Tensile Testing of Wire Joining Systems

Solution

• Universal Testing Machine with 50 kN capacity
• Grips adapted for wire, joiners, and tensioners
• Flexible, software-driven testing protocols

Benefits

• Eliminates the need for outsourced testing, with rapid evaluation of proof-loads on components and finished assemblies
• Interchangeable grips allow minimal setup and secure clamping of smooth or slippery metallic surfaces
• Reliable results free from previous variability caused by knots or temporary holding methods

Before using the dedicated rope grips, we had to tie the wire rope in a choke knot to perform tests. We can now make a good and reliable performance evaluation of the wire rope.

Requirement

Gripple has designs and manufactures wire joiners and tensioners in wide use in the construction of building services, agriculture, civil engineering, viticulture, and seismic construction. Their novel wire-fastening plastic components have guaranteed the safety and functionality of their products in various uses, such as suspending HVAC pipework in commercial buildings and attaching trellises to vineyards.

As part of continuous quality improvement, Gripple wanted to review and standardize in-house testing procedures for measuring the break loads of cable assemblies. Wire rope fastening systems are engineered to a minimum rated load; exceeding this load produces a controlled failure in the wire rope. The test system needed to accommodate wire diameters from 1.5 mm to 6 mm, while verifying a 5:1 safety factor against safe working load (SWL).

Solution

Presto Stantest provided a solution based on the MultiTest 50-i Universal Testing Machine, coupled with Emperor™ software for programmable and repeatable testing. This system measures the tensile strength of wire strands and cores, the pull strength of joiners and end fixings, and the performance of specialized seismic restraint devices.

The MultiTest 50-i twin-column machine was equipped with lever-action wedge grips and custom capstan rope grips, all rated to 50 kN. Earlier methods using choke knots introduced variability and inconsistent failures. To eliminate this, multiple grip configurations were evaluated:

• Upper and lower wedge grips with choke knot clamping
• Capstan rope grip paired with a wedge grip holding the choke knot
• Dual capstan rope grips securing both the bale and choke knot.
• Round-robin tests at a controlled extension rate of 100 mm/min confirmed that dual capstan rope grips provided consistent and repeatable results, independent of wire size.

Additional tests for seismic restraint devices to ANSI 171‑2017 standards were implemented easily using Emperor™ software and wedge grips. Longer eye-loop fixings were accommodated by extending the test space, modifying the moving crosshead, and adding a full-length interlocked safety guard, ensuring operator protection.

To support Gripple’s global operations in France, India, and Poland, the system allowed software licensing for seamless sharing of test programs and results across all locations, maintaining uniform test procedures and enabling direct comparison of performance data.

Test Equipment

• MultiTest 50-i twin-column universal tensile tester
• ILC-P 50 kN intelligent cell
• Capstan rope grips and lever-action wedge grips
• Emperor™ fully programmable force testing software