Impact wrench banning by the NASC?

aom said:
220nm is a lot of force, the answer you would get for that one is after continual abuse it will fail eventually. I think it's fair to assume the problem doesn't lye with the wrench but the fittings are piss poor and the wrench is an ideal tool to muddy the water, same as any other claim I have ever been involved with really. In the absence of any other solution I also think it's fair to assume an everyday torque wrench calibrated and fit for purpose should be sufficient for my wee yard experiment and also to fill in my RAMS until further information becomes available.

The things you have to do just to get by.:(

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Alan, I don't suppose you fancy a bash at trying to explain why that initial resistance could or should not be counted as the torque of the fitting? I have been trying to work that one out for a while now and my head is beginning to nip a bit searching the interweb.:(
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I was winding the fittings up to see if I could break them to get some idea of the load required but with my 500mm wrench and me swinging on it I see no sign as yet. I even thouch I would get some adverse reaction due to the 48deg heat but bugger all!!

With regards the initial resistance it was a question from me also not a statement.
Again though I am not sure loosening torque id the same as tightening torque I will give it some thought????
 
I am glad someone is. Which fitting are you using? Obviously not the same one as I am using as 500nm would see the back of mine no problem I'm sure of it.

Let me know any conclusions you come to as I am quite keen to get this done but don't want to go off on a tangent.
 
aom said:
I am glad someone is. Which fitting are you using? Obviously not the same one as I am using as 500nm would see the back of mine no problem I'm sure of it.

Let me know any conclusions you come to as I am quite keen to get this done but don't want to go off on a tangent.
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500mm not nm!!!!

---------- Post added at 02:17 PM ---------- Previous post was at 02:13 PM ----------

I have a feeling that there is an issue with the "T" bolts They are hot formed and may have been allowed to cool too quickly which could lead to them becoming brittle.
This combined with the IW use could have brought a hidden problem to the surface.

---------- Post added at 03:03 PM ---------- Previous post was at 02:17 PM ----------

Can’t stop thinking about this thing now but here are my thoughts on the over torque of a bolt and why it is poor practice to do so.
The first step is to understand how these bolts function. By torqueing a bolt you are in fact stretching it. It is the ability of the bolt to stretch and recover (return to its original length) that makes it effective thus keeping the fitting tight. If the bolt is stretched beyond its elasticity it will not recover and as such is useless. This situation is not necessarily visible to the naked eye and the fitting with the useless T bolt is reused on a further occasion, remember the bolt has previously been overstretchd and has no elasticity so when next tightened it just stretches more and eventually the bolt fails.
 
haha 500nm.:embarrest::nuts:


I get that Alan and love the fact that this is now ingrained in your mind as it is mine. The thing that get's me is, how do I prove that despite the concerns that these machines can tighten a fitting without over stretching the bolt? I thought a simple spanner would do the trick but your question has now made me doubt if that is the correct method, would a simple torque wrench give a dumb skiffolder an accurate enough reading to state unequivocally that our own IW's are not in fact reaching the full advertised ratings?
 
If what you are aiming to test is, whether or not your IW has exceeded the 50Nm then a TW will tell you that, what it will not tell you is to what torque it has been torqued.

By setting your TW to the stated 50Nm and testing your fixing, if the TW clicks off then the bolt is in excess of the test load. If it continues to tighten then the desired torque has not be reached.
 
What about the old type with the gauge on the handle, when the fitting cracks the torque will be recorded?
 
id put it to the hse like this,if you can set a wrenches capacity to 50nm,every fitting is then literally tested to 50nm,then put up a scaffold by spanner and test however many you have to with a torque wrench,which is going to be more accurate,its nonsensical!

the detail of all the failure rates and how they fail dont really come into it,if a fiitting snaps you know about it straight away and rectify it,i understand their has to be in depth detail to go into it,but i also know from experience making an argumented point look foolish and not giving it credence can dismiss the point straight away,

i would say once their is enough blokes using these,ignore what they say as a spanner is far less accurate,their is no argument against that,its fact!
 
As Alan has eluded too, Although this is a complex subject the answer may lay in the plastic and elastic ranges of the Coupler and its several different parts.

When the T bolt is subjected to the shear forces applied it stretches and if the optimum yield stress is applied it will stretch and come to rest at it optimum elastic range, however, if the T bolt is subjected to shear force beyond its optimum plastic range it will move into its plastic range and will not recover and come to rest at its elastic range = if the T bolt cannot recover to its elastic range this reduces frictional stress applied Coupler to Tube.

The same applies to the humble washer, if the washer is subject to compression stress beyond its optimum elastic yield range it will go into it plastic range and will not recover = as with the T bolt this will reduce the frictional stress applied Coupler to Tube.

Summary: Stretch the T bolt to its optimum and it will torque slightly beyond the torque applied ( due to heat expansion of the molecular structure ) it will ( contract ) recover and rest within its elastic range. As with the washer, however, this happens in compression.

Well thats my take on it, but hay, wat the feck do I know. Im only a hairy assed Scaffolder...PMSL ;)
 
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Good to see you back Gary, where have you been?

My take on it has to be a bit more simplistic as I really am only a hairy assed skiffolder and have no idea about plastic or elastic so I have spoken to an automotive supplier who assures me he can furnish me with a digital torque meter able to test a selection of my fittings for a measly 100 brick. Money well spent in my opinion that will at last allow me to write a set of RAMS.
 
Hi Alistair

I was captured by then Al kieeda Bubs, they eventually payed me a ransom to me to get rid me and I followed on to a Job in Saudi...

Aye, this Torque Business has been going on for years now eh, but , I tell you this much there are a few SAcaffold Engineers considering putting the Torque Values into their Calcs and Drawings---so your on the right route...

Gar...
 
haha, money well spent in their opinion.:laugh:

It's turning into a bit of a nightmare especially as most measure in degree's for some reason instead of NM but good to know you think I'm on the right route.
 
joebag said:
id put it to the hse like this,if you can set a wrenches capacity to 50nm,every fitting is then literally tested to 50nm,then put up a scaffold by spanner and test however many you have to with a torque wrench,which is going to be more accurate,its nonsensical!

the detail of all the failure rates and how they fail dont really come into it,if a fiitting snaps you know about it straight away and rectify it,i understand their has to be in depth detail to go into it,but i also know from experience making an argumented point look foolish and not giving it credence can dismiss the point straight away,

i would say once their is enough blokes using these,ignore what they say as a spanner is far less accurate,their is no argument against that,its fact!
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Morning Joebag,
not sure there is a problem with the IW persay but with IW's not set to the correct torque. If all were to use a "50Nm" IW there would/could be little objection I feel.

Your comment with regards the failure rate not coming into it is however not the case. The failure rate is what determines how many scaffold fail. The problem with these fitting failures is thay do not always fail whilst you are doing them up they fail over a period of time whilst under stress, they have a progressive creep which can allow the fitting to become loose or some, as we have seen reported crack at the T and eventually shear off.

---------- Post added at 03:19 AM ---------- Previous post was at 02:07 AM ----------
Alan Reade said:
If what you are aiming to test is, whether or not your IW has exceeded the 50Nm then a TW will tell you that, what it will not tell you is to what torque it has been torqued.

By setting your TW to the stated 50Nm and testing your fixing, if the TW clicks off then the bolt is in excess of the test load. If it continues to tighten then the desired torque has not be reached.
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OK I have now carried out a highly scientific experiment in the yard and the results are in, not sure what you can conclude from these results but here we go……..
Some weeks ago I installed 4 couplers in the yard and torqued each ranging from 50-220Nm just for the hell of it. Subsequently I re-torqued each up to 220Nm to see what would happen (toss all to the naked eye)
Following numerous back and froths with regards the use of a torque wrench to test how tight a fitting was done up by in fact undoing it with said wrench I have now completed this exercise.
ALL 4 fittings set at 220Nm undone without any effort with the wrench set on 50Nm. Assuming via one of my earlier posts that this was due to the move from elastic to plastic mode of the T bolt (overstretching) I then reset 4 further couplers (previously untested) ranging from 50 -220 and reversed the wrench, reset to 50Nm again ALL released at 50Nm without any effort.
 
surely though alan not being set to the right torque is semantics?if your trusted enough to put a scaffold up you must surely be trusted to set a wrench correctly,if the arguement is then that you wouldnt trust people to set their own then surely you wouldnt trust them to accurately wrap a spanner,or get a supervisor to do it ;), i take your point on failure rate but surely throwing fittings in a bin and the stick they take everyday from just being tipped out of a bucket say in cold weather must put stress on them,if we have to go into it that far is normal battering took into account in tests rams etc,,,if so why is there not like a use by date of say 5 years on fittings?

apologies if some of these queries have been answered or are ridiculous,you have had some brilliant and in depth answers and im a fuker for satisfying my own curiousity:D
 
joebag said:
surely though alan not being set to the right torque is semantics?if your trusted enough to put a scaffold up you must surely be trusted to set a wrench correctly,if the arguement is then that you wouldnt trust people to set their own then surely you wouldnt trust them to accurately wrap a spanner,or get a supervisor to do it ;), i take your point on failure rate but surely throwing fittings in a bin and the stick they take everyday from just being tipped out of a bucket say in cold weather must put stress on them,if we have to go into it that far is normal battering took into account in tests rams etc,,,if so why is there not like a use by date of say 5 years on fittings?

apologies if some of these queries have been answered or are ridiculous,you have had some brilliant and in depth answers and im a fuker for satisfying my own curiousity:D
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Hi Joebag
no correct torque is not semantics and its not a matter of trusting guys to do the right thing because clearly they are not at the moment. If your IW has no adjustment for torque or is a fixed preset at 30Nm then the wrong thing is already being done.

With regards the stress applied to couplers on a day to day basis the stress created by overstressing the bolt is a way bigger problem.

Always happy to try and answer questions but not sure I can answer them all adequatley
 
so the answer is either get iw with clearly stated adjustable settings or maybe hilti etc developing a 50 nm lightweight scaff iw,,,,,alan leave that with me ;)

however the issue of undertightening/stressing the fittings with a spanner must hold equal if not more worry than overstressing surely or am i missing the point :unsure:
 
Correct on point one
On point two, I remember quite some years ago there were some longer swingovers in use but these were also removed from use.
There were tsts of some description carried out where by the "average weight Scaff" Would impose an "average force" through a swing over with an optimal standard length.

This gave a "known load" and a known lever arm which equated to the optimal torque.

It was all a long time ago now so a bit foggy around the edges
 
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joebag said:
surely though alan not being set to the right torque is semantics?if your trusted enough to put a scaffold up you must surely be trusted to set a wrench correctly,if the arguement is then that you wouldnt trust people to set their own then surely you wouldnt trust them to accurately wrap a spanner,or get a supervisor to do it ;), i take your point on failure rate but surely throwing fittings in a bin and the stick they take everyday from just being tipped out of a bucket say in cold weather must put stress on them,if we have to go into it that far is normal battering took into account in tests rams etc,,,if so why is there not like a use by date of say 5 years on fittings?

apologies if some of these queries have been answered or are ridiculous,you have had some brilliant and in depth answers and im a fuker for satisfying my own curiousity
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man after my own heart am like a dog with a bone until i think av got what i need from an answer sometimes it bite me in the @rse when am sort of rong and keep pluging for the answer am not goign to get as what i have in my head is way off what is correct suppose that a bit like you and you 6 standasrd tower but hey you win some you loose some ;):laugh::laugh:
 
you show me were it says a tower has to have only four legs and i will give up scaffolding and just be a normal millionaire :D
 
I am sorry guys,

I can not see the appeal in this impact wrench,why would anyone want to drag that thing around,the amount of pressure this machine would put on the fitting and tube would be over the top from what i have seen,maybe there is a place for this when useing unit beams,what happens if the next gang that comes to strike your job only has a scaffold spanner,will they be able to undo the fittings,maybe I am old fashioned but for 25 years a spanner has done me so far.Make materials lighter,stronger,come up with a smaller hoist option instead of rope and wheel,Better conditions and wages for all scaffolders,.......BUT THIS,NOT FOR ME EVER.
 
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