Use a rope type that’s been used successfully to do the same kind of work you’re doing, and confirm that your choice has the proper characteristics and a working load limit for the specific task at hand. Some industries, especially those involving overhead work – tree trimming, window washing, any job requiring use of scaffolding or climbing – have very clear specifications, often as required by OSHA. When in doubt, check with an engineer or other qualified person experienced in rope use.
Having the right rope is a good start. But as with any tool, it must be used properly. When any of the following conditions exist, we strongly recommend expert guidance:
Abrasive conditions such as exposure to sharp edges, rough surfaces, and improperly sized pulleys
Exposure to hazardous chemicals that can weaken some fibers
Dynamic loading, which occurs when the stress on a rope is increased – by picking up a load, or if a load stops quickly or is otherwise subjected to shock, or when it is swung or held over a prolonged period of time
Rope use at elevated temperatures, which can weaken or even melt the fibers
The rope source, age, or history is not known
There are no provisions for frequent inspection based on specific standards
There are knots or splices in the rope
Exposure of polypropylene or polyethylene rope to sunlight – ultraviolet degradation can dramatically reduce the working load limits of these products
Rope stored dirty, wet, or near sunlight or heat – especially natural fiber rope such as manila, which will rot and weaken dramatically from moisture
Dielectric properties will be greatly reduced when the rope is dirty or wet, causing increased danger of electric shock
Rope under tension can recoil if it breaks or is released suddenly, causing serious injury to anyone in front of or behind it.
You may have noticed the terms ‘breaking strength’ or ‘tensile strength’ have been avoided here. This is because rope ‘strength’ is based on breaking a new, unused rope in a test laboratory. The number of pounds to break in a test lab is not an indication of the force the rope will handle on the job, but is a number used in calculating the “working load limit”.
The working load is the weight or force exerted on a rope at work.
The working load limit is a guideline number representing the maximum rope capacity. For general use, the working load limit is based on normal loading. It is calculated by dividing the new rope minimum breaking strength by a design factor based experience with the work to be done.
At this point, we suggest you visit the Cordage Institute guideline titled.
Safer Use of Fiber Rope (this link opens in a new window, so when you leave the Cordage Institute site you’ll return here).
Remember taking “defensive driving” courses in high school? It makes sense to adopt the same attitude when working with rope: even when you’re doing everything right, be prepared something to go wrong.