Offshore Crane Curve (DAF applied)

Cengsubsea · May 2, 2022

Hi there,

I am wondering if someone may clarify a query relating to offshore/subsea crane charts.

I have a requirement to lift a static load from a vessel and place it subsea. The crane curves I have available have a DAF applied of 1.3 (subsea DAF as per DNV) but I have an analysis DAF of 1.4 which needs applied. How do I approach this? Can I multiply my static load by 1.1 to make up for the crane curve only having a DAF included of 1.3?

Further, what would I do in the case of only having a calculated DAF of 1.2 but a crane curve chart DAF of 1.3? My available radius for lifting will be unknown.

SwinnyGG · May 2, 2022

Your best resource by far is going to be to call the crane manufacturer and tell them you need assistance engineering a critical lift. I doubt anyone here (certainly not me) is going to give you direct advice which might cause a subsea lift to fail... You're on dangerous ground.

chicopee · May 24, 2022

Can you define the initials DAF?

SwinnyGG · May 25, 2022

Dynamic Amplification Factor.

The short explanation is that this is a crane derating multiplier which accounts for the fact that if you're lifting a load in the ocean, that load is experiencing sinusoidal movement, which increases the actual load applied to the crane by a load of a given mass.

It's not something to be messed with arbitrarily for a crane pick anywhere near load or radius limits.. which is why OP needs to call the manufacture of their crane, or whomever they are leasing the crane from.

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Offshore Crane Curve (DAF applied)

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