DTI washers show visually that a structural bolt has reached its required pretension, which removes the guesswork from turn-of-nut and calibrated-wrench methods. We stock ASTM F959 / EN 14399-9 DTIs in Umm Al Quwain from M12 to M36 and ½" to 1½" for grade 8.8 / 10.9 and A325 / A490 assemblies, plain and galvanized, with feeler gauges.
A direct tension indicator is a hardened washer with raised protrusions (bumps) on one face. Placed under the bolt head or nut, the bumps flatten as the bolt is tensioned; when a 0.4 mm (0.015") feeler gauge is refused at the required number of gaps, the bolt has reached its minimum pretension. DTIs are recognised by RCSC, AISC, EN 1090 and BS 5950 as a bolt-tension verification method and are especially useful on galvanized and large assemblies.
Applications
- Bridge and highway structure bolting
- High-rise and long-span steel frames
- Tower, mast and wind-turbine flanges
- Crane girders and heavy industrial connections
- Inspection-critical and QA-audited projects
- Retrofit and strengthening works
Standards, grades & finishes
Indicators to ASTM F959 / F959M (Type 325 and 490) and EN 14399-9 (HR / HV 8.8 / 10.9), hardened, with matching nut-face and bolt-face washers where required. Plain or mechanically galvanized (ASTM B695) / hot-dip; coated DTIs with squirter silicone available for one-sided visual inspection. Supplied with feeler gauges and installation guide; calibrated in accredited lab (ISO / IEC 17025) per lot.
This item is imported from approved mills and held in stock in our Umm Al Quwain warehouse alongside the anchor bolts, studs and plate washers we manufacture ourselves, so complete bolt sets ship from one source. Tensile, hardness and chemical testing is carried out by independent UAE-accredited laboratories, and EN 10204 3.1 certificates are issued with every batch. We supply across the GCC, MENA and Africa.