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Posted By DavidHaddon
Does anybody have any experience of using two overhead cranes in tandem to perform a lift?
I have been unable to find anything written which prohibits this, however my concern is that the mass of the lift may not split evenly between the cranes, and that one may fail.
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Posted By peter gotch
David,
To be avoided where possible!
Needs specialist consideration and downrating of each crane as per guidance in BS7121.
Regards, Peter
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Posted By Peter MacDonald
David
You need to examine the object to be lifted. Can you ascertain it's weight, centre of gravity and lifting/slinging points. From there you will be able to calculate the load on each crane.For example an object with a centre of gravity in the middle of the load and symetrical slinging means the weight will be evenly distributed between lifting tackle. If the centre of gravity is off centre or there is complex slinging then the distribution changes accordingly. Remember that the calulated weight will not change during the lift, only the capacity of the cranes at different radi. If you mean to use fixed position cranes on an overhead rail then the calculated load will remain constant if the weight, centre of gravity and sling positions don't change during the lift.
Remember to consider the 'angle of dangle'of lifting gear and how this can affect the load bearing capacity.
In short a tandem lift does not have to be complicated but make sure it is carried out by competent people. Do you have an appointed person for lifting to hand ? legally you need one.
Cheers
Peter
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Posted By Steven Taylor
David,
You can also acquire specialist lifting beams that will, in a crude way, link your 2 overhead cranes together, to essentially give you one crane with a greater lifting capacity from one central lifting hoist. However the previous comments of downgrading the capacity and the slinging techniques will still have a bearing.
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Posted By alex mccreadie
David
As normal many sensible suggestions regarding Tandem Lifting. If you can get copies of BS7121 PART 1 & 3 it will help you. As stated there are many factors to take into consideration most of all you need an Appointed Person to plan the lift.
If you are not happy call in some lifting experts to ensure the lift is carried out safely.
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Posted By Robert K Lewis
David
This is really a specialist job and you need to get it undertaken as a Contract Lift and not on the basis of a CPA hire of a crane and driver working to your methods.
The contract lift effectively contracts out the whole of the process to those who are experienced, they will provide slingers, signallers, driver, co-ordinator and design input as necessary. You will still need to vet the method to ensure there are no clashes with other work and aspects immediately outside of the lift parameters but this is much simpler for the general person than doing all the work & calculations.
ps It will cost more though!!!!!
Bob
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Posted By DavidHaddon
Thanks for your postings everybody.
Does anybody have a PDF copy of BS7121?
Can anybody confirm that it has been superceded by LOLER?
Any assistance will be most appreciated.
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Posted By Calum R Cameron
You should use the BS in addition to LOLER 98. Take great care with this tandem lifting operation as it has the potential to go wrong in a big way.
Calum
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Posted By Kevin Irwin
David,
Just to throw my two penneth in! Tandem lifting is no major problem if you take the advice above. I used to work in a rail engineering works and tandem lifting of rail vehicles was an hourly occurrence.
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Posted By RP
I did this operation when in the army and we enlisted the help of a canadian firm to oversee the operation. One thing not mentioned here which we had to do was to fit safety check chains with a SWL exceeding the total weight of the lift. The operation involved lifting and replacing an iron girder bridge in another country. Not an experience for the faint hearted. We had to do it because there were no cranes in the country that could do it singularly...now where is my spell checker gone??
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