There are two ways to get a copper alloy flange, and they come from different standards. Either you buy a cast copper alloy flange to ASME B16.24, or you have a steel flange pattern machined out of a copper alloy. Both are legitimate. They are not the same product and they do not carry the same rating.
What B16.24 is
ASME B16.24 covers cast copper alloy pipe flanges and flanged fittings. It is the copper alloy flange standard proper: it defines the dimensions, the facings, the tolerances and the pressure-temperature ratings for flanges cast in copper alloy, in the bronze casting grades such as C83600.
Class 150 and Class 300 are the workhorses of the standard, and the current edition carries higher classes as well. Sizes run through the mid range rather than out to the large diameters that the steel standards cover.
Note the word cast. B16.24 is written around castings. A flange machined from wrought copper-nickel plate is not a B16.24 product even if it ends up dimensionally similar.
The detail that matters: the bolt template
B16.24 Class 150 drilling follows the same bolt template as the steel Class 150 pattern. Same bolt circle, same hole count, same hole size. A cast bronze flange therefore bolts straight onto a carbon steel Class 150 flange with no adapter.
This is genuinely useful, and it is also why the galvanic question is so common on copper work. The standards made it mechanically easy to create a dissimilar metal joint. Nothing in the standard makes it electrically wise. See galvanic corrosion in dissimilar metal flange joints.
B16.5 patterns in copper material
ASME B16.5 is a steel standard. It sets dimensions for steel pipe flanges from NPS 1/2 through 24, and its rating tables are computed from steel allowable stresses.
When a seawater project wants a Class 150 or Class 300 footprint in C70600 or C71500, the practical answer is to machine the B16.5 geometry from copper-nickel plate, bar or forging. The part then bolts into a standard system and looks like a Class 150 flange.
Do not read the rating off the B16.5 table. That flange has the geometry of a Class 150 flange and the strength of copper-nickel, which is a lower number. The rating has to be worked from the design code, ASME B31.3 for process piping, using the certified allowable stress for the actual alloy at the actual temperature. Class in this context describes the bolt pattern, not the pressure capability.
Which to use
| Situation | Route |
|---|---|
| Moderate water service, small to mid size, cost sensitive | Cast bronze to ASME B16.24 |
| Seawater piping in copper-nickel | B16.5 pattern machined from C70600 or C71500 |
| Naval shipboard | MIL-F-1183 and related naval fitting specifications |
| Large diameter seawater header | Plate or ring flange cut from ASTM B171 plate, often to print |
| Erosion or cavitation service | Aluminum bronze, cast to C95800 or machined from C61400 or C63000 |
| Off-pattern or retrofit geometry | Machined to drawing. Send the print |
Related standards you may see
ASME B16.15cast copper alloy threaded fittings, Classes 125 and 250ASME B16.18cast copper alloy solder joint pressure fittingsASME B16.22wrought copper and copper alloy solder joint fittingsASTM B62composition bronze castings, the material behind much B16.24 productASTM B148aluminum bronze and nickel-aluminum bronze castings
Which route your job needs usually falls out of the fluid and the size. Send us the service conditions and the pattern you have to bolt to, and we will tell you which one to buy.