The search for a proper recovery pump..

[A6 Grower]

Isnt That BHOgart pump just a rebranded KNF diaphragm pump?
http://www.knfusa.com/products/oem-...vhrQ3gUqatvisFUoGsaIxWXz4W3wh2ihvkaAmMq8P8HAQ
Thier dual diaphragm pumps look nice! With most of us using after coolers now wouldn't the 60PSI limit be more than enough?

There seems to be a TON of diaphragm pumps available, lots with custom features like PTFE and SS parts. Some even meet FDA regulations. Im even finding some bigger ones with max pressures of 100psi. I rarely seen pressure about 60psi with my appions and aftercooler

 

[Gray Wolf]

Isnt That BHOgart pump just a rebranded KNF diaphragm pump?
http://www.knfusa.com/products/oem-...vhrQ3gUqatvisFUoGsaIxWXz4W3wh2ihvkaAmMq8P8HAQ
Thier dual diaphragm pumps look nice! With most of us using after coolers now wouldn't the 60PSI limit be more than enough?

There seems to be a TON of diaphragm pumps available, lots with custom features like PTFE and SS parts. Some even meet FDA regulations. Im even finding some bigger ones with max pressures of 100psi. I rarely seen pressure about 60psi with my appions and aftercooler

They also have to pull a vacuum. They won't put out 14.7 psi vacuum and still put out 60 psi.

 

[Gray Wolf]

A little bit of context for that calculation:


Correct math, but only valid at atmospheric pressure with no compression ratio. I'm guessing the 60LPM is basic displacement. For comparison the Gast DAA is 108LPM and (from memory) the G5 is almost 28LPM.

A diaphragm pump's compression ratio is going to change with output pressure increase as the diaphragm is going to flex. This will cause the output to degrade faster than a piston pump of equivalent displacement.

Gast gives a graph of pressure to output: http://www.gastmfg.com/support_documents/RTD795rA.pdf

The recovery rate will also depend on the condenser flow and efficiency. A dual diaphragm pump can be run in series to increase the compression ratio.

Actual recovery rate isn't going to be even a fraction of .357lb/min. and it'll vary greatly depending on tank pressure (temp.) and the aftercooler design.

When I first suggested the Gast I meant for it to be used as a booster pump for a piston type recovery pump. To use a diaphragm pump standalone will need a lot more hardware than just a pump.
It will need a very efficient condenser, an unloader for starting and an overpressure switch.

The pump shown on the last page was from KNF: http://www.knf.com/products/process...-pumps-and-compressors/explosion-proof-pumps/

Very nice hardware, but it needs some extra bits to function in a CLS extractor...

RB

True, that is free air, which goes down as the back pressure goes up.

Also true that a diaphragm pump isn't suitable for the application by its lonesome. We made it work by using an interim tank, and a conventional recovery pump for the second stage.

The primary advantage was speed and never having to run the oil less pump dry.

 

[A6 Grower]

They also have to pull a vacuum. They won't put out 14.7 psi vacuum and still put out 60 psi.

What if i dont need a vacuum pulled. I usually just recover to 0 to 5psi and pour out a liquid. With aftercoolers and an oversized storage tank(maybe have it in ice water also) I should be able to keep the PSI down around 40 or less? I like the liquid pour as it saves A LOT of time in a full days work. Vacuuming down and doing the cotton candy method cuts one or two runs from my day because of the extra time recovering down to -15 and then full vac for 15 minutes. And i have a nice outside covered loading dock to do my pours at so i figure i might as well use it, Now that winter time is almost over, humidity was messing with my pour.

 

[Rickys bong]

What if i dont need a vacuum pulled. I usually just recover to 0 to 5psi and pour out a liquid.

It boils down to compression ratio. If you have some positive inlet pressure and limit the outlet to 60 psi a diaphragm pump should work. You might need to unload the outlet by putting in a three way valve on the outlet port. An unloader circuit that routes the outlet back to the inlet so it starts without load and once it's running flip the valve so the outlet goes to your aftercooler/ tank. I'm too lazy to draw a diagram...

A rough calculation for the Appion gives somewhere over 60:1 compression ratio. I'm doing this from memory but the piston to head gap at top dead center is ~0.010" and 0.625" stroke.
That's why it will produce high output pressure and still pull good vacuum. You might get 5:1 or 8:1 with a diaphragm pump.

With a two chamber unit you can run them in series for better vacuum and higher output pressure. It would be easy to valve them to run parallel or series and flip between the two.

You mentioned the dual diaphragm pumps from KNF which might be confused with dual chamber pumps. (two pumping sections like the Gast DAA. Those would be ideal but their max pressure is 45psi.)

"A second diaphragm is located underneath the working diaphragm. The safety diaphragm has a significantly longer service life than the working diaphragm, thus ensuring that no gas can escape into the environment even if the working diaphragm ruptures." (from the KNF site)

The pump on the previous page looks to be single diaphragm and their "dual diaphragm" will be two pumping chambers for twice the flow. It looks like a single diaphragm per chamber which has a very nasty failure mode.
If the diaphragm fails you have a big leak.
Cue the "It was custom designed just for us!" bullshit in 3...2...1...

Running diaphragm pumps near their rated outlet pressure limits the life of the flexing diaphragm.

GW, didn't mean to correct you but some might take the .357 lbs/min as gospel and declare that one a winner...

There are a ton of diaphragm pumps on the market from cheap lab vacuum pumps to ones with pressurized oil activating the diaphragm. These will achieve high output pressure but need high inlet pressure as well.

Peace... RB

 

[Gray Wolf]

GW, didn't mean to correct you but some might take the .357 lbs/min as gospel and declare that one a winner...

Not a problem and why I post my math.

Also a valid point, that a pumps actual performance will be less than its free air capacity, because as you note, the pressure in the pot and the storage tank have direct effect.

When I purchased pumps in most applications, they were supplied with a pressure/flow curve, but in the absence I did rule of thumb flow comparisons using free air flow and maximum head.

That gets it in the ball park on similar designs, but is less meaningful as designs vary, along with their flow/head curves.

 

[Permacultuure]

The not so stainless trs21.....as RB pointed out the spark proof really doesn't mean squat except that the outlet is hard wired. It looks to be mostly aluminum and some steel. Did not have the stainless flare fittings like it does on the johnstone website.

 

[GratefulOne]

Is that really a TRS? The wiring does not look very spark proof. Does everyone else have stainless fittings like the pictures on Johnstone?

 

[Permacultuure]

If you look close the sticker even says tr21 but it is actually the trs21. They are in such A High demand they are making them to order, obviously they are using parts from tr21, such as warning stickers and manuals, and apparently flare fittings. At least they recover quick but definitely nothing special and I'm not sure it's worth the extra coin...

 

[GratefulOne]

So what is different from the base model? The wiring does not looking spark proof. Did they just pot the wires where they enter the motor? Is this the only change?

 

[Permacultuure]

I'm not really sure, it's hardwired....but I think were being taking advantage of. I didn't want to dig any deeper into the Pistons heads but it's all the same other than the plastic housing, hard wired plug......please someone correct me if I'm wrong

 

[Rickys bong]

Perma, can you measure the bore and stroke of the pistons plz? How much extra cost is the explosion proof model?

Thanks, RB

 

[SkyHighLer]

Comes to mind to check that every termination is solid, either soldered, directly crimped like a butt splice or to an under screw crimp term, or if a push-on quick connect, it should be on firmly, there should be no wiggle. Does the switch have mechanical contacts? Can butane laden air reach the contacts? Any internal fuses or overheat cutouts that may go berserk?

Nice pics Perm.

 

[Rotel]

I doubt it's fully constructed of explosion proof electrical components, but I could be wrong.

 

[Permacultuure]

Perma, can you measure the bore and stroke of the pistons plz? How much extra cost is the explosion proof model?

Thanks, RB

After a couple days running I'll peel one apart again. These cost 750 wholesale but after shipping ect they were about 1k a piece. I'm less than impressed, they do have a fancy new switch on the back which adds to its spark proof ness.

 

[GratefulOne]

I think they have picked crafty wording with "spark proof". The industry terms I have seen in standards are "Hazardous Location" and "Explosion Proof". I have seen the wording "spark proof" used in blower standards in regards to the blades rubbing the housing. I have not seen the term used in an official way with a defined meaning.

 

[Sunfire]

Lol maybe they mean the same thing, like the Pistons won't spark on the cyclinders. I've read that appions can do this and cause an explosion when they leak but everyone I know that's rebuilt them said they never saw any scoring or abrasions.

Gw has talked before about nema7 rating, I thing that's what it is. If it doesn't have that, it prolly doesn't mean much.

I'm waiting for the cmepol to go through a few rounds of design improvements or for more test conclusions of the high pressure diaphragm pumps but the bit about the diaphragm possibly rupturing is scary.

 

[stonedm]

So GW I read earlier that you have run the cmep recovery pump. Did you have a problem with it contaminating your gas with oil?If so how to you remedy the situation? I was thinking of put a catch all filter on the input and output of the recovery pump but have been told that a filter on the output side would cause the pump to burn out? Any info would be greatly appreciated.

 

[Sunfire]

How would a filter on the out put side burn out your pump??? Look at the molecular sieve thread, gw posted a great design that would be perfect you. It's a water trap molecular sieve combo.

A filter experiencing positive pressure can cause the gas to condensate into liquid so proper routing of the lines should be payed attention to.

 

[GratefulOne]

Lol maybe they mean the same thing, like the Pistons won't spark on the cyclinders. I've read that appions can do this and cause an explosion when they leak but everyone I know that's rebuilt them said they never saw any scoring or abrasions.

Gw has talked before about nema7 rating, I thing that's what it is. If it doesn't have that, it prolly doesn't mean much.

I'm waiting for the cmepol to go through a few rounds of design improvements or for more test conclusions of the high pressure diaphragm pumps but the bit about the diaphragm possibly rupturing is scary.

NEMA ratings are standards for electrical enclosures. NEMA 7, 8, 9 and 10 are all different types of "explosion proof" enclosures. A properly rated NEMA enclosure/motor housing makes NFPA standards easy but they cost.

You can save money sometimes by using "hazardous location" equipment - for example most blowers in spray booths. The blades and housing of the blower are spark proof. The motor is located outside the area of flammable vapors. A belt and pulley are used to transfer power to the blades. Hazardous location installs are not always possible but when you can it saves a bunch of money.