adding gussets to a pipe

[joedirt9]

looking to add 4 gussets to a dip tube for extra support. not sure how to take into account the gussets when looking at the pie as a cantilever beam. the dip tube is 1 1/2" SCH40 and is 8' long. no way to support at the bottom of the pipe. fear is the pipe will break and be in the tank which would be a problem. goal is to limit the stress on the 304L pipe to 12000 psi. thinking of running gussets to a certain point to limit the stress. not sure how to calculate the gusset dimensions required. any ideas?

 

[racookpe1978]

What does the tank "do"? Basically, why would the dipstick "pipe" break off?

Does it (the tank) move like a railcar or truck? Is it fixed in place? Any pressures/vibrations from flow or shock or moving fluid? Any internal or operating pressure or pressure changes or flow changes?

See, if there is no abrupt or sudden forces on the pipe, you need only very small gussets.

 

[joedirt9]

well, the pipe will be discharging a mixture of vapor/liquid. so assume all vapor at a rate of 25500 lb/hr. this will shake the pipe some. but, the plant has has issues recently with dip tubes breaking and wants a design that remove any worries. so, the thinking is define a maximum stress value and design around that.

also, this tank could have the process changed from current configuration and the dip tube will need to be overbuilt for its current use

 

[desertfox]

Hi joedirt9

A sketch would be useful, for what reason can't the pipe be supported at the bottom?
What forces are acting on the pipe we can't tell from your post.

desertfox

 

[joedirt9]

only known force at this point is reaction force due to discharge. the thrust of the discharge would be the force. this is calculated out to be 634 lbf. what i am looking to do is design a dip tube with gussets coming down a few feet to limit the stress to 12,000 psi on the dip tube. i can get to how long a 1.5" pipe can be to have a stress of under 12000 psi.

 

[desertfox]

Hi joeirt9

How about a sketch it seems to me the discharge reaction would be parallel with the pipe so unless there's a bend in it I don't see how analysing it as a cantilever beam fits, perhaps I'm missing something hence the request for a sketch.

desertfox

 

[dhengr]

Joedirt9:
You’ve got to give us more info. if you want real help. Provide a sketch showing dimensions, loads, how the pipe is supported, and fitted out, your force calcs., etc., etc. How are the current pipes supported, where are they breaking, lets see some pictures of the broken ends of the pipes? If you’re are talking about a vapor/liquid mix, and it isn’t really imparting a large bending load on the pipe, I wonder if you don’t actually have a dynamic/fatigue problem with these pipes. If the breaking pipes are all about the same age, you have found their fatigue life. In which case gussets may not be an improvement at all. They might just introduce new stress raiser and stress concentrations, at all the wrong places.

 

[btrueblood]

It does sound like there is two-phase, or "slug flow" through the pipe, exciting dynamic motion and fatigue. Just stiffening the pipe might help, but - is the wall of the tank where the dip tube is secured fairly flexible? Do you see damage to the entrance end of the tube? Is there any way to bleed off gas first, or liquid first, to avoid two-phase flow until the pressure is reduced?

 

[MiketheEngineer]

There are companies that build these things everyday - we help repair them. Contact them for some help.