(Small bore) bracing

[Muckerj]

Hello all,

This is something that has bugged me for awhile and I don't know how to tackle the issue so any inputs would be most appreciated.

We have identified a number of cases where we may have vibration issue. Any local drain and vent points that comes off those systems will need to be braced in two planes. My questions are as follows:
1) Angle iron vs flat bar? How is angle iron providing better support?
2) Can one angle bar provide two plane support?
3) I have an example of how it is done right now- see attachment. Can we improve the bracing installation (discounting the fact you can weld another one)? I would like some installation detail. Right now, as you can see, the angle iron only welded along one edge only.

 

[BigInch]

Caution, not allowed to weld supports directly onto pipe in pipeline codes.
For one, start using XXS pipe and reinforcing pads, not weldos on vibration sensitive pipe, and do not use pipe less than 50mm diameter.

For something apparently so small, you can get away with petty much whatever you want. If you can't, you don't want anything stronger than the pipe anyway, or the pipe will break first.


you must get smarter than the software you're using.

 

[LittleInch]

1) I've seen both, but angle probably has less welding length to get a similar effect ( flat bar would be vertical in your example)
2) Not as far as I know
3) looks a pretty standard detail to me

Maybe a bigger weldolet or reducing tee then reducer then flange might be better?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Muckerj]

Hi Little inch,

Thanks for your input.
3) I actually have found another drawing and will upload later. So if we weld the same way as in the first attachment, are we just getting effectively a flat bar anyway because it's only welded on one edge with the other one cut and not really doing anything.

Yes that will be better but we aren't changing that now so will have to make do with what we got.

 

[dhengr]

Muckerj:
Big and Little know the piping codes much better than I do, so follow their advice on most matters. But, a couple comments on your question and detail from the structural, welding, dynamics and brace buckling standpoint. The flat bar as a brace is more likely to flutter (vibrate) in the breeze or vibrate in unison with the piping system, whereas the angle is stiffer w.r.t. these conditions. As the brace gets longer, buckling can become a problem, and again the angle is stiffer/stronger under these conditions. The single leg angle weld is likely better because it acts a bit more like a hinge and doesn’t induce significant concentrated bending moment into the pipes or the repads. Furthermore, welding up or out on the vert. leg has a weld termination at a point which is highly susceptible to cracking and crack propagation, which is certainly not desirable. Your detail is pretty simple to fabricate and install. But, on a small enough dia. vert. pipe, you may want to shape the horiz. angle leg to match the pipe shape to improve welding fit-up. The full analysis of that type of detail is considerable more complicated than the above, but in a nut-shell the above gives you some of the simplified thinking.