Fittings and flanges are small items on a piping bill of materials, but they are where most mismatches between pipe, valves and equipment show up during installation. An elbow with the wrong wall thickness, a flange with the wrong facing, or a material grade that does not match the line class can stop fabrication. This article covers what to specify so that every offer matches your piping specification.
Start from the piping class
On oil, gas and petrochemical projects, fittings and flanges are defined by the piping class in the project specification: the material, the pressure rating and the design conditions of each line. Send the piping class sheets with your enquiry. If you only send a list of sizes, suppliers will fill the gaps with their own assumptions.
Butt-weld fittings
Butt-weld fittings — elbows, returns, tees, reducers and caps — are welded directly to the pipe and are the usual choice for process and pipeline service. For each item, state:
- The dimensional standard (commonly ASME B16.9) and the material standard and grade, for example carbon steel, low-temperature carbon steel, stainless steel or a nickel alloy.
- Size and wall thickness or schedule, matching the pipe it will be welded to.
- Seamless or welded construction, if your specification restricts it.
- End preparation (bevel) and any special requirements such as sour-service qualification.
See our butt-welding elbows and returns, concentric and eccentric reducers and seamless and welded butt-weld fittings.
Flanges
A flange has to match the pipe on one side and the valve, vessel or equipment nozzle on the other. Specify:
- Type: weld neck, slip-on, blind, socket weld, threaded or lap joint.
- Dimensional standard (commonly ASME B16.5, or ASME B16.47 for larger diameters) and pressure class.
- Facing: raised face, flat face or ring-type joint, and the surface finish required for your gaskets.
- Bore or schedule for weld neck flanges, so the bore matches the pipe.
- Material standard and grade, and any impact-testing or sour-service requirements.
See our forged weld neck flanges, forged slip-on flanges and forged flanges.
Documents and marking
Ask for mill test certificates that cover chemical composition and mechanical properties, with heat numbers marked on each piece so that fittings can be traced after fabrication. Agree the marking and the packing — end protection for bevels and facings matters — before production. For critical lines, third-party inspection by a body such as SGS or BV is common practice; where you request it through us, the fee is paid by the buyer.
Order fittings with the pipe
Fittings and flanges are often ordered late, after the pipe, and then hold up the fabrication shop. Ordering them on the same schedule and in matching materials avoids that. If you are also sourcing line pipe or casing, read our guide to specifying line pipe and OCTG.
How we work
YuxingCorp coordinates supply from manufacturers we have visited and qualified, together with supplier coordination and shipping and freight logistics coordination. Each shipment comes with a complete export document pack — commercial invoice, packing list, certificate of origin and bill of lading. Import customs clearance, duties, taxes and local registration are the buyer’s responsibility. Our standard payment terms are T/T: 30% deposit and 70% before shipment.
Related reading
- Line pipe and OCTG: what to specify
- How to source steel materials for infrastructure and industrial projects
- Tower packing and column internals: what to specify
Send us your piping class and quantities
Send the piping class sheets, the item list with sizes and quantities, the destination and your timeline. We respond within one business day.