ASME B16.20: Metallic Gaskets for Pipe Flanges
ASME B16.20 Standard covers materials, dimensions, tolerances, and markings for metal ring-joint gaskets, spiral-wound metal gaskets, metal-jacketed gaskets, and grooved metal gaskets with covering layers. These gaskets are dimen-sionally suitable for use with flanges described in refer-ence flange standards ASME B16.5, ASME B16.47, API Specification 6A, and ISO 10423.
Table RJ-3.2-1 Maximum Hardness for Ring Gaskets
| Ring Gasket Material | Maximum Hardness | |
| Brinell | Rockwell "B" Scale | |
| Sof Iron [Note (1)] | 90 | 56 |
| Low-carbon steel | 120 | 68 |
| 4-6 chorme 1/2 Mo | 130 | 72 |
| Type 410 | 170 | 86 |
| Type 304 | 160 | 83 |
| Type 316 | 160 | 83 |
| Type 316 | 160 | 83 |
NOTE: (1) Maybelow-carbonsteel,nottoexceedmaximumhardness of 90 Brinell — 56 Rockwell “B.”
Table RJ-4-1 Ring Gasket Markings
| Ring Gasket Material | Identification | Marking Example[Note (1)] |
| Sof Iron | D [Note (2)] | R51D |
| Low-carbon steel | S | R51S |
| 4-6 chorme 1/2 Mo | F5 [Note (3)] | R51F |
| Type 410 | S 410 | R51S410 |
| Type 304 | S 304 | R51S304 |
| Type 316 | S 316 | R51S316 |
| Type 347 | S 347 | R51S347 |
NOTES:
(1) This number shall be preceded by the manufacturer’s name or identification trademark.
(2) May be low-carbon steel, notto exceed maximum hardness of 90. Brinell — 56 Rockwell “B.”
(3) F5 identification designates ASTM specification A182-72 chemical composition requirements only.
