Breakaway Torque and Opening Torque: How the SkillTork+ Measures Both in a Single Test

Two torque peaks, one test: full traceability for tamper-evident caps

On a tamper-evident cap fitted with a security ring, opening it produces two distinct torque events rather than one: first the breakaway torque needed to snap the tabs of the guarantee ring, then a lower opening torque needed to actually unscrew the cap. This second value is systematically lower than the first ( a mechanical consequence of how thermoplastic polymers relax internal stress once the ring has broken ). The two values behave independently: a cap can pass on breakaway torque while failing on opening torque, for instance if the capping machine has drifted and over-tightened.

Most torque testers on the market are built to capture a single value ( either the maximum peak or the final value at the end of rotation ) which works fine on caps without a ring, but creates a blind spot on tamper-evident closures. A tester running in "final value" mode will simply ignore the breakaway peak; a defective batch with an out-of-tolerance breakaway torque can pass every test and reach the market with no real tamper-evidence, unnoticed until it's too late.

The SkillTork+ from ACRN addresses this with a 1,800 Hz sampling rate and a dedicated peak-transition detection algorithm: as soon as torque drops sharply after the first peak, it identifies the transition and keeps the test cycle running until the second peak occurs. At the end of the test it displays and logs both values simultaneously — breakaway torque and opening torque — each with its own instantaneous, average, min/max statistics and independent Pass/Fail result against the selected product recipe, plus the inter-peak angle to flag ring geometry anomalies.

Covering sensor ranges from 1 to 25 N·m, the SkillTork+ is built for cosmetics, pharmaceutical, food and industrial chemistry packaging lines. It is calibrated to ISO 6789:2017 with COFRAC-traceable certification, supports AIAG MSA (4th edition) GR&R studies and SPC monitoring via independent Cp/Cpk indices per peak, and its Ethernet connectivity with embedded web server enables direct MES/LIMS integration with full CFR 21 Part 11 traceability.