[TowerTalk] Phillistran

[Grant Saviers]

EHS guys may still be standing after the fires described, but only if 
the wind didn't blow, since most of the strength will be lost at the 
wildfire temperatures quoted.

from a wiki post "At about 550° C (1,000° F) Steel is at 50% Strength 
and at about 800° C (1472° F) structural steel loses 90% of its strength"

 From ASTM 475 (a standard for guy wires) a 1x7 1/4" EHS single strand 
is 0.080" diameter and has a specified minimum breaking strength of 
650lbs which works out to ultimate tensile stress of 130,000psi,  about 
the low end of what would be expected of a heat treated alloy high 
strength steel.  The alloy or heat treatment aren't specified in the 
ASTM standard, just the performance parameters.  The fire temperature 
will anneal the wire to some lower yield and breaking strengths, perhaps 
a 50% or more reduction.

So any EHS guy system exposed to fire of the temperatures mentioned 
should be replaced. The Zn galvanizing will also be badly damaged since 
Zn melts at under 800F.  A tower section exposed to these temperatures 
is also suspect, but I haven't seen any specs other than "high strength" 
for the steel used.

Grant KZ1W


EHS wire is tempered so if exposed to fire will be annealed to a 
fraction of its factory strength.
On 5/26/2014 2:52 PM, W0MU Mike Fatchett wrote:
> Sorry to hear of your loss.  I am surprised that an Engine crew would 
> have been in the area with temps so hot.  Maybe they got  in right 
> after the flame front?
>
>
> Having steel at the bottom may also discourage vandalism. Phillystran 
> is really easy to cut through with a knife.  As N2IC said it wouldn't 
> have mattered with the temperatures of the fire.
>
> Was the area around the tower mowed and cleared of heavy fuels?      
> How close were the trees and other heavy fuel loads to the tower and 
> outbuildings.   More curious from a Firefighting standpoint than 
> anything.  The books are not always right!
> *
> At what temperatures do forest fires burn?
>
> *An average surface fire on the forest floor might have flames 
> reaching 1 meter in height and can reach temperatures of 800°C (1,472° 
> F) or more. Under extreme conditions a fire can give off 10,000 
> kilowatts or more per meter of fire front. This would mean flame 
> heights of 50 meters or more and flame temperatures exceeding 1200°C 
> (2,192° F).
>
> If you live in an area that could see wildfire check out Firewise.org 
> for information on how to properly make your home defensible for 
> wildfire.  Get rid of wood piles next to your house, remove the pine 
> duff or straw and other fuels from around your house and gutters.  
> Clean your gutters regularly.  Be aware if you live on a hill that 
> there may be what we a call a chimney that will help fuel the fire.  
> Fires love to burn up hills.   In some cases, you can't do enough.  
> Mother nature does what she wants.
>
> Good luck on the rebuild!
>
> Mike W0MU
>
> On 5/25/2014 12:56 AM, Chuck Smallhouse wrote:
>> A story for those of you using Phillistran cable for guying a tower.
>>
>> I was talking to a ham that lives in far N. CA, in area that is 
>> subject to wildfires.  A couple of years ago the area had a bad 
>> wildfire that moved in the direction of his QTH, in a somewhat rural 
>> area.  Even though the area around his home was quite well cleared, 
>> they couldn't save his workshop where most of his test equipment and 
>> ham equipment was located.
>>
>> When he returned after a mandatory evacuation and surveyed the damage 
>> , he found that not only was his ham shack destroyed, but also his 
>> guyed tower had fallen over.   It turned out that he had guyed it 
>> using Phillistrand and that the fire had burned the guys through and 
>> which resulted in the catastrophic demise of his tower and beams.
>>
>> I guess that the lesson to be learned is, to at least have the bottom 
>> sections of your  guys be of steel cable and not any type of 
>> flammable material, especially if you live in a wildfire prone area.
>>
>> Chuck,  W7CS, with no Phillistrand guys .
>>
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>>
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