When does a Piece of Pipe become a Vessel?
When does a Piece of Pipe become a Vessel?
(OP)
When does a section of pipe need to be coded as a ASME Vessel? I am planning to install a “wide spot” in a line below a small tank to allow time to depressurize and refill on the run. We currently use the tank's sightglass for this, but it is not large enough for a new product I will be running. The piping is ¾” and I plan to cut it and add a section of 10” about a foot long to store ~25# of material. Does this need to be a vessel?
Thanks for any help or suggestions!
Matt
Thanks for any help or suggestions!
Matt





RE: When does a Piece of Pipe become a Vessel?
RE: When does a Piece of Pipe become a Vessel?
Just be careful with the 3/4" to 10" connection as you can get a pretty large stress concentration at this point.
RE: When does a Piece of Pipe become a Vessel?
Also, the system pressure ~600 PSI. I will have someone double check how we make this connection. This is not my specialty...
Regards,
RE: When does a Piece of Pipe become a Vessel?
The code comes into play at 1 1/2 cu ft volume and 600# psi. Your vessel is getting close to falling under the code. As it on the line your jurisdictional authority or your insurance AI should sign off on it.
This makes you connection a little more critical, so I would let some with Code experience look at the design and installation.
RE: When does a Piece of Pipe become a Vessel?
RE: When does a Piece of Pipe become a Vessel?
RE: When does a Piece of Pipe become a Vessel?
Ultimately it matters most whether or not it looks like a vessel. Lots of 16" pipe is used to connect one vessel to another and it's not designed in accordance with ASME VIII Div 1- it's designed as pipe in accordance with ASME B31.3. An expansion in a line without additional connections (vents, drains, pad ports etc.) looks like pipe, so people won't give you grief if you design it as such. Put a flanged cover or legs on it and suddenly it looks like a vessel and the inspector may treat it as such.
Agree about the stress concentration at the 3/4-10" transition. Make sure it's well reinforced and you don't hang the 25# of material plus the weight of the "vessel" on the pipe by itself- and make sure that thermal expansion/contraction are considered if you support this "vessel" to the structure separately.
RE: When does a Piece of Pipe become a Vessel?