Tex style self tapping screws used to mount flood lighting to steel????

[Darkwood]

Been subbing to help out a company while hes on his jollies, hes requested me to mount floodlighting external on a structural steel tubular girder, its approx 6" 150mm diameter, i have it down to use stainless strapping with a crimping device similar to what they strap heavy products to pallets for transport, he's shunned that idea and said use tex screws, now i know the steel thickness isnt an issue been about 6mm but my problem is the job they will be doing, normally they are used for the likes of cladding etc where they have exceptional vertical strength to hold down the clad but when you put a fitting up subject to high winds etc this put lateral forces on the screw 90degrees to the shaft. I cant see how this can be acceptable, ive also contacted the manufactures of the screw who informed me that their product wasn't really designed for the use i want.

Thoughts please as other manufacturers make similar products but are my concerns correct.

 

[Guest123]

What sort of size of fitting are we talking here DW, 70w, 150w etc??

 

[Darkwood]

Its not the heaviest thing its 4kg LED flood but it 30m above the public outside and exposed to what the weather can throw at it, ive 9 to fit and the existing sons have used 20mm wide stainless crimped metal band, they may be up there many yrs as access is very expensive to hire.
I see a tex maybe sufficing indoors where the fitting wont be subject to high winds even though i see this as out of their character of use but 4kg is many times that in 60 to 100mph gust that some areas see and it geographically exposed looking out over many miles so very exposed.

 

[Marvo]

Self drilling screws would easily be capable of holding 4kg. They're also electro-galv finished so corrosion shouldn't be a problem unless they're close to the sea. You could always add a s/steel safety anchor wire if you think it's necessary.

edit....I assume you're talking about the hex head ones, not the poxy phillips head type.

 

[JD6400]

We only use these to fit up to 150w flood fittings on grain stores / stable yards , and hopefully without tempting fate !
I think you are looking at fixing to a tube though , and if so i would definitely be concerned with the fixing being able to rock maybe ?

 

[Darkwood]

It wasn't the 4kg that is the concern its what force 4kg becomes when pushing side on to the tex screw in gales, if i was to drill and tap i would be using M8 bolts in this situe to withstand any directional force, it just seems a very slim thread to take these forces yes agree with the safety anchor but dont want to pay £400 quid to hire the lift again if it did end up hanging on the anchor.
As mentioned the manufacturers have stated their tex screws are not suitable for the side loading and if they were for outdoor use they would be stainless or hot dipped needed and not the standard ones the wholesales was trying to flog me.
If they explain the side loading is an issue which was my first thought before the phone call surely this situe is been taken out of the design use of the screw itself normally used externally for roof cladding etc where spacing is so that each individual has little side force if any but alot of clamp damp pressure.

 

[Silly Sausage]

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[Marvo]

Maybe 6mm or 8mm clinchnuts (aka rivnuts), depends on the wall thickness of the structure, if it's more than 5mm they're also not ideal but 5mm+ should be fine for tapping a thread.

 

[Darkwood]

We only use these to fit up to 150w flood fittings on grain stores / stable yards , and hopefully without tempting fate !
I think you are looking at fixing to a tube though , and if so i would definitely be concerned with the fixing being able to rock maybe ?

Its 18" circumference solid steel no real movement as its part of a steel frame stadium my issue is looking and asking everywhere there is no mention of using these screw to support anything other than cladding, paneling or anything that falls within them lines, just seen mention of mounting switchgear to internal steelwork but again cant find anything relating to using it for this my lighting application, reviewing force calculation from different manufactures they are all worked out on uplift forces of roof cladding in the vertical plain which is its strong point.
think im gonna just do my method and stainless strap and ratchet crimp, get plenty evidence that the existing is still fastened as good as the day it was fitted

 

[Darkwood]

Maybe 6mm or 8mm clinchnuts (aka rivnuts), depends on the wall thickness of the structure, if it's more than 5mm they're also not ideal but 5mm+ should be fine for tapping a thread.

Estimate it 5-7mm thick wall, the strap idea is as existing with original lighting the fastest method as i see it in my mind and was the way of choice all other methods require drilling etc and start to be time consuming but just got this company adamant they they are the best way and the bee's knees but on enquiry im been told they are not suitable. This was the initial query as ive already got a fixing solution just wondered on thoughts of his fondness of using tex screws for other than their original design, yes indoors they would hold a switch box up indefinately to a steel upright but i believe my situe it pushes their use beyond what i could be considered acceptable.

 

[Marvo]

The most common place I've seen Tec screws used is for HVAC ducting erection. I've never seen a failure unless it's where they're overtightened and stripped into 0.9mm galv sheet when installed with a drill without a clutch, I've never seen corrosion issues either even with the standard galv ones. As for your application I would say they would be fine, the sheer force won't be that great it will be more of a leverage force which pulls mostly in the direction they're designed to take. I'm not sure how easily they'd drill into 5-7mm walled stainless tube. That's helluva thick and depending what grade it might be quite hard as well.

I've never used s/steel strapping for anything other than fixing large cables to trays. The strap would need to be well tensioned to prevent the fitting rotating or moving around on the tube in the wind. Any stretch over the 18" strap would be a problem but if it's asystem you've use in the past then maybe stick with what you know and experiment with Tec screws on a job that you don't need access equipment for....just in case.

 

[alarm man]

ive used those for mouting cctv cameras and they do give a good fix,those i agree with marvo an additional safety chain or 2 would be a must if your concerned about them coming off if its a public area,the cost of refixing a fitting thats hanging on a chain even with access hire is no where near the cost of it falling and hitting someone or something,or you could try looking at a pole mount bracket for cctv cameras,they wil be easily adaptable for a fitting as will give a flat surface to bolt your fitting to,something like this maybe

 

[alarm man]

bracket.wouldnt load on prev post.