Will increasing 1/2 to 2" vapor line help recovery if pump port is only half inch

Since I often run fresh frozen and am now located in a humid area. I’m making a few upgrades to my quipment one of which is upgrading my molecular sieve (hereafter abbreviated as MS). As I change out my old 6 by 48 nonjacketed columns for jacketed ones I’m taking one of those and repurposing it as a MS; it will replace a 2" by 36. My collection vessel is a horizontally mounted tank ,you may recognize it as one from SlowGart, anyway I have a 2" manifold that rises from the tank to the MS, which was originally mounted directly on top of the manifold. I’m going to come from the top of the manifold with a 2 in Teflon lined stainless steel braided hose with Tri clamp fittings, to the bottom of the MS via a 6 to 2" conical reducer. My initial inclination was to come from the top of the MS’s cap through both half inch ports to the input of the MVP150 vapor pump. However, somewhere along the way those 2 lines would need to be teed together since there’s just one input to the pump that’s half inch JIC.

But then I said to myself, I said “hey Self why don’t you use some of the same 2” flex hose to come from the top of the MS with another one of the conical reducers you’ve got laying around." This would mean reducing down to the half inch JIC at the pump. I happen to already have a 2" cap to 1/2 JIC…parts are parts.

My thinking is that if one is going to increase the size of their system in any way, focusing on the vapor side and increasing diameters and (hopefully) flow is going to increase recovery time and efficiency. But my contrarian (and possibly inscure) self began to argue with me, pointing out that of the 7 letters in degrees I have there only one S and not a lot of science…ok none in thermodynamics, mechanical engineering, and such…and that what I know in these fields is self taught and I may have had a fool as an instructor.

The contrarian self’s arguments are that since I’m dropping down to that half inch connection which has a bit of half inch stainless steel tubing before goes directly into the pump, that this may be the limiting factor, and that I really don’t know and that relying on intuition is a mistake. Contrain Self said no downstream in increases in diameter and tube size will really help because the 1/2 in connection is the “weakest link in the chain”. However, I feel that since I’m pulling from the pump instead of only relying on thermal dynamics (that class I never took) to generate the force, that the large diameter run (which by the way would be a distance of about 12’) will help increase vapor flow and thus recovery.

So to settle this argument with myself I’m reaching out to you good folks, however I’m sure I’m right. I would like to thank everybody in advance and I would really like to take this moment to voice my appreciation for this forum and all the contributors who who make it great.


One way we can find out for sure fire it up chuck!!

If your going 2" why not go passive?:thinking:
Keep the pump to help the fill and finish


Going from your 1/2" pump outlet up to 2" will almost defeat the purpose of having a pump in the first place!

A pump works by putting energy into your fluid and this energy is conceptualized as “head” (don’t laugh, it’s real google it). This extra energy manifests as a.) Increased flow rate and/or b.) Increased pressure of varying degrees depending on how your system is designed for a lot of complicated fluid-mechanics reasons.

Pressure differential is the driving force pushing your liquid through your pipes. By putting a sudden expansion from 1/2" to 2" you’re going to lose a large portion of the increased pressure being imparted on your fluid by your pump. It’ll still pump, but you’ll likely slow your recovery to a crawl because the pump will struggle to actually move fluid through the much larger pipe. Fun fact, this is exactly why most pumps have a smaller diameter outlet compared to inlet, because it enhances the “pressure-differential creating” capabilities of the system.


We are just pumping vapor on the recovery side wanting to be sure our solvent stays dry! So the bigger mole sieve . The vapor is warm from jacketed collection vessel I feel like it recovers faster passive I just can’t pull all vapor from the material columns then I use the pump to pull into a vacuum before c/o material in columns.
I definitely do not know the actual science of it all I was HVAC tech before a grower recently converted to extraction. I am able to run 1/2" or 2" on and off of the repurposed material column that holds mole dessicant. The inlet on the MVP 150 is 1/2"
Therefore a restriction in the line, and I would have to build pressure in the m/s (head) and it would still pushed it through but am I moving any more solvent through my condenser.?

The short answer is: no.

If your only upgrade is increasing the collection gas outlet size then all you’re doing is changing the point at which restriction occurs.

If you think of your collection like a big pipe that gas is traveling through, then each successively smaller pipe size restricts the flow to an maximum level at that size.

Typically I find that people are nowhere close to the pipe restriction flow rate and that their heating and cooling are too slow.


This has always been my intuitive understanding.

When I was working for ~redacted fortune 500 oil and gas company~ I was confused why the senior engineers talked about sizing ports (inlets and outlets of vessels) as separate from the sizing of lines leading to and from those ports. The convention I observed was sizing lines based on flow regime (and therefore V/L composition) and then making the ports the same diameter as the lines. In a way, we didn’t really do a calculation to size ports to vessels - we calculated a pipe diameter and made the ports match that diameter. There were select instances where this was not the convention - where expansion or restriction at the port was part of the mechanism by which that particular unit operation functioned. For instance, throttling though an orifice to create some specific spray pattern or pressure drop.


@mcpikeig it is the pump inlet where the size increase would be made. I appreciate your input, so can you please address the dynamics of the flow considering that? Sorry if I was unclear in my description.


I could skip the vapor pump and go to the top of the tube and shell (only about 7 feet) but it also has a 1/2" port.

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Have you ever tried building a manifold/multiple 1/2" ports for the inlet and outlet on the MVP? Im in the process of testing that out now on my pump. My luck prob wont work :face_with_hand_over_mouth:

Ah shit my bad, I didn’t read your writeup close enough.

In that case, I don’t think your setup would be have a bad impact on the system, but I’m not entirely sure that it would help either, because at the end of the day you’re still going to be limited by your 1/2" port most likely. I will say that your 2" line with a 1/2" JIC will probably be preferable to your proposed dual 1/2" teed into one 1/2" setup.

This genuinely made me laugh out loud. I’m a sucker for self-deprecating humor. :joy: