Safe Working Loads for Rope
The safe working loads of rope vary. They change according to the rope’s material and diameter. Employers and workers should never assume that all rope is more or less the same. This point becomes critical when a business uses rope for securing and lifting. Knowledge of safe working loads is essential. And even then, there are other safety measures that workers must observe.
NylonThe three common types of nylon rope are twisted, diamond braid and solid braid.
- Generally speaking, twisted nylon rope can bear the heaviest loads. The weight of such loads alters according to the rope’s diameter.
- A ½ inch twisted nylon rope, for example, can bear a load of approximately 520 lbs. A ¼ inch twisted nylon rope can bear around 120 lbs.
- The load bearing weight of diamond braid nylon is similar. But across the full range of diameters, twisted nylon is better.
- ½ inch solid braid nylon can take up to 320 lbs, and ¼ inch can carry 90 lbs.
PolypropylenePolypropylene rope tends to come in four types: twisted, diamond braid, solid braid and hollow braid.
The load bearing abilities of twisted and diamond braid polypropylene are similar. Hollow braid is the next strongest with a ½ inch diameter rope able to take a load up to 350 lbs. The maximum weight for a ½ inch solid braid polypropylene rope is around 210 lbs.
Other RopesAlthough nylon and polypropylene ropes are popular, polyester, sisal and Manila ropes are also available.
Polyester is man-made. Sisal originates from the fibre of the agave, a plant belonging to the family of succulents. Manila comes from Manila hemp. This is a fibre extracted from leaves of the abacá plant.
The weakest of these three ropes is sisal. ¼ inch sisal can bear loads up to 40 lbs; ½ inch can take weights of about 230 lbs.
Manila is slightly better. ¼ inch, for example, has a working load of about 50 lbs.
The strongest of the three is polyester.
General SafetyAs a rule, it’s unwise to use rope for lifting heavy items above workers. Rope may fray over time. Constant contact with materials can also cut through the fibres. Either way, weakened rope has nothing like the load bearing abilities mentioned above.
Similarly, safety experts recommend that playground and athletic equipment does not use rope. This is why metal chains usually support playground swings in parks. Even tough man-made rope succumbs to the effects of usage and weather.
If a rope is taut, avoid standing close. A rope under pressure may recoil. This is a danger with all types of rope but especially nylon.
Never exceed the working loads of rope. If in doubt about such loads, contact the manufacturer for details. It’s also vital to bear in mind that these loads are for rope in normal use. This does not include what safety experts refer to as rope under stress or shock. Any jerking movement or stress can cut back a rope’s load capacity by 33%.
Finally, don’t tie down large, flat items with rope. If air pressure builds up, the rope may not be able to hold the items in place.