Pipes & Fittings
Flanges: weld neck, blind, slip-on and spectacle blinds
CRS PLUS sources forged steel flanges for oil & gas, process and utility piping — weld neck, blind, slip-on, socket-weld, threaded and lap joint flanges, together with spectacle blinds, spades and spacers. Flanges are quoted to the size, pressure class, facing, bore schedule and material on your bill of materials, and every flange is supplied with its mill test certificate.
Flange types we quote
Sourced through the qualified supplier base. Sizes, ratings and grades are shown as ranges; send your bill of materials and every line is quoted against its exact specification.
| Product | Standard | Sizes | Rating / class | Materials |
|---|---|---|---|---|
| Weld neck flange (WNRF) | ASME B16.5 / B16.47 | NPS ½ to 60 | Class 150 to 2500 | A105N, A350 LF2, A182 F304L / F316L, F51 |
| Blind flange (BLRF) | ASME B16.5 / B16.47 | NPS ½ to 60 | Class 150 to 2500 | A105N, A350 LF2, A182 stainless |
| Slip-on flange (SORF) | ASME B16.5 | NPS ½ to 24 | Class 150 to 1500 | A105N, A350 LF2, A182 stainless |
| Socket-weld and threaded flange | ASME B16.5 | NPS ½ to 3 | Class 150 to 1500 | A105N, A350 LF2, A182 stainless |
| Lap joint flange with stub end | ASME B16.5 / MSS SP-43 | NPS ½ to 24 | Class 150 to 600 | A105 backing ring; stainless stub end |
| Spectacle blind, spade and spacer | ASME B16.48 | NPS ½ to 24 | Class 150 to 2500 | A516 Gr 70, A105N, A350 LF2, stainless |
| Ring-type joint (RTJ) flange | ASME B16.5 / API 6A | NPS ½ to 24 | Class 600 to 2500 | A105N, A350 LF2, F316L |
| Orifice flange | ASME B16.36 | NPS 1 to 24 | Class 300 to 2500 | A105N, A350 LF2, stainless |
How a flange is specified
A flange line is defined by five things: nominal size, pressure class, facing, type and material. A weld neck flange also carries the bore schedule, which must match the pipe it is welded to — for example "WNRF 4 in class 150 Sch XS, A105N". Facing is raised face (RF) on most class 150 and 300 lines, with ring-type joint (RTJ) common from class 600 upwards; flat face (FF) is used against cast-iron or non-metallic equipment.
For carbon steel service the default material is ASTM A105, usually ordered as A105N (normalised). Low-temperature lines use A350 LF2, and stainless and duplex lines use the matching A182 grade. Where the piping class calls for sour service, NACE MR0175 / ISO 15156 hardness limits are written onto the order.
Weld neck, slip-on or blind — which flange where
Weld neck flanges have a tapered hub butt-welded to the pipe and are the standard choice for pressure, temperature cycling and hazardous service. Slip-on flanges are fillet-welded inside and out, are cheaper and easier to align, and are used on lower-pressure utility and tank nozzle work. Blind flanges close the end of a line, a nozzle or a vessel opening. Spectacle blinds and spade-and-spacer pairs allow a line to be positively isolated and reopened without removing pipework.
Documentation and supply terms
- Mill test certificate
- EN 10204 3.1 certificate for every line, traceable to the heat number marked on the item. EN 10204 3.2 with third-party witness on request.
- Marking
- Material grade, size, rating and heat number marked on each item to the governing standard (MSS SP-25 for valves, flanges and fittings).
- Inspection
- Positive material identification, dimensional checks and third-party inspection arranged where the project specifies them.
- Sour and low-temperature service
- NACE MR0175 / ISO 15156 hardness limits and impact testing applied where the piping class calls for them, and stated on the certificate.
- Quotation
- Each line states the standard, grade, origin, lead time and certification before you commit. Listing does not indicate stock held by CRS PLUS.
Frequently asked questions
What does "150#" or "class 150" mean on a flange?
It is the ASME B16.5 pressure class. Each class has a pressure–temperature rating that depends on the material group: a class 150 carbon steel flange is rated at roughly 19–20 bar at ambient temperature, falling as temperature rises. Higher classes (300, 600, 900, 1500, 2500) have thicker flanges and more or larger bolts.
What is the difference between A105 and A105N?
Both are ASTM A105 forged carbon steel. "N" indicates the forging has been normalised, which refines the grain structure and improves toughness. Many oil & gas specifications require A105N, and the mill test certificate states the heat treatment.
Why does a weld neck flange need a schedule?
The bore of a weld neck flange is machined to match the inside diameter of the pipe, so the flange hub and pipe wall line up at the weld. A 4 in WNRF Sch 40 and a 4 in WNRF Sch XS are different items; the schedule is taken from the pipe it connects to.
What is a spectacle blind used for?
A spectacle blind is a plate with one solid disc and one open ring joined by a web. It sits between two flanges; rotating it switches the line between open and positively isolated. It is specified to ASME B16.48 by size, class and facing.
Can you supply flanges with matching gaskets and stud bolts?
Yes. Flanges are usually quoted together with the gaskets and stud bolts for each joint, so that facing, class and bolt sizes are consistent across the package.
What documentation comes with the flanges?
An EN 10204 3.1 mill test certificate traceable by heat number is standard. Positive material identification, third-party inspection and 3.2 certification can be arranged where the project requires them, and are stated on the quotation.
Request a flange quotation
A structured offer follows within 72 hours.
Manufacturer and brand names, where mentioned, are used for identification only. CRS PLUS sources these products through its qualified supplier base and holds no distributor, reseller or agency appointment from any manufacturer.