Flanges for US oil and gas: pipelines, gas plants and stations
Gathering lines, gas processing plants, compressor and pump stations and transmission pipelines use more flanges per mile of pipe than almost any other industry. Here is what they specify, and what we supply from our forge in India.
US oil and gas piping uses forged weld neck, blind and ring type joint (RTJ) flanges to ASME B16.5 in Class 150 to 2500, and to ASME B16.47 above NPS 24, in ASTM A105 carbon steel, A350 LF2 where the design metal temperature is below -20 °F, and A694 F42 to F70 high yield steel to match API 5L line pipe. We make all of these, with an EN 10204 3.1 mill test report for every heat, and our quality system is certified to ISO 29001, the quality management standard for the petroleum, petrochemical and natural gas industries.
Where flanges are used in oil and gas
| System | Flange | Class and material |
|---|---|---|
| Gathering lines and well pads | Weld neck RF; blind flanges at pig traps and future tie-ins | Class 300 to 900, A105 or A694 |
| Gas processing plants | Weld neck RF and RTJ; spectacle blinds for isolation | Class 150 to 1500, A105, LF2, 316L |
| Compressor and pump stations | Weld neck RTJ on discharge headers; orifice flanges at meter runs | Class 600 to 1500, A105 or A694 |
| Transmission pipelines (ASME B31.4 and B31.8) | High yield weld neck flanges bored to the pipe wall | Class 300 to 900, A694 F52 to F70 |
| Tank farms and terminals | Weld neck and slip-on RF, flat face at cast iron pumps | Class 150 and 300, A105 |
Codes and specifications on a US oil and gas line list
| Standard | What it covers | Where it applies |
|---|---|---|
| ASME B31.4 | Pipeline transportation systems for liquids and slurries | Crude, NGL and product pipelines, pump stations, terminals |
| ASME B31.8 | Gas transmission and distribution piping systems | Gas gathering, transmission pipelines, compressor stations |
| ASME B31.3 | Process piping | Gas processing and treating plants inside the fence |
| ASME B16.5 | Flange dimensions and pressure-temperature ratings, NPS 1/2 to 24, Class 150 to 2500 | Most flanges on the line list |
| ASME B16.47 | Large diameter flanges, NPS 26 to 60, Series A and B | Large pipelines and headers |
| ASME B16.20 | Metallic gaskets, including ring joint gaskets | RTJ flanges |
| ASTM A694 | High strength forgings for pipe flanges in high-pressure transmission service | Flanges welded to API 5L X52 to X70 line pipe |
The flange grade should be at least as strong as the pipe it is welded to. A694 grades are named for their minimum yield strength in ksi: F52 matches X52 line pipe and F65 matches X65. Order the grade that matches your line pipe, and give the pipe wall on each line so we bore the weld end to it.
Ring type joints for the higher classes
From Class 600 up, many operators specify ring type joint facing: a grooved face that takes an oval or octagonal metal ring gasket to ASME B16.20. The ring seats under bolt load and holds high pressure without a soft gasket that could blow out. We machine RTJ grooves on weld neck and blind flanges to ASME B16.5. Order the ring number (R or RX) that matches your gasket, and the groove hardness requirement if your specification sets one, so we can confirm both in the quotation.
A Class 600 flange is not a 600 psi flange. ASME B16.5 rates A105 at 1,480 psig from -20 to 100 °F, falling as temperature rises. A350 LF2 carries the same rating and adds Charpy impact tests at -50 °F, which is why it is used where winter conditions or blowdown cooling take the metal below -20 °F.
Materials
| Grade | Specification | Typical service |
|---|---|---|
| A105 | ASTM A105 | General carbon steel flanges from -20 °F up |
| A350 LF2 | ASTM A350, impact tested at -50 °F | Cold climate and low temperature lines, blowdown and flare headers |
| F42 to F70 | ASTM A694 | Pipeline flanges matched to API 5L X42 to X70 pipe |
| F304L, F316L | ASTM A182 | Instrument, chemical injection and produced water lines |
| Duplex S32205, super duplex S32750 | ASTM A182 F60 and F53 | Seawater, produced water and offshore topsides; our duplex and super duplex are qualified to NORSOK M-650 |
Ordering for a US project
Send your line list with the standard, type, size, class, bore or schedule, facing, material and quantity for each line, and we quote every line as specified. Every order ships from our works in Gujarat, India; we have no US office or warehouse. Each line is supplied to your line list, and ordering from India explains the documents, marking, packing and customs.
Frequently asked questions
Do you supply flanges with RTJ grooves?
Yes. Weld neck and blind flanges can be supplied with ring type joint facing to ASME B16.5. Tell us the ring number and any groove hardness requirement on the line list.
Can you match a weld neck flange bore to heavy wall line pipe?
Yes. Give the pipe outside diameter and wall thickness, or the schedule, for each line and we bore the weld end to match, so the weld prep lines up with the pipe.
What test certificates come with the flanges?
An EN 10204 3.1 mill test report for every heat, showing chemistry, mechanical tests and heat treatment. With your inspector or a third-party agency, EN 10204 3.2. Impact test results are on the report for A350 LF2.
Can you ship to Houston?
Yes. We quote FOB India, CIF Port Houston or another Incoterm you name, and the quotation states what is included.
Sources
- ASME B31.4, Pipeline Transportation Systems for Liquids and Slurries
- ASME B31.8, Gas Transmission and Distribution Piping Systems
- ASME B16.5, Pipe Flanges and Flanged Fittings, NPS 1/2 through NPS 24
- ASME B16.20, Metallic Gaskets for Pipe Flanges
- ASTM A694/A694M, Carbon and Alloy Steel Forgings for Pipe Flanges, Fittings, Valves, and Parts for High-Pressure Transmission Service
- ASTM A350/A350M, Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Components