Direct tension indicators are hardened washer shaped components with 4 to 6 small arch-like protrusions on the bearing surface that are designed to deform in a controlled manner when subjected to appreciable tightening torque.
Basically the Direct tension indicators washers work on the principle that appreciable tightening force on the bolt nut assembly the arch like protrusions collapse under the applied load and this indicates that the required torque has been applied in tightening the assembly. The gaps in between the washer and nut are normally checked with thin feeler gauges. In some cases the protrusions are filled with certain silicone material which flows out from the protrusions and through the crevice in the washer towards the outer edge thus indicating that appreciable torque has been applied in tightening the assembly. These washers are known as Squirter Washers because the silicone is squirted out from the protusions as the washer flattens out with increasing load.
DTI (Direct Tension Indicator) Washers manufacturers, suppliers, exporter in India - Bhalla Fasteners. DTI washers are used to control the tensioning of bolts.