What is a Self-Retracting Lifeline (SRL)?

If you’ve ever wondered how a Self-Retracting Lifeline (SRL) works, you’ve come to the right place.

Self-Retracting Lifelines function in a way that is similar to how the seatbelt in your car does. When a certain level of force or speed is attained, a locking mechanism is activated. This prevents and further length of the lifeline cable or webbing from extracting or becoming unwound.

Just like with a seatbelt, if you were to steadily pull the on the lifeline cable, you would be able to pull it out as far as it will go. However, if you were to try pulling on it with a very quick tug, if would only go so far before it stops.

There are a number of parts that make up the SRL.

The housing may be either a plastic or metal enclosure. Inside this enclosure is where you will find the locking mechanism, the drum, and the shaft.

The lifeline cable or webbing is wound onto the drum.

In the center of the drum, there is a metal rod known as the shaft. This allows the drum to rotate to either unwind, or retract.

The locking mechanism is a motor spring that keeps tension on the lifeline when it is unwound, as well as the lifeline itself.

The lifeline cable or webbing is usually fitted with a snap-hook at the end for attachment purposes.

The word “retracting” can be somewhat misleading as some may think that the cable will automatically pull you back if you were to fall. But this is not the case.

Whatever amount of the lifeline cable that is already played or pulled out will remain that way. It doesn’t just wind back up to pull you in.

There are actually two different classes of SRL’s; Class “A”, and Class “B”.

A Class “A” SRL has a maximum arrest distance of 24 inches, whereas a Class “B” SRL has a maximum arrest distance of 54 inches.

The maximum arrest distance is the length, in inches, that the SRL will allow the lifeline to extend or unravel before the locking mechanism engages.

In order for the SRL to properly protect you from a possible fall is to anchor it at the height of your harness. This is typically where the D-ring is located.

Taking care of your SRL is also extremely important. Any amount of dirt, grease, or any other materials that may have built up on, or coated the lifeline, or even gotten inside the casing, could cause the SRL to not function properly.

Also, using the wrong type of cleaning agent could even be as detrimental as not maintaining the equipment at all. Certain chemicals can damage or ‘eat away’ at the lifeline, and even cause the parts inside the housing to malfunction. Always follow the manufacturer’s instructions when cleaning your SRL.