A standard flange is picked from a pattern. A specialty flange usually differs from that pattern in exactly one respect, a bore that is not a schedule, a facing that is not raised face, a tapping for an instrument, a longer neck, and that single departure means the item is machined to a drawing rather than selected from a table. The practical consequence for an enquiry is simple: without the drawing or the departure stated in full, the item cannot be quoted. Specialty flanges go onto process and pipeline work across Oman and the GCC. The parent range is on the pipe fittings and flanges hub.
What Counts as a Specialty Flange
| Type | What it is | What the enquiry needs beyond the usual |
|---|---|---|
|
Orifice flange |
A pair of flanges with pressure tappings either side of an orifice plate, for flow measurement |
Tapping size and orientation, jack screws, whether the plate and carrier are in scope |
|
Long weld neck |
An extended hub that acts as a nozzle, welded directly to a vessel or header |
Overall length and the bore, which is often not a standard schedule |
|
Reducing flange |
Full flange dimensions of one size with a bore for a smaller pipe |
Both sizes, flange size and bore size, stated separately |
|
Spectacle blind |
Two discs on a hinge, one solid and one open, swung to isolate or pass |
Line size, class, facing, and the gap between flanges it has to fit |
|
Paddle blind and spacer |
A single blind or spacer used as a pair, slid between flanges |
Line size, class, facing, and the required thickness |
|
Expander and swage flange |
Changes diameter within the flange itself |
Both diameters and the transition required |
|
Nipoflange and weldoflange |
A branch outlet and flange combined in one item |
Run pipe size and wall, branch size and class |
|
Non-standard bore or facing |
A B16.5 flange with a departure from the standard |
The departure, dimensioned |
RTJ ring type joint flanges and large diameter ASME B16.47 flanges have their own pages.
Why the Drawing Matters More Than the Description
A standard flange is fully defined by four pieces of information: type, size, class and facing. Everything else follows from ASME B16.5. A specialty flange breaks that chain, because at least one dimension now comes from the design rather than the standard.
Three failures follow from a description without dimensions:
- Orifice flanges quoted without the tapping orientation arrive with tappings in the wrong plane for the installation
- Long weld necks quoted without an overall length arrive at a standard hub length and will not reach the vessel wall
- Reducing flanges quoted with one size arrive bored to the wrong pipe
What to send: a dimensioned drawing where one exists, or the full set of dimensions where it does not, together with type, size, class, facing, bore and material grade. Where the item replaces something already installed, the existing item's dimensions are the specification.
Sour Service
Specialty items carry the same obligations as standard ones. Under NACE MR0175 / ISO 15156, carbon and low-alloy steel needs a hardness limit of 22 HRC with an accepted heat treatment condition, and stainless, duplex and nickel alloys fall under Part 3 with environmental limits by alloy. Heavier machined items such as spades and long weld necks are thick sections, so the heat treatment response through thickness matters and hardness testing on the finished item is worth specifying. State your sour service requirements in the RFQ.
What Moves the Price of Specialty Flanges
- Material grade and alloy content, which carry market surcharges
- Type, size, pressure class and facing
- Matching pipe schedule or fitting wall
- Forged or wrought, and seamless or welded construction
- Testing: hardness, impact testing, NDT, PMI and ferrite checks where they apply
- Quantity against mill or forge minimums
- Certification level (EN 10204 3.1 or 3.2) and third-party inspection
- Incoterm and destination port
Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.
What to send for a quotation: item type, material grade and standard, size, pressure class, facing, schedule or wall, quantity, testing, certification, inspection, destination port and required date.
Specialty Flanges: Certificates and Inspection
Supplied with EN 10204 3.1 certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. The certificate should carry the material standard and grade, heat number, heat treatment condition and mechanical results, and the drawing revision the item was machined to. PMI on receipt is worth specifying wherever grades share a store or a fabrication shop, since a stencil is only paint. See the MTC and EN 10204 certification guide.
Packing, Delivery and Gulf Site Storage
Lead time is confirmed at quotation. Items are packed in crates or bundles, with bevels and machined faces protected. On Gulf laydown yards the two things that cause rework are a damaged sealing face and surface contamination, so keep face protectors on until assembly and store alloy items clear of carbon steel racking, slings and grinding dust.
Related Flanges
- RTJ ring type joint flanges
- Large diameter flanges to ASME B16.47
- Weld neck flanges
- Blind flanges
- Pipe fittings and flanges
Specialty Flanges: Buyer Questions
Why does a specialty flange need a drawing?
Because at least one dimension comes from the design rather than from ASME B16.5, so type, size, class and facing no longer define the item completely.
What is a long weld neck flange used for?
It acts as a nozzle, with an extended hub welded directly to a vessel or header. The overall length and the bore both have to be stated, since neither follows a standard pattern.
What is the difference between a spectacle blind and a paddle blind?
A spectacle blind is two discs on a hinge, one solid and one open, swung between positions. A paddle blind is a single disc used with a matching spacer, slid in and out.
Which standard covers orifice flanges?
ASME B16.36, which sets the tappings and the dimensions that go with them. The tapping size and orientation have to be stated on the enquiry.
Which standard covers spades and spacers?
ASME B16.48, which sets the thickness against the pressure class and size. That thickness is why a spade for a high class line is a substantial machined item.
What should I send for a quotation?
Send a dimensioned drawing where one exists, or the full dimensions, with the type, size, class, facing, bore, grade, quantity, testing, certification and destination port.
Request a Quote for Specialty Flanges
Send the drawing where you have one, or every dimension that departs from the standard where you do not. An enquiry that names a specialty type without the departure is returned with the questions rather than quoted on an assumption.