What is a Proof Load Test, and Why is it Non-Negotiable?
Key Takeaways
A proof load test is a mandatory strength and safety verification performed on lifting equipment before it enters service or after a significant repair. The test applies a load that is substantially greater (typically 125% to 200%) than the equipment’s rated Working Load Limit (WLL) to expose any hidden defects. Passing this test is a non-negotiable legal and safety requirement, as it provides documented certification that the equipment is structurally sound and safe for its intended use.
Core Answer
A proof load test is a deliberate, controlled overload of a piece of lifting or rigging equipment to verify its integrity and safety. Unlike normal operation, which stays at or below the Working Load Limit (WLL), a proof load test stresses the item to a predetermined percentage above its rating (e.g., 125%). This process is the only way to definitively confirm that the design, materials, and fabrication of the equipment are free from hidden flaws that could cause a failure under a normal load. A successful test results in certification, providing the auditable proof required by regulatory bodies to show the equipment is fit for service.
The Difference: Working Load Limit (WLL) vs. Proof Load
It is critical to understand that these two terms are not interchangeable. Confusing them can lead to dangerous operational errors.
- Working Load Limit (WLL): This is the maximum mass or force that the equipment is certified to handle in day-to-day, routine lifting operations. You must never exceed the WLL in a normal lift.
- Proof Load: This is a much heavier, factory- or laboratory-tested load applied in a controlled, non-operational environment specifically to find the breaking point or prove structural integrity. It is performed only by a competent, certified authority.
What Happens During a Proof Load Test? A Step-by-Step Overview
A certified proof load test is a meticulous and documented process. While specifics vary, the core steps remain consistent.
- Pre-Test Visual Inspection: Before any load is applied, a certified inspector conducts a thorough visual examination of the equipment to check for any obvious defects like cracks, corrosion, deformation, or improper assembly.
- Application of the Load: The equipment is set up in a testbed or secure area. The specified proof load is then applied smoothly and carefully, without shock-loading.
- The Holding Period: The proof load is held for a specific duration as required by the relevant safety standard. During this time, the equipment is under immense stress, which will reveal any hidden material or structural weaknesses.
- Post-Test Examination: After the load is released, the inspector conducts another meticulous examination. They look for any signs of cracking, elongation, twisting, or other forms of permanent deformation. If the equipment returns to its original shape and shows no signs of damage, it passes.
When is a Proof Load Test Legally Required?
Proof load testing is not optional; it is mandated by law and industry standards under specific circumstances. The most common triggers include:
- Before New Equipment Enters Service: All new cranes, hoists, and rigging gear must be proof load tested and certified before they can be used for the first time.
- After a Major Repair or Alteration: If a critical, load-bearing component is repaired (e.g., by welding) or modified, the equipment must be re-tested and re-certified before returning to service.
- Re-Certification: Periodic re-testing may be required by certain industry or national standards to ensure the equipment remains safe over its service life.
Follow-Up Questions
- Who can perform a proof load test?
Proof load tests must only be conducted by a competent, trained, and certified person or organization with calibrated testing equipment. Partrid Investments offers certified testing services for this purpose. Attempting to perform your own test is extremely dangerous and does not meet legal compliance standards. - What happens if a piece of equipment fails the test?
If the equipment fails a proof load test, it must be immediately removed from service, clearly marked as “Failed and Unsafe,” and permanently destroyed so that it cannot be accidentally used in the future.
Proof load testing is your ultimate assurance of safety and compliance. It is a critical investment in risk mitigation. Contact Partrid Investments today to schedule a certified proof load test for your lifting equipment.