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Torque Values

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THE EFFECT OF BOLT LUBRICATION

Bolt lubrication greatly affects the torque values used when installing gaskets.  To achieve the same gasket compression, a much higher torque value is required for a dry bolt versus using a lubricant.

In a dry bolt up, or where an inefficient lubricant is used such as light oil, the effort used in tightening is overcome by the frictional forces between the bolts and nuts and to a greater extent between the nuts and nut facings.

This can result in a lower gasket load and inadequate stress on the bolts, which can result in torque loss and eventual leakage in service.

RELATED: Torque Value Calculator

Torque Values – ASME B16.5 Flanges

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

Flange
Size
B16.5 Class 150 RF/ Ring Gaskets B16.5 Class 150 FF/ Full Face Gaskets
Torque / Round (ft-lbs) Bolt Tighten Sequence* Torque / Round (ft-lbs) Bolt Tighten Sequence*
1st 2nd Final Dwg*/No. Bolt Size 1st 2nd Final Dwg*/No. Bolt Size
1/2" 10 20 30 4-bolt 1/2" 20 40 60 4-bolt 1/2"
3/4" 13 27 40 4-bolt 1/2" 20 40 60 4-bolt 5/8"
1" 15 30 50 4-bolt 1/2" 20 40 60 4-bolt 5/8"
1-1/4" 20 40 60 4-bolt 1/2" 20 40 60 4-bolt 5/8"
1-1/2" 20 40 60 4-bolt 1/2" 20 40 60 4-bolt 3/4"
2" 40 80 120 4-bolt 5/8" 40 80 120 4-bolt 5/8"
2-1/2" 40 80 120 4-bolt 5/8" 40 80 120 8-bolt 3/4"
3" 40 80 120 4-bolt 5/8" 40 80 120 8-bolt 3/4"
3-1/2" 40 80 120 8-bolt 5/8" 40 80 120 8-bolt 3/4"
4" 40 80 120 8-bolt 5/8" 40 80 120 8-bolt 3/4"
5" 60 120 200 8-bolt 3/4" 60 120 200 8-bolt 3/4"
6" 60 120 200 8-bolt 3/4" 60 120 200 12-bolt 3/4"
8" 60 120 200 8-bolt 3/4" 60 120 200 12-bolt 7/8"
10" 95 190 320 12-bolt 7/8" 95 190 320 16-bolt 1"
12" 95 190 320 12-bolt 7/8" 95 190 320 16-bolt 1-1/8"
14" 147 294 490 12-bolt 1" 147 294 490 20-bolt 1-1/8"
16" 147 294 490 16-bolt 1" 147 294 490 20-bolt 1-1/4"
18" 213 426 710 16-bolt 1-1/8" 213 426 710 24-bolt 1-1/4"
20" 213 426 710 20-bolt 1-1/8" 213 426 710 24-bolt 1-1/4"
24" 300 600 1,000 20-bolt 1-1/4" 300 600 1,000 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.

*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

Flange Size B16.5 Class 300 RF/ Ring Gaskets
Torque / Round (ft-lbs) Bolt Tighten Sequence*
1st 2nd Final Dwg/No. Bolt Size
1/2" 10 20 30 4-bolt 1/2"
3/4" 15 30 50 4-bolt 5/8"
1" 21 42 70 4-bolt 5/8"
1-1/4" 30 60 100 4-bolt 5/8"
1-1/2" 45 90 150 4-bolt 3/4"
2" 33 66 110 8-bolt 5/8"
2-1/2" 42 84 140 8-bolt 3/4"
3" 60 120 200 8-bolt 3/4"
3-1/2" 60 120 200 8-bolt 3/4"
4" 60 120 200 8-bolt 3/4"
5" 60 120 200 8-bolt 3/4"
6" 60 120 200 12-bolt 3/4"
8" 95 190 320 12-bolt 7/8"
10" 147 294 490 16-bolt 1"
12" 213 426 710 16-bolt 1-1/8"
14" 195 390 650 20-bolt 1-1/8"
16" 273 546 910 20-bolt 1-1/4"
18" 300 600 1,000 24-bolt 1-1/4"
20" 300 600 1,000 24-bolt 1-1/4"
24" 465 930 1,550 24-bolt 1-1/2"

NOTE: This is a general guide only and Gasket Resources Inc. does not accept responsibility for negligence or misuse of this information. 

Torque Values are in ft.-lbs. and assume new A193 Gr. B7 studs with 2H heavy hex nuts; with studs, nuts and the nut bearing surfaces lubricated with a never-seize type paste (k = 0.17) using the installation and bolt tightening practices outlined on  this website or the Durlon Technical Handbook.  Lubricant should not be applied to the gasket or flange faces as a release agent.  Hardened steel washers are also recommended to reduce friction.  

* Refer to the appropriate bolt tightening sequence drawing under gasket installation on this website or the Durlon Technical Handbook for the number of bolts listed.

NOTE: Bolt stresses may exceed ASME allowables.