Pipe connection

[hdalebennett]

Realizing that butt welding or bolted flanges are the traditional methods for joining pipe, I want to ask about the structural integrity when using an alternate method.

I have two 40' pipes. 10" diameter with a .135 wall thickness (10 gauge). I want to join them (end to end) with an inner sleeve - again, using a custom made 10 gauge inner sleeve pipe, 4' long (providing a 2' overlap). Will I maintain the structural strength of the joint using this method? I will be raising the two joined pipe to an upright position which will, of course, put stress on the joint.

My question only concerns the structural integrity of the joint - not the method of raising the structure.

Thanks,

Dale

 

[shobroco]

How are you fastening the sleeve to the pipes? If the pipes are not welded together, are you counting on the friction between the sleeves & the pipe? What load is it carrying? pressure, bending, tension? I'm scared of a 40' long 10 ga tube standing on end, never mind an 80' one, & with no connection between the halves I'll be sure to stay 120' away.

 

[hdalebennett]

The sections will, of course, be bolted together by being bolted to the inner sleeve. The total structure will be guyed at multiple levels. This type of pipe is used for identical structures 80 meters tall - so that is not the issue. The load is minimal. The ONLY issue is the structural integrity of the joint as the pipe is being tilted up. Tilting is common practice. Again, can you simply address the issue of the sleeve?

 

[ahmedhegazi]

Sketch if possible Would Help to understand

 

[dhengr]

“Butt welding or bolted flanges are the traditional methods for joining pipe” (stacks) for a reason. The butt weld makes for a continuous pipe with no discrete high (concentrated) load/force/stress points. While the bolted flange has 10 or 12 bolts around the circle, it stiffens the pipe and puts the loads into the pipe in a fairly uniform fashion. Both are relatively tight connections, non leaking.

But, it is still very difficult to discuss your splice meaningfully, when you won’t discuss some of the worst loading it might see. These various loadings will dictate how the joint is designed, the number, size, spacing of bolts, shell material thicknesses, etc. The fit-up btwn. the 10"dia. I.D. and the sleeve O.D. must be very good and very tight or you will likely be inducing the start of some wrinkles (crimping) in one part or the other part during the bolt-up. These wrinkles might be the starting point for a buckling condition. And now, the bolt forces are discrete high stress points in the shell structure, never a good condition. You have discontinuities at the lower and upper bolting details, some joint slip to really bring all the bolts into play, bolt to thin sheet bearing to deal with, etc. Furthermore, how do you get inside a 40' long 10" dia. pipe to apply the nuts, washers and bolts? Are contoured washers required for good fit-up and tightening and holding power, both convex and concave, one of each at each bolt?

What you are trying to save in field welding, shop applied bolt flanges, or transportation problems, might be outweighed by the difficulties of tight field assembly, bolting difficulties, and design problems.

 

[SAIL3]

I investigated a similar situation a few years back...no bolts, just slip fit between outer and inner pipe with blank-off pl reinf on open end of inner pipe.
Loading was bending moment only.
The unexpected result was that the joint may be stronger than the individual pipes...assuming sufficient overlap...
In the overlap the primary mode of failure for the outer pipe is to oval vertically while the inner pipe is trying to oval horizontally and tend to act to cancel each other out forcing a secondary type of failure..ie. chrushing , splitting etc.
The weak area seems to be just outside the overlap on the smaller pipe.
It was too complicated to put any numbers on it but left me with some degree of confidence that the weak area was in the weaker pipe from typical bending moment.

 

[SnTMan]

hdalebennett, any way you could hole the outer pipe(s) only and plug weld to the sleeve?

Regards,

Mike