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- เผยแพร่เมื่อ 5 ก.ย. 2024
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t is important to understand what vacuum is and
how it is measured in order to correctly apply it in
the hvacr industry. The dictionary defines vacuum
as “a space with nothing in it.” In the real world
there is no such place because molecules of
various elements are everywhere. It is the density of
these molecules within an enclosed space that we
measure as pressure.
For our purposes, a vacuum is a space where the density
of molecules is less than that of the earth’s atmosphere.
In other words, a space with a vacuum has less
than atmospheric pressure.
The inventor of the mercury barometer, Evangelista
Torricelli, first measured atmospheric pressure in 1643. A
long glass tube with one sealed end was filled and then
inverted in a bath of mercury.
Torricelli found that at sea level the earth’s atmosphere
exerts enough force to support a column of mercury 760
millimeters (29.921 inches) high at a temperature of 32°
F. The resulting empty space at the top of the tube was a
(nearly) total vacuum.
The unit of measurement for vacuum was named for
the inventor, and one atmosphere of pressure is now
referred to as 760 Torr, a measurement of absolute pressure.
If it were possible to achieve a vacuum of zero Torr,
we would have a perfect vacuum or zero absolute pressure.
When vacuum is measured in inches of mercury it
must be remembered that atmospheric pressure (gauge
pressure) is the starting point and that the gauge readings
are negative numbers. Thus, -29.921 inches Hg is a perfect
vacuum. It is not practical to measure a deep vacuum (low
absolute pressure) in inches of mercury because the units
are so large; it is measured in microns. There are 1,000
microns in a millimeter (Torr) and 25,400 microns in 1 inch
of mercury, so the use of this unit makes the measurement
of deep vacuum much more precise.
Applying vacuum to hvacr
Refrigeration and air-conditioning equipment must properly
be evacuated prior to charging to prevent unwanted
molecules - primarily water vapor - from damaging the
system. Moisture in a system can cause freeze-ups in capillary
tubing and expansion valves. The natural tendency
of moisture to cause corrosion is multiplied when it reacts
with certain refrigerants and forms hydrochloric or
hydrofluoric acid.
Refrigeration oils - especially the newer POE and
PAG oils - absorb moisture, and the combination forms
what is commonly referred to as sludge. The most practical
method for removing these molecules is to connect a
high vacuum pump to the system and reduce the absolute
internal pressure (vacuum) to less than 1,000 microns.
Reducing the pressure lowers the boiling point of water
vapor so it can be removed from the system at temperatures
below 32° F.
If a system is wet, reaching this pressure may take
quite some time and require several changes of pump oil
due to water vapor contamination. After evacuating, the
system must be isolated and the pressure must be maintained
at less than 2,000 microns for a reasonable length
of time. This ensures that there are no leaks or significant
contamination present. Either of these conditions
may result in premature system failure and a warranty
service call.
Understanding th
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You should have removed the little crappy springs from the vanes. They are not needed and they will break apart, the shrapnel will get caught between the rotor and housing and seize up the pump. This is what happened to me, but I was lucky enough to be there to turn the motor off before the stator burned up. I took mine apart and removed about 5 or 6 pieces of the spring that was left; including the piece that was jammed between the rotor and housing (put a nice indentation in the metal). I put it back together without the springs and it pulls the same as it did before. It turns out that the centrifugal force causes the vanes to hug the wall tightly, sealing the pump without needing the springs. If I bought one new, the first thing I'd do is remove those crappy springs that will most definitely fail.
Don't worry about the plastic vanes. They need to be plastic to avoid metal on metal. With those springs in there the pump will seize from those stupid springs long before the vanes wear out.
Hey thanks brother , thats a fantastic comment , and yes i totally agree . im gonna pin your comment
Your comment is really helpful. I had a problem with those springs once already and I replaced them. I would like to ask you few questions. If you have time to talk please write to my FB fanpage "Sword Addict"
I don't use Facebook. You can ask questions here though.
jjenson2006 Could you write to me (email: lukaszmalinowski1989@gmail.com) ? I would like to attach pictures
I'll assume your pump isn't working well. I sent you an email, but ask your questions here so others can benefit from it. You probably won't have to show me any pictures.
I bought my 2 stage 3CFM Harbor Freight vacuum pump more than 8 years ago and have had no issues with it. My micron gauge actually got down to 25 mircons to my surprise. It works better than my 7CFM Yellow Jacket pump.
Thanks for the input good to know
Ideally they should all work well but quality control is iffy
Good to know although 8 years ago it's likely not even the same unit
So much negativity toward cheap tools. Why people expect exceptional quality from cheap tools is just amazing..
That pump is a rotary vane and its build is almost exactly the same as any sort of rotary vane. Including many of the so called name brands. You can tell for sure if it is a 2 stage pump by the sets of vanes there are... Each set is another stage. Also anyone that has pulled those pumps apart can verify that the rusting is nornal, many brands do it. Also it always appears that the ports don't line up. That is also normal. They are a PITA to line everything back up with the screws all threading back properly but after taking them apart half a dozen times trust me, you will be a master at reassembling them. Also notice there are no gaskets between the plates... Make sure they have no material or dirt between them or your vac will suffer. And last, watch for the motor binding as you reassemble it or you will tear the pump up when restarting.
Another comment here confirming the vanes on commercial pumps are often also plastic - or to be more precise; a composite. To me it looks like G11 or G10, at least from what I have seen in Pfeiffer / Busch pumps.
I’ve had the opportunity to use and abuse quite a few vacuum pumps (including this one) in the HVAC field. I bought this one to get a job done on the road when my YJ Bullet smoked and I was too far from our supply houses. I was surprised how well it worked, being rated at 1/3hp and “only” 3cfm. It got the job done, sub 500 microns in just a bit longer than my other pumps. This exact pump is sold as both a Robinair and Uniweld model as well as a few others I believe. Most “economy” pumps now are virtually identical and you really need to invest a bit in a quality pump (JB Enterprise, Appion etc.) to get something that lasts.
Two stage means just that. The first stage feeds the second one which takes the vac down even more. Your pump is a dual single stage pump. Most folks that work with vac pumps in HVAC applications doen't care much as those pumps do well either single or dual staged. That pump you have there is a generic China pump. They sell them to many manufactures in the USA that put their brands on them. I've tested them and NO WAY they get down to 21 microns. Most are lucky to get to 2000. Which is fine for HVAC applications. The vanes are made of nylon which is preferred over steel. It doen't etch the chamber walls and given how these things work sealing efficiency is the name of the game. The vanes are nut subject to forces that require steel or aluminum. Research level pumps and those used for freeze drying are much better built than that thing you have there but use phenoloic or nylon vanes.
The ports you saw on the top of the chambers are the exit vents. The vanes grab a small pocket of air from the inlet and moves it around on an eccentric axis that squeezes it down until it vents at that port. The valve checks flow in that one direction. The baffle blocks the splash made by the exiting air . Better pumps have "oil mist recovery" stacks that gather the mist, condense it and return it to the sump.
"dual single stage pump', then can you explain true two stage pump
great input , i was very interested in the mist recovery statement , i seen that being a problem .
@@sureshlingabathina he did ?
I love how he steadily gets more and more irritated 🤣
just took apart my robinair 15500 because it was rusted shut after many years of misuse by yours truly. Looks essentially the same, with come additional perks, like a sponge filter at the exhaust and a small plastic cover ontop of discharge ports. And yes, both of my robinair pumps (5cfm and 8 cfm mist toot...)
I'm in the market for a quality vacuum pump for some hobbyist casting projects. I know next to nothing so want to do arm chair research. Your break down video was very fun to watch, and I learned quite a deal! Thank you for sharing :)
thanks , find an old ac or refrigerator and take the pump out , i have a video on those and they work great
Motor oil will vaporize under vacuum, which will prevent the pump from pulling a deep vacuum. You need to use vacuum pump oil, which is refined to the point where it will not vaporize under vacuum.
Thanks for the input , i was under the impression it would degas and then be ok
Motor oil is not used in vacuum pumps. They have oil specifically designed and formulated for low oil vapor pressure. If you are needing oil, pure mineral oil will do. NOT motor oil!
The motor would certainly be an induction motor, with the coil pack on the outside, directly connected to the aluminium shell. It does not need any air passing through it, and sealing it makes it more reliable.
this is dual single stage pump not two stage, as you said in two stage you should have only one discharge valve.
I figured out these pumps at work. I have to clean them on a regular basis because of the torture the poor little pumps are subjected to.
It take longer to get to sub 500 microns but it does it no problem. I seen commercial quality pumps with those plastic vanes. It actually preferred as it is wear resistance and seals better.
The vanes can be replaced far more easily than the housing. Not to mention, they’re extra long and lubed up. They should last exactly as long as anyone would expect a product like that to last.
Where can you buy these vanes? H-F sells only a complete pump when I looked a few months ago.
I work with vacuum pumps in my lab. Even high end rotory vane pumps such as the alcatel 2021 use plastic (phenolic resin or carbon fiber). So this is nothing unusual.
Its odd to not see an oil pump in a vacuum pump...
Also the construction is typical of 2 stage rotory vane pumps. The 2 stage pumps from alcatel dont look much different in the general design though much better made
Hey thanks for your input ,very valuable info
@@NOBOX7 i could probably talk days about vacuum technology, seeing as i do it semi professionally. though such pumps are only for roughing in my applications. I work mainly with high and ultra high vacuum, which uses completely different forms of pump, such as oil diffusion pumps (supersonic jets of oil vapor do the pumping) or turbomolecular pumps (basically giant turbines spinning at breakneck speed), and ion getter pumps which are basically just traps that allow gas to enter but not leave.
@@NOBOX7 also, i should probably add that the ultimate vacuum of a oil sealed rotatory vane pump is dependent on not just the seal integrity and design, but also the vapor pressure of the oil used. depending on the oil you can have orders of magnitude worse ultimate vacuum.
My $2K Leybold Trivac is dual stage and it also uses the plastic vanes. Unless you really don't have to pull hard vacuums it's a bad idea to use anything other than vacuum oil. Rule of thumb is that if you can smell the oil then that very smell is what will be gasing off from the oil and preventing lower vacuum from being reached.
Yeah i think i was out at the time . I never used it to pump down an ac like this . Ive seen that oil can be degassed so i degassed this oil hoping it would work but if i had Mineral oil i would of went with that
not plastic vanes, nylon which is wear resistant
The veins in my old 1/2 hip vacuum pump I beat to death for years were a plastic type material they held up well
great input thanks
is not odd sealing motor because some oil from pump can leak into motor if the main shaft seals are not good
The Veins are not plastic. they are glass fibre resin epoxy something something ... they offer lower coefficient of friction than a metal one...
I see , thanks for the input friend
The veins are obviously cheap plastic nylon. these are not industrial machines made to run thousands of hours.
The plastic/fiberglass vanes protect the more expensive parts.
13:19 I'm seeing potential for the first discharge port to only open under extremely weak vaccuum, allowing the pump to work like many 2-stage high flow/low pressure && low flow/high pressure hydraulic pumps. (I.E. if stage 1 compression builds enough pressure to discharge into out-flow, bypass stage 2)
Oops, just realized youtube dropped me into a years-old video again
you have to remember the money you have invested in the unit compared to a Robin Air. Tare down a Robin air and see what the difference is
The reason i speculate it wasn't to stage after opening it is because it had to discharge ports , why wouldnt one discharge go straight into the other vain pump ? , why isnt second stage smaller ? it would have to be to have any effect at all in that capacity .
Normally, industrial electric motors never have air openings; there are always sealed. The only windings are in the stator, and that's thermally coupled directly to the outer housing with the cooling fins. The rotor has no windings and doesn't need much cooling. With drilling holes, you only allow water to seep in. I would'nt do that.
The other thing is the oil: AFAIK vacuum pump oil is specially formulated to not gas out in vacuum. Engine oil can have components that can gas out (sometimes that's for fighting corrosion in engines that are sitting for a while). That might be giving the pump something to pump even when you block the vacuum inlet, and decrease the vacuum. It might get better after running the engine oil for a while. But even when you're going back on using real vacuum pump oil, you're right: I wouldn't use the cheap oil that came with the pump. Maybe only for running it in.
I agree , great input friend , i have degassed motor oil in the past so you are correct , i assumed the minor film in the pump wouldn't have much to offer but another Gentlemen mentioned this. I also didnt trust the oil they sent thats why i put royal purple full synthetic in it .
Better oil is always better!
They really need to make oil resistant cameras. That would make life better for all. Water submersible with light maintenance and oil safe and easily cleaned. I know we have the technology. We just need to speak up and create a demand. Making technical equipment user serviceable would make cleaning parts so much easier. Heck we all want the new stuff but we want out old stuff to keep working. If my cameras work and we’re easy to repair I’d keep them all. They aren’t big. Don’t take up too much space but obviously I’m still going to buy the new cool shit.
Which is the best material for replacement of vanes in Dual stage pump.
Mine is Roairvac 9, 9CMF.
I want to know the oil path inside the pump
The reason why the motor is totally enclosed is so that a seal is not needed between the motor and and the vacuum pump.
good point
I disagree. A totally enclosed motor is used where there is a potential of a fire or fire or a possible explosion risk. The fan will "ventilate" or diffuse external combustible vapors, keeping such vapors isolated from inside an electric motor. Otherwise, vapors could enter the electric motor, where there may be a potential source of an electric spark. Oil vapor, in the right air to vapor mix, under some rare circumstances, could possibly be explosive, or perhaps start a low grade "fire" or combustion process. This could be considered similar to what causes a bundle of oily rags to generate heat and eventually catch fire, or in rare circumstances, can cause jet fuel in a jet aircraft tank to somehow oxidize and begin a low grade combustion process during fueling. Hot gases will then emerge from the tank vents when fuel combines with oxygen in these tanks resulting from a low level "combustion" process. This has happened with no consequences in rare circumstances because this heat is vented to the atmosphere through the tank vents, unpressurized, at fairly low temperatures.
Thanks for doing this, my JB pump was delivered seized and caked with rust on the cartridge. I dont know anything about pumps but I'm going to try and fix.
Jb is easy to fix just pull the 6 bolts on the front and clean out the oil and rust in the cartridgeand put the black gold oil back in and check the tabs on the top of the cartridge make sure they are tight and not falling off those are reed valves
Cheers, I've successfully fixed the pump. Again, thanks to your video. Saved me $500 CAD.
GOOD VIDEO , I just bought a 2 stage pump to replace my 1 stage because I couldn't pull a decent vacuum on a ac install I am doing. The 2 stage replacement looks just like the 1 stage I am replacing and I wanted to take the pumps apart and do some investigating to make a comparison, but fortunately you save me the trouble and I am a lot more knowledgeable of what I am dealing with.
Well, I tear down my Mastercool 7.5 cfm double stage. The big chamber has plastic (composite) vanes and the second chamber has steel vanes also no spring( but it has place for one spring). I still think it is weird!
Is there a way to control the pressure on a vacuum pump
Yes , a needle bleed valve
i love the oil upgrade as it was most likely mineral oil or vegetable mix something shity
Does anyone know what is the hole in the middle at the bottom for? You can see it in this video at @3:21 right after he takes off the stand. Two holes for the allen screws holding the stand plate but my pumps leaks oil from the middle hole at the bottom. Any comment is appreciated.
plaqstic is good on vanes easy to replace to,,do not over think it man use it n abuse it ;]
Biggest issues are not the manufacturer as much as the seller not knowing what they are actually selling...
Did you drain the oil or did you run it dry?
I have a pump that looks just like this that I got at Napa, for an AC set up. how fare down in PSI can this pump down to. the one I have is a 1.8 CFM but Looks Identical to that one just a different name plate. The one I have is a Evercraft, but like I said looks Identical.
PSI is pressure, vacuum is measured in Inches of Mercury or In Hg
@@harrier331 Yes I didn't clarify vacuum is the lack of pressure. Technically one can measure VACUUM as negative pressure. But I've never seen it on a Guage or described as anything other than In of Mercury(Hg)
Do you have a wiring diagram of the electric motor or do you know where I can find it? Thanks
its just standart 1 phase AC motor with switch.
I really like this video and help me out a lot with mine
Ive had a Robinaire for 40 years and a Yellowjacket for almost 20 years and the Robinaire will out pull the Yellowjacket...!!
Thanks for the input , ill keep Robinaire in mind
the cooling is the fan blowing air forward thru the cooling ribs on the outside!! almost all motor is like this, it's what we call water resistant motor, what you are talking about is a pre ww2 motor with internal cooling . :-) here the stator is cooled from the outside.....
i had a Robinair vacuum pump that it last me 17 years of use very please with it.
That was when they were made well. New ones not near as good.
Can i use Royal Purple as a direct oil replacement?
Its best to use mineral oil but i used it and every thing has worked fine
@@NOBOX7 Thanks for your feedback..
So where is the damage observed, and why do you think running motor oil in a vacuum pump in a device engineered to use mineral oil is a good idea? proper case of "just because you can, doesn't mean you should" video.
I was out of mineral oil and i hoped that after running it for some time the gasses would be pulled out , i hoped any way . I did not notice a difference on the gauge but i get your point.
No damage i just wanted to see what was inside and turns out this is not a 2 stage pump its a dual single stage , if it was 2 stage the second pump would be smaller . Confirmed by people who know what they are talking about i might add this is not opinion . Dale stop being such an asshole for no reason , it does you no good brother
It is a 2 stage man. And always change the oil after evory use. I don't understanding why u dismantled that pump. I have one of them pumps and I know it's a 2 stage. All u needed to do was pulled the 4 scruws to cleen out the frount housing. Then replace the oil. U can find the manual on line with a good display of the pump breakdown.
I made $24 dollars showing people whats inside and will probably do well over 200 by the time its over , not sure why this video stirs up so many shitty comments . I state in the video its 2 stage , i was analyzing it and you decided to leave your 2 cents before watching the entire video. I dismantled the pump so i could pay for it .
@@NOBOX7 don't bother those smartasses. Wish you opened it up before me so I didn't have to spend the night doing it.
It is a 2 stage. The second reed is for the gas ballast. It's used to introduce air to avoid oil contamination with water
@@NOBOX7 It probably "stirs up shitty comments" because you it appears you did this video the for no reason other than to do an analysis of the pumps design and build quality (and apparently make money) yet it's clear you have no clue what your talking about when it comes to that subject resulting in the viewer wondering why they just wasted 33 minutes to make you $24.
two stage pumps connect in series this vacuum pump is parallel pump single stage, usually two stage will have two different size compressors bores.
i agree friend
Great video
Hey, is it still working?
yes , but dont use it much
First. You will not get 30Hg while on planet earth with that pump you will get 29.9Hg maximum. 30Hg is an absolute vacuum and for those who do not know what that means, it means there is no air. Think Outerspace. Second, you are talking bad about Harbor Freight. Every employee of that place is instructed to counter any negative remarks made towards their company on any social media site. Third. A two-stage design has two rotors and vanes. This means that the first stage generates a vacuum and the second stage cleans the system, leading to a deeper ultimate vacuum level. As a result, two-stage pumps can produce a deeper vacuum than single-stage pumps.
One Inch of mercury is equal to about 25,000 microns. If atmospheric pressure is 29.9 Inches of Hg (mercury), assuming 30 inches of Hg is an "absolute" vacuum, this is nowhere near an approximation of an actual absolute vacuum, which theoretically can never be attained. 29.9 Inches Hg is really not even close to an absolute vacuum, being more like 22,000 microns. Even outer space may not be an absolute vacuum, which on average, will contain a few molecules of gas, namely hydrogen, which theoretically is not an absolute vacuum. A level of about 500 to maybe 1000 microns of vacuum is appropriate to boil off the water from inside a refrigeration system in a reasonable amount of time. This pump advertises a vacuum of 25 microns. It is unlikely that this is achievable with most of these inexpensive HVAC vacuum pumps. A good digital vacuum gauge can measure necessary micron levels of vacuum, but it isn't particularly precise at these levels. Without pulling such a vacuum in a newly evacuated system, some moisture will likely remain. Eventually, remaining moisture will combine with common refrigerants to create acid that may damage the internals of a refrigeration system. It is good practice to always install a new filter dryer in any system that has been opened to the atmosphere, even when using a decent vacuum pump.
All that oil mist is from the oil being used as a seal.
It's two parallel stages. They allow the pump to lower the vacuum quickly, while not stalling at higher loads/vacuums.
Thanks for you input friend .
Yep i totally agree , at first i thought they cheated me as the device does not look like its 2 stage at first then i also came to the same conclusion . Its actually an ingenuous Design .
That mist is coming from the exiting compressed air being vented into the sump. The "oil seal" refers to the fact the entire pump is submerged in oil and relies on that oil to seal it.. That's why there were no gaskets on the machined end plates. The mist is easily recovered with a mist recovery attachment.
That mist is also the moisture from the air re condensing
Two stage design has two rotors and vanes, that pump is a 2 stage .
yeah i know but did not not see the dual discharge ???? it made it look like something was up . turns out during high flow it is only one stage .
@@NOBOX7 strange, I'm going to get me one of those dore refrigerators.
Right. It looks as if one stage discharges an initial high volume of air, followed by a second stage that actually draws down a micron level vacuum. The second stage feeds internally from the first stage. Both stages vent to atmospheric pressure in the pump housing. The video never showed if the vanes were parallel or if they were rotated relative to one another, which might account for an internal pressure differential between the first and second stage. That way, low pressure vacuum is fed to the second stage, which further reduces the vacuum.
The maximum vacuum is dependent on atmospheric pressure. The max vacuum at sea level is approx 14.7 psi or 29.9 inches of mercury (Hg) with a perfect vacuum. In reality you can get to 27 Hg you are doing pretty good. You can hook up as many vacuum pumps as you want you will never get more than atmospheric presser. If you need moor pressure you will need an autoclave to bust vacuum.
Great point
Not true. An electronic gauge set like a Fieldpiece 460 measures low vacuum in microns which is far lower than 28 inches of vacuum.
It is made by synthetic Regina
WTF? Of course it's a 2-stage!
Yeah i point that out in the video , it didnt look like it at the time and china often pulls one over on you so i was just discussing what i was seeing
I am watching after my vaccume pump teardown.
😂your 😅lost
LOL youtube would not allow my comment
Harbor fraud
Want to see fraud, look at craftsman tools now. Absolute joke.