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Torque Values

Torque Values – ASME B16.5 Flanges

CLASS 150 ANSI B16.21-78
DURLON® Gasket Material
Torque: ft-lbs

Flange Raised Face/Ring Gaskets Flat Face/Full Face Gaskets * Bolt Tighten Sequence
Size 1st 2nd Final 1st 2nd Final Dwg*/No. Bolt Size
1/2" 4 8 16 15 35 70 4-bolt 1/2"
3/4" 6 12 23 15 35 70 4-bolt 1/2"
1" 8 15 30 15 35 70 4-bolt 1/2"
1-1/4" 12 24 45 15 35 75 4-bolt 1/2"
1-1/2" 14 28 56 15 35 75 4-bolt 1/2"
2" 25 50 113 35 75 150 4-bolt 5/8"
2-1/2" 25 50 113 35 75 150 4-bolt 5/8"
3" 33 66 130 35 75 150 4-bolt 5/8"
3-1/2" 36 92 140 35 75 150 8-bolt 5/8"
4" 25 50 113 35 75 150 8-bolt 5/8"
6" 25 50 113 65 130 270 8-bolt 3/4"
8" 50 100 202 65 130 270 8-bolt 3/4"
10" 80 160 327 110 220 436 12-bolt 7/8"
12" 80 160 327 110 220 436 12-bolt 7/8"
14" 120 240 492 160 320 655 12-bolt 1"
16" 120 240 492 160 320 655 16-bolt 1"
18" 180 365 731 240 480 975 16-bolt 1-1/8"
20" 180 365 731 240 480 975 20-bolt 1-1/8"
24" 260 520 1036 345 680 1380 20-bolt 1-1/4"

Note: It is assumed that new ASTM A193 Gr. B7 studs with 2H heavy hex nuts and hardened steel washers are used and studs, nuts and nut facings are lubricated with a never-seize paste using the installation and bolt tightening practices outlined above. Torque is based the higher of 40% of bolt yield, T3 or 4800 psi gasket stress up to either the maximum allowable material stress or a maximum bolt yield of 60%. The above was calculated using the proposed ASME Gasket Constants (ROTT Testing, Ecole Polytechnique) for each material.

* Flat face flanges using full face gaskets, the recommended torque value is generally the maximum allowable torque based on the allowable bolt area. Flat face flanges have the same bolting as raised face flanges but roughly 3 to 4 times more surface / contact area. This makes flat face flanges very difficult to seal unless using a gasket with low compression characteristics such a a rubber gasket.

The user should be aware that there most likely is insufficient bolt area to adequately seal flat face flanges.

NOTE: Bolt stresses may exceed ASME allowables.

CLASS 300 RF
ANSI B16.21-78 - RING GASKETS
DURLON® Gasket Material
Torque: ft-lbs

  ANSI B16.5 Class 300 RF
Flange Torque / Round (ft-lbs) Bolt Tighten Sequence*
Size 1st 2nd Final Dwg/No. Bolt Size
1/2" 4 8 16 4-bolt 1/2"
3/4" 10 20 40 4-bolt 5/8"
1" 10 20 40 4-bolt 5/8"
1-1/4" 14 28 55 4-bolt 5/8"
1-1/2" 23 46 90 4-bolt 3/4"
2" 15 30 60 8-bolt 5/8"
2-1/2" 23 46 90 8-bolt 3/4"
3" 31 62 125 8-bolt 3/4"
3-1/2" 35 70 140 8-bolt 3/4"
4" 45 90 180 8-bolt 3/4"
6" 45 90 190 12-bolt 3/4"
8" 75 150 297 12-bolt 7/8"
10" 78 156 310 16-bolt 1"
12" 115 230 460 16-bolt 1-1/8"
14" 100 200 400 20-bolt 1-1/8"
16" 143 286 570 20-bolt 1-1/4"
18" 161 322 645 24-bolt 1-1/4"
20" 178 356 710 24-bolt 1-1/4"
24" 275 550 1100 24-bolt 1-1/2"

Note: It is assumed that new ASTM A193 Gr. B7 studs with 2H heavy hex nuts and hardened steel washers are used and studs, nuts and nut facings are lubricated with a never-seize paste using the installation and bolt tightening practices outlined above. Torque is based the higher of 40% of bolt yield, T3 or 4800 psi gasket stress up to either the maximum allowable material stress or a maximum bolt yield of 60%. The above was calculated using the proposed ASME Gasket Constants (ROTT Testing, Ecole Polytechnique) for each material.

NOTE: Bolt stresses may exceed ASME allowables.