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Rigging screws - SWL marks


TomHoward
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Our rig has just been pulled up for having rigging screws in it that have no SWL marking, tensile steel marking or locking nuts / clevis pin on the jaw pins at the end.

 

The installation is from 2006 and I've contacted the installer for any further info on them but not heard anything back yet.

 

Looking at them, the turnbuckles are marked 3/8", and the two threads are marked L & R, but it's right there are no SWL markings etc.

The engineer is concerned they are not rated for lifting and only tensioning.

 

Looking in the Flints catalogue and elsewhere, Flints sell a US federal spec unit that looks like it is also unmarked in terms of SWL, but at least comes with their own certificate of inspection and conformity. The item is on the website here, in the catalogue it's marked with a hook as lifting suitable.

 

It's a valid complaint as some of the nuts on the jaws have worked loose and are needed pinching up.

 

Does anyone know of an equivalent which comes marked with an SWL loading, or is it common place to use the Federal spec ones in a UK installation?

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Here is a photo of the item questioned for clarity - it's unmarked with any SWL etc, and the bottom nut had worked loose on this one we looked at, as it had no method of locking / anti vibration like a spring washer etc.

We have 4x turnbuckles per bar on 10x moving pile wound bars so 40x of these connections.

 

GOPR0389.jpg

GOPR0393.jpg

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The Flints PDF (which you allude to) on rigging screws may prove helpful, if only to see what alternatives you might find that will satisfy someone. Clips or wires are common on some designs but on ones with a bolt, I feel that Nylocs would be adequate. After all, we use them throughout flying systems where a nut is needed.

 

https://www.flints.co.uk/pdfcatalogue/riggingscrews.pdf

 

In general, I find that if you need theatrical rigging knowledge and 'compliant' kit in the UK, Flints are the place to help. It's difficult to tell if the listed screws are high tensile from the photo, although again Crosby is a brand that one can have confidence in and potentially argue to be the 'right brand for the job' (a bit like being able to wave your Fluke meter at someone). But Flints will be able to advise.

 

Yours look not unlike a common type of bottle screw used in theatres for years, but do lack a few bits and pieces that satisfy inspections these days. As an example, if you do a search in one LOLER guidance for the word "marked" it appears 22 times. :-)

 

I know someone that throws the 'rated' expression around with somewhat reckless abandon. Anything can be rated. What applies here is that there is no manufacturer displayed WLL, hence the inspector really means "we have no way of knowing the rating of this lifting accessory." What could be open to question, is if the bottle screw is actually just a part in an assembly of lifting equipment which is marked with a rating. After all, every link in a motor chain isn't marked with a WLL. However, we can't unscrew a chain link and use it for a different operation.

Edited by indyld
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I found the Green Pin catalogue has a one with both nut and clevis pin and that is probably more likely to be marked with load rating (though I haven't checked yet).

Green Pin turnbuckle catalogue page

 

I've heard back from the original installer who have provided a certificate of conformity and say that the loose nut should have been picked up by us during routine maintenance, which is fair enough really.

Might swap them out for the Green Pin variety just to keep it up to date.

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It may be a perspective thing, but in your lower photo the bolt with the loose nut appears to be bent (which would really worry an inspector)..

I was pondering that too. Is it bent or is it just an illusion.

 

Uh-oh. Now that's just made me think of the Imagination track.

Now I realise why they were so successful. They love the camera.

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The bolt isn't bent but it certainly looks it, it's a combination of them being a sloppy thread, so the nuts have room to wobble left and right when they are loose, and the picture being taken on a GoPro with its fish-eye lens.

 

Like we are going to swap for these Green Pin variety if I can find them

Turnbuckles.jpg

Edited by TomHoward
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I found the Green Pin catalogue has a one with both nut and clevis pin and that is probably more likely to be marked with load rating (though I haven't checked yet).<a href='https://I.ibb.co/K729Sxz/Turnbuckles.jpg' class='bbc_url' title='External link' rel='nofollow external'>Green Pin turnbuckle catalogue page</a>I've heard back from the original installer who have provided a certificate of conformity and say that the loose nut should have been picked up by us during routine maintenance, which is fair enough really.Might swap them out for the Green Pin variety just to keep it up to date.
Personally I'd say that if you have a company supplying a 'Certificate Of Conformity' and they are a trusted company and qualified to issue such certificate then the inspector should accept it as honourable.

However if the kit has been there for a long time (I think this may have been shown earlier) then they would be foolish to issue a retrospective certificate without their own inspection as they have no idea what changes may have happened in the meantime.

Edited by sunray
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In the rise to full implementation of LOLER even the military got rid of lots of visually OK but "not permanently marked by the maker" equipment. Maybe you've got away with it so far, til now. If I was your inspector and I saw that "possible bent" bolt, I'd be condemning the rig til fully serviced by the maker/installer.

 

The original installer should have left you with a safe completion certificate, BUT without full serial number markings you'd be hard pressed to state and show evidence that nothing had been changed since installation.

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Do you actually /need/ this type of fine tune adjustment on the bars? The design intention for something like this is that you need to adjust the hang on the bar fairly regularly and without tools. If that’s not what you’re doing then your RA should really push you towards a more permanent solution surely?
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I'd be getting any replacement specified and supplied by a company, rather than in-house, for reasons of indemnity insurance. It may be that you can fit it yourself, but not sure I'd want the legal responsibility of specifying the replacement.

 

As Tom says, if you don't need to be able to relevel the bars, is it worth getting it level and set with a more permanent system. If it were ladder truss I'd be looking at bar diverters and clamping the steel further along the horizontal bar, but that is a pain on single bars as it limits rigging positions.

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Do you actually /need/ this type of fine tune adjustment on the bars? The design intention for something like this is that you need to adjust the hang on the bar fairly regularly and without tools. If that’s not what you’re doing then your RA should really push you towards a more permanent solution surely?

I don't think so, I don't know why they aren't terminated directly. We have some other bars that have diverters and clamps as detailed avocet, but there doesn't look to be the wire left on the hoists to convert these.

 

They Green Pin units are under a tenner a piece inc VAT so not too bad..

 

The thing that surprises me more is this a full refurbishment (essentially just the bricks short of a new build) in 2006 from a couple of major companies do it's not a local install, so the requirement would have been there in 2006 as well.

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I think it's just that the install used bottle screws to allow for the lines settling and the fact that they are swage terminated. Sadly they have arguably introduced another rigging accessory that gives rise to the issue you are facing.

 

Obviously there are other ways to adjust individual lines in a system at one end or the other but this looks like what the designer/installer chose at the time.

 

Maybe the wires were cut a little short. It's not like these kinds of things don't happen during an install and then stuff gets 'adjusted' to solve a problem. While this is obviously a small LOLER foul-up, it's not like brand new builds never have silly little things that occur. When installing into an established venue, stuff crops up due to things that emerge in the existing building. However, this doesn't mean that new builds go completely to plan on a day to day basis. In fact, with multiple trades still finishing off it can be worse!

 

Total speculation, of course, but a potential way that these mysterious bottle screws exist in system that also uses diverters. Stuff happens on site. Not enough diverters, change of plan, mis-measuring or moving of a lineset, whatever.

 

Install bod goes out to the van to scrabble together enough bits to finish off the final few bars in time for the deadline. Who knows? But anyone who has worked on installs knows the random things that end up with a few bits dug out of the van and a lunchtime trip to the local electrical merchant on the last day of the build. :-)

 

Edit to add: As an aside, the difference between lifting and 'tensioning' is only a product of LOLER anyway as force is force. Lifting isn't inherently heavier than tensioning. In tensioning, a theoretically full 180 degree horizontal catenary with even just a mouse tightroping across could have a theoretically infinite force pulling at each end. If that tensioning is part of a lifting operation, now we have other problems including an unmarked accessory. But it's a LOLER problem rather than an engineering one.

Edited by indyld
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I think they're there by design, but I meant more the use of Fed Spec ones considering SWL marked are available, and the inconsistency between companies taking it as legitimate or recommending its replacement, but surprising is the wrong word really - it isn't surprising.
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