Lexco^® Cable is an industry-leading wire rope assembly manufacturer offering extensive proof-loading and pull-testing services to ensure safety and quality in our wire rope assemblies.

Proof-loading and pull-testing ensure that our wire rope assemblies meet your safety, quality, and application requirements. Routine proof-loading is recommended for critical load applications and destructive pull-testing is recommended for any load-bearing cable to qualify its design. Proof-loading and pull-testing can be a vital part of the quality control process, and our equipment is calibrated in accordance with UCC Procedure 100 and meets the requirements of ASTM E4-16. We can provide you with pull-testing and proof-loading up to 180,000 lbs.

A proof-load test is a controlled, measured application of force over a specified time period to a given piece of rigging equipment. The results of a proof-load can help discover defective parts by finding subtle issues that some visual and dimensional inspections can miss. If the part fails a proof-load test prematurely it can be further investigated as appropriate. Assemblies that pass proof-load testing provide extra quality assurance.

Proof-loading is commonly required when the assembly will play a critical role in an application. Such critical applications include using the wire rope assembly for lifting, overhead safety, structural support, aerospace, and military use cases, or situations requiring a MIL-DTL-6117 or MIL-DTL-5688 certification. Applications that are commonly proof-load tested include critical lifting, where the load may be overhead or of high volume, and structural assemblies, such as suspension cables on a bridge. After a proof-load is done, the assembly is inspected for defects, and, at your request, we can apply a proof-load tag to the assembly and proof-load documentation.

For commercial-grade assemblies with terminations that hold to the wire rope’s nominal breaking strength, a nominal break of 40% or 50% is common. If the proof-load is in compliance with MIL-DTL-6117 or MIL-DTL-5688, then the test load shall be 60% of the terminal break strength or 60% of the wire rope nominal break strength, whichever is lower. It is not recommended to proof-load above 60% of an assembly’s nominal break strength to avoid fatiguing the assembly.

A pull-test is when one end of the cable is fixed while the other end is attached to a movement force, such as a hydraulic cylinder, typically along a linear axis. Pull-tests create a specific force over a set period of time to test the cable under set force and time parameters. As demonstrated in this pull-testing video, pull-tests are designed to test tensile strength – the resistance of a material to breaking under tension. The results of a pull-test will indicate the break strength of a cable assembly based on a gradual linear pull.

Pull-testing can be destructive or non-destructive. Destructive pull-tests are used for process setups, while non-destructive testing is used for the final quality control testing. Our pull-testing machines are on a regular calibration schedule to maintain accuracy and ensure the safety and reliability of your assembly. The typical proof-load and destructive pull-test we perform are with a gradual and linear applied load. For applications involving a shock load, a higher safety factor is required. Whereas a general rigging safety is 5:1, a critical or shock load safety factor may need to be 10:1.

We can also perform pre-stressing (aka pre-stretching) on structural cables to reduce constructional stretch. Pre-stressing subjects the wire rope to three cycles of tensile loading at 40 percent of its nominal strength for 5 minutes and returns the tensile load to 5 percent of the nominal strength between cycles. After the last cycle, the tensile load is completely released. When specified, ropes may be pre-stressed using either a process of static or dynamic loading. Commonly pre-stressed applications include suspension bridge structural cables, barrier cables for parking garages, elevator cables, and cables used in seismic bracing. Pre-stressed loads shall not exceed 55% of the minimum breaking force for the rope, and stranded ropes are not pre-stressed unless otherwise specified.

Our team has been conducting proof-load tests and pull-tests for decades, but only you can determine the necessity of a proof-load or pull-test for your application. Lexco will only proof-load or pull-test if specified in your RFQ, PO, or drawing. If you are uncertain whether your application requires proof-loading or pull-testing, our team is here to help. We can assist you in determining how your working load limit intersects with your assembly’s strength. Once determined, you can verify whether a proof-load or pull-test is necessary, appropriate for a single piece, needed for a percentage of your assemblies, or required for every piece. When you need to ensure the reliability of your assembly and the safety of your project, look no further than Lexco.