Industrial range
ASME B16.5 flanges
Pipe flanges to ASME B16.5 for process, utility and pipeline piping: six types, seven pressure classes and three facings, in carbon, low temperature, chrome-moly and stainless steels.
ASME B16.5 sets the dimensions, tolerances, materials and pressure-temperature ratings of pipe flanges from NPS 1/2 to 24 in seven classes, Class 150 to Class 2500. We supply weld neck, slip-on, blind, threaded, socket weld and lap joint flanges to B16.5 with raised face, flat face or ring type joint facings, forged in ASTM A105 carbon steel, A350 LF2, A182 chrome-moly and stainless grades, and in AISI 4130 to order.
Flange types
| Type | How it joins the pipe | Use it for |
|---|---|---|
| Weld neck | Tapered hub butt-welded to the pipe | High pressure, high temperature and cyclic service |
| Slip-on | Slides over the pipe, fillet welded inside and out | Lower pressures, easy alignment |
| Blind | No bore; closes the end of a line | Dead ends, test points and future connections |
| Threaded | NPT thread in the bore | Small sizes where welding is not allowed |
| Socket weld | Pipe sits in a socket, fillet welded | Small-bore, high-pressure lines |
| Lap joint | Loose flange behind a stub end welded to the pipe | Lines that are often dismantled, or where the flange need not match the pipe |
Classes and ratings
The class sets the pressure a flange can carry at each temperature for its material group. These are the ratings at -20 to 100 °F for ASTM A105 and other material group 1.1 steels:
| Class | 150 | 300 | 600 | 900 | 1500 | 2500 |
|---|---|---|---|---|---|---|
| Rating, psig | 285 | 740 | 1,480 | 2,220 | 3,705 | 6,170 |
Ratings per ASME B16.5 for material group 1.1 at -20 to 100 °F (-29 to 38 °C). Ratings fall at higher temperatures and differ by material group. Class 400 is also covered.
Facings
| Facing | Gasket | Typical use |
|---|---|---|
| Raised face (RF) | Spiral wound, sheet or kammprofile | Most process piping |
| Flat face (FF) | Full-face sheet gasket | Mating cast iron or nonmetallic flanges |
| Ring type joint (RTJ) | R or RX ring gasket | High pressure and oil and gas service |
Face finish to ASME B16.5, or to your specification.
Weld neck flanges are bored to the inside diameter of the pipe schedule they are welded to, so the bores line up at the weld. State the pipe schedule with every weld neck flange.
Materials and documents
Flanges are forged in ASTM A105, A350 LF2 for low temperatures, A182 F11 and F22 for high temperatures, F304 and F316 stainless and F51 duplex, and machined to B16.5. Each flange is marked with our mark, the material, size, class, facing, bore schedule and heat number, and certified to EN 10204 3.1.
Ordering
Weld neck flange, NPS 4, Class 600, raised face, bored for Schedule 80, ASME B16.5, ASTM A105, EN 10204 3.1, 12 pcs
Blind flange, NPS 3, Class 1500, ring type joint, R-35 groove, ASME B16.5, ASTM A105, EN 10204 3.1, 4 pcs
Frequently asked questions
What pressure is a Class 600 flange rated for?
It depends on material and temperature. For ASTM A105 (material group 1.1) a Class 600 flange is rated 1,480 psig from -20 to 100 °F, and less as temperature rises. The full tables are in ASME B16.5.
Raised face or ring type joint?
Raised face flanges with spiral wound or sheet gaskets are the common choice up to Class 600 or 900. Ring type joint (RTJ) flanges, sealed by an R or RX ring, are used at higher classes and in oil and gas service where a metal-to-metal seal is preferred.
Can I get B16.5 flanges in 4130?
Yes, made to B16.5 dimensions in AISI 4130 and heat treated to your order. 4130 is not one of the materials listed in the B16.5 rating tables, so the rating of a 4130 flange is set by your designer; for wellhead and manifold service, API 6A flanges are the usual choice.
Do you supply flanges above NPS 24?
B16.5 stops at NPS 24. Larger flanges follow ASME B16.47 Series A or B, and are quoted to order.