FLANGES should be even and parallel and also sufficiently rigid not to be distorted by the bolt load.
FLANGE FINISH is important. Concentric groove finish is ideal for high pressure. Spiral (gramophone) groove finish give a continuous path for leakage and is not recommended for gases. For flanges with flat surface a finish equivalent to is considered best.
BOLTS should be tightened with a torque spanner, working at diametrically opposite nuts alternately. First turn all bolts to about half the recommended torque, then follow up to full assembly torque. It is important to follow up the bolts about 4 hours later or 1 hour after the gasket reaches its working temperature.
PIPELINES undergo longitudinal thermal expansion which generates forces that can crush the gasket. On the other hand, contraction of pipelines can reduce teh gasket surface stress below the minimum required for sealing, Pipe expansions and contractions must therefore be compensated by suitably selecting the gasket material and its thickness.
Flat Ring Gasket to ASME B16.21
To Suit ASME / ANSI B16.5 & BS 1560 Flangers
| NOMINAL PIPE SIZE | INSIDE DIAMETER | OUTSIDE DIAMETER | |||||
|---|---|---|---|---|---|---|---|
| CLASS 150 | CLASS 300 | CLASS 400 | CLASS 600 | CLASS 900 | CLASS 1500* | ||
| mm | mm | mm | mm | mm | mm | mm | |
| % | 21.4 | 47.6 | 54.0 | 54.0 | 54.0 | 63.5 | 63.5 |
| 3/4 | 27.0 | 57.2 | 66.7 | 66.7 | 66.7 | 69.9 | 69.9 |
| 1 | 33.3 | 66.7 | 73.0 | 73.0 | 73.0 | 79.4 | 79.4 |
| 11/4 | 42.1 | 76.2 | 82.6 | 82.6 | 82.6 | 88.9 | 88.9 |
| Vh | 48.4 | 85.7 | 95.3 | 95.3 | 95.3 | 98.4 | 98.4 |
| 2 | 60.3 | 104.8 | 111.1 | 111.1 | 111.1 | 142.9 | 142.9 |
| 2Vz | 73.0 | 123.8 | 130.2 | 130.2 | 130.2 | 165.1 | 165.1 |
| 3 | 88.9 | 136.5 | 149.2 | 149.2 | 149.2 | 168.3 | 174.6 |
| 331/2 | 101.6 | 161.9 | 165.1 | 161.9 | 161.9 | - | - |
| 4 | 114.3 | 174.6 | 181.0 | 177.8 | 193.7 | 206.4 | 209.6 |
| 5 | 141.3 | 196.9 | 215.9 | 212.7 | 241.3 | 247.7 | 254.0 |
| 6 | 168.3 | 222.3 | 250.8 | 247.7 | 266.7 | 288.9 | 282.6 |
| 8 | 219.1 | 279.4 | 308.0 | 304.8 | 320.7 | 358.8 | 352.4 |
| 10 | 273.1 | 339.7 | 361.9 | 358.8 | 400.0 | 435.0 | 435.0 |
| 12 | 323.9 | 409.6 | 422.3 | 419.1 | 457.2 | 498.5 | 520.7 |
| 14 | 355.6 | 450.8 | 485.8 | 482.6 | 492.1 | 520.7 | 577.8 |
| 16 | 406.4 | 514.3 | 539.7 | 536.6 | 565.1 | 574.7 | 641.3 |
| 18 | 457.2 | 549.3 | 596.9 | 593.7 | 612.8 | 638.2 | 704.8 |
| 20 | 508.0 | 606.4 | 654.0 | 647.7 | 682.6 | 698.5 | 755.6 |
| 24 | 609.6 | 717.5 | 774.7 | 768.3 | 790.6 | 838.2 | 901.7 |
* Class 1500 rating is no longer specified in ASME B16.21
* Gaskets also available in higher Nominal Bore
