Lift Bag Calculation

[noob024]

Thank you for all your help. I have lifted cars and boats before, mainly in shallow water, but the point of this exercise was to attempt to deduce the formula so I can deploy the correct number of bags. Up to this point, I have been using surface weight since I generally raise the objects to the surface. I have seen various attempts at explaining this and I think my main problem is forgetting to convert the displacement volume into density.

 

[DA Aquamaster]

Overkill is preferrable. For example, we used to chase rising and falling water levels in marinas on man made reservoirs. That meant moving a lot of weights in a short time with a minimum number of bags and minimal surface support. On a bad day that could mean trying to lift a 500 pound concrete with 600 pounds worth of lift bags. With some bottom suction that could mean rocking the anchor to get it to break free, they offsetting laterally as fast as you could in zero viz to avoid the weight should a bag or line fail sending the weight back down faster than it went up.

I much prefer just using a lot of excess lift and not having to worry about rocking anything loose.

 

[Mark Michaud SELAUSAR]

Hi Mark,

I am no expert on shallow water salvage, and personally find it to be amongst the most dangerous salvage because of the great instability introduced in shallow water lifts, when the lift bag is very close to the CG of the load. You obviously need great expertise and caution using the method you describe.
And i do agree, cranes are very expensive, but in my opinion the safest way to do such an extraction. Nice pictures.

Thanks. Agreed on cranes. The most important thing I have found is that you do everything slow and methodically, or with a purpose. I do most of my work alone, as far as the in water portion. I have boat or shore support but keep them where they can be the most help. Once you have your "set up" right, the rest of the job goes smoothly. Inshore salvage is so different because many time you are limited on resources and the ability to get them where you are. Lots of physics in moving things. You have to think outside of the box sometimes, but it is amazing how easy some things go when you can do that. I have been fortunate. Always slow and safe. I have also found, it is time to stop when you get tired. I have had good teachers and, fortunately, have never even had a close call. Are you from there or here? I have a good friend who broke out on his own several years ago and works in Mumbai. He is from here and used to work for Mcdermot, and Maybe Cal Dive.

 

[Bombay High]

Thanks. Agreed on cranes. The most important thing I have found is that you do everything slow and methodically, or with a purpose. I do most of my work alone, as far as the in water portion. I have boat or shore support but keep them where they can be the most help. Once you have your "set up" right, the rest of the job goes smoothly. Inshore salvage is so different because many time you are limited on resources and the ability to get them where you are. Lots of physics in moving things. You have to think outside of the box sometimes, but it is amazing how easy some things go when you can do that. I have been fortunate. Always slow and safe. I have also found, it is time to stop when you get tired. I have had good teachers and, fortunately, have never even had a close call. Are you from there or here? I have a good friend who broke out on his own several years ago and works in Mumbai. He is from here and used to work for Mcdermot, and Maybe Cal Dive.

Used to be based in Aberdeen, Scotland. Now in Mumbai, India, but work wherever the pay is.
Most of my work has been deep water drilling - Dry Bell Mixed Gas.

The North Sea is not the gold mine for divers it once was

 

[VooDooGasMan]

Spd 135 I could not agree more on post #13. And for DA and cable breaking that is not good, not sure of cable size, or if tow truck was hooked to front end. I used a landowl flatbed where the frame splits and the cab articulates then raises and from suction it would then just have drop to tires before engaging winch again, with tackle blocks. If rigged wrong so dangerous, and maybe bad cable, always inspect cable every time it is out.

As it has snowed all night I was missing life back when I did this daily in the winter months and do miss it.

 

[Mark Michaud SELAUSAR]

Used to be based in Aberdeen, Scotland. Now in Mumbai, India, but work wherever the pay is.
Most of my work has been deep water drilling - Dry Bell Mixed Gas.

The North Sea is not the gold mine for divers it once was

Do you know Richard "Dick" Lenzen? He's in Mumbai

 

[Bombay High]

Do you know Richard "Dick" Lenzen? He's in Mumbai

What company ? Is he a diver or a supervisor / superintendent ? Offshore I am guessing (almost all the work here is offshore)

How long has he been in Mumbai ? His name is not familiar, but thats not unusual ... if he is in Stena or Rockwater, chances are I would have run into him at some point.

 

[Mark Michaud SELAUSAR]

What company ? Is he a diver or a supervisor / superintendent ? Offshore I am guessing (almost all the work here is offshore)

How long has he been in Mumbai ? His name is not familiar, but thats not unusual ... if he is in Stena or Rockwater, chances are I would have run into him at some point.

He broke out on his own maybe 5 years ago (or more). I am not sure, now that you ask, of his company name. I see him every few years these days.

 

[Bombay High]

He broke out on his own maybe 5 years ago (or more). I am not sure, now that you ask, of his company name. I see him every few years these days.

Lots of independent contractors here now. Bombay (Mumbai) is a great place to recruit Commercial Divers. There are very few recreational divers and LOTS of commercial divers. Easy access to a lot of the offshore oil patches from Bombay. Its the Aberdeen of India