at work today i asked to perform a havs test on a hydraulic breaker for one of our subsea clients for them to work out how many man hours they would need for there divers. After successfully completing this and documented this for the client i then thought how would it be possible to judge the vibration of the breaker when indeed it is to be used under water and therefore the vibration would be less. so i ask you my fellow colleagues is there a way to calculate this process?

I'd have to agree with the above, mostly. Although I will admit I am speaking from a divers perspective not a underwater HAV's tester (gap in the market?!) From feeling various things 'move' under water I would expect there would be a bit of both some vibration would be damped as it were and some may be worsened by conditions etc. In the end though there will still be a similar contact between the tool and user as would be expected on dry land. Have you considered alternatives to the breaker if its looking like a very high magnitude, I assume it must be if HAV's is looking to be an issue given the naturally reduced use-age time for divers. Not knowing quite what the work is its hard to say but UHP water jetting is a fairly commonly used technique for underwater cleaning/deconstruction - with its own set of not insignificant risks. Can you test the rig underwater? Otter box and cable gland or even a plastiv bag type affair to confirm if there is much change? Or is there any research or figures quoted online for the tool, in use underwater. I imagine somewhere there is a scientific formula that may get you an answer but I would be looking at the simpler solutions first!

I'd be wary of using extended cable. Calibration and response is often wholly dependent on the cable length.