What are Class 1500 Flanges?
Kalp Alloys is a leading manufacturer and supplier of Class 1500 Flanges (also known as 1500 lb flanges or 1500# flanges) conforming to ASME B16.5 standard. We supply Class 1500 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 1500 flange is a pressure-class designation under the ASME B16.5 standard (Steel Pipe Flanges and Flanged Fittings). The "1500" refers to the pressure class — built for ultra-high-pressure and extreme-temperature piping systems. Class 1500 flanges are rated at approximately 3705 psi (255 bar) at ambient temperature (38°C) for carbon steel.
They are widely used in high-pressure steam systems, hydrocracking units, deep-water oil & gas pipelines, power plants, and critical refinery piping where extreme operating conditions demand the highest structural integrity. Because of their exceptionally thick bodies, heavy bolt patterns, and superior pressure capacity, ASME B16.5 Class 1500 flanges are specified for the most severe service conditions in industrial piping.
Class 1500 Flanges (ASME B16.5)
SLIP-ON (SOF)
Slips over the pipe and is fillet-welded top and bottom — easy to align and economical at this pressure class.
WELDING NECK (WNF)
Butt-welded to the pipe through a tapered hub for the strongest, most fatigue-resistant joint.
SOCKET WELDING (SWF)
Pipe seats into a socket bore and is fillet-welded — used on small-bore, high-pressure lines.
THREADED (THDF)
Screwed onto threaded pipe with no welding — suited to small sizes and flammable areas.
LAP JOINT (LJF)
Used with a stub end so the flange rotates freely for fast bolt-hole alignment.
BLIND (BLF)
Solid disc that blanks off the end of a line, valve or vessel.
ASME B16.5 Pipe Flanges
Unit : mm
| NPS | Outside Diam. D |
Diam. of Hub X |
OD of RF G |
Thickness (Min) t |
Bore | Length Thru Hub | 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 | |||||||||||
| 1/2 | 120 | 38 | 34.9 | 22.3 | See Note (1) To be specified by Purchaser | 22.2 | 22.9 | 23.6 | 60 | 32 | 32 | 82.6 | 4 | 22.2 |
| 3/4 | 130 | 44 | 42.9 | 25.4 | 27.7 | 28.2 | 29.0 | 70 | 35 | 35 | 88.9 | 4 | 22.2 | |
| 1 | 150 | 52 | 50.8 | 28.6 | 34.5 | 34.9 | 35.8 | 73 | 41 | 41 | 101.6 | 4 | 25.4 | |
| 1 1/4 | 160 | 64 | 63.5 | 28.6 | 43.2 | 43.7 | 44.4 | 73 | 41 | 41 | 111.1 | 4 | 25.4 | |
| 1 1/2 | 180 | 70 | 73.0 | 31.8 | 49.5 | 50.0 | 50.6 | 83 | 44 | 44 | 123.8 | 4 | 28.6 | |
| 2 | 215 | 105 | 92.1 | 38.1 | 61.9 | 62.5 | 63.5 | 102 | 57 | 57 | 165.1 | 8 | 25.4 | |
| 2 1/2 | 245 | 124 | 104.8 | 41.3 | 74.6 | 75.4 | 76.2 | 105 | 64 | 64 | 190.5 | 8 | 28.6 | |
| 3 | 265 | 133 | 127.0 | 47.7 | – | 91.4 | – | 117 | – | 73 | 203.2 | 8 | 31.8 | |
| 4 | 310 | 162 | 157.2 | 54.0 | – | 116.8 | – | 124 | – | 90 | 241.3 | 8 | 34.9 | |
| 5 | 375 | 197 | 185.7 | 73.1 | – | 144.4 | – | 156 | – | 105 | 292.1 | 8 | 41.3 | |
| 6 | 395 | 229 | 215.9 | 82.6 | – | 171.4 | – | 171 | – | 119 | 317.5 | 12 | 38.1 | |
| 8 | 485 | 292 | 269.9 | 92.1 | – | 222.2 | – | 213 | – | 143 | 393.7 | 12 | 44.5 | |
| 10 | 585 | 368 | 323.8 | 108.0 | – | 277.4 | – | 254 | – | 178 | 482.6 | 12 | 50.8 | |
| 12 | 675 | 451 | 381.0 | 123.9 | – | 328.2 | – | 283 | – | 219 | 571.5 | 16 | 54.0 | |
| 14 | 750 | 495 | 412.8 | 133.4 | – | 360.2 | – | 298 | – | 241 | 635.0 | 16 | 60.3 | |
| 16 | 825 | 552 | 469.9 | 146.1 | – | 411.2 | – | 311 | – | 260 | 704.8 | 16 | 66.7 | |
| 18 | 915 | 597 | 533.4 | 162.0 | – | 462.3 | – | 327 | – | 276 | 774.7 | 16 | 73.0 | |
| 20 | 985 | 641 | 584.2 | 177.8 | – | 514.4 | – | 356 | – | 292 | 831.8 | 16 | 79.4 | |
| 24 | 1170 | 762 | 692.2 | 203.2 | – | 616.0 | – | 406 | – | 330 | 990.6 | 16 | 92.1 | |
Frequently Asked Questions
A Class 1500 (also written 1500# or 1500 lb) flange is a pressure-class designation under ASME B16.5, rated at approximately 3705 psi (255 bar) at ambient temperature for carbon steel.
Slip-On (SOF), Welding Neck (WNF), Socket Weld (SWF), Threaded (THDF), Lap Joint (LJF) and Blind (BLF), in raised face, flat face and RTJ facing as applicable.
NPS 1/2 inch to 24 inch to ASME B16.5, with larger diameters supplied to ASME B16.47 on request.
Stainless Steel (304, 316L, 321), Carbon Steel (A105, A350 LF2), Alloy Steel (F11, F22, F91), Duplex, Super Duplex and Nickel Alloys.
Material Test Certificates per EN 10204 3.1 and 3.2, plus radiography, ultrasonic, magnetic particle and hydrostatic testing, with third-party inspection on request.
Yes. We regularly export to the UAE, Dubai, Abu Dhabi and the wider GCC along with 100+ countries, with correct export documentation and on-time delivery.