Flanges are chosen by type first and class second. The type decides how the flange joins the pipe — welded by the neck, slipped over and fillet welded, threaded on, or left loose on a stub end — and the class fixes the bolt circle, thickness and pressure-temperature rating from the standard's tables. Everything else on this page exists to help you land on the right type; each type then has its own page with its specification range.
The bolt circle is the fingerprint of a flange class: its diameter, hole count and hole size decide whether two flanges can be bolted together at all. Two flanges of the same NPS and class from different makers bolt together because B16.5 fixes those numbers. Two flanges of different classes do not — the most common flange error on site is assuming they will.
| Item | Range / Options |
|---|---|
| Types | Weld neck, slip-on, blind, threaded, socket weld, lap joint, orifice, long weld neck, spectacle blind, loose plate |
| Standards | ASME B16.5 (NPS 1/2 - 24), ASME B16.47 (large diameter), ASME B16.48 (line blanks); further patterns (DIN, SABS, JIS) appear in individual catalogue listings and are confirmed per product at enquiry |
| Size range | Per type — each type page states its anchored executions; sizes confirmed per product at enquiry |
| Pressure classes | Per type and product — confirmed at enquiry (catalogue executions include Class 150 and Class 300) |
| Faces | Raised face (RF), flat face (FF), ring-type joint (RTJ) — by type; see the type pages |
| Materials | Carbon steel ASTM A105 and low-temperature ASTM A350 LF2 in the catalogue executions referenced on this site; further grades are assessed against your enquiry for the specific product |
The Types at a Glance
ASME B16.5, B16.47 and the PN World
Buyers usually specify flanges to ASME B16.5 in inch sizes and pound classes, with large diameters continuing into ASME B16.47. Individual catalogue listings also carry metric PN patterns — the weld neck listing's title names DIN 2501 / 2673, PN10 / PN16 and SABS 1123, and JIS 5K / 10K slip-ons are listed in A350 LF2. The systems are not interchangeable: a PN16 flange does not bolt to a Class 150 flange of the same nominal size. Name the governing standard on every enquiry — and note that the standard for a specific flange product is confirmed against your specification before order.
How Flanges Are Made Here
Flanges start as forgings, are machined on vertical machines and drilled on drilling machines in our works, faces finished to the serration the facing type requires, and bolt holes drilled to the standard's bolt circle — the geometry this page is drawn around. Low-temperature A350 LF2 flanges are supplied with test certificates for low-temperature service, as listed for our JIS slip-on range.
Frequently Asked Questions
What information does a flange order need?
Type, NPS, class (or PN), facing, material grade, and for weld neck flanges the pipe schedule for the bore. For example: weld neck, NPS 6, Class 300, RF, A105, bore to Schedule 80. With those six items the flange is fully defined.
Can you produce flanges to EN or DIN standards?
DIN, SABS and JIS patterns appear in individual catalogue listings alongside the ASME range. State the standard clearly on the enquiry — ASME and PN flanges of the same nominal size have different bolt circles and do not interchange — and the execution is confirmed for the specific product before order.
Do you supply matching bolts and gaskets?
Bolting and gaskets are normally specified separately from the flange itself. If you need them included, say so on the enquiry and we will confirm what can be supplied with the flanges.
Send Your Specification
Tell us the size, schedule or pressure class, material grade and quantity for the pipe flanges you need. MOQ and lead time are confirmed in the quotation for your exact specification.