DTI washer: for quality tightening of bolts

Panchsheel fasteners is a manufacturer and supplier of high-strength structural fasteners (HSFG) Fasteners. Over 200 customers are regularly using its products since last 40 years.

Panchsheel fasteners identified a need of “Direct Tension Indicating Washers” (popularly known as DTI washer) to ensure the proper tightening of the HSFG bolts.

Panchsheel fasteners have developed the manufacturing inspection and testing process at their Ludhiana works.

Tightening of HSFG bolt is critical. One must ensure that sufficient ‘clamping force’ is generated and two components of the joint are firmly held.

Correctly, what they expect is accuracy in measurement, consistency and reliability, ease of installation, less involvement of skilled persons, ease of inspection, standardisation and cost effective.

There are six methods of controlling the tightness of HSFG fasteners.

Use of DTI washer is most popular because it meets all the expectations.

DTI washer is a specially hardened washer with protrusions on one face. DTI is placed under the bolt head or between the plate and bearing face of the nut. The protrusions create the gap. As the bolt is tightened, clamping force is generated. The DTI washer also experiences this force, resulting in collapse of the arch like protrusions. This reduces the gap. This deformation is co-related to the bolt tension. The gap is verified with help of feeler gauge.

Authored by:
J.H.Pavnaskar
Technical Head
Panchsheel Fasteners P.Ltd