A direct tension indicator (DTI) washer provides a way to verify bolt tension through compression of its indicator features. Its acceptance depends on the applicable standard, bolt series, washer configuration and installation procedure. This table reproduces selected compression-load ranges published by STS Industrial for DTI sizes. It helps identify the load band associated with a nominal size and series. It is not a torque chart, a general bolt-preload table or a substitute for the project specification and manufacturer’s current lot documentation.

Direct Tension Indicator Washer Specifications

In the inch series, loads are stated in kips; in the metric series, loads are in kilonewtons. The source labels the inch columns Types 325 and 490, including their Type 3 variants, and the metric columns Types 8.8-1/8.8-3 and 10.9-1/10.9-3. The table keeps the load units tied to the series so they are not compared as if they shared one unit.

Reading a compression-load band

The lower and upper numbers define a range for the listed DTI size and series. They describe compression load at the washer under the source’s specification. For example, the STS table lists the 3/4-inch Type 325 series from 28 to 34 kips, while the M24 metric 8.8 series is 205 to 246 kN. Do not convert one into the other and assume interchangeability: the nominal sizes, bolt standards and washer configurations differ.

The ranges are not the exact installation tension for every joint. Proper DTI use depends on the specified minimum bolt pretension, the correct washer orientation and location, the hardness of the supporting surface, coating, and whether a hardened washer is required. A gap or feeler-gauge criterion is tied to the applicable standard and product documentation. Squirter-style indicators may also use a visual extrusion indicator, but that does not remove the need to follow the instructions.

Use the table during selection and inspection planning

First identify the structural bolt diameter and grade or property class, then choose a DTI type explicitly approved for that assembly. Confirm that the compression load range corresponds to the required pretension method and the exact product. The erector and inspector should have the installation instructions, required gap criteria and any lot-specific load-gap chart before work begins. If a DTI is installed under a nut, bolt head or hardened washer, use the manufacturer’s approved stack-up for that configuration.

Pre-installation verification can be required for each combination of bolt assembly and DTI. That check demonstrates that the assembly and indicator work together under the prescribed conditions. The DTI should be inspected at the appropriate locations, and the result recorded according to the project’s quality plan. A single gap measurement on the wrong side of the washer may not represent the required check.

Limits and common errors

Do not calculate a tightening torque from these ranges. Torque depends strongly on friction, lubrication, thread condition and the assembly; this dataset reports compression-load bands. Do not infer that a dimensionally similar washer has the same load response, or substitute a product based only on nominal diameter. Do not transfer an inch-series rating to metric hardware or assume a galvanized coating has no effect on installation guidance.

The source page identifies its values as ASTM F959 technical data. Confirm the current edition, product certification and project-adopted standard before specifying. The actual manufacturer’s test certificate and load-gap chart govern the product lot. Consult a qualified bolting engineer when the connection is safety-critical or when the assembly differs from the published installation methods.

Source

Compression-load values are from STS Industrial’s ASTM F959 Technical Data. Installation details should be checked against the DTI manufacturer and the project requirements; the table alone does not verify an installed connection.