If you’re a rigger or work in material handling, you likely encounter webbing slings often in your work. A synthetic webbing sling is fantastic to lift delicate or soft materials, since their soft surface offers more protection than abrasive materials, like wire rope.
Webbing slings come in two types — duplex and simplex. A duplex webbing sling is made with two synthetic fabric layers stitched together for extra reinforcement. A simplex webbing sling is made with only one synthetic fabric layer.
“Just one layer? That won’t do anything,” you might be thinking—but how wrong you’d be! Even though a webbing sling may not have the same reputation for strength as say, steel, a webbing sling is surprisingly strong.
There are some misconceptions and often-asked questions about synthetic materials in the industry—so we’ve asked Hercules SLR experts from our Brampton, Ontario branch to help.
Read on to find out the questions we hear about webbing slings, and how our experts’ answer.
Q: What are they usually made from?
Answer: A flat webbing sling is usually made from woven polyester, nylon (otherwise known as polyamide) and polypropylene.
Q: Do flat webbing slings come in just one width?
Answer: Flat webbing slings come in different widths – but their ultimate flexibility and strength is noted by the number of webbing layers stitched together.
Q: Should I use paint or dye to colour code webbing slings? This should help me identify them quickly and easily, right?
Answer: NO! Don’t use paint to colour code webbing slings—the solvents in the paint could corrode the synthetic material. A torn or broken sling is unsafe, and will drastically reduce it’s SWL. To identify a synthetic sling’s material, look for the label colour:
Polyester (PES)—Blue Label, or blue with a green line down the center of the webbing.
Polyamide (PA)—Green label
Polypropylene (PP)—Brown label
Q: What chemicals will affect webbing slings?
Answer: Polyester isn’t affected much by acid, but alkali’s will damage a polyester webbing sling. An alkali, or alkaline is basically a substance with a pH level higher than 7. Examples of alkali substances are sea water, baking soda, bleaches, lye and even blood. Polyamide’s are basically immune to alkali damage, but are damaged by even moderately-strength acids. They can also lose up to 15% of their SWL when wet. Polypropylene is resistant to acids and alkali’s, which makes them a good choice when you have to lift something which needs protection from chemicals. Be sure the polypropylene is stabilized to protect from ultraviolet degrading.
Q: What markings should I look for on a webbing sling?
Answer: Look for the safe-working load (SWL), identification number and the label’s colour code.
Q: How do I store my webbing sling?
Answer: It definitely matters! Be sure to store your slings in a dry, cool place. Keep them out of sunlight or other ultra-violet radiation, and don’t store them in damp conditions.
Q: So, they’re really strong – does that mean I can use them to lift anything?
Answer: Don’t use a webbing sling for a critical lift! Make sure you use extra caution and have a detailed lifting plan for using a webbing sling with delicate or fragile lifting operations.
Q: Okay, so what’s a critical lift?!
Answer: A critical lift is defined by WorkSafe BC as a lift with high risk factors that could cause the crane or hoist to fail, or poses a significant potential harm to human life. A critical lift is also one that needs a detailed rigging plan before the operation.
Other factors that can make a lift critical are:
- When a piece of powered lifting equipment exceeds it’s rated capacity by 75%;
- A mobile crane or boom truck goes over rated capacity by 90% lifting a load over 50% of its maximum permitted load radius;
- Tandem lifts— which is when more than one piece of powered lifting equipment is used, or is used to lift another piece of lifting equipment);
- A person is being lifted;
- The load is under-water or submerged.
Q: Can I tie a knot in a webbing sling to make it shorter?
Answer: Never! Don’t knot, tie or twist a webbing sling. Don’t manipulate the sling’s angle, either—use the sling however the angle forms naturally.
Q: When should I not use a webbing sling?
Answer: Don’t use a webbing sling if you don’t know the SWL. Don’t use if the eyes or other part of the webbing sling is damaged, if the sling’s eye opens more than 20°. There are 5 different types of possible webbing sling eye formations—see figure 1. If using a Type 1 webbing sling (called a choker sling), be sure to protect the eye before use.
Q: What should I keep in mind when using a webbing sling?
Answer: There are a few things to consider to use a webbing sling safely—you should always:
Avoid shock-loading; Protect the sling with sleeves when sharp edges could tear its fabric—friction can cause heat damage, which is the most common form of ‘heat’ damage to webbing slings. To prevent, don’t let the sling run along the load’s surface and that it’s not pulled on any sharp corners. This is also known as ‘point loading’, when the load is pulled on a sharp corner, creating heat which results in heat fusion in the sling material. Never pull a sling from underneath a load.