vac max on a zero tank

[poolguy]

hi i am looking for info on how much vacuum a 325 zero tank will take. i want to mount it at the lowest point in the woods where all lines meet and use it like a releaser. then my hopes are to put a submersable well pump on a float switch to pump sap to the sugar house. the tank doesnt say not to vacuum so i think it will work. also does any one know if a gast model 2080-p01 vacuum pump is acceptable for my application? i have 1100 taps now but want to enlarge to 3000 in the next couple years. any advice would be greatly appreciated. thanx dave

[Haynes Forest Products]

Tell us more. First look on the end of the tank that doesnt have the bottom drain. Look at the very top in very light letters for the word NON VACUUM its at the top if you dont find it GOOD. Now tell us how your going to pump the sap out of the tank? Will it be while the tank is under vacuum? Will you be shutting the vacuum off releasing the vac from the tank and pumping? How tight are your woods? Lastly I didnt find that pump on Google so tell us more about it..............Skip the color I dont care. HP. CFMs, HG rating, vane or piston.....if its a small duel piston medical type...............NO

[poolguy]

here is the link to the vac pump http://cgi.ebay.com/Gast-Vacuum-Pump-2HP-3-phase-15PSI-2080-P101-/400163199012?pt=BI_Pumps&hash=item5d2b95d824 i think its a vane style but not sure. as far as the tank i have looked it over and cant seem to find anywhere that is says "do not vacuum". it also has the heavy dished ends and a hatch rather than the easy to lift lids for cleaning. the farmer also said they used it as a vacuum tank so i THINK im ok there. im hoping to put the the submersible well pump inside the tank, which is 325 gallons, and have the pump set on a float to kick on when there is 300 gallons or so in it and then pump the entire amount up to the tank at the shack. im hoping to do this while yet under vacuum and just put a check valve on the pump discharge. as far as how "tight" the woods is,im presuming your talking about the tubing leaks and those are allways a battle with those tree rats runnning all over. we have gotten pretty good at finding vac leaks as we so far have allways used a 3 diphram pump powered by a 5 hp honda and have allways gotten 17 inches of vac.......but to do so you need EVERY LITTLE vac leak fixed as it doesnt have alot of cfm. nice thing was that it also pumped the sap to the tank at the shack at the same time....the drawback was you had to go out at 1 oclock or so in the morning and winterize it and unhook the suction pipe and let it gravity flow into a holding tank. my hopes are with the new pump (now that we have electric:D) can be put on a temp switch to shut off. i would love any input on what the majic number is to have the pump shut off....im thinking around 25 degrees? im sure there is no "PERFECT RECIPE" to any type system but we have used ALOT of advice and ideas from this forum that have saved us bunches of time and work and im sure you guys can let me know if im heading in the wrong direction here. thanks again for such a great site. dave

[Haynes Forest Products]

Numbers look good on the pump. Do you think the pump will be able to overcome the vacuum? As far as putting a thermostat on the vacuum pump what will it measure ambiant temps, mainline temps. I like timers better start it at 6 AM and staop at 10.00 at night. I have a Farmer friend that would turn on his pump when the puddles thawed after a few days using my vacuum beast and releaser he found out how much sap was waiting in the lines to be sucked out by 6am.

[Teuchtar]

Poolguy
You can download product information for all the current Gast pumps from their site:
http://www.gastmfg.com/pdf/rotvane/rotaryvane_catalog.pdf
Gast pumps are bulletproof, no worries about freezing like liquid ring pumps. And used ones are cheap, but sometimes defective and obsolete on eBay.
That 2080 pump might be ok for your tapcount. If you can seal the leakage to 20"Hg you'll be able to pull 6 cfm through the pump. Maybe a bit low for 1100 taps, and I don't think is sized to grow with you.
Looks like from the Cat number "P101" that your pump is set up as a compressor. I believe the core machine is same as vacuum pump, you just need to get rid of the intake filter, and change the pressure relief valve to a vacuum relief.
I notice the eBay ad says the motor are three phase. Is your power supply at the farm 3-phase ? If not, you'll need to change the motor. (coupla hundred for a farm duty TEFC Motor). Given the motor is 1/2 the shipping weight, maybe the seller will strip the motor off before shipping if its unuseable to you.
I have a 600 gal Zero vacuum tank. I daren't run it above 20" vacuum. There's been some threads in the past year or two from Zero owners who limit vac to 18 or 20. Above that they collapse violently. Zero tanks are dependable, easy to clean, no sticky releaser !

[poolguy]

hfp, not sure what you mean by "will it overcome the vacuum". and i was thinking of the temp switch to measure ambient air....but have also thought of drilling a hole in a non spieces tree near the pump and putting the temp sensor inside the tree and see what temps the maples start running and set it accordingly. has anyone tried that? also im wondering if i will have overheating problems with the pump in question and have to build a flood oiler with cooler like i see some doing here. you say you start your pump at 6am? wow we never started the diaphram pump untill 9 or 10 when the lines thawed but that style pump would also not make vacuum untill it was pumping SOME liquid. i hear some saying here that they leave them run nonstop? i cant believe that would be cost effective? teuchter thanks for the link on specs for the pump! i was told once that 10 cfm per 1000 taps was a good formula to work by......so wouldnt this mean it would work for 2500 taps being its a 25 cfm pump? and yes ive read some posts on zero tanks and i see some running up to 24 inches on them but thought that was pushing it...my hopes are for 22 to 24 inches. and yes the pump is set up currently as 3 phase but the guy says he will put a single phase on it for me and hes local as well as a customer of mine so no shipping either! he aslo said these were taken of from a working application (company went out of bussiness) so im pretty sure they are ready to go and hes gonna let me have one for 3 hundred bucks! thanks again for the replys and the help. hope to hear more. dave

[Haynes Forest Products]

Poolguy Trying to pump out of a vessel thats under vacuum is not all that easy. Pumps Pump by creating a pressure differential. When pumping from a vacuum tank to high pressure out side the tank the law of physics take over and the liquid wants to move from HIGH pressure to LOW pressure. Now putting a pump in a tank 1/2 full of sap under vacuum and having the pump run within the confines of the tank is one thing BUT now try and pump the liquid out of the tank to HIGH pressure is a whole differant thing. A pump in a closed loop pumping HIGH pressure liquids or gases doesnt know its pumping HIGH pressure because its in a closed loop. Just like in a steam or hot water heating system the pump is in a closed loop. Now cut a hole in the pipe and you will have pressure differantial and all heck breaks loose.......SORRY I can get carried away;)

[maple flats]

I am also setting up a Zero tank. I find no label where you indicated for non vacuum. I am thinking for this year I will do18-19". How do you get the sap out? Must I drop the vac to pump? Is there a realistic way to get sap while maintaining vac without a second vac reserve vessil?

[Haynes Forest Products]

Maple Flats When I used a tank as a releaser I learned alot fast. I made up a real cool looking manifold that had a quick connect with valve for pumping out the tank and I had all the mainlines into the same manifold. Problem was the vacuum had to transfer thru the sap in the tank out to the sugar bush:mad: Didnt work for CRAP. Then I went to pump out the tank didnt work with a centrifical type pump. DIDNT WORK. So I put the mainlines into the top 1" agitator hole. Sap ran in like crazy:) Then when I pumped the tank out I had to release the vacuum on the tank lid to drain worked good:) BUT I didnt realize that was shooting the sap back in the lines A NO NO:cry:
If I was to do it again I would put vacuum resevoirs on each mainline coming in with a check valve between it and the tank. They would be 6" X10' PVC standing on end so the vacuum would help store the incoming sap during the pump cycle. They would help reduce sap surge back into the bush. I would use the CV taps. I would also pump the tank out ASAP like a NASCAR pit crew and get it back up to high vacuum.

I know guys that shut the vac off and tow the tank back to the shack and fill the bulk tank They lollygag around doing it that same old way they always did but they are seeing the errors of their ways. After using my pump and releaser They say it saved there season last year.

[maple flats]

Thanks HFP. I'll try your second idea. I'm sure as I get into this, I'll have lots more questions. I have to come up with a safe way to move the Zero tank and set it down into an old cellar on the property I tap. This cellar is well drained, no water pools, the whole hill is gravel. If I can lower it into this cellar I can eliminate a 5-6' ladder and the tank will be out of sight of the road which should make it more secure. This cellar is only about 40' from the road and hidden by lots of brush. I can't start doing the work until after hunting season because the landowner asks me to wait. Then it is go time and a mad rush to be ready. Lots of limbs down, need to add the dry lines and manifolds as well as set up the vac with a gas engine and do the plumbing. Also need to add about 150 more taps in a section needing a sap ladder or 2.

[poolguy]

HPF i thought you were talking about the vac pump overcoming the vacuum ....my bad. well...thats why im here! im not sure if the well pump will overcome the vac. the well guy im buying it from thinks it will as it is a 3 stage pump designed for very deep wells. he also has a bulk head fitting to mount in the top of the tank that will compress around a 1 inch pipe and electric cord when tightened to seal them. i can pick up the pump and fitting for 70 bucks, the 325 gallon vac tank for 400 bucks....pretty cheap considering it becomes my releaser, storage tank sap transfer pump all in one. if i were to go with a releaser i would have to pump UP into a tank as well and if i understand this correctly the electric releasers use a deep well centrifugal pump to transfer the sap to the holding tank all while under vacuum.. is this correct? i seen a set up like this at a supplier and the pump had a check valve on the suction and discharge so as to not loose the prime or the vacuum on the releaser. i await any input on what you guys think. dave

[Beweller]

The problem pumping out of a vacuum tank is not so much discharging against the atmospheric pressure as it is getting the sap into the pump. Water pumps normally have a specified maximum suction head, which may be anything from 10 ft of water to something in the 20s. That tells you the maximum vacuum you can expect to pump from. So, in evaluating a pump to pump sap out of your separator you should look at the specified maximum suction (draft) head (net positive suction pressure).

There are ways to design to achieve high suction heads but these designs are typically found only on large (expensive) pumps. A common technique is to design in an axial flow pump at the inlet, known as an "inducer". Pumps that run slowly and smoothly, with minimal smooth turns and inlet section changes, tend to have better suction characteristics. It is easy to imagine a positive displacement pump, running slowly with a large displacement, that could operate with suction pressures very little above the vapor pressure of water.

If you have/can find a pump that will produce even a small pressure rise with the inlet pressure at your vacuum condition, it can serve as an inducer to feed a second pump that provides most of the pressure rise needed to overcome the atmosphere.

I have wondered if a conventional water pump could be driven slowly to improve its suction characteristics. That would reduce the output pressure (proportional to the square of speed) and discharge (proportional to speed)
but would reduce the tendency of the pump to cavitate and vapor bind. The loss of output pressure, if limiting, could be overcome by a second pump running at normal speeds, the first slow pump acting as an "inducer" for the second pump, and the low discharge by using an "oversize" pump.

Has any one tried? Want to try?

[Beweller]

Tank collapse? It the tank runs at 20 in and collapses at 24 in (Teucher) the running safety factor is only 1.2. Even rocket designers use larger safety factors! (I am reminded of a real case many years ago. Someone asked very well educated man if it would be safe to use a 5 gallon glass water bottle as a vacuum reservoir. After considerable calculation,he announced that it would be OK with a mechanical pump, but should not be used with a diffusion pump(!). (Good education, not much sense.) With an aerospace safety factor of 1.5, your 20 in vacuum tank should be rated for a pressure differential (outside to inside) of 14.7 psi. On this basis, the tank is unsafe operating at 20 in Hg.

When you think that resistance to collapse can be destroyed by a relatively minor dent, or by the local loss of wall through corrosion, or collapsed by a better performance by the vacuum pump, or by reduced leaking in the bush, ...

I would want my tank to have a collapse pressure differential of at LEAST a full atmosphere (including safety factor), and would feel better it it were one and a half atmospheres.

[Teuchtar]

My recollection of the several discussions is that zero tanks were intended for use with dairy vacs running in the 15-18" range. We would all agree that Liquid ring pumps are capable of practically full vacuum. Who knows what design margins the tank designers chose for 18", and its unlikely we'll ever find out now. I've searched the net, and haven't found any certs or CE's on those designs.
I can share pictures of milk transport tanks collapsed by the transfer pump because the operator failed to open the vent.
I can also show you more pictures of railroad tanks collapsed by steam condensation after cleaning. Any tank can be made resistant to vacuum, but the cost will climb in direct proportion to the margin.
My advice remains, don't go above 20", and put a good big vacuum relief (similar to the CDL design ) to protect the pump when the mainlines freeze up and vacuum climbs.

[poolguy]

getting complicated here isnt it lol. my question still remains as to how the electric releasers do it. leader quotes that being the vessel is under vacuum you have to oversize the discharge pump to compensate. and im quite sure they use a centrifugal pump to do this. im hoping to avoid that so i dont have to winterize the pump every night or build a heated building around it.

[ToadHill]

Electric releasers do it by placing vacuum on both sides of the discharge pump. There is a suction line from the releaser to the suction side of the pump and then there is a small line from the discharge pipe back into the releaser. This way you are pulling vacuum on the suction side of the pump and the discharge side. You will need a check valve in the discharge line to prevent the vacuum from pulling sap back through the discharge pump when it isn't pumping. With vacuum on both sides the pump is essentially operating in a vacuum and doesn't have to overcome it. Is that clear as mud?

Randy

[Haynes Forest Products]

Poolguy Now if you wanted a pump that could over come the vacuum of a tank full of sap under vacuum you could use a gear pump. You do stand the chance of collapsing the tank into a crumpled up mass of scrap. With any pump you use if your tank is getting past 1/4 full and you pump all the sap out while its still under vacuum you will increase the vacuum level (HGs) past the recommended level and you could implode it that way also. HAVE A NICE DAY:)

[treefinder]

i bought a zero tank last year and not looking at it good enough when i bought it , that it says non vacuum tank on the end but it looks like somone at the milk plant where it was from labeled it for there own use. so anyways i put vacuum to it anyway.. seeing thats what i bought it for and i run 18"-22" and it hasn't sucked in yet. i bought it so i could eliminate buying a releaser and a tank. i would not try pumping the tank out with vacuum on it , your just asking for trouble your not going to lose that much sap in the few minutes it takes to suck out the tank. i shut mine off and take off the cover and suck out with a hose with a 3/4" wand on the end with a ball valve

[Beweller]

One way to pump out of a tank under vacuum is to place the pump at the bottom of a barometric leg. At the worst, you would need to dig a hole.

[poolguy]

HFP im not worried about imploading due to pumping the sap out, as a vacuum relief HAS to be in the plan even without trying to pump sap. at 22 gallons a minute the relief valve only needs to be capable of 3 cfm......and i doubt ill get anywhere close to 22 gpm while pumping agianst 22 inches of vac and 50ft of lift to the tank at the shack. ive thought about the gear pump a well as others but i want to stay with a submersable IF POSSABLE to avoid having to winterize along with the fact its NOT a positive displacement pump. my existing diaphram pump has blown the discharge line to the shack a couple times when it was still a little slushy where as a submersable should cavitate and only allow what will pass by the slush untill the warmer sap thaws it. TREEFINDER thats very encourging (22inches on a non vac tank) i should have NO problems then lol....i hope. BEWELLER yes that im sure that would work.....hmmm how deep would it have to be to outweigh 22 inches of vac.....and doesnt that mean that as long as the pump will lift it higher than the the depth of the barametric leg i should be ok?