Design, Fab, & Inspection Requirements for non-Code "Vessel"? 1

[KernOily]

Hi guys. I'd like to hear opinions/experience on design and fabrication requirements for a non-ASME Code "vessel".

The "vessel" in question is a discharge separator for a liquid-ring vacuum pump. Operates at atmosphere and ambient temperature, 304SS construction, RFSO flanges, no PSV, no instruments or controls, 6' OAL x 22" diameter, flat bottom, 2:1 top head. Anchorage is by feet/brackets welded to the shell and bottom, and bolted to the concrete foundation. Foundation and anchorage will be engineered and permitted (it's located in the People's Republik of Kalifornia).

I am struggling with how to communicate requirements to the vendor. Beyond telling him, say, 15 psig MAWP, hydrotest to 1.5 x MAWP, RT 10% of all pressure boundary welds, clean and prep for shipment, provide seismic calcs for the supports, what else could I say? I am concerned about taking his offerring "off-the-shelf". My common sense tells me it's OK to do that since the risk to personnel is very low should there be some type of failure, e.g. a weld seam opens.

Thanks guys! Pete

 

[LittleInch]

If this is an atmospheric vessel with no pressure relief system, why are you listing it with a MAWP of 15 psi? As soon as you give it a pressure rating, you really should be providing the vessel with a means to prevent that pressure from exceeding your design / MAWP pressure. If it's never ever going to see any pressure just put down "atmospheric" as the pressure. Will it ever see negative pressure? If not then don't list it.

It sounds to me more like this is just a tank, so I would look up the requirements for something like an API 650 tank for atmospheric or 620 if you really want to give it a pressure rating.

Normally you just fill it with water to max liquid level and if I doesn't leak or fall apart then it's good to go. If you add extra requirements then you're paying for something you're not going to use.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JStephen]

You COULD spec this as an API-650 tank. That would give you 3/16" minimum shell, bottom, and roof thickness. The main drawback is that a lot of potential (vessel) vendors might not be that familiar with API-650. Even at that, it might be better if the specifying engineer did the design work as well.
I would omit the radiography in this case.
If you could adapt your design to some ready-made equipment, it might simplify things for all concerned:

https://www.mcmaster.com/#stainless-steel-tanks/=1bnkp7e

 

[r6155]

Design, fabrication and inspection code: NONE
100% filled with water in vertical position to check leaks. Quality of water must be under control.
All welds in shell and nozzles: full penetration.
Minimum thickness of shell and heads : 0,5 mm (check for seismic).
Supports: 3 pipe legs

Regards
r6155

 

[KernOily]

Guys thanks for the great comments. Much appreciated!