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Tower crane safety bulletin

D&G cranes of Australia has issued a safety alert relating to a tower bolt failure on a Comedil CTT 561-A24 crane, working on a site in Canberra.

Earlier this month a new tower bolt suffered a catastrophic failure, the crane was working at the time and the initial report suggested that the failure was caused by fatigue, even though it was new.
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The end of the failed bolt

On further investigation it was revealed that scaffold and formwork had been attached to and braced against the tower, close to the failed bolt. Suggesting that vibrations and changed dynamics from the attachments may have played a role in the bolts failure.
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The base of the tower was connected to a scaffold and formwork

The company has sent the bolt to a laboratory for further analysis, but in the meantime it removed and checked all tower bolts and replaced and re-tensioned them and a new dynamic load test was conducted.
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Some of the formwork and scaffold was clamped onto the tower

It also checked conducted a check on all other cranes on site and ordered a check of all of its cranes for similar scaffold/formwork or other attachments to the tower structures and implements a new rule that no structural alterations or attachments can be made by clients to its cranes without its prior consideration and approval.
You can go directly to the actual bulletin, which is now hosted on our site by clicking here

Vertikal Comment

This is a classic case of what should occur when a ‘near miss’ occurs, all too often companies, hush this type of thing up, especially if they are of the opinion that the actions of an employee may have been to blame.

OK in this case it would seem that no matter what actually caused this incident the crane company is unlikely to be ‘in the frame’ …..although if further analysis suggests that the bolt was over torqued??

The point is that the industry would be a significantly safer and more professional place if all incidents were covered in this way.

Tomorrow there will be a one day summit in Hamburg, covering safety in wind lifting. This has become a dangerous industry where even some almost ‘household names’ chose, for whatever reason, to hide and even bury information on incidents that occur on their sites, rather than share the information in the way that D&G has.

Hopefully the conference tomorrow will address this issue head-on and do something to address it. In the meantime congratulations to D&G cranes for this first class example.

Sadly I am not holding my breath – But I go with a positive and hopeful attitude, in meantime congratulations to D&G for showing the rest of hos how it is done.


My understanding is that the tower crane should be a free standing structure and only connected by the correct tie collar according to the manufacturer’s recommendations. Special arrangements may be possible in consultation with the crane manufacturer’s and with their permission and agreement only. How many times do you see shuttering propped from the tower at the floor slab levels and left in situ longer than is really required.
Does this company have a procedure for checking the bolts prior to reusing them on the next erection, i appreciate their openness and this will benefit all the industry in looking at these issues again

Mar 17, 2012

Good Afternoon Mr Editor,

Regular visitors to your excellent Vertikal website, will have recognised that the Bolt depicted above had been defective for some time. This is evidenced by the Rusty Red area in the centre and lower right quadrant of this fastener. All of which is indicative of a metallurgical defect that goes back a long way, maybe even to the date of production ?

The effect of this is to produce a defective bolt, in which the defect is invisible to the human eye and which would only show-up after some type of Non-Destructive Test or Metallurgical X-ray procedure. ( Should the Mfr modify his QA process ? ) But what is of real concern is that when a Bolt like this is used in a Safety Critical Role such as the Mast of a Tower Crane.

Even more so when we ask the rhetorical question, if we have found one defective bolt, then how many more there in use in the Construction Industry ?

Kind Regards
Mike Ponsonby BA

Mar 13, 2012

J Albrecht
"...although if further analysis suggests that the bolt was over torqued..."

Yes, unfortunately, sometimes bolts are missed and they remain loose. However, this only happens when the assembler is grossly negligent. What is more common is that the bolts are indeed torqued yet DO NOT CARRY THE PROPER PRELOAD. This occurs even when calibrated wrenches are used. Alas, too many installers, engineers, inspectors and other authorities are oblivious to this terrible and dangerous misunderstanding of the torquing process.

Here's a link to a non-commercial explanation which hopefully will open some eyes so that failures such as this can eliminated:

Mar 13, 2012