-on/lap-joint flanges; Type B have a shorter barrel with a larger lap outside diameter designed to match ASME B16.5 lap joint flanges. Both are made to ASME B16.9 / MSS SP-43 and selected to suit the backing flange used.
Which certificates and documents come with your stub ends?
EN 10204 3.1 certificates as standard, 3.2 with third-party inspection, IBR Form IV (Part D) (formerly Form III-C) where the fittings are for Indian boiler piping, plus export documents: commercial invoice, packing list and certificate of origin.