Verify load on roof - API 650 tank

[garfio]

I have a small API 650 tank (12' diam), with self-supporting cone roof (3/16") where I need to install an agitator in a roof center nozzle. The total weight is close to 1000 lbs so I need to check the loads and probably reinforce the roof accordingly.

Any suggestion about how could the roof be verified against this concentrated load?

 

[JStephen]

Probably the best approach is to put beams across the top of the tank above the roof to support the load.

You can check loads on a roof like that using the approach in API-620. But it won't account for bending in the plate, and won't let you check deflections, which could be an issue (IE, vibrations). The beam approach at least allows you to do a proper design more easily.

 

[MJCronin]

I agree with JStephen.....

Remove the cone roof, install a flat roof with integral beams ( I suggest 10" minimum depth)for agitator support. Relocate vents nozzles etc as necessary.

Size the beams for the bending, deadload and torsionalloads imposed by the agitator. (this is a new agitator....right ?) These loads are available from the agitator vendor.

The final reinforced tank/mixer roof should look like this:

(See Tank L-4 on this website)

http://www.centralfabricators.com/storagetanks.php

All of this equipment is new, right ? You are not trying to perform "junkyard process plant design" isn't that right ?


regards

-MJC

 

[garfio]

Thanks for your response. The tank and agitator are new. The tank has a cone roof with the nozzle for the agitator, and also has some 2" radial angles as partial reinforcement (angles are not connected to the cilinder). With 3/16" roof thickness, even with a reinforcing pad, does not seem sturdy enough for the agitator (loads are around 600 ft-lb torque, 900 lb weight and 1600 ft-lb bending moment).

Removing the roof as suggested should be done only after verifying that the current tank cannot support the agitator adequately, that is why I am looking for ways to verify this.

For people with previous experience in similar situation, do you have a "feeling" of this tank been not sturdy enough for the loads I mentioned? I am still looking for a way to to the calculation to check this, though.

 

[TankDude]

You may be able to install external structure to support the mixer loads. The structure would have to be tied into vertical supports off the shell plate. The design and analysis for this option could get pretty involved and would likely require an FEA. The flat roof option may be easier/cheaper.

 

[MJCronin]

Here are some examples of bridges:

http://www.aaronequipment.com/UsedEquipment/Tanks/Stainless++500-999+Gal/81737.html

http://www.ecrecon.com/items.php?cat_id=21&item_id=279

-MJC

 

[Stl63]

You may have a nozzle for the agitator, but that is typically only for the shaft to penetrate. The agitator itself is going to need aan elevated flat surface for mounting. Putting an agitator on a cone roof is just not typically done. Flat roof with beams is typical.