Use of air bags to lift horiz. full tank. 2

[deanquest]

Can anyone offer any advice on the use of air bags to lift a full, horizontal pressure vessel(approx 7ft dia, 26 ft lg) in order to install a load cell weighing system? The vessel WITH liquid contents weighs approx 60K lbs.. I've been told using the air bag approach to lifting the full tank is a safe and reliable method of lifting the tank 12" or so. In the past, we've always emptied the tanks and used a crane to lift the tank by its lifting lugs. Using the air bags to lift the full tank would certainly be a more economical solution. Although I'm trying to keep an open mind, I have doubts on the use of air bags in lifting large, live loads.

 

[prex]

Yes, it is a viable solution, your weight is not a problem.
What you need to check first is where you will put the bags so as to transfer the loads correctly without damaging the tank or sunking into the soil. Normally you would only be allowed to use the saddles, right where you need to install the cells.
Your figure of 12", though feasible, seems a bit high for this application. You should check with actual products the lifting capacity wrt lifting height.
Also at that height and mass you should be concerned about correctly laterally restraining any movement of the tank when lifted. Also consider, supposing you'll use four bags, that one or two of them might lose pressure accidentally, and your load must remain stable and not be damaged under that condition.



prex

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[MJCronin]

dean...

Is the tank currently supported by two saddles ?

If so, then it would be prudent to lift the tank in two places (nearby the saddles).

With a two(or more) point lifting scheme, there is a possibility that the tank will become unstable and roll.

The fluid contained within the tank could shift....

Hire a crane.....

 

[deanquest]

Thanks for the feedback. Looks as if lifting a full tank with air bags is a viable albeit more risky alternative to using a crane. Considering the number of things that can go wrong or be unsafe with the use of air bags, I'm going to stay with the more reliable and safe method of using a crane to lift the tank. There's simply less guesswork and finger crossing than if we use the more expensive but more reliable crane.

One more observation. Tanks have been around for a long time. Air bags have been around for a long time. However, overwhelmingly, generations of contractors have shown a preference for cranes to safely lift tanks. I've known contractors to be a pretty sharp bunch. There must be good reasons why they still use cranes instead of air bags. BTW, I'm not a crane contractor. Just someone trying to find the best way to lift full, horizontal tanks a few inches.

Thanks again,
Dean Quest

 

[PersonalProfile]

Need to consider failure modes (i.e. use enough bags so that if one or so fails it doesn't matter, consider use of water cf air to fill the bags, use of pilot valves to prevent unintentional discharge etc).
Maybe Enerpac (some of the above still need to be addressed - though they have standard solutions which are used all the time).

Regards,
Lyle

 

[zdas04]

The construction industry (like any other) is full of people who find a single way to do things and will not listen to any alternatives. I do a lot of out-of-the-box stuff and have found more than a few contractors who refused to do things my way. A good example is hydrovac. The first time I needed to trench across a highly congested part of a compressor station, everyone I talked to said my only option was to shut down the station and relocate equipment. I searched around and found a company in another region that was doing hydrovac and they said that they could trench under the equipment in place and in service. Two local contractors refused to do the pipe part of the job (and I've never used them since), the third was uneasy but willing. The job went perfecty and now just about every job in this area has a hydrovac truck included somewhere. People's arguments agianst the process read just like the posts in this thread and they all boil down to "that's not the way we do it".

If I had to move a tank "a few inches", I'd certainly look at doing it with air bags. Cranes do an amazingly lousy job of moving a heavy load a short distance. With the air bags you never have the load suspended in air and subject to wind currents. Write a heavy-lift procedure with enough safety factor to account for the issues above (e.g., maybe use 50% more bags than necessary, manifold the air supply so all get air at the same time, specify a slow rate of pressurization, etc).

David

 

[MJCronin]

Zdas...

What will prevent the liquid from shofting/sloshing form one end of the tank to the other ?

This will occur if there is the slightest difference in the rate of filling of the air bags or if one saddle support becomes caught in any way

 

[racookpe1978]

Using airbags to lift a small (empty!) tank like this?
Not a bad idea. Good objections and recommendations have been made above.

Using airbags to lift a small (completely full and well-capped) tank like this?
Might work. I would not do it, but it might work.

Using airbags to lift a small (partially full) tank like this?
Priceless.
No, literally, priceless. You'll never stop paying after the load shifts off "perfectly flat" by even a little bit.