Kalp Alloys is a leading manufacturer and supplier of Class 300 Flanges (also known as 300 lb flanges or 300# flanges) conforming to ASME B16.5 standard. We supply Class 300 pipe flanges in all standard types — Slip-On (SOF), Welding Neck (WNF), Socket Welding (SWF), Threaded (THDF), Lap Joint (LJF), and Blind (BLF) — in sizes ranging from NPS 1/2″ to NPS 24″. Our flanges are manufactured in a wide range of materials including Stainless Steel (SS 304, 316L, 321), Carbon Steel, Alloy Steel, Duplex, and Nickel Alloys to meet the most demanding industrial requirements.
A Class 300 flange is a pressure-class designation under the ASME B16.5 standard (Steel Pipe Flanges and Flanged Fittings). The “300” refers to the pressure class — the second most commonly used class in industrial piping, offering significantly higher pressure capacity than Class 150. Class 300 flanges are rated at approximately 740 psi (51 bar) at ambient temperature (38°C) for carbon steel.
They are widely used in oil & gas, chemical, petrochemical, power generation, and high-pressure industrial piping systems where medium-to-high pressures are encountered. Because of their superior pressure rating and structural strength, ASME B16.5 Class 300 flanges are the preferred choice for applications where Class 150 ratings are insufficient.
| NPS | Outside Diam. D | Diam. of Hub X | OD of RF G | Thickness (Min) | Bore | Length Thru Hub | Depth of Socket Y | Drilling | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| WNF SWF B1 | SOF SWF (Min) | LJF (Min) | THDF Counter bore (Min) | WNF T1 | SOF THDF SWF | LJF T3 | BCD C | Number of Bolt Holes N | Diam. of Bolt Holes (*) H | |||||||
| B2 | B3 | B | T2 | |||||||||||||
| t | t1 | |||||||||||||||
| 1/2 | 95 | 38 | 34.9 | 12.7 | 14.3 | See Note (1) To be specified by Purchaser | 22.2 | 22.9 | 23.6 | 51 | 21 | 22 | 10 | 66.7 | 4 | 15.9 |
| 3/4 | 115 | 48 | 42.9 | 14.3 | 15.9 | 27.7 | 28.2 | 29.0 | 56 | 24 | 25 | 11 | 82.6 | 4 | 19.1 | |
| 1 | 125 | 54 | 50.8 | 15.9 | 17.5 | 34.5 | 34.9 | 35.8 | 60 | 25 | 27 | 13 | 88.9 | 4 | 19.1 | |
| 1 1/4 | 135 | 64 | 63.5 | 17.5 | 19.1 | 43.2 | 43.7 | 44.4 | 64 | 25 | 27 | 14 | 98.4 | 4 | 19.1 | |
| 1 1/2 | 155 | 70 | 73.0 | 19.1 | 20.7 | 49.5 | 50.0 | 50.3 | 67 | 29 | 30 | 16 | 114.3 | 4 | 22.2 | |
| 2 | 165 | 84 | 92.1 | 20.7 | 22.3 | 61.9 | 62.5 | 63.5 | 68 | 32 | 33 | 17 | 127.0 | 8 | 19.1 | |
| 2 1/2 | 190 | 100 | 104.8 | 23.9 | 25.4 | 74.6 | 75.4 | 76.2 | 75 | 37 | 38 | 19 | 149.2 | 8 | 22.2 | |
| 3 | 210 | 117 | 127.0 | 27.0 | 28.6 | 90.7 | 91.4 | 92.2 | 78 | 41 | 43 | 21 | 168.3 | 8 | 22.2 | |
| 3 1/2 | 230 | 133 | 139.7 | 28.6 | 30.2 | 103.4 | 104.1 | 104.9 | 79 | 43 | 44 | – | 184.2 | 8 | 22.2 | |
| 4 | 255 | 146 | 157.2 | 30.2 | 31.8 | 116.1 | 116.8 | 117.6 | 84 | 46 | 48 | – | 200.0 | 8 | 22.2 | |
| 5 | 280 | 178 | 185.7 | 33.4 | 35.0 | 143.8 | 144.4 | 144.4 | 97 | 49 | 51 | – | 235.0 | 8 | 22.2 | |
| 6 | 320 | 206 | 215.9 | 35.0 | 36.6 | 170.7 | 171.4 | 171.4 | 97 | 51 | 52 | – | 269.9 | 12 | 22.2 | |
| 8 | 380 | 260 | 269.9 | 39.7 | 41.3 | 221.5 | 222.2 | 222.2 | 110 | 60 | 62 | – | 330.2 | 12 | 25.4 | |
| 10 | 445 | 321 | 323.8 | 46.1 | 47.7 | 276.2 | 277.4 | 276.2 | 116 | 65 | 95 | – | 387.4 | 16 | 28.6 | |
| 12 | 520 | 375 | 381.0 | 49.3 | 50.8 | 327.0 | 328.2 | 328.6 | 129 | 71 | 102 | – | 450.8 | 16 | 31.8 | |
| 14 | 585 | 425 | 412.8 | 52.4 | 54.0 | 359.2 | 360.2 | 360.4 | 141 | 75 | 111 | – | 514.4 | 20 | 31.8 | |
| 16 | 650 | 483 | 469.9 | 55.6 | 57.2 | 410.5 | 411.2 | 411.2 | 144 | 81 | 121 | – | 571.5 | 20 | 34.9 | |
| 18 | 710 | 533 | 533.4 | 58.8 | 60.4 | 461.8 | 462.3 | 462.0 | 157 | 87 | 130 | – | 628.6 | 24 | 34.9 | |
| 20 | 775 | 587 | 584.2 | 62.0 | 63.5 | 513.1 | 514.4 | 512.8 | 160 | 94 | 140 | – | 685.8 | 24 | 34.9 | |
| 24 | 915 | 702 | 692.2 | 68.3 | 69.9 | 616.0 | 616.0 | 614.4 | 167 | 105 | 152 | – | 812.8 | 24 | 41.3 | |
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