Fall Arrest Anchors: Strong Enough or Not?

Fall Protection

Fall arrest anchors are the foundation of the fall protection system.

If a fall arrest anchor can't withstand the forces generated, nothing else matters. But when a worker clips in, how can they be assured that the anchor will function if and when it's needed?

This is essentially a quality assurance question and assuring quality requires a variety of processes, none of which are complicated but each are required to make the system work. In this blog we have broken the processes down into various steps with the focus on fall arrest anchors. These topics will also be covered in our Fall Protection Competent Person and Train the Trainer class.

Step 1: Analyze the Forces

What forces are you expecting the fall arrest anchors to withstand? Fall forces vary widely. A single user of fall arrest equipment equipped with a shock absorber and falling six-feet or so will impart about a 900-1000 pound load on the anchor. A longer fall may impart a greater force if the shock absorber ends up being completely deployed by a heavier worker. If you have more than one worker on an anchor point, you have to assume that all of them will fall (and use the anchor) at the exact same time.

If you built a horizontal lifeline with little sag and placed several workers on it, you could impart many tons of force on the anchor and structure (which is why job-built horizontal lifelines are invariably a lousy idea).

Remember, OSHA requires anchors to withstand 5,000 pounds per attached worker or twice the expected force (as calculated by a Qualified Person). The presence of shock absorbers in fall arrest systems are an asset when it comes to estimating the arresting forces. In general, you estimate the arresting force by taking the weight of the worker (in pounds) times the freefall distance (in feet) and dividing that number by the stopping distance which is aboput 0.4 feet. This calculation is used if there's no shock absorber, but if there is a shock absorber, use the 900-1000 pound figure.

Step 2: Analyze Structure.

Fall arest anchors, whether temporary or permanent, must be attached to something and unless you are an engineer, it can be challenging to look at a structural component of a building and know its strength. By and large structural members of modern industrial facilities (e.g., I-beams and columns) will be able to withstand considerable force. But when you look at older, wooden or cement structures it may be more difficult to ensure the integrity of the anchoring structure. Pipe-hangers also come in a variety of sizes, some of which might be adequate while others aren't.

In addition, when installing anchors on roofs you need to know the roof construction to ensure that the anchor is connected to a structural member. If in doubt, consult someone with a structural engineering background or degree.

Step 3: Use Certified Fall Arrest Equipment

One of the temptations when setting up fall arrest anchors or systems is to use material-handling equipment available on site such as shackles, eye-bolts and rigging slings. While this equipment might be strong enough, the employer would be required to conduct their own testing and certification (and who has time to do that?). In addition, California requires fall protection and rescue systems to be labeled with the identity of the certifying standard or agency.

Any of the major certifications is adequate. We're all familiar with ANSI but the European standard (CE), the Canadian standard (CSA), or NFPA are considered equivalent. Note that there are some newer types of equipment that may not carry a separate certification. This is usually due to the fact that the standards organizations haven't yet developed the new requirements for that type of equipment. If in doubt, deal with a recognized and well-known manufacturer who will stand behind their product.

Step 4: Inspection

OSHA requires fall arrest equipment to be inspected before use, but people often overlook inspecting the anchor. Users should be taught to assess the integrity of all anchor points they use. Basically they should be looking for corrosion, deformation, and deployment of any impact indicators.

In some locations, there are self-retracting lifelines that are (more or less) permanently installed. Given the fact that a worker might not be able to access the anchor to inspect it, you need to implement processes to ensure that the anchor is inspected on a regular basis. The inspection interval depends on a variety of factors. Our sense is that assessing the the anchor every three months would be adequate, but check with the equipment manufacturer if in doubt. Pre-use inspection of anchors can also be an issue for workers accessing towers or ladders that use a cable as fall propection when climbing given that the top and any intermediate anchors cannot be inspected without climbing up to them. Again, some sort of regular inspection is indicated in addition to asking workers to evaluate the anchors on an ongoing basis when they are climbing the structure.

What about pull testing? While this is done in some locations it is not required by OSHA standards. What is required is ensuring the anchor will hold the expected loads. While pull testing is one method of accomplishing this, there are some downsides including the cost and scope of testing scores of anchors at a location.

 

Hopefully this post answered some of your questions about ensuring the quality of anchors at your location. Learning how to ensure the quality of all the components of your fall protection systems are an important learning outcome in our Fall Protection Competent Person and Train the Trainer. If you have any other questions, feel free to call us at 800-551-8763.

Jim Johnson June 24, 2015

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