Thick Walled Pressure Vessel for Pressure Testing 1

[bekks]

This is my first vessel I have designed and probably my last. We are wanting to build a vessel for pressure testing (with water) downhole tools. The ID of the vessel would be 6 inches and 8 feet long. The maximum pressure we would need to test at would be 20,000 psi at room temperature. This vessel will be small enough that it does not fall within ASME Section VIII Div.1's scope, but that is the code I am designing to (anyone have a more appropriate code?). So far, I am just considering the shell and haven't started considering the fittings that will need to be installed. I calculate a required wall thickness of 2.2 inches based on a max. allowable stress of 40,000 psi. This max. allowable is loosely based off of SA 693 (17-4 PH) material. Now I realize that this won't actually work forming a plate this thick into this tight of a radius, for a couple reasons.
So, my question is really, what do people make such a vessel from? Am I going to have to have this cast or forged?

 

[JStephen]

I would say that is a bad vessel to learn on. You'd be better off getting someone to design and fab that routinely does this.
There is an ASME Section VIII Div. 3 that would fit the application.
"2019 ASME Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 3: Alternative Rules for Construction of High Pressure Vessels"
I would expect it to be made from some form of pipe. I would specify the volume required, and let the designer select ID and length for best economy.

 

[SnTMan]

Agreed, design conditions make it poorly suited for Div. 1 and for learning on. Contract it out.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[bekks]

I appreciate the advice. Contracting it out is kind of what I was thinking as well, but I wanted to at least get an idea for myself what was required. I'll look through Div. III.
Using a pipe would be great, but I don't know of any off the shelf pipes that would come close to these dimensions.

 

[TGS4]

It won't be an off-the-shelf pipe - it will be custom-forged. And certainly get some help with this. At 20ksi internal pressure, water is ever-so-slightly expansible/compressible. A failure in this has a high likelihood of killing someone or doing serious damage to equipment.

 

[EdStainless]

IF you really want that strength level then you should use 15-5PH, it is designed for thicker sections.
This would be a custom forged piece of pipe, but likely made to a pipe spec.
Or they would take a 12" piece of bar and gun drill it out.
Hire someone to do this, design and fabrication.
Your full breach opening will be very difficult to get right.
This is closer to a hydrostatic press than a pressure vessel.



= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

 

[KevinNZ]

You could consider designing to API 6A. The code has dimensions and material requirements for bore and OD for 138 MPa (20000 ksi) parts.

 

[blacksmith37]

It sounds like you need API CASING, 5CT. That is what is going to be used with your down hole tools. Grade Q 125 with "good" NDE ( I do not have a current 5CT so can't give a supplemental requirement). End caps will be interesting as normally the casing is threaded to couplings. There are a variety of threads available ; working with a supplier would likely be the best way to find end caps and threads. Likely a vendor of down hole accessories and pup joints may have something on hand. There will be no welding on the tubulars. Depending on availability other grades could be used T-95, C110, etc. Also check with wellhead manufactures , 20 ksi and 25 ksi equipment is not common but it is made ( and pressure tested). Start with Cameron , Grey, FMC - I expect these names have changed because of various business changes since I retired. Actually with the 125 ksi yield material , the wall thickness would be about 1.25" with a 2:1 safety factor . So very likely some facility has this small length in inventory.

 

[marty007]

It sounds like your vessel would be a one-off, which means you'll want to find stocked materials. The few times I've ventured into the very high pressure world, it's always been for one-offs and this company has come in handy:

http://specialtypipe.com/steel-pipe-and-tube-inventory

They stock SA-106 GrB/C pipe in much thicker walls. A quick look found one 12"OD x 6"ID for example.

-Marty