Markets: Cable Management
Last week a discussion arose regarding cable grips during our training session. The choices and options among grips vary and most contractors become accustomed to one type of grip. I thought it would be good to explore several options and discuss the pros and cons of each.
One of the most common “grips” that I’ve seen is no grip at all but a simple half hitch method on the last couple feet of the cable. This is very similar to a MaxCell header and works fine if the pull is not difficult. One issue that can arise from half-hitching is the cable head will bow if under a high amount of tension causing the head to drag. All the tension will be on the last hitch and I’ve seen a cable actually snap at this last hitch before. This problem with half-hitching can arise whether someone is installing a cable in MaxCell or just a bare duct.
The second type of grip is a metal wire mesh, commonly know as a Kellems grip. Basically, a Kellems grip is a braided wire sleeving grip with a pulling eye. The wire sleeving works on the “Chinese finger” principle to lock down on the cable as a force is distributed longitudinally. These grips are great but have a few drawbacks, namely, the head itself will take up to 1/8” (3mm) of additional space due to the grip profile.
The third type of grip is a fabric mesh grip. These are a class of braided circular fabric sleeving and work on the same principle as a Kellems grip but with a much lower profile. A fabric grip is optimal in ducts under 2” (50mm) where every bit of space is critical. Fabric grips come in mainly two options (polyester and a synthetic, high tensile strength material). A PET or polyester grip is the most economical but the synthetic grip will be much stronger. For instance a 0.5” (12mm) PET grip has a breaking strength of around 700lbs (320kgs) whereas the same size synthetic grip will be rated to roughly 2500lbs (1135kgs). The loop at the end will require a knot and will weaken the overall strength by 40-50%.
*MaxCell® is a registered trademark of TVC Communication, a division of WESCO Distribution, Inc.