Rank: Forum user 
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I sat through a webinar with American Colleagues regarding Lift Planning and Liftng safety last week, the discussion was primarily based around the safe use of overhead cranes.
Terminology is a bit differrent in lift classification, however, one thing that caught my attention was that an 'Engineered Lift' could exceeed the SWL of the crane as long as the lift is approved by Global Technical Authority.
Although this Operation could only happen 2 times in a twelve month period!
Jason Kavanagh AP/CPCS
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 1 user thanked jasonkav for this useful post.
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Rank: Super forum user
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Obviously not ideal practice to exceed the recognised SWL.
By how much is the SWL being exceeded?
A small amount wouldn't be of too much concern, but there has to be an ultimate 'no' limites.
Sounds like poor lift planning though. If the weight of a load is unknown, it would seem logical to assume the worst case/weights and to over specify the lifting equipment an/or consider if the load can be broken down into smaller weights.
You would certainly have some explaining to do if an accident was attributed to exceeding an SWL.
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Rank: Super forum user
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SWL is about half the design load. There are other factors taken into account by the design engineers before you reach your failure load for example the wire stretching before beam failure, deflection, robustness, wind loading etc. So working over the SWL is not inherently dangerous providing there is oversight by a competent engineer/authority, hence I suspect the Global Technical Authority. For one off mega/complex lifts using designed temporary works often the SWL is closer to the design load. It can also be impracticable to achieve double the design load so you highly engineer and supervise the lift. For every day lifts it is double to allow for the idiot factor, miss use, poor maintenance, corrosion etc
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Rank: Super forum user 
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Rank: Forum user
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Thanks Guy's much appreciated, I understand the there is a generous factor of safety regarding SWL's an example would be the 'test to destruction' loads applied to strops are well in excess of the SWL's my thoughts are more in line with what insurers would claim if exceeding the SWL, albeit by a small margin, resulted in an accident.
Also, if they can only repeat this once more in a 12 month period, why not get suitable equipment in?
Not Maritime Ron, Global Technical Authority being Expert Senior Manager/Engineer.
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Rank: Forum user 
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Good morning all,
From my experience, installed overhead cranes are tested to 125% once installed, you are allowed 1 mm of deflection for every 750 mm of bridge beam. So for example a 10 ton SWL crane would be tested to 12.5ton with the hoist positioned in the centre of the beam. If the crane was a 15 meter span, you would be allowed a maximum deflection of 20 mm measured at center point of span. The overloads on the hoist would then be set to the SWL of the crane and tested with the calibrated weight ie, set to 10 Ton I used to work for a crane manufacturer and installer; we would certainly not honor the warranty. Kind Regards Angelo
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Rank: Super forum user 
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This is currently under investigation, not an installed overhead crane but ... http://www.telegraph.co.uk/news/2017/05/10/falmouth-docks-evacuation-crane-collapses-yard/
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