The strength of the section is made up of its parts. If the section fails to
provide a 5000lbs anchor point, in no way will any of the welds, legs or
lattice, provide it either.
I am not stating the 25g tower is worthless. I actually quite fond of this
tower and own several gin poles that are made of 25g, 45g and 55g sections.
What I have stated are just the facts. Like it or not, take it to heart, or
with a grain of salt.
Ever wondered why Rohn used to make comments about climbers being less than
250lbs in their field erection manuals ? (Hmmmm ...250lbs ...10-1 safety
factor for positioning.... I must not know what I am talking about.)
Seriously though however, I am open to discussion on what you see as
erroneous in my post, since it is the same lecture given in all comtrain,
belltech, and Radian fall protection classes.
Richard
----- Original Message -----
From: "Bill Aycock" <baycock@hughes.net>
To: "Richard Elizondo" <relizondo@ionoscom.com>; <towertalk@contesting.com>
Sent: Monday, November 24, 2008 8:31 AM
Subject: Re: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
> 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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