Content with Pre-load

02 March 2021
When ordering Preloaded Assemblies (EN 14399-1) to be installed with Direct Tension Indicator Washers (DTIs) , there are 4 different methods of how they can be installed. Depending on the access or preference, you may choose one method, over another. At the purchase stage, we may not know how you will be installing your assemblies. Please read below, as you may require an additional washer(s) to be purchased. Figure 1 Figure 2 Figure 3 Figure 4 Installation methods: Installing DTI under the bolt head when the nut is rotated (Figure 1)
Read more about Do I need Bolt Face Washer or Nut Face Washer (EN 14399-9) with DTI's?

29 January 2016
Due to the compression ability of paint, galvanising coating and other types of surface protection , it is required that places of joints for high-strength structural bolting assemblies for preloading are cleaned from any coating before installation. After the installation process, depending on the type of coating of the assemblies, the whole surface can be further covered to restore corrosion protection in joint places. Please refer to EN 1090-2:2018 pt. 8.
Read more about Can high-strength structural bolting assemblies for preloading (HSFG) be used on painted or galvanised surfaces?

12 January 2016
The minimum thread length is calculated strictly according to EN 14399-3 for high-strength structural bolting assemblies for preloading - System HR and EN 14399-7 for high-strength structural countersunk bolting assemblies for preloading - System HR . In calculation, you need to consider standard reference thread length (b), minimum length of the shank - un-threaded part of the bolt, and distance from the head of the bolt till the first full thread.
Read more about What is the minimum thread length on high-strength structural bolting assemblies for preloading?

18 December 2015
For high-strength structural bolting assemblies for preloading to BS EN 14399 an overall recommendation is to have a minimum of 1 (one) thread above the unloaded face of the nut, and a minimum of 4 (four) threads before the shank of the bolt and the nut.
Read more about Are two threads protruding through high-strength structural bolting assemblies for preloading enough?

18 December 2015
Due to safety reasons and according to BS 4604-1 (Withdrawn): “If after final tightening a bolt or nut is slackened off for any reason, the bolt, nut and washer shall be discarded and not re-used.” Under the latest BS EN 14399 standard: If the assembly has been tightened to the minimum force of 70%, the assembly cannot be re-used. Andrews Fasteners recommend, once assembly has been preloaded, in any form and needs to be de-assembled, to discard it and replace it with fresh assembly (and relevant components like DTI washers) due to wearing off applied lubrication which may invalidate torque figures supplied for installation (k-Class K1 or K2) or cause difficulty to compress DTI washers at the right level (k-Class K0).
Read more about Can high-strength structural bolting assemblies for preloading (HSFG) be de-assembled once they have been assembled?

18 December 2015
To accommodate the thickness of zinc it is normal practice to over-tap the nut thread. This operation reduces the strength of the nut and the overall strength of the nut and bolt assembly. To improve the strength of the assembly manufacturers use either a thicker nut (increasing the number of threads between the nut and the bolt in the assembly) or a higher-grade nut. BS EN 15048-1: To achieve full tensile resistance, hot-dip galvanized assemblies can require special measures, see EN ISO 10684, Annex F.
Read more about Should higher-grade nuts be specified for use with galvanized or sherardized set screws and bolts on CE (UKCA) approved assemblies?

18 December 2015
HR should stand for High Resistance and HV for Hochfeste Bolzen mit Vorspannung (in English high resistance bolts for pretension). The second is an official description, and they should serve the same purpose. See also: What is the difference between HR and HV bolt assemblies?
Read more about What does the HR & HV symbols mean?

18 December 2015
HR (British/French) bolt The British/French approach following BS EN 14399-3 and BS 4395 is to use thick nuts and long thread lengths in the bolt assembly to obtain ductility predominantly by plastic elongation of the bolt. The longer thread length is necessary to ensure that the induced strain is not localised. These bolts are relatively insensitive to overtightening during preloading although suite control is still important. Furthermore if severely over-tightened during preloading the ductile failure mode of the bolt assembly is predominantly by bolt breakage, which is readily detectable.
Read more about What is the difference between HR and HV bolt assemblies?

18 December 2015
According to standard requirements, during assembly, you should not use any additional lubrication apart from that originally supplied. BS EN 14399 standard is leaving a clause, that additional lubrication should be used if it is subject to supplier recommendation. Andrews Fasteners BS EN 14399 Assemblies are supplied to k-Class k0 and are offered pre-lubricated. We are supplying lubricated parts of the assembly. Lubricated parts are used where due to surface coating , maximum tension needs to be controlled to prevent seizure.
Read more about Should high-strength structural bolting assemblies for preloading be assembled with lubrication?

01 February 2015
Andrews Fasteners company in manufacturing Direct Tension Indicators Washers (DTI Washers) in well know in construction industry company based in United States – TurnaSure . All our washers are marked with our headmark FAST (previously AND.). Benefits of using Direct Tensions Indicators Washers: The use of DTIs is the simplest way of ensuring that bolting assemblies are tensioned properly; The use of DTIs saves cost on inspection; No torque figures are required, only feeler gauges; Risk reduction on over tightening; DTIs are manufactured in compliance with EN 14399-9 and can be supplied with CE approved preload bolting assemblies; Unique curved protrusion design of Turnasure DTIs reduce necessary of using nut face / bolt face washers for 8.
Read more about Direct Tension Indicators Washers (BS EN 14399-9)