Apart from dimensional differences ( bigger heads of bolts and bigger nuts on preloaded assemblies), the main difference is in the way how these goods are installed.
Non-preloaded bolting assemblies are generally tightened to at least snug-tight. The connected components are drawn together to achieve firm contact without any specific preload.
The “snug-tight” is generally referenced as tightening the assembly by one man using a normal-sized spanner without an extension arm until the wrench starts hammering.
See more: Tightening of non-preloaded bolts
Preloaded bolting assemblies are tightened to at least a minimum specified force (preload). The tightening is carried out according to specified installation methods (with DTI washers , using part-turn, torque figures or tension controlled). This type of product is generally used for critical, slip-resistant, seismic connections, fatigue resistance, execution purposes or as a quality measure (for example: for durability).
Preloaded bolting assemblies can be used as non-preloaded bolting assemblies, where non-preloaded shall not be preloaded unless specified by the construction engineer.↫ Go back