Sorry, I was headed out the door, so limited my input to asking for your details.
As originator of the basic Terpenator, Lil Terp designs under consideration, who got those designs third party certified to ASME Section VIII, I have some insights to share whether you have require a licensed facility or not.
The first decision is whether the system must be certifiable or not, and if so who pays for the certification. It is typically cheaper of the manufacturer supplies those certifications, than if you pay for them yourself.
I got the basic Mk III through Mk V ASME certs done relatively cheap bartering in the good ole boy network with a local ME PE, but it cost me $12K to get the Mk IVC and VC third party PE certified in five states to meet ASME, NFPA NEC, and IBC requirements for an installation.
If certifications are required, then ask for them up front, because it is way cheaper of supplied by the manufacturer.
If you have to determine from just the components themselves, ASME Section 8 was developed for a reason and divides piping and fitting 6” and below as pressure piping, and above as pressure vessels when they will operate above one atmosphere (14.7 psi) pressure.
Requirements for LPG pressure piping is 350 psi, and for pressure vessels, 3X the highest pressure the system may see, which ostensible includes system cooling failure.
70:30 is a common mix and a good example. Look at the attached chart to determine what pressure ranges you might be operating in:
See chart below.
The following is the pressure rating of the different sanitary clamps, which are the limiting factor in most systems: Rather than just look at the package offered, may I suggest that you look at the components used?
If you are building and testing our own, when I worked at an ASME fabricating shop, we hydrotested our products to certify them and fully flooded them and brought the pressure up using a Sprague hydrostatic pump, with no compress gases involved.
If we are operating a certified system that is at least 3X stronger than the pressure we are testing it to, and are just looking for leaks, we don’t have to hydrostatically test it, we can simply use air. If you doubt its capabilities, hydrostatically test it first and then with air so you can see the bubbles.
That doesn’t mean we stand in harms way when doing so. We tested our units in a plastic barrel full of water, but only went to 100 psi looking for leaks. We also stood beside it, with it tilted away from us, not over it.
As noted, compressed air rebounds like a big spring when released and at 100 psi is compressed air looking to occupy about 6.7 times more space. In pressure testing a sanitary assembly, the clamps are the weak link, so failures will launch the components vertically from a barrel.
As far as features, above the basic Terpenator/Lil Terp design, there are a couple of schools of thought on chilling the column, chilling the injected LPG, or chilling them both.
The column are typically chilled with a dry ice alcohol slurry in a column jacket, and the injected LPG is can be cooled in the storage tank and dropped further using a coil in a dry ice bath or LN2 counter flow heat exchanger between the storage tank and the column.
I prefer both, but only chilled the columns to -18C/0F before hand and chilled the injected LPG using either dry ice or LN2.
ASME also requires a PRV valve set at 130% of test pressure, also a good idea.
Some evolution since the original design. We discovered that it was handy to be able to watch what was going on in the recovery tank, so we added view ports. Check the pressure ratings of the view ports offered, as they should be at least 350 psi to meet ASME.
We also used modified flat lids on the original design, which attempts to become hemispherical under pressure, lifting the edges off the gaskets, so moved to lids that start out hemispherical and deform less, so are less prone to leaks.
I realize this post is a little like taking a sip from a firehose, but feel fee to ask questions, as well as submit what you have decided on for discussion!
