This Whole post contains a major flaw that makes the real part irrelevant.
The statement about the strength of 25g is worthless, because the shear
strength is not define with respect to direction and method of loading, and
is not related to the type of load applied by a falling body.
If the loading is cleared up, the rest might be germane.
Bill-W4BSG
----- Original Message -----
From: "Richard Elizondo" <relizondo@ionoscom.com>
To: <towertalk@contesting.com>
Sent: Sunday, November 23, 2008 10:43 PM
Subject: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
> Seems there have been several discussions on climbing lately, and since
> this
> happens to be a subject that I have more then adequate experience in, I
> thought I would share with everyone some of the same info we provide to
> our
> technicians about the Rohn 25g/45g series towers and fall arrest.
>
>
>
> First - Understanding the difference between fall protection and
> positioning:
>
> A fall protection/arrest system consists of the following:
>
> A harness with a dorsal (center of back between shoulder blades) D-Ring,
> and
> means of attachment that can limit the falling force to less than 1800lbs.
>
> The human body can exert several thousand pounds during a fall arrest
> situation. In order to protect the climber most fall arrest lanyards
> utilize
> a dampener/shock pack to dissipate the fall force to less than 1800lbs.
> All
> fall protection/arrest lanyards should be double legged/(Y) and be used to
> maintain a 100% attachment to the tower at all times. They should NEVER
> exceed 6' in length.
>
> Positioning devices are used in conjunction with Fall arrest to create a
> working position while on the tower. These are static lanyards and devices
> that do no have shock packs. While in use, these devices should be
> positioned so that a climber can not move more than 18" vertically. As a
> rule of thumb, your primary connection to the tower should always be your
> fall protection, and then your Positioning device.
>
>
>
> Now the Numbers:
>
> It is recommended that Fall Protection/Arrest lanyards be anchored to a
> point on tower that can hold 5000 lbs. OSHA claims that the human body
> should not be able to produce more than 5000lbs during a free fall arrest
> with a 6' lanyard.
>
> Positioning devices should be attached in fashion that can hold the weight
> of the climber and rigging with a 10-1 safety factor. (300lbs climber -
> 3000
> lbs attachment)
>
>
>
> Here is the shocking sad truth:
>
> Rohn 25g section shearing strength - 2500lbs (this is the strength of the
> entire section, all three legs and lattice, not just that one leg you may
> be
> attaching to.
>
> So a Rohn 25g section could fail if a climber falls and the lanyard shock
> pack does not activate, or the climber is using a lanyard without a shock
> pack.
>
> Sadly enough the Rohn 45g section is not that much stronger.
>
>
>
> Solutions for the Climber:
>
> First and foremost - Never attach to the Z lattice of these towers for any
> reason.
>
> Second - Try to use a 3' shock absorbing lanyard for fall protection. The
> reasoning behind this goes back to the numbers. OSHA claims that the human
> body should not be able to produce more than 5000lbs during a free fall
> arrest with a 6' lanyard... so if we limit the fall distance by 1/2 (3'
> instead of 6') the arresting force is also reduced by half. (2500lbs) The
> shorter 3' lanyard also allows you to position the lanyard an arms length
> overhead. By doing this the fall distance is greatly reduced, in many
> cases
> (depending on body size) to less then 12-18 inches, thusly greatly
> reducing
> the force to a safe limit for the 25g towers strength. Something to also
> consider, when positioning your fall protection overhead, is the swing
> zone.
> Should you fall with you lanyard positioned directly overhead (same tower
> face), your dorsal D Ring will pull you forward and swing your upper body
> and head into the tower. For those who do wear hardhats (as you should)
> this
> should not be a big deal. If however you would like not to have this
> problem, position your lanyard hook overhead and around to another face
> (to
> your strong side) so that during a fall arrest situation, your shoulder
> will
> roll onto the tower first and your lead arm either grab the tower or cover
> your face and head.
>
> Third- Never rely on one point of attachment for positioning. On the 25g
> and 45g tower, it is recommended that the climber choke at least 2 legs
> with
> a positioning lanyard, to create a solid point of attachment. Another
> recommended procedure is to use two large hooks, one on each side, to
> connect to two different points on the tower. This actually works very
> well
> and is known as the "gunslinger method" since a climber can attach and
> detach very quickly with this setup.
>
>
>
> Working up top - Working on the very top of a 25G/45G tower can provide
> some
> challenging issues, one of which is positioning. If your harness has a
> seat,
> do yourself a favor and don't try to use it while at the very top. While
> sitting in the saddle is comfortable, it does not provide enough upper
> body
> leverage to position or stab a large antenna. Instead use the side D rings
> so that your upper body and arms can be used freely above the tower. When
> attached to the top of this tower, a fall arrest anchorage point also
> becomes an issue. If your work could take some time, use a 4' long choker
> sling to create an attachment point by wrapping it around and choking all
> three legs independently. When used in conjunction with your 3' fall
> arrest
> lanyard, this setup will create a suitable anchorage point. Also something
> to consider, whenever possible, use a ginpole to help position and hold
> large items over the top of the tower. While it is possible to stack a
> large
> antenna or even another tower section without a gin pole, using a gin pole
> makes it much easier and safer for the climber.
>
>
>
> Richard Elizondo
>
> Senior Consultant
>
> Ionos Communications
>
> 361-887-6700
>
> relizondo@ionoscom.com
>
>
>
> _______________________________________________
>
>
>
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