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Posted By Garry Adams
Can anyone explain to me why it is considered acceptable to mix Ferrous and Non-Ferrous Scaffolding tubes on a Structure.
In regard to manual handling, I would rather erect with an aluminium tube or ladder beam.
However, I was allways taught/instructed (CITB) not to mix component parts due to the effects of electrolyte on the molecular of the tubes.
Question, why is it now considered acceptable to mix these metallic amalgams, has there been cathodic and anodic improvements ?.
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Posted By RP
CITB have it wrong, poor advice.
The amount of contact between tubes is minimal and not for a long period of time to allow the rubbish sold by CITB to you.
We often mix steel tubes with lighweight towers to afford extra stability using ties. Never had a problem at the molecular level...
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Posted By Mark Eden
Gary
I think one of the main concerns is the use of steel couplings on aluminium tubes - the steel tends to crush Ali tubes thus weakening them
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Posted By Garry Adams
Hi RP,
Thanks for your reply...ye Iv used mixed tube on numerous occasions and been glad to do so especially when erecting under deck Structures which require ladder beams to be used in the design. (Id much rather use aluminium than do 3 rounds with a steel beam).
I was told that the outside diameter of the aluminium tube would be compromised i.e. thinning of the wall...given the harsh environmental conditions (offshore) in which these tubes are subject too and on occasion the longevity of service, is there a cause for concern?.
Regards, Garry...
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Posted By Chris Packham
Offshore is different. Mixing ferrous and non-ferrous in a marine environment is not a good idea. Salt water conducts electricity and is can accelerate corrosion to a surprising degree. This is why boats tend to be fitted with sacrificial anodes so that these corrode first before the propeller shaft, etc. A salt laden atmosphere can trigger this, but I think it would be unlikely in an inland situation (unless close to a salt mine!)
Chris
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Posted By Garry Adams
Chris,
Thanks for your input,At a recent Safety Meeting I suggested that Scaffolding Structures should be constructed using a generic and compatible type of amalgams and outside diameter tube.
I put it to the powers that be that it may prove prudent to adopt such a strategy, this was met with resistance, costs being the main point of contention and the lack of evidence that the Scaffolding Structures are being compromised.
Regards, Garry...
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Posted By Garry Adams
Mark,
Your quite right, there are variations in the outside diameters and wall thicknesses of Scaffolding tube, the mismatch of Scaffold fittings and Scaffold tube may be a marriage of convenience, however this could prove costly.
When one conducts an inspection prior to deployment, the overt patent defects are plain to see i.e., dimples, gouges, ect. However it is the covert defects that one must pay critical attention too i.e. wall thinning , stress fractures ect.
Regards, Garry...
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