Vertical Pipe - Internal Pressure, Pipe Weight

[gtzaki]

Ok here's the situation.

I'm currently working on a project to develop some downhole monitoring tools for coal seam methane. In order to lower the tools, we've developed our own pipe/coupling systems of 3/8" Schedule 80 pipes and API type thread couplings. On top of that, we're sealing the lowered pipes via the use of O-Ring seals at the coupling shoulders, meaning that the seal makes up after the threads are screwed in.

The pipes will be subjected to its own weight (about 2500kg) and internal water pressure of 3000psi (20.7MPa). The OD of the O-Ring placement points is 49mm. 3/8" Sch80 pipes are 1.05" (26.7mm) OD and 0.74" (20.8mm) ID.

What will the axial force be acting on the pipe due to the internal pressure?
I reckon it would be due to the projected area of the O-Ring clearance (0.0025" either side of the 49mm) added on to the internal area of the pipe. My boss seems to agree to it but I thought it'd be good to double check.

What do you think?

 

[MikeHalloran]

At 3000 psi, o-rings act more like caulking than like rigid objects. They will ooze through very small clearances. You may need backup rings to prevent that.

Additionally, if I'm interpreting the geometry correctly, the effective area is that of a 49+mm circle; the bore of the pipe is irrelevant.




Mike Halloran
Pembroke Pines, FL, USA

 

[gtzaki]

Mike

Thanks for the reply.
It makes sense that the effective area would be the 49mm circle (plus clearances). Thanks for tip on the backup rings, will be looking at that more closely.

Cheers!