Breakaway (Slip) Torque Testing

Definition and importance

Breakaway torque, also known as slip torque, refers to the rotational force required to initiate movement in a threaded closure, such as a bottle cap or medical connector. It represents the moment the static friction holding the closure in place is overcome, allowing it to "slip" or begin to turn.

This measurement is distinct from bridge torque, which refers to the point at which tamper-evident features or safety bridges break during rotation.

Understanding breakaway torque is essential because it directly impacts:

• Consumer usability - Closures must be firm enough to avoid leaks but still easy to open.
• Product protection - Proper torque prevents contamination or spoilage.
• Regulatory compliance – Particularly in pharmaceuticals, food and drink, and medical sectors, torque values must fall within accepted limits.

Where breakaway torque is critical

Breakaway torque testing is vital in any application where closure integrity and ease of access must be carefully balanced:

• Child-resistant closures (CRCs) - Such as those used in pharmaceutical and cleaning products, where safety is legally mandated.
• Medical luer lock connectors - Require precise torque for secure connections without over-tightening.
• Beverage and household packaging - From carbonated drinks to household cleaners, packaging must resist leaks while remaining user-friendly.
• Screw caps on PET bottles - Often need specific torque settings to maintain carbonation or avoid breakage.

Torque failure, whether through overtightening or inadequate resistance, can lead to serious issues, from consumer frustration to non-compliance and product recalls.

Mecmesin offers a full suite of equipment to meet the torque testing needs of both R&D labs and production environments, from manual testers to fully automated systems.

Manual equipment for R&D or small-batch QA

For quality control checks, product development, or limited throughput, Mecmesin’s manual torque testers offer dependable performance with straightforward operation:

• VTG Tornado - A digital tester with advanced features for real-time analysis.
• Tornado - Compact and intuitive, ideal for portable testing and training.
• Orbis - Cost-effective and simple to use, suitable for basic torque checks.

These devices are ideal for settings where portability and ease of use are priorities, and where sophisticated automation may not be required.

Automated systems for slip torque measurement

In higher-volume production environments, repeatability and precision are essential. Mecmesin’s motorised torque testers provide consistent application and removal speeds, advanced data capture, and integration with quality management systems.

• VortexPro - An advanced motorised system with superior control and software features, ideal for precise slip torque analysis using Mecmesin’s VectorPro software.
• Vortex-dV - A streamlined version offering essential motorised functionality at an accessible price point.

Both systems ensure reliable test replication, critical for demonstrating compliance with international standards.

Breakaway torque testing is governed by a range of industry-specific standards designed to ensure safety and consistency in packaging performance.

ASTM D2063 and child-resistant packaging

ASTM D2063 outlines the procedures for testing CRCs, focusing on torque measurement as a key performance indicator. It provides:

• Defined pass/fail criteria
• Torque range benchmarks
• Methods for assessing closure functionality across user age groups

Compliance with this standard is essential for pharmaceutical and chemical packaging targeting households.

ISO/BS standards for medical and consumer closures

Other applicable standards include:

• ISO 8317 - For reclosable CRCs for children
• BS EN ISO 17480 - Guidelines for packaging accessible to older persons and those with disabilities
• ASTM D7860 - For automated torque measurement in closure systems

Each standard defines the parameters and environmental conditions under which torque testing should be conducted, ensuring consistent, repeatable results across sectors.

Understanding test outputs is as crucial as conducting the tests themselves.

Slip torque vs bridge torque

Slip torque reflects the resistance encountered before rotation begins—a measure of seal integrity and usability.

Bridge torque occurs after slip torque and indicates the force needed to break tamper-evident features.

Comparing these values can reveal design flaws or inconsistencies in manufacturing, allowing packaging engineers to optimise closure performance.

Pass/fail criteria for common applications

Torque thresholds vary depending on product type and application:

• CRC caps - Must meet minimum torque for child resistance while remaining openable by adults.
• Food and drink containers - Require a balance between leak prevention and consumer ease of use.
• Personal care packaging - Often prioritises aesthetics and tactile feel, but must not compromise on seal strength.
• Medical connectors - Demand extremely tight tolerances to prevent failure during critical procedures.

Failure to meet these benchmarks may result in regulatory issues, recalls, or damage to brand reputation.

Accurate and repeatable torque testing depends on attention to several technical factors.

Calibrating torque sensors

Regular calibration ensures that readings remain accurate and traceable to national or international standards.

Validation routines should be documented and included as part of a broader quality system.

Consistent cap application and removal speed

Variations in rotational speed can skew results.

Motorised testers like the VortexPro help enforce consistent torque ramp rates, improving repeatability.

Environmental conditioning of samples

Torque performance can change with temperature, humidity, and product ageing. Best practice includes:

• Conditioning samples to room temperature or specified test conditions
• Accounting for time-based factors such as storage duration
• Documenting all environmental variables during testing

Mecmesin offers an unmatched combination of reliability, support, and industry insight:

• Expert support and calibration services - Technical teams provide guidance from setup to compliance.
• Modular equipment options - Covering a wide range of closure types, industries, and budgets.
• Trusted by leading brands - Mecmesin systems are used globally by top-tier packaging manufacturers and labs.

From initial test design to data interpretation, Mecmesin provides a comprehensive solution tailored to industry needs.

Have questions about selecting the right torque tester or meeting standards such as ASTM D2063 or ISO 8317? Our engineers can help you ensure compliance and accuracy in your packaging process. Speak to our technical team or request a product demonstration.