Boot calculation fails App. 1-7(b)

[raf2007]

hi
I have a 9' ID vessel with a 4.5' ID drop leg (boot), but it's failing cause of bending moment due to large diameter, acc. to App. 1-7(b).
Is there any way to solve this problem without boot diameter changing?

 

[vesselfab]

insert plate

 

[raf2007]

Thanks,

Do you mean repad? I have added a repad already and it passes for internal pressure, the problem is about bending moment cause of big boot diameter. Although I increase repad, it doesn't help

 

[doct9960]

raf2007,

Try the following:

1. Increase boot thickness
2. Increase vessel shell thickness (at the can where the boot is located)
3. Both 1 & 2 above

 

[raf2007]

Thanks doct9960, it worked increasing boot thk. As it is an existing vessel, can't increase vessel thk (1.328"), of course new boot thk is very thick now= 1.6875"

 

[TomBarsh]

doct9960 was way ahead of me (he is good). Increasing the boot thickness is more effective in increasing the moment of inertia of the cross-section resisting the bending moment than would be if increasing the shell thickness or adding a reinforcing pad.

For such a large diameter nozzle I would expect a large thickness at that location. You can use the heavy thickness for a short distance near the junction, then transition to a thinner plate for the balance of the nozzle's projection.

 

[AravindSujay]

hi Raf2007,

hope you misunderstood Vesselfab's word "Insert Plate". This is different from Repad.

A part of the shell is cut and welded with a plate known as "Insert plate" which is 2d of the boots dia. Usually IP has a higher thickness than the local shell thickness and the boot hole will be cut in the IP and fabricated.

This eliminates the use of repad or increase in shell thickness.

 

[jehan17718]

raf2007,

If increasing boot shell thickness or insert plate is infeasible/ not solving the problem, then make the boot shell into a self reinforced one as shown in sketch Fig UW-16.1 g. this can then be welded to a shell plaate and a head therby forming a boot (or sump)

Obviously, since you are now using a forging cost will increase.

hope this helps.

-jehan