June 29, 2016
All Cable Grips Are Not Created Equal

Posted by: Lee Bedingfield

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. 

 

OVis_Pull_Tape_half_hitch_knot_white.jpgne 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%. 

 

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*MaxCell® is a registered trademark of TVC Communication, a division of WESCO Distribution, Inc.

 

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Category: Feature Articles, Cable management

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