DTI Washer

Description

DTI WASHER F959 / F959M

DTI washer F959 / F959M simple washer type load cells known as a Direct Tension Indicator or a Load Indicating Washer. Moreover Load cells that are manufactured with raised dimples that are used to indicate when the proper tension level has been achieved during tightening. Since tension is what we are after NOT TORQUE. Thus DTI’s are manufactured to the F959 specification.

General:

The Standard for DTIs in North America is the ASTM International series of standards and the specific designation for testing and manufacturing DTIs is ASTM F959.  Standard Specification for Compressible-Washer Type Direct Tension Indicators for Use with Structural Fasteners. They are generally installed in accordance with the Research Council on Structural Connections Specification (RCSC) for Structural Joints using High Strength Bolts.

Load indicating washers (LIW) are used to develop the correct tension when installing A325 or A490 structural bolts. DTIs are made to ASTM F959. Load indicating washers may be available for other bolt grades as well.

When the direct–tension-indicator pretensioning method is used, an ASTM F436 washer shall be used as follows:

1. When the nut is turned and the direct tension indicator is located under the bolt head. An ASTM F436 washer shall be used under the nut;
2. When the nut is turned and the direct tension indicator is located under the nut. An ASTM F436 washer shall be used between the nut and the direct tension indicator;
3. When the bolt head is turned and the direct tension indicator is located under the nut, an ASTM F436 washer shall be used under the bolt head; and,
4. When the bolt head is turned and the direct tension indicator is located under the bolt head, an ASTM F436 washer shall be used between the bolt head and the direct tension indicator.