Page 692 - Mastik®

Preload and tightening torques for Preload and
high strength structural bolts tightening torques

according to EN 14399

Dimensioning, layout and installation of – ISO 898, part 1 for bolts, EN 14399-4 To tighten the joints any of the following
high strength structural joints is specified – ISO 898, part 2 for nuts, EN 14399-4 methods may be used:
in EN 1090 part 2. – Washer EN 14399, part 5-6, Steel – Manual & hydraulic torque wrenches
Mechanical properties of high-strength hardened to 295–350 HV 10 (~29–36 (torque controlled)
structural bolts are specified in ISO 898. HRC) – Impact wrenches, nut runners (torque
controlled)
– Turn of nut method (torque angle con-
trolled)
Table 1, Specified preloads and torques for 4 tightening methods: torque control method, air driven impact wrench method,
angle-controlled method, combined preloading method for 10.9 HV-assemblies.

1 2 3 4 5 6
Torque control Air driven impact Turn of the nut Combined method
method wrench method method
Specified
Dimensions Tightening torque MA Set preloading force, Angle-controlled Pretightening torque
preload FV
to achieve the to achieve the M VA,DW ** M VA,KW **
specified preload FV specified preload FV
mm kN Nm kN Nm Nm
Protection and lubrication: hot dip galvanized and lubricated a
1 M12 50 100 60 10 75
2 M16 100 250 110 50 190
3 M20 160 450 175 50 340
4 M22 190 650 210 100 490
5 M24 220 800 240 100 600
6 M27 290 1250 320 200 940
7 M30 350 1650 390 200 1240
8 M36 510 2800 560 200 2100
a Nuts lubricated with MoS 2 or equivalent lubricant

Table 2, Required additional angle of rotation ˽and value of rotation V for the combined tightening method for 10.9 HV-bolts.

1 2 3
Clamping length L k * of the package
Additional angle of rotation ˽ Value of rotation V
(incl. shims and washers)
1 t < 2 d 45 1/8
2 2 d ≤ t < 6 d 60 1/6
3 6 d ≤ t < 10 d 90 1/4
4 10 d < t no recommendation no recommendation

Table 3, Inspection of the specified bolt preload

Additional angle of rotation Conclusion Measure to be taken
< 30° Preload was sufficient none
Leave the inspected assembly but inspect two
30° – 60° Preload was only partly sufficient
more bolts in the same connection
a
Replace the inspected bolt by a new one and
> 60° Preload was not sufficient
inspect two more bolts in the same connection
a In case of statically loaded bearing type connections with HV bolts or with HV fit bolts without axial forces the inspected bolts may remain in the
construction.