BOLT TIGHTENING IN OIL ND GAS ( CONSTRUCTION PLATFORM)

 BOLT TIGHTENING IN OIL ND GAS ( CONSTRUCTION PLATFORM)

1.0 GENERAL NOTES 3

2.0 STANDARD (GENERAL) TIGHTENING MOMENTS VS BOLT SIZE, MATERIAL

AND LUBRICATION METHOD 5

2.1 Metric Bolts 5

2.2 Un Imperial Bolts (Un 8 For Bolt Size ≥ 1”) 7

88

3.0 CL 150 WN ASME B16.5 RF FLANGES

3.1 Titan Gr. 2 & AISI 316L (Non-Magnetic)

3.2 22Cr Duplex & 25Cr Duplex (Magnetic) 9

4.0 CL 300 WN ASME B16.5 RF FLANGES 10

4.1 Titan Gr. 2 & AISI 316L (Non-Magnetic) 10

APPENDIX A.1 DESIGN RECOMMENDATIONS VS BOLTING 11

1.0 GENERAL NOTES

This procedure for tightening of bolts is valid for all bolted connections as long as no other information

concerning the tightening moment is given in a mounting procedure or on an assembly drawing.

Standard (General) bolt tightening moments are shown in Chapter 2.0. Bolt tightening moments for

Flat Ring gaskets for flange facing Raised Face (RF) according to ASME B16.5 Class 150 have been

especially evaluated in Chapter 3.0 with respect to bolt material, gasket crush strength, flange

material allowable stress and lubricant friction coefficient. For Full Face gaskets for flange facing Flat

Face, use tightening moments in Chapter 2.0.

Bultens recommendations concerning calculation of the required tightening moment from the

prestressing force when including scatter have been applied for torque-controlled tightening. If

pneumatic or electric hammer is used during assembly, this should be used for light tightening,

followed by tightening with a torque wrench.

If no tightening moment is specified in service instruction or on drawing, use tightening moment

according to following tables which are based on recommendations in BULTENS HANDBOOK BH 67.

BULTEN gives an improvement in the calculation method compared to VDI 2230, “Systematic

Calculation of High Duty Bolted Joints” since it includes the possible scatter in the prestressing force.

A scatter of 23 % (assembly uncertainty factor) is used with torque-controlled tightening with a torque

wrench. Framo Standard calculation procedure 2025-026-4 is used for calculation of all tightening

moments included in this document.

In order to obtain correct prestressing force, it is essential that the threads of cap bolts and threads

between studs and nuts, plus screw heads and contact surface of nuts against foundation, are clean

and lubricated before tightening (see figure below). The friction factors μ for Molycote (2 types),

Chesterton 785 and Loctite 243 threadlocker are based on data from Statoil TR 3125 and tests

performed by Frank Mohn Flatøy (1995).

Suppositions For the Tables:

a) Connected components should have metallic contact.

b) Screws and nuts should be paired, A4-80 / A4-80, 8.8 HDG / 8.8 HDG etc..

c) Tightening moments are based on lubrication of both the threads and under bolt head / nuts,

except for Loctite threadlocker that shall only be used on threads and not under bolt head /

nuts.

d) Special for Flat Ring Gasket for Flange Facing Raised Face (RF):

Retighten all flange bolts after 24 hours due to gasket shrink and creep under load.

Suppositions For the Tables:

a) Connected components should have metallic contact.

b) Screws and nuts should be paired, A4-80 / A4-80, 8.8 HDG / 8.8 HDG etc..

c) Tightening moments are based on lubrication of both the threads and under bolt head / nuts,

except for Loctite threadlocker that shall only be used on threads and not under bolt head /

nuts.

d) Special for Flat Ring Gasket for Flange Facing Raised Face (RF):

Retighten all flange bolts after 24 hours due to gasket shrink and creep under load.

Tightening of Flanges:

When tightening flanges with circular hole pattern:

1. First tighten one round (diagonally) with ¾ of full tightening moment,

2. Then with full tightening moment until the bolts are firm and without movement when full

tightening moment is achieved.