Torque values for High-Strength Structural Bolting Assemblies for Preloading with specified k-Class

High-strength structural bolting assemblies for preloading with specified k-Class shall be tightened using below methods
(See BS EN 1090-2:2008+A1:2011, Table 20 for more details).

Torque methodK2
Combined method (torque / part-turn)K2 or K1
Direct Tension Indicators (DTI)K2, K1 or K0

k-Class K2 using Torque Method

Torque method uses a torque wrench in two steps of assembling. km figure is required for calculating first tightening torque value and Vk is required for calculating final tightening torque.

High-strength structural bolting assemblies for preloading (System HR or HV) according to EN 14399-1:2005 (k-Class K2) are supplied with km and Vk figures. Engineers, follow the formula from EN 1090-2 to calculate required torque reference value for each step of tightening.

According to EN 14399-1:2015, assemblies to k-Class K2 are supplied with km (required) and Vk (optional) figure together with torque values (required) for both steps of the assembly (these values are supplied in technical documentation or/and on labels).

k-Class K1 using Combined Method

Combined method uses a torque wrench in the first step of assembly. Second tightening step is done by specified part turn.

To calculate torque value, km figure for assembly classified as a k-Class K1 is required. For simplification, use km=0.125 can be used (as per EN 1090-2:2018, pt. 8.5.2 a.1.), however we strongly recommend using provided km figure that been evaluated through testing.

Please be advised, that not all k-Class K2 assemblies are automatically classed as k-Class K1, but still k-Class K2 can be used with combined method.

Torque value calculator

To calculate Torque reference values for High-strength structural bolting assemblies for preloading (System HR and HV) with specified k-Class please use below calculator:

km value (as declared)
Vk value (as declared)
Torque value T1 (first tightening step):
Torque value T2 (second tightening step):
Version: JS/1.00.220721

The figures from this calculator are provided in good faith and is for your guidance only. Our company cannot accept any liability for actions taken by third parties based on this information. To validate archived results, please follow formula from BS EN 1090-2:2018, pt. 8.5.2.

Don’t know which components to use on HR assembly?

Looking for torque value for non-preloaded bolt assemblies?

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