Proof Load Testing
Application of a load above rated capacity to demonstrate structural margin, followed by re-examination for damage.
Proof load testing applies a load deliberately in excess of the rated capacity to demonstrate that a machine has the structural margin its design promises. It is most often required after new manufacture, major structural repair or modification, and it is always followed by careful re-examination to confirm the overload has left no permanent deformation or damage. It is a searching test that gives confidence a lifting appliance is genuinely fit for its rated duty.
What proof loading demonstrates
By loading above the rated capacity by a defined margin, the test confirms that the structure, welds and mechanisms carry more than they will ever be asked to in service, without yielding. The before-and-after examination is essential: a machine passes only if it shows no permanent set, cracking or damage as a result of the overload.
This makes proof loading the definitive acceptance test for repaired and newly manufactured lifting equipment.
- Load applied above rated capacity by a defined margin
- Demonstrates structural margin without permanent set
- Before-and-after examination for deformation and cracking
- Definitive acceptance test after manufacture or repair
How we conduct it
A test plan defines the proof load, the load cases and the acceptance criteria in advance. Calibrated weights or load cells apply the load under controlled conditions, and the machine is examined, often with NDT, both before and after to confirm it is undamaged.
Reporting
The report records the proof load, the observed response, the post-test examination and a signed pass or fail against the acceptance criteria, forming part of the machine's compliance record.
Frequently Asked Questions
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