Round Slings Nylon or nylon with steel

[DuckJordan]

So I heard the other day that some places are requiring that anything hanging above peoples heads hung with a round sling is required to have the steel cable inside, due to fire issues. To me if the flames were getting high or hot enough to burn the nylon that the steel is going to melt with it.

Am I crazy or does it seem that with the recent stage collapse's hitting the news that every road house and arena is now clinging to whatever a slick snake oil sales man has said will help prevent and just causing a headache to all the small guys who invested in round slings but didn't get the steel cable.

 

[Les]

I can see your point, unless the fire is actually IN the truss. Then, it makes a bit more sense.

 

[DuckJordan]

But even then, the things that most will put in a truss (apart from you pyro junkies) won't burn through a nylon sling if its been properly cared for (They are required to be fire rated).

 

[derekleffew]

So I heard the other day that some places are requiring that anything hanging above peoples heads hung with a round sling is required to have the steel cable inside, due to fire issues. ...

It's been industry standard procedure for some time now (10-15 years?), that if a GAC Flex sling is not used, every "regular" SpanSet is backed up by a 3/8" GAC steel safety and 1/2" SPAS.

The wiki entries for GAC Flex and polyester round sling detail some of the pro/cons for each method.

But even then, the things that most will put in a truss (apart from you pyro junkies) won't burn through a nylon sling if its been properly cared for (They are required to be fire rated).

Lay a Source Four on, or point a Sharpy at, a polyester sling and it WILL melt.

From http://www.google.com/url?sa=t&rct=...GXzoFo&usg=AFQjCNHbs36-KQDS8bglvzzN6fihw__Owg :

All temporary suspended truss components, whether supported from the ground or from a building’s
ceiling, shall have either a steel aircraft cable 3/8” galvanized wire rope safety backup protecting
standard polyester spansets (polyester roundslings) or use a roundsling that has a load-bearing
member made of galvanized steel aircraft cable with a minimum vertical rated capacity of 5,300
pounds, and a temperature rating of 400° Fahrenheit. In the event the roundsling is encased in a
jacket, the jacket shall be constructed in a manner that permits the galvanized steel aircraft cable core
to be inspected for broken wires and corrosion.

-----

... Am I crazy or does it seem that ...

Regarding the latter: as I said, the requirement to back up polyester with steel has been in place long before the recent spate of stage disasters. No one is trying to screw over the little guy (in this instance). As to the former: only your psychiatric therapist knows for sure.
.

 

[LavaASU]

Also like Derek said, the slings typically used in this industry are polyester, not nylon. And the polyester (or nylon should it be used for some strange reason) will melt way before steel. Like, melts at 260C. Steel melts at around 1400C depending on composition. One of the big reasons is if the building were on fire you don't want the truss falling on the firefighters heads.

That said personally we use normal polyester slings and back up with steel if needed/required. We mainly do ground support outdoors, so it's rarely required, and I'd rather have the soft polyester on the truss than gac-flex.

 

[DuckJordan]

The steel used as far as in gac flex steal will melt before 1400C but either way it seems like just the polyester (sorry not nylon) slings are useless for our industry so why do they continue to buy them?

 

[derekleffew]

...so why do they continue to buy them?

Why do people continue to buy 360Q s? EHG s? Burlap?
.

 

[soundman]

The steel used as far as in gac flex steal will melt before 1400C but either way it seems like just the polyester (sorry not nylon) slings are useless for our industry so why do they continue to buy them?

I will get a bunch on every show for cable strain-reliefs and cable picks. I find it harder to get a nice bite into the cable with GAC flex.

Remember last year when the truss spot chair on a Rihanna tour was lit on fire? Link. Great reason to use GAC flex. Or if there is any pyro on the ground being pointed up. If an accident happens and the pyro goes higher than intended, using GAC can prevent it from getting to travesty level.

 

[StNic54]

The argument between Gacflex and standard spansets is always a good one. You'll notice that usually the rating is exactly the same for either spanset type, and there have been many examples of fire on sets that would justify Gacflex over non-GAC. There was a WWE show not that long ago where the LED screen caught fire and it was healthy time period before it was extinguished - it's a prime example that the fire can creep and burn along, so steel is good.

Oh, and riddle me this one: How long would it take a Sharpy to set fire to a spanset?

 

[derekleffew]

... How long would it take a Sharpy to set fire to a spanset?

It won't set one on fire, polyester won't sustain a flame, but it may melt it. From http://www.claypaky.it/media/documents/Sharpy_Manual_Rev.0_(05.12)_EN.pdf :

• MINIMUM DISTANCE OF ILLUMINATED OBJECTS
The projector needs to be positioned so that the objects hit by the beam of light are at least
12 metres (39’-4”) from the lens of the projector.

They're not kidding either.

We've all heard of a fixture's beam burning, charring, or smoldering IFR drapes. But one example: http://www.controlbooth.com/forums/news/23310-fire-star-plaza-theatre-merrillville.html .

 

[Sony]

DuckJordan, just for clarification are you asking why GACFlex is used over regular 100% Polyester Spanset's or are you asking why GACFlex is used over straight 3/8" Steel Cable?

Sorry, your questions are a bit unclear.

 

[DuckJordan]

It was more of a rant of why regular spans are used if you still need a steel safety