DTI Washer

[JATE]

Good Morning:

The same bolt is tensioned with a torque meter and gives a much greater value than the one obtained by applying a DTI washer. why?


Bolt: A325
Diameter: 7/8 "
Torque value: 890 lb-ft

JATE

 

[dik]

Because of surface conditions, a calibrated torque meter does not provide consistent results. The Canadian steel code does not recommend use of this. DTI washers or turn of nut gives a much better indication of the torque provided.

Dik

 

[JATE]

What happens if the bolts break before the DTI washer of the indication;

 

[dvd]

A DTI is a direct tension indicating washer. Torque is only sort of an indication of tension. You could probably benefit from the videos and information at this website:

https://www.appliedbolting.com/video.php

 

[3DDave]

If the bolt breaks before reaching the required tension as indicated by the washer then the bolt is either the wrong choice or a defective bolt or the wrong DTI washer. The defect might be from manufacture or from mishandling/corrosion.

 

[HTURKAK]

The same bolt is tensioned with a torque meter and gives a much greater value than the one obtained by applying a DTI washer. why?

If the difference is 10% , it is O.K...For preloading of bolt with torque control method, the torque is applied in two steps. The first step is to apply a torque of up to 75% of the required torque value to all the bolts and second step is to apply additional torque so applied torque is 110% of the nominal torque value. when the tightening wrench is removed , torsional relaxation will occur this is the extra 10% of preload.