BS 4504 PN40 flange dimensions provide legacy dimensional and bolting data for PN40 steel pipe flanges. The tables below cover nominal sizes from DN10 to DN600 and include flange outside diameter, thickness, bore and hub dimensions together with bolt circle, bolt-hole and bolt-size information.
Legacy standard: BS 4504 has been withdrawn and superseded by BS EN 1092-1 for PN-designated steel flanges. BS 4504 data remains useful when identifying, maintaining or replacing components on older plant and piping installations. For new designs and safety-critical applications, requirements should be verified against the applicable current standard and project specification.
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| DN | Nominal size |
| D | Flange outside diameter |
| A | Outside diameter of neck |
| B1 | Bore of Type 101 and 112 flange forms represented by this legacy table |
| C1 | Plate flange thickness |
| C2 | Weld-neck and boss flange thickness |
| N1 | Weld-neck diameter |
| N2 | Boss diameter |
| R | Corner radius |
| H1 | Boss flange length |
| H2 | Weld-neck flange length |
| H3 | Neck length |
| d1 | Raised-face diameter |
| f1 | Raised-face height |
The flange forms represented in the diagram and table are only part of the range originally covered by BS 4504.
The dimensions shown relate to the facing identified in the legacy data as Type B - Raised Face. Other facing forms listed in the former standard include Type A flat, Type C tongue, Type D groove, Type E spigot, Type F recess, Type G O-ring recess and Type H O-ring groove.
Engineering note: Flange compatibility involves more than matching DN and PN designations. The applicable standard, flange type, facing, dimensions, drilling, materials, gasket arrangement and service conditions should all be checked when specifying or replacing a flange.
DN is the nominal size designation used for the flange and associated piping components. It is a designation rather than a direct measurement of the pipe bore.
PN is a nominal pressure designation. PN40 identifies the flange pressure designation but should not be interpreted as a universal allowable working pressure of exactly 40 bar under all operating conditions. Permissible pressure depends on factors including flange material and temperature and must be established from the applicable standard and design requirements.
Select the required nominal size DN in the first column and read across the row to obtain the corresponding flange dimensions. All dimensions in the table are in millimetres.
The separate bolting table below provides the bolt circle diameter, bolt-hole diameter, number of holes and nominal bolt size.
Reference use: These legacy dimensions are useful for identifying existing BS 4504 components, preliminary engineering work and maintenance of older plant. For pressure-containing, safety-critical or new-design applications, dimensions, materials, pressure-temperature capability, bolting and other requirements should be verified against the applicable current standard and project specification.
All dimensions are in mm.
| DN | D | C1 | C2 | H1 | H2 | H3 | R | A | N1 | N2 | B1 | d1 | f1 |
| 10 | 90 | 14 | 16 | 22 | 35 | 6 | 3 | 17,2 | 28 | 30 | 18 | 40 | 2 |
| 15 | 95 | 14 | 16 | 22 | 38 | 6 | 3 | 21,3 | 32 | 35 | 22 | 45 | 2 |
| 20 | 105 | 16 | 18 | 26 | 40 | 6 | 4 | 26,9 | 40 | 45 | 27,5 | 58 | 2 |
| 25 | 115 | 16 | 18 | 28 | 40 | 6 | 4 | 33,7 | 46 | 52 | 34,5 | 68 | 2 |
| 32 | 140 | 18 | 18 | 30 | 42 | 6 | 5 | 42,4 | 56 | 60 | 43,5 | 78 | 2 |
| 40 | 150 | 18 | 18 | 32 | 45 | 7 | 5 | 48,3 | 64 | 70 | 49,5 | 88 | 3 |
| 50 | 165 | 20 | 20 | 34 | 48 | 8 | 5 | 60,3 | 74 | 84 | 61,5 | 102 | 3 |
| 65 | 185 | 22 | 22 | 38 | 52 | 10 | 6 | 76,1 | 92 | 104 | 77,5 | 122 | 3 |
| 80 | 200 | 24 | 24 | 40 | 58 | 12 | 6 | 88,9 | 110 | 118 | 90,5 | 138 | 3 |
| 100 | 235 | 26 | 24 | 44 | 65 | 12 | 6 | 114,3 | 134 | 145 | 116 | 162 | 3 |
| 125 | 270 | 28 | 26 | 48 | 68 | 12 | 6 | 139,7 | 162 | 170 | 141,5 | 188 | 3 |
| 150 | 300 | 30 | 28 | 52 | 75 | 12 | 8 | 168,3 | 190 | 200 | 170,5 | 218 | 3 |
| 200 | 375 | 36 | 34 | 52 | 88 | 16 | 8 | 219,1 | 244 | 260 | 221,5 | 285 | 3 |
| 250 | 450 | 42 | 38 | 60 | 105 | 18 | 10 | 273 | 306 | 312 | 276,5 | 345 | 3 |
| 300 | 515 | 48 | 42 | 67 | 115 | 18 | 10 | 323,9 | 362 | 380 | 327,5 | 410 | 4 |
| 350 | 580 | 54 | 46 | 72 | 125 | 20 | 10 | 355,6 | 408 | 424 | 359,5 | 465 | 4 |
| 400 | 660 | 60 | 50 | 78 | 135 | 20 | 10 | 406,4 | 462 | 478 | 411,0 | 535 | 4 |
| 450 | 685 | 66 | 50 | 84 | 135 | 20 | 12 | 457,0 | 500 | 522 | 462,0 | 560 | 4 |
| 500 | 755 | 72 | 52 | 90 | 140 | 20 | 12 | 508,0 | 562 | 576 | 513,5 | 615 | 4 |
| 600 | 890 | 84 | 60 | 100 | 150 | 20 | 12 | 610,0 | 666 | 686 | 616,5 | 735 | 5 |
| DN | D | C1 | C2 | H1 | H2 | H3 | R | A | N1 | N2 | B1 | d1 | f1 |
The following table provides the bolting geometry associated with the PN40 flange dimensions above.
K = Bolt circle diameter (PCD), L = bolt-hole diameter, No. = number of bolt holes, Size = nominal metric bolt size.
All dimensions are in mm.
| DN | K | L | No | Size |
| mm | mm | mm | - | mm |
| 10 | 60 | 14 | 4 | M12 |
| 15 | 65 | 14 | 4 | M12 |
| 20 | 75 | 14 | 4 | M12 |
| 25 | 85 | 14 | 4 | M12 |
| 32 | 100 | 18 | 4 | M16 |
| 40 | 110 | 18 | 4 | M16 |
| 50 | 125 | 18 | 4 | M16 |
| 65 | 145 | 18 | 8 | M16 |
| 80 | 160 | 18 | 8 | M16 |
| 100 | 190 | 22 | 8 | M20 |
| 125 | 220 | 26 | 8 | M24 |
| 150 | 250 | 26 | 8 | M24 |
| 200 | 320 | 30 | 12 | M27 |
| 250 | 385 | 33 | 12 | M30 |
| 300 | 450 | 33 | 16 | M30 |
| 350 | 510 | 36 | 16 | M33 |
| 400 | 585 | 39 | 16 | M36 |
| 450 | 610 | 39 | 20 | M36 |
| 500 | 670 | 42 | 20 | M39 |
| 600 | 795 | 48 | 20 | M45 |
BS 4504 was a British Standard covering PN-designated circular flanges for pipes, valves and fittings. This page provides reference dimensions for PN40 steel flanges from the former BS 4504 system.
No. BS 4504 has been withdrawn and superseded by BS EN 1092-1 for PN-designated steel flanges. BS 4504 dimensions remain useful when working with legacy drawings, existing installations and replacement components.
PN40 is a nominal pressure designation. It should not be interpreted as a universal maximum working pressure of 40 bar because allowable pressure depends on factors including flange material and operating temperature.
DN is the nominal size designation of the flange and associated piping. It identifies a standardised component size and should not be interpreted as a direct measurement of the actual pipe bore.
PN25 and PN40 are different nominal pressure designations and can require different flange dimensions and bolting arrangements. A PN40 flange should not be selected simply by assuming it is a thicker version of a PN25 flange. The applicable standard, dimensions, drilling, facing, material and service conditions should be checked.