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LET THIS SIGNAL THE END OF THE FRIDGE PUMP QUESTIONS!

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Mossydie - 5-2-2011 at 16:56

I really can't thank you enough for your post peach, it's fantastic.
I have a very basic knowledge of electronics (AS physics, building a usb throttle quadrant, wiring plugs) but the stuff about capacitors and those wiring diagrams sort of scared me. I'll read over what you've written a couple of times and then try starting the pump up.

I've tested the no.1 push fit fitting with my multimeter - there's no connection at all between it and the L plate. The no.2 slot doesn't appear to have any metal inside it at all. Perhaps they're for some sort of monitoring device?

I'll definitely use an RCB and a 3A fuse - thanks for the advice

Rather than crimping the service pipe, how about attaching an adjustable air bleed to it?


peach - 5-2-2011 at 17:27

I remember being in AS physics and someone had discovered they could generate sparks by shorting the Unilab (orange and brown) bench supplies out. The teacher quietly walked over to point out that, whilst it was 12Vdc, the supply was plugged into the mains.

Another funny one, although in the GCSEs, was watching one of the guys who was about to leave igniting the gas taps. Again, he didn't realise the teacher was stood literally a foot behind him, facing him.

With regards to testing the 1 and 2 fittings, I suspect they are connected to something somewhere on the pump it's self, as there'd be little point to them otherwise. Touch one probe against it and then go over every other metal contact on the pump and see if there's a zero or low resistance reading for any of it, including the casing (you'll need to touch it against the tubing to get a good contact for that).

Before you ever use a multimeter, set it to resistance and try touching the problems together first to check the thing is actually working. This is particularly important if you're about to check if the mains circuit you're going to be fingering is dead.

I've had a really nice Fluke 123. Those things are absolutely beautiful, and also extremely expensive and excessive for a lot of work. One nice feature of it (amongst the arsenal of others) was that it'd beep on continuity checks. I had to sell that, to cover university debt, and now have a £5 analogue one from Toolstation. An annoying, and potentially lethal, feature of this one is that the probe connections will disconnect themselves mid work, but remain in the holes. Which means it needs checking every single time I'm making a new check on a different, possibly live, wire.

If you place you're multimeter probes across the two contacts I've labelled as live and neutral, you will likely measure a small resistance; which is the winding inside the pump.

You could attach an air bleed to the spare service pipe yes.

The only thing you may want to consider when bleeding gas in is what it will do in terms of the flammability of the things inside the pump. All fuels have an ignition band, the ratio of fuel to oxygen needed. If the fuel is very dilute, it won't ignite. If it's very concentrated, it won't ignite. If the pressure is very low, it won't support stable combustion. By bleeding air in, you may create a good mix for ignition.

In the US, people have air conditioners to cool their house. The 'fridge' is mounted outside and pipe work carries the refrigerant to the grills inside. These are full of flammable gas. The conditioners sometimes need recharging. The system is put under vacuum to remove any moisture, contaminated refrigerant and oxygen before the new gas goes in. They get very upset when they have home owners doing it half arsed on their forums, due to the potential for it to incinerate the house.

With these pumps, without bleeding air in, even if the exhaust caught fire as a solvent went through, it'd only burn outside of the pump, where there's oxygen and where it's being pushed to by the pump. It could possibly be more dangerous bleed atmosphere into the casing, where the mixture would be in a sealed system.

It depends entirely on what you're putting through it in the first place. And, given the lack of any brushes inside the motor, sparks aren't a likely possibility. That leaves the only source of ignition as hot surfaces. For something to ignite without a spark, it has to be mixed with oxygen in the ignition band and reach it's autoignition temperature. The lowest of those, for a solvent you're likely to come into contact with, is diethyl ether, at 160C; and the heads of the pumps don't get much hotter than 50,60,70C. Carbon Disulphide will go at 90C, but that is a fairly odd solvent to have at home.

There is a long list of them here, and you can see they're all in the hundreds***

To give you an example of why the semiconductor people end up spending a fortune on their stuff, one of the things they routinely use is Silane (the silicon analogue of methane), which will autoignite at room temperature.

If one of the electronics guys, who can build VFD's and program microcontrollers, was feeling the urge, they could even make a little controller to spool the motor of the pump it's self. That could be used to regulate pressure without having to bleed gas in.

You could do that with a variable transformer, or an off the shelf VFD drive, but those would require manually adjusting. What's be neat about doing it with a microcontroller would be you could then have the pump spool to the correct pressure for the solvent and condenser type / temperature you're using.

Buchi make controllers and pumps like this. Needless to say, the price is eye watering.

I have tried three or more times to get my microcontroller on, but am never happy when the guides simply say "Type this... it will make this flash". I'm always left thinking... "There's stuff happening here that isn't being explained". BUT... I WILL get it on, they and FPGA's are far too useful to simply ignore.

***Autoignition and flashpoint are two different properties. The flashpoint is the temperature a material will form a flammable mixture with the air at, but it needs a spark to ignite it. The autoignition is the temperature something will ignite at without a spark present.

[Edited on 6-2-2011 by peach]

Mossydie - 5-2-2011 at 17:43

The most stupid thing I've done in school science lessons was to put some calcium carbonate in the 5L container of molar HCl during a GCSE chem experiment. I guess luckily, our teacher noticed before the gas pressure had built up too much and had a major go at the class. I'm now doing A2 and have a very relaxed and friendly relationship with the same teacher, but I still haven't had the heart to tell him it was me.

Bad news with the pump: wired it up and earthed it (connected the live wire to the 'L' side and the blue to the 'N' side) with a 3A fuse and an RCB. Tested the RCB, flicked on the mains switch, and...nothing :|.

I guess I've missed something in the wiring, because the fuse wasn't blown and the RCB didn't flick off. I also tested everything else beforehand for good connection (multimeter, fuse, plug, cabling).

Perhaps I need some sort of connection across the starter?

peach - 5-2-2011 at 17:51

Did the pump hum at all?

Some of the older ones do need a starting capacitor, but they can hum without one. The capacitor is there to provide a pulse of energy to help get the motor spinning. The newer pumps tend not to need one.

It's also possible one of those other connections went off to the thermostat. Well, it's not possible, it WILL have.

That means there will be a block on there where the mains comes in and goes off to the thermostat, and another which comes back and connects the live to the motor when the thermostat says it time to cool the fridge.

Try measuring the resistance between the two I've marked live and neutral. If it reads a high resistance, an open circuit, it's unlikely those are directly connected to the motor.

You will need to have a poke around until you find one that doesn't read zero to the case, but does read a low resistance. Those two should be the ones for the windings.

I have seen this happen myself, where two contacts need shorting to start the pump. Usually, it's not too difficult to find those if you're pulling it out of a fridge, as you can see where the thermostat used to connect.

[Edited on 6-2-2011 by peach]

peach - 5-2-2011 at 17:57

I will give you a head start, I suspect it may be the one I've labelled as 1. I'm not sure what you mean by L plate, if you mean the thing I've labelled as live or not.

Failing that, it's the pink / purple one, but I can't see if that's actually a spade terminal from the angle of the photo.

The only others are the ones I've circled in green and yellow, but they don't look like they're actually connected to the relay and pins.

Mossydie - 5-2-2011 at 18:02

Nope, no hum.

The resistance between the live and neutral is above even the 2Mohm reading. No suggestion of a connection between them at all, even.

None of the obvious connections give a show continuity between the case (I used the earth connection) other than the three outlets.

I also retested the no.1 push fit and I do get a reading of continuity between it and both the metal on the relay and the neutral connection. Both have a low resistance of about 20ohms.

Mossydie - 5-2-2011 at 18:04

Green and yellow are definitely earth - I noticed the earth symbol on the plastic and they are both attached to the casing.

Sorry - 'L' meant live (there's an L in the plastic next to the connection)

peach - 5-2-2011 at 18:06

I have just edited the post on the other page, having noticed I've been calling it a starting relay when it's not, it's the overload switch for the motor.

That aside!

If the terminal labelled 1 is showing about 200 ohms to the neutral block, that is likely the point at which the live returns from the thermostat to the motor.

{edit}Now that you've established the green and yellows are the earths, that doesn't leave a lot left.

[Edited on 6-2-2011 by peach]

Mossydie - 5-2-2011 at 18:09

I tried attaching the live to terminal 1 with the other connections the same - again, nothing, not even a hum

Mossydie - 5-2-2011 at 18:12

Sod that...it blew the fuse.

I replaced it with a 5A one though, which didn't go, nor did I get any sign of life.

I tried again with brown attached to the piece of metal on the overload switch. This time I got a hum and a vibration, but I didn't notice any airflow. Switched it off fairly quickly though, in case I was frying it.

[Edited on 6-2-2011 by Mossydie]

peach - 5-2-2011 at 18:30

I'm beginning to wonder if that switch may need adjusting.

The fact the compressor hums when you touch the live directly to it, but doesn't when it's connected to the remaining terminals, suggests it may be in a permanently open state at the moment.

You could try connecting the live back to the terminal marked 1 and then adjusting the screw on the switch. Be careful with it live on the mains as you do this. You really want screw drivers with insulated blades for doing that kind of thing.



[Edited on 6-2-2011 by peach]

Mossydie - 5-2-2011 at 18:35

The screw is pretty difficult to move. It doesn't have a normal head, it just ends in a flat piece of metal and I'm having trouble budging it even with pliers.

I've noticed that on the motor there are three marked points (labelled 1, 2 and 3). 1 and 2 are metal connections, 3 seems to just be a raised piece of black plastic. 1 was the bit I was attaching the live to before to get a hum. 1 shows continuity with 2, and with the screw in the middle.

I tried attaching the live to 2. Sparks, but nothing. And now nothing when I put it on 1, either, which is worrying - didn't blow the fuse. The whole overload is also noticeably warm. I have a feeling I've blown it...perhaps I'd be better off removing the whole assembly to reveal the three prongs, and start from there?

Doing some more tinkering:

The whole unit easily slides away to reveal the three prongs.
Removing the plastic cover on the back of the unit reveals that the live input isn't connected to anything at all - so it would definitely go through something else before returning to the pump.

Disconnected from the prongs, there is no continuity between the overload and either the push fit (no.1) input or the neutral. The continuity I got before was reading through the motor.

There is continuity between the push fit input and the neutral (low resistance) explaining why I blew the fuse before - the circuit was presumably shorting across the two.

There is also continuity between the 1 and 2 connections on the overload.

Finally, I noticed the statement on the side of the pump 'no start without starting device' - perhaps something I'm missing?

Not much else I can think of, really....

Thanks again for the help, peach. It's been fantastic, even if I haven't got the bloody thing running.

[Edited on 6-2-2011 by Mossydie]

peach - 5-2-2011 at 19:57

My contacts are gluing themselves to my eyes! Don't give up yet, I doubt you've ruined it.

Having scrolled through the PDF and searched around for a good while, I've discovered the P in the code on the side of compressors standards for "PTC + Run Capacitor (optional)"

The PTC is a disc of material, it's called a Positive Thermal Coefficient relay. When it's cold, it has a very low resistance and will energise the start winding. It almost instantly warms up, the resistance rises, and it disconnects the starter winding - largely.

Here's a picture of one, it's the cylinder in the centre.



Here's the assembly off the side of one of the pumps I have. You can see inside the overload switch, although a piece of it is missing. The thing below it, the thin cylinder, is this one's PTC.



If I flip it over... you can see the PTC is sitting a bump sticking out the plastic moulding. This may be what the plastic bump is in yours between the two blocks I've labelled as live and neutral. Which suggests you have the PTC it needs.

You can see I also have some spare starting capacitors, if you find you need one you can have it for the postage.



The rest of the code standards for Embraco Mini Compressor, 2nd generation, R-600a refrigerant, Low Back Pressure, PTC + Run Capacitor (optional)

This band of units, it appears, are low starting torque units. Not only does the P code say the RUN capacitor is option, it states that is a START capacitor is mandatory for others. All that suggests you don't NEED any form of capacitor.

The question is now where to connect the live and neutral connect. Scrolling through the schematics, only two of them use a PTC, and only one of them is for the EM line - on page 23, the top left schematic.

The mains goes to pin 3 on the OVERLOAD switch, and pin 2 on the PTC.

I can see a pin marked 3 on the overload.

The PTC looks nothing like the circuit schematic drawing, and I can't see any numbers in the photo. Can you have a closer look at it in person and see if you can find any more numbers.

Are pins 2 and 3 on the overload switch even separate spade connections, or connectors?

In the meantime... here are some top trump factors for your compressor!

It has a 5.19 cubic centimetre displacement, a 64W heat moving capacity, a 0.98 Co-efficient Of Performance and is using ester based oil.

Curious, because further up the PDF it says the R-600a's use alkylbenzene and mineral naphthenic. The letter L in the code on the casing is also not used in the EM range of codes, yet the compressor clearly belongs to the EM range.

Have a GOOD look over the other terminals for some more numbers. If there is a spade connection on pin 3 of the overload switch, that should be one point for the mains.

On the PTC, that looks nothing like the schematic drawing of it. There is only one point the mains needs to connect to on the PTC, and I think it may be the one I've labelled as 1. Again, check for numbers around there.

Also, try sticking the multimeter on pin 3 of the overload switch, and then the pin I've labelled as 1. In the schematic, if these are the two pins they're on about, that should have a motor winding and the PTC between it. Which should give a low resistance reading, but one more than zero.

[Edited on 6-2-2011 by peach]

peach - 5-2-2011 at 20:23

Quote: Originally posted by IrC  
I think you guys are wasting your time using these pumps unless you are looking for a distillation setup or a roughing pump.

[snip]

For a decent laser you need to get down to say 60 microns or lower.


Indeed.

However this is primarily a chemistry forum, as opposed to physics, so I assumed most people would be more interested in filtration, distillation and vacuum drying.

And your point about the cheap rotaries is one I made myself in the video. But quite a lot of people here also have next to zero money to spend on individual parts when they need so many different, and equally expensive, things for at home science. It is there hobby, they make no money out of it, a good number of them are young (which also means not particularly good money wise) and, since they're interested in science, they will be in for a rough ride when it comes to paying for the rest of their education.

I'm not messing people around when I say I still use fridge compressors for chemistry. In fact, I use them most of the time and one of them is running right now.

This is not because I can't produce a higher vacuum, there are other factors at work.

A lot of the fun of doing science at home for me is trying to see how little I can get away with using to produce the same result. In the case of vacuums, it goes further in that, if you connect a rotary to a volatile solvent, without a dry ice or liquid nitrogen trap, it's going through to the pump.

There is also a reasonable possibility that the pressure these pumps can achieve can be lowered. It's just that I haven't got round to checking all of the ideas yet. Pfeiffer have managed <0.1mBar with piston layouts; with 0.1mBar being 75 microns.

It's worth remembering that a lot of the poorest people in the world, who can't afford a physics lab vacuum pump, also have access to piles of fridges and freezers. It's quite likely the progress of science in these areas is being blocked by things like... them not being able to get a pump to do a filtration or to pull a flash column. The wider spread the information is, the better.

In terms of those people being stupid or too cheap to spend money when it's needed, I have seen more than one chemistry blog online by someone who has a PhD who is also connecting solvent boil offs to high vacuum lines, and then complaining about it getting through the trap.

Also, in more than one example, their solution was to simply throw more and more money at it rather than swap the vacuum source to something more suitable. We should not be blindly throwing tens of thousands of pounds at boiling a solvent when it can be done with something from the tip and tuition fees are having to be tripled, effective immediately.







[Edited on 6-2-2011 by peach]

aonomus - 6-2-2011 at 00:14

Quote:
Buchi make controllers and pumps like this. Needless to say, the price is eye watering.


These controllers usually go on 10-20L preparatory rotovaps like the ones they make. I happen to use these on semi-frequent occasion as well. Its neat, the pumps are all inert with teflon/glass innards and the motor will run at high speed until reaching the rough set point, where the motor spins down and it can even execute individual pump strokes to maintain the pressure within +/- 1 torr ripple.

Regolith - 6-2-2011 at 02:39

Greetings all, It's been several years since the days of the E&W forums. Having looked around and found a source of rogue research lacking in my life. I've decided to crawl back out from the rock I was quite comfortable living under.

My father before me was/is a journeyman appliance repairman. I took up his mantle adding several sciences and computer technician to the list. I figured a first post here squarely in my back yard was a good choice.

Peach, Kudos for taking a compressor. They are soo not intended for open (but can be repaired once open) maintenance as you have well now discovered. Also congrats on a similar pile of old tech to my own if the pictures are indeed your house. I saw large old caps and what appeared to be a large toroid transformer in the piles behind the pictures. It needs about a dozen MOTs and random glassware scattered about and it would be home. OH I also understand your pain at kissing goodbye a fluke123 I had one and turned it in because i needed a feature it was lacking, can't member what... Anyway a uni-T ut55 and a Fluke Pv350 fills the void, with less void in my wallet mind you.

Mossydie, you pretty much can't kill the compressor by wiring it wrong, the windings for example are already just a short across the terminals with a couple hundred feet of motor windings between them and having 2 mains wires on the same terminal will simply blow your breaker(also a good suggestion Peach). More likely whats happened since its a brand new compressor is it's become frozen in its state. The oil used isn't exactly top shelf and it can cause parts to adhere if left for long periods of time. Warming the entire unit up maybe an option as would a start capacitor. Your idea of removing the whole plastic housing crap is what I would do to get to the bottom of this. the 3 exposed terminals can be wired to directly and in fact a commercial start cap has special spade connectors that also fit tightly on the round pins of the compressor housing.

Pictures really are worth a thousand words can you take more of the plastic POS and the compressor itself the 3 pins (on the housing itself) will be marked either with numbers or better yet, letters. Often that plastic housing has bi-mettalic straps or likewise to pull the connector pins away from the connection with the compressor housing(once started). Hence the reason the commercial starter repairs are designed to fit right onto the pins.

I've attached a couple pictures of start caps there cheap like 10 bucks cheap. The high voltage one is usually what comes in a microwave. It was sold to me at my usual parts watering hole as a start cap but my own experience tells me otherwise (that and the only 2k voltage rating you will find in a house is your microwave, or a CRT tube but that doesn't need a start cap). A 10 MegOhm resistor is inside it and will discharge the cap under normal power down circumstances.

The second big chunky guy is more like it 17.5 MicroFarads and 370 volts 50 or 60hz , universal no matter which side of the pond your on.

Finally I don't understand the haters for these machines. A more lowly appliance doesn't exist and yet your simple fridge compressor can heave over a 1000 psi and draw vacuum in excess of -27 inches of Hg. A scrapped fridge and 100 bucks of ebay glassware lets you distill anhydrous nitric acid. What on earth is there to complain about ? It doesn't grant wishes and offer sexual favours?

02062011253.jpg - 108kB 02062011254.jpg - 128kB 02062011255.jpg - 291kB

Mossydie - 6-2-2011 at 05:16

Here are three labelled pictures of all the connections I can find:


The pins with the unit removed


The front of the unit


The back of the unit


The resistance between the push fit connection and the neutral connection on the front (when the unit is removed from the pins) is almost identical to the resistance between the lower two sockets for the pins - so I'm guessing this is actually a measure of the resistance of the pcb when cold.

I tried connection the mains a different way: neutral to neutral, live to the piece of metal I've labelled as suspected 'pcb connection'. I got a similar vibration and humming but no obvious movement of air.

There is a number three on the overload switch, but it's next to just a raised bit of plastic. I though it might refer to the metal connection underneath the overload ('pcb connection')?

[Edited on 6-2-2011 by Mossydie]

Regolith - 6-2-2011 at 06:20

Excellent, Of the 3 pins top is common left is start right is run(you have a normal hermetic compressor, nothing oddball about it). Put the plastic back on the motor and connect your Live to the pin coming from the overload connector 1 (which I believe is actually pin 3 on the diagram and thus the correct connection) and the neutral to the obvious. Problem is as mentioned it's one single chunk of plastic and they have made it for many models thus the trouble...

Erm odd question you have all the plastic caps off the copper right, if you have noise there should be air movement, it's not gonna be an airbrush on its own the air movement may be difficult to detect the vacuum however is usually pretty obvious, sticks fingers etc to the intake.

Something else occurred to me after the fact, once you have known good pins running noise/vibration you may want to try this without the fuse. Reason being while a compressor doesn't take much to be running the start surge can be significant and without this surge the compressor sometimes wont run correctly, hence the need on larger models for a start cap and yet low amp draw on the nameplate.

Btw as mentioned on here these things DO get murderously hot which is why you want the thermal protection in place they can exceed 160C right on the housing. They are built for it, keep the stock thermal in contact the way it should be and sleep well knowing it shouldn't burst into flames in the night if your running it unattended(you should never do that btw, unless your distilling WATER under vacuum all night never leave a project unattended).

Side-note, in case you are curious why the live isn't connected to anything. It functions as a connector bridge if your adding start caps, thermal overloads etc. From the factory this unit IN something this would have likely had an 3cm double female spade connector bridging the thermal to the Line allowing the use of the screw-downs for attaching bare wire to the terminals.

[Edited on 6-2-2011 by Regolith]

Mossydie - 6-2-2011 at 09:13

Erm...nope, the caps were still in *leaves forum in shame and never has the guts to return*
I didn't actually realise that they were blocking the airflow - I thought they were some sort of connection fitting.

With that wiring, it's working very nicely. Please accept my most sincere apologies peach! If there's anything I can do to make it up...
Anyway, I suppose what counts is that it's working. I owe a huge thanks to you and regolith for helping me with this.

Incidentally, is it worth changing the oil? I know the ester stuff can be problematic because of its reaction with water.

[Edited on 6-2-2011 by Mossydie]

peach - 6-2-2011 at 14:50

Quote: Originally posted by Regolith  
OH I also understand your pain at kissing goodbye a fluke123 I had one and turned it in because i needed a feature it was lacking, can't member what...


Let us both have a moments silence as we remember, those good times with the 123.

Press the green button... click... nice...

I wanted the thermocouple for mine. I actually had two, because I sold one, then found I needed it for something, so bought another and then sold that as well.

The second one had the FlukeScope optical isolation lead and software, which only made it even more bad ass!

At the same time, I found myself thinking, this is without question the best multimeter on the planet, yet the scope isn't all that great. But then, a scope of the same price probably isn't going to have the multimeter functions the 123 has.

I can appreciate how someone who works in industry, wandering around plants, would love having so much in one thing that can be put back in the bag, and wouldn't be too bothered about the lack of detail on the scope so long as they could spot some triggering glitch and report it.

The big capacitors are part of some 30 amp linear regulators. There are indeed toroidal transformers, MOTs and magnetrons on the desk. I have tons of photos of my glassware and other things on my facebook page. I'll send you a link in a second if you want to troll through some nerd porn.





Quote: Originally posted by aonomus  
Quote:
Buchi make controllers and pumps like this. Needless to say, the price is eye watering.


These controllers usually go on 10-20L preparatory rotovaps like the ones they make. I happen to use these on semi-frequent occasion as well. Its neat, the pumps are all inert with teflon/glass innards and the motor will run at high speed until reaching the rough set point, where the motor spins down and it can even execute individual pump strokes to maintain the pressure within +/- 1 torr ripple.


I'm sure I know someone who can program microcontrollers on here... just trying to remember... who.... :P

Quote: Originally posted by Mossydie  
Erm...nope, the caps were still in


Quote: Originally posted by peach  

Awww..... it still has the caps on from the factory, the innocence! :P


The problem more like!

I was standing in the kitchen at 4am thinking, maybe he's left the caps on, and thought.. "Nah... he's not left the caps on". :D

Never mind! So long as it's working, it's good.

The little puck shaped thing isn't a PCB, it's a PTC, a thermistor which changes it's resistance based on it's temperature.

In this case, it's starts off with a low resistance, a big surge of current goes through when the mains is applied, it warms up and it effectively switches off the circuit it's connected to by putting a big amount of resistance in the way. So it's normal for them to warm up.

PTC is actually telling you the type of thermistor, that it has a positive temperature coefficient.

There is an opposite to that, called the NTC (negative temperature coefficient).

They get used to prevent surges. Say you have a lot of capacitance in a power supply, straight after the transformer and rectifier (almost directly on the mains), as soon as the supply is plugged in, the capacitors look like a near perfect short circuit until they're charged up.

You can add NTC's to the supply which block the instant surge and only let the supply function at it's maximum current once they've warmed up.

Those power supplies above do it. They have zero form of surge protection, but have very large capacitors pretty much directly on the mains. If I plug them into a normal ring socket, they'll trip the breaker. They have to go on the cooker socket, the cable and breaker for which is designed to handle three to four times more than a ring mains. It's one thick cable, directly from the breaker board. The only other such line you'll find in a house is for an electric shower. Both are extremely dangerous in terms of shocks and fires, and subject to special notice in the Part P regulations of the building codes.

In terms of changing the oil, someone on the last page mentioned Silicone oil. The things to consider in terms of changing the oil are;

a.) will it decompose when contaminants get through and
b.) what is it's vapour pressure

Vacuum pump oils need to have a low vapour pressure, or they'll start counteracting the effect of the pump by releasing gas of their own. Silicone is used in diffusion pumps, where the oil is going to be heated, encouraging vapour pressure problems.

Quite a common theme with low vapour pressure oils is that they typically have a higher boiling point and, more importantly for us, they are usually thicker!

The thicker the oil is, the more energy the pump has to put into churning it. As I say earlier on in the thread, I have tried replacing the oil in one of these with actual rotary pump oil and, without checking it with the thermometer, I seem to remember it was running a bit hotter with it in place.

It had gone from a normal cup of coffee temperature to one that's just come out the kettle, so perhaps 10-20C hotter.

Using thicker oils, I would recommend you think about sticking a computer fan to the top of the pump. I doubt it'll overheat without one, but running the pump a little cooler will improve the vacuum and make it less likely to seize.

I've never had a single fridge compressor stop working in the middle of something. The one I have switched on now has been on for over two days, and it's still running.

If they're going to seize, it's when you switch it off. As the metal inside has warmed up, expanded and needs a little time to cool down. It's a good idea to leave the pump running all the time as you work, rather than switching it on and off and risking it needing time to cool down when you need to do something quickly.

[Edited on 7-2-2011 by peach]

Mossydie - 6-2-2011 at 15:44

Gah, 'PCB' was a slip, I knew it was called a PTC because I looked over the circuit diagrams last night and googled the term. Thanks for the info about them though, it's interesting stuff.

I'm not sure about the oil. I don't need a higher vacuum than the one it pulls already (main uses will be filtration, possibly a reduced pressure distillation or two), so my concern was about hydrolysis. But it should be easy enough to stop water getting in with a cold trap / conc. H2SO4.

Thanks for the advice about the fan, I'll rig something up. Considering the average temperature of my lab at the moment though, anything being too warm is pretty much impossible.

I did a great test just now with DCM: put a small amount in a flask then applied vacuum. It very quickly started to evaporate and then to boil (extremely bumpy). There had also been some water droplets in the flask before which formed a layer of ice around the edge of the DCM. Very cool.

[Edited on 6-2-2011 by Mossydie]

peach - 6-2-2011 at 16:26

The only real reason for wanting a higher vacuum is for distillation of oils, which tend to boil closer to 300C at room temperature.

Ideally, you shouldn't be running borosilicate glassware, or organic chemistry, over 250C. Once it starts getting toward 4 and 5 hundred, you can fix strain in borosilicate glass. There are more issues as well;

1.) Most common thermometers, even mercury ones, reach their limit around 250 to 300C. A lot of them are below 200C.
2.) Roasting the ass out sensitive organic compounded will cause them to either react with something in the remaining atmosphere or thermally decomposed / rearrange
3.) Normal keck clips melt around 125C, and PTFE ones start going over 250C (and releasing HF fumes)

With a fridge pump as it is, you can get the temperature of those distillations down to about 150->175C. But it would be nice if they could squeeze the temperature down a bit more without having to do much to the pump. As an example, if the pumps could reach 1mBar, that'd mean the distillation could run around 110C. A deeper vacuum is also good for getting salts really thoroughly dried when they'd react or decompose in a normal atmosphere. You can, however, still dry a lot of things with the pumps as they are.

I'm beginning to enjoy this nasty weather we're having. I too do experiments out in the garage, where there's no heating, and the near freezing temperature certainly does make condensing things a lot easier.

I do not think your fridge pump is going to have problems with overheating as it is. I have actually stuck data-logging thermometers on the pump heads and left them going for hours, and the temperature stabilises somewhere around 50 to 70C from memory. I have never seen one come close to getting hot enough to boil water, which means they are well below 100C. And I have certainly spent enough time over the last decade running them for 12h+ each go to be confident in that.

DCM has a particularly low boiling point, even when compared with the other volatile solvents, making it difficult to condense anywhere close to 100% of it if it's being distilled under vacuum and the condenser isn't being run from an ice slush.

It's BP is so low (40C), I've thought about distilling it directly out of the metal cans paint stripper comes in rather than getting it on my glass. To put it into perspective, the radiators in my house are at 45C, so it would boil off if I simply sat the can on top of one.

The best forms of cold traps, at present, for a vacuum pump are dry ice and liquid nitrogen. Both of which are far harder to find in small quantities in the UK than they are in the US. But, I rarely ever, in fact never, see anyone on here from the US using them either.

If you put a H2SO4 trap before the pump, you will want to have an empty trap after that and preferably something filled with activated carbon after that.

The first empty container is needed because there's a high chance that you will end up sucking liquid acid into the pump at some point if there's a surge in the flow going through it. The activated carbon would be to avoid any mist from the acid going through.

Letting solvents into the pump will cause the vacuum level to temporarily decrease. The solvents have high vapour pressures compared to the oil. You may wish to run the pump, with the intake blocked, for a few hours after an experiment if you think your condenser hasn't been catching it; to boil the remaining solvent back off.

Solvents like acetone, DCM and ethyl acetate will boil off quicker, as they boil around the temperature inside the pump. The bigger ones will take longer.

Technicians in university departments will complain that students have let large amounts of solvent into the vacuum line. As they're dealing with bigger pumps, deeper vacuums and lines going all over the department, it can mean effort to get the solvent back out.

Saying this, in terms of filtration, the drop in vacuum doesn't really matter all that much. You can reduce the amount of solvent that makes it to your pump during a vacuum filtration by cooling the collection flask first, and then wrapping it in a dry towel. If the solvent tries to boil in the collection flask, it will cool it's self as it evaporates. Because the flask is already cool, it happens quickly, and because it's insulated, there is nowhere for the solvent to get more heat to boil from. In effect, it traps it's self.

This is only a problem if you're filtering some fine sludge, where it's going to clog the filter, pull a strong vacuum in the flask and take tens of minutes or an hour to get through. There isn't usually a strong, long duration vacuum in the flask if the cake is made of sizeable precipitate.

When you filter fine sludges, and the filter clogs, it has the added disadvantage that the filter gets very cold, and the flow slows even more. It can actually come to a full stop if the filtrate solidifies in the element.

[Edited on 7-2-2011 by peach]

Regolith - 7-2-2011 at 00:26

Your very welcome Mossydie as I said it's kinda what I do :)

To everyone who is curious about changing the oil in the pumps. The short is answer is yes you can use whatever fluid in the pump you want but as mentioned its vapour pressure has to be such that it doesn't vaporize under the vacuum and the heat of the pump, also it must not react with the gas your passing through it (there shouldn't be any contamination going through the pump though, more on that in a sec).

It's uncommon for a repairman to have to add oil or change the oil in a compressor but leaks happen and it does occasionally happen. There are many kinds of compressor oil, esters, several hydrocarbons with anti-foaming additives etc.

Food grade Mineral oil is what I feed my pumps (can be had at most drug stores). To drain cut the oil fill line the one near the bottom of the compressor and open the vacuum in line to allow airflow. This works best right after an hour or so run to warm the oil up and decrease the viscosity. Old oil REEKS don't get it on you since you have no idea what it was some of the esters and even mineral oil will break down over time under the heat of the pump. Tilt the compressor to drain if you have a bucket or something that can support the pump at the correct angle that would be advantageous.

Filling is the easy part reseal the oil line and simple run the compressor and let it suck up the same volume of oil you recovered from the pump. Under normal condition mineral oil shouldn't eat rubber seals etc if your pump has them(mineral oil doesn't leech chemicals from the seals).

Now onto why your pump shouldn't be sucking up anything. There should be a trap on the line out from your compressor a stainless steel can or otherwise (I have an oil trap somewhere but I can't find the damn thing its looks exactly like my vacuum bottle minus the internal implosion support and the vacuum gauge). Even with the measures put in place to try and keep compressor oil in the compressor it will push oil out over time and ESPECIALLY when you break a hard vacuum seal on your glassware when distillation is complete. The oil capture bottle should be above the level of the compressor so as to try and keep oil from even getting to it but no more than 30cm away from the compressor otherwise it could pump all its oil out before you even knew it. After each distillation throw away the oil that has been aspirated out and let the compressor eat new oil of the same volume. In this way I avoid doing a full oil change over time and the oil that is aspirated out doesn't smell of Ass mixed with More Ass.

The vacuum bottle shown is your first/last line of defence in keeping your pump happy. Before the compressor but after the bottle. I use a 20cm length of pvc pipe with caps and plastic connectors at both ends and the pipe is secured to the wall so as not to disrupt the contents. These pipes (I have a couple depending on what I'm distilling) can be filled with something as simple as anhydrous magnesium sulphate (epsom salts) to capture water from the airstream. To something way more hardcore like large prilled Sodium Hydroxide to scrub oxides of nitrogen out of the air and acid vapour that you don't want in the pump.
NOTE: these pumps are Hermetic meaning under normal operation (if your name isn't Peach) there isn't an exchange of air from the compressor circuit. So when distilling things like Nitric Acid it CAN (be insanely super careful and at the very least get a full face shield or a good pair of goggles, skin can regrow the clear proteins of your eyes will denature and be lost forever) be done inside with the output of the pump connected to a good hose that goes way outside. An NaOH scrubber removes pretty much all the NO and NO2 from the air and when it becomes ineffective from use you dump the scrubber contents into water and separate out the moles of Sodium Nitrate you made.

Many lab pumps don't have things like acid traps before the pump and/or there not used always which is why lab pumps often look great outside and beat/eaten to sheeet inside.

Finally Mossydie: shown is a beaker from a recent experiment. While drying a nitrate in my lab microwave (don't use the food microwave for chemistry, random poisoning < Good times) the water boiled off as I watched and then the reaction continued the microwave happily melted my sodium nitrate sample right to it's decomposing temperature. I ran and grabbed my respirator so as to watch this more carefully as the nitrogen oxides smell like nothing else and you don't want them IN you. Indeed no water was left and it was an anhydrous sample. More amazing the beaker didn't crack or shatter upon cooling from the stresses in the glass.

Curious I fired up the hotplate and took a sample of the same nitrate to molten. The beaker is the one shown in the picture. The microwave acted as a furnace containing heat and heated the sample not the glass meaning there were far less stresses placed on the glass beaker. I have yet to really play with this as it happened a couple days ago. I very much wish to attempt a reduction of nitrate to nitrite via a microwave, of all things.

Peach is right about organic chem temps. The most badass glass mercury thermometer I have goes to 320C (I only have a couple left, try getting bubbles out of mercury when you have to take the glass to 350C to max it out and clear the bubbles). I bought them then ironically figured out to use a broken thistle tube with the end melted shut and a type K thermocouple inside the tube with a drop of mineral oil to make better contact with the tube itself. The whole point of distilling things like nitric acid under vacuum is to lower the boiling point beneath that of its decomposing temperature (and save glassware). Essential oils with very high thermal mass will almost certainly be destroyed taking them to there (natural) boiling point to distill them.

02062011260.jpg - 78kB 02062011262.jpg - 139kB 02062011258.jpg - 126kB 02062011259.jpg - 128kB 02062011257.jpg - 105kB

[Edited on 7-2-2011 by Regolith]

peach - 8-2-2011 at 12:51

For those in doubt, please have a read of the following post for why fridge compressors are a good idea

entropy51 - 8-2-2011 at 13:41

Quote: Originally posted by peach  
For those in doubt, please have a read of the following post for why fridge compressors are a good idea
What's all the yelling about? Amateurs have been cognizant of, and extensively using, fridge compressors as vacuum pumps since even I was a wee lad. Does "re-inventing the wheel" ring any bells? Sheesh.

There's an old thread on this topic from 2003. Old news.

The thread you are so proud of gives your measurements of ultimate pressure reached by the different pumps. As this sorely needed tutorial makes crystal clear, ultimate pressure is no predictor of pump performance in actual use. For that you need the pumping speed curve. This is particularly true in a system with generation of vapor, such as a distillation or rotovap. Read the tutorial and you will have a much better understanding of these vacuum fundamentals. If you had measured pumping speed and compared that all important measure of performance, I might have been impressed. Ultimate pressure, not so much.

[Edited on 8-2-2011 by entropy51]

[Edited on 8-2-2011 by entropy51]

peach - 8-2-2011 at 14:28

Quote: Originally posted by entropy51  
What's all the yelling about? Amateurs have been cognizant of, and extensively using, fridge compressors as vacuum pumps since even I was a wee lad. Does "re-inventing the wheel" ring any bells? Sheesh.

There's an old thread on this topic from 2003. Old news.


Quote: Originally posted by IrC  
I think you guys are wasting your time
[Edited on 12-19-2010 by IrC]


Saw the Bell Jar page, many, many moons ago. Doesn't actually discuss practical chemistry and how the pumps relate to laboratory pumps does it?

And your reference thread...

Diffusion pumps pulling a ^-23 torr vacuum.

That's pretty darn impressive, since the cold trap at CERN can only manage ^-17 mBar and interstellar space is ^-18.

Having the balls to start threads complaining about content dropping and then complaining when someone bothers sitting around working all the numbers out for other people is even more impressive.

Quote: Originally posted by entropy51  


1. Connecting the house mains current to the two proper terminals and

2. Momentarily connecting a starting capacitor across the two proper terminals with a pushbutton switch. The switch is depressed until the unit starts (a second or two) and then released.

If your compressor is this simple you basically just have to identify the proper terminals and find a start capacitor of the proper rating (microfarads and voltage). The tables in that pdf should help with this. Good luck!


1.) He doesn't know which terminals are the mains terminals

2.) The pump doesn't need a capacitor, as evidenced in the PDF

Noise.

IrC - 8-2-2011 at 15:42

Posted on 2-8-2011 at 04:28 PM by peach:

"Quote: Originally posted by IrC
"I think you guys are wasting your time"

Saw the Bell Jar page, many, many moons ago. Doesn't actually discuss practical chemistry and how the pumps relate to laboratory pumps does it?

And your reference thread...

Diffusion pumps pulling a ^-23 torr vacuum.

That's pretty darn impressive, since the cold trap at CERN can only manage ^-17 mBar and interstellar space is ^-18.

Having the balls to start threads complaining about content dropping and then complaining when someone bothers sitting around working all the numbers out for other people is even more impressive
"



Just exactly what are you talking about peach. "Having the balls to start threads complaining about content dropping"

I start a thread last year to cover the general topic of vacuum and have said nothing here, nor to you since. I did not start it complaining about anything, it had nothing to do with you or your thread. I have said nothing to you in the recent past. Yet you take a snippet from last year out of context and use it this year to say my sources are crap and I 'have the balls' to start the thread in a way which suggests to the forum you are merely defending yourself against an 'attack' of your thread and statements you made, said 'attack' which exists only in your own mind?

The links I posted I found online and were merely intended to provide a general source of reading material on the subject of vacuum. If you do not approve of what claims were made by people in the links I posted why don't you go bitch at them about it, I could care less. Are you sure your exhaust systems are working properly? I mean I would hate to see someone going schizo on us from aberrant fumes or something. Your post today implies I am somehow RIGHT NOW attacking the idea of using fridge pumps? I was using them in 1964 and for half my life as I grew up in the largest family owned refrigeration business in downtown Kansas City. I was surrounded by fridge and freezer compressors, when I was 9 I was on the rooftops of the largest buildings in the city helping install industrial systems and yes I had those monster compressors as play toys. Only in the 80's when I started building lasers did I give up on these pumps choosing to obtain better equipment.

Let us see what the context was, posted on 12-18-2010 at 10:31 PM: "I think you guys are wasting your time using these pumps unless you are looking for a distillation setup or a roughing pump. 40 mb = 30,000 microns if I did the math right. For a decent laser you need to get down to say 60 microns or lower".

Where is the error in this statement? And where is there an attack against the use of fridge pumps for general vacuum needs? Nowhere. A sane person if they were so upset with this comment would have responded to it LAST YEAR!

Not taken it out of context today to defend themselves in a purely imaginary flame war. Unless of course your entire motivation is to presently START ONE TODAY OUT OF THIN AIR. As I have said nothing recently in your thread nor towards you or any ideas you have posted I can only assume this indeed is your motivation for this recent post.

On 12-18-2010 at 11:21 PM, aonomus replied:

"I would argue the point that these setups are 'useless'. These are good for a roughing pump and/or distillation/convenience vacuum filtration pump there is nothing as cheap and sacrificial. Not everyone has access to cheap pumps from Harbor Freight either. I'd agree that a $75-100 rotary from Harbor Freight is essentially sacrificial, but if you can't get your hands on one....

For physics experiments however, I agree that these are mostly useless
."

And on 12-19-2010 at 07:17 PM I replied:

"No argument, this is precisely what I said in my first line.

"unless you are looking for a distillation setup or a roughing pump
"".

In your own thread you said nothing after these posts until 1-4-2011 at 04:44 AM, and you did not even mention what I had said. One would think this was the proper time to comment on my statements if you so rabidly disagreed with them.


On 2-5-2011 at 10:23 PM you finally made a post mentioning my comment:

"Indeed.

However this is primarily a chemistry forum, as opposed to physics, so I assumed most people would be more interested in filtration, distillation and vacuum drying.

And your point about the cheap rotaries is one I made myself in the video
."

I never replied again in this thread, two pages further along until now. However if I had I would have stated then they screwed up naming this place 'ScienceMadness', they should have called it 'ChemistryMadness' if I am in error to post things non chemistry related on this board. Especially since virtually everything in science I do is more high energy physics related than anything else.

I should not need to be wasting this time replying to you. However if attacked especially out of the blue for no reason I sure as hell will defend myself. Freud would have much to say about this subject. Most notably "everything is not all about you".

Yes, if I dug Him up I am positive this would be His words.



peach - 8-2-2011 at 17:22

Entropy started a thread a while ago in which he's complaining about how the science content of the forum is dropping <---

The majority of his replies to me look like this <---

Since this entire thread was about chemistry applications, I am bothered by the words wasting your time being involved, even though it's followed by the word distillation. You have to appreciate how easily that will either confuse or sway people who aren't sure of what they can and can't do with these kinds of things.

For instance, if you follow entropy's referenced thread, you'll find you can reach better than outer space conditions with a diffusion pump (which is incorrect), and little else. Yet he quotes it like some diamond in the dirt, starts a thread complaining about there not being enough science based information on the site, then replies to me with the above. The looping irony is quite outstanding.

I don't see the need to imply people are wasting their time with fridge pumps in that regard. As an example, I could have replied in your thread saying you are wasting your time with a rotary pump for the physics experiments, when a diffusion, turbo or ion pump is the correct way to do high vacuum work, using conflat flanges - not bell jars and neoprene. I didn't. But surely you can see how that could also be taken out of context if I had.

{edit}
Here's another example of a thread I'm not even involved in, where he's doing it again with entirely different people. And there are others, for example, accusing a teenager of being a neo-nazi.

[Edited on 9-2-2011 by peach]

IrC - 8-2-2011 at 18:25

That all makes sense, I thought you were going bonkers ragging me as you quoted me then started in on what looked like it was directed at me. Damn, ruined a perfectly good counter reply. I worked so hard, my fingers are sore, I walked miles in the snow.

Actually if it were not for fridge pumps my first quarter century of madsci would have all been done at atmospheric pressures. Took a long time before good surplus along those lines coincided with my actually having money. My bad. Yes my little bell jar setup is not for super high vacuum, mostly playing with plasmas and neat glowy things. I saw the turbomolecular pump you were holding, as I calculated if I could afford the gas to go swipe it. Then I remembered all that water between us and decided against it.


Have to add though that there is something in what he was saying, I have noticed this in electronics forums as well for a few years now. I meet adults in their 20's who cannot even change a tire. I thought the human race was supposed to get smarter over time yet my dog is asking questions they are too stupid to answer. Especially lately. Items like jo blow jihadi asking about initiators for 15 kg of you name it while making statements which lead one to think they were clueless in general. Or at the least are insulting to intelligence. Yes jo blow I really want to tell you how to wreck my Christian way of life and my country. Especially as you sound like a total F-tard. This last rant aimed at all the jo blows out there.


[Edited on 2-9-2011 by IrC]

Regolith - 8-2-2011 at 23:08

If I may make a hypothesis based on observations here. This board much like past boards I have been on has a significant Kewl population, so much so my laptop runs colder just being here :D.

That said I'm not implying that irc or peach are kewls (or mossydie for that matter, only through asking questions can we increase our knowledge). It seems though for a lack of a certain green preying mantis (I miss you meglo), this forum causes as much frustration at times as it does provide useful knowledge.

Irc is working on a plasma vapour deposition rig, Peach is looking to continue his education to further increase his human Ark potential. Mossydie is making a pressure chamber to test gerbil space suits for his mutant gerbils, all hail our gerbil overlords long may they rain(this last part MAY not be true).

The point is there isn't a need for those of us who pursue true science to chew at each other, especially when we pursue goals that are different. I mean how Irc is measuring his double digit (or single depending on the Mayan gods and nature abhorring a vacuum) micron vacuum without a visible non manifold based gauge has thus far eluded me. I'm not ripping on him for it though. As a fellow scientist I conclude he must have a means of testing his own experiments.

My own personal example is thus. Upon seeing Irc's footer of "There is no magic, only science". I took this to assume he had no faith in a christian God. My patience was rewarded by his counter rant "wreck my Christian way of life". As with science life requires patience.

IrC - 9-2-2011 at 02:23

"I mean how Irc is measuring his double digit (or single depending on the Mayan gods and nature abhorring a vacuum) micron vacuum without a visible non manifold based gauge has thus far eluded me. I'm not ripping on him for it though. As a fellow scientist I conclude he must have a means of testing his own experiments."

You do not seriously think the equipment I show or talk about is all there is? There is that which I own and that which I can borrow when I like. Only fools let the world in on all of their secrets. When dealing with strangers all things are on a need to know basis and as for me there is little I feel anyone I do not know needs to know. This covers both what I own and all that which I have access to. Every time you read a story about a private experimenter and all their loss and legal problems you can right off assume they did not live by this principle. Otherwise there would not have been a story to read. Further, all the high vacuum work I do is with metal gasketed chambers previously used in laboratory fusion experiments sponsored by university and/or governmental entities. Only an idiot would put a video on You tube of his neutron beam experiment. I find living under the radar is the most intelligent way of existence. This does not preclude one from ever talking about anything they do.

On the bell jar the pump can get to one micron if I seal it off ahead of the jar inlet. With my original setup I could get the jar down around a hundred or a little less. Still looking for a gasket material as good as the original but I do not have access to the materials I did when I first built it. My fusion chamber is a different story but I really do not want to show and tell with it. I obtained a second chamber I am desiring to turn into a lens coating setup. Helps to have family who's career has been with various IC manufacturers in the ion implanting and doping part of the industry. For both the surplus and the insight.

On the insight side I will quote a little text from my brother in various emails when I need to pick his brain for my next experiment:

"Electron beam deposition is using high voltage DC to produce electrons in a very heavy duty light bulb filament in a high vacuum, (3x10-6 Torr), then using a big magnet to turn the electrons 270* so they come right back down and smack whatever material you put in the crucible (pocket right behind the filament) where it melts and ballistically transports up and out and coats whatever you want with whatever material you are burning away with an electron beam. Cool part is you put two coils next to the crucible pocket to steer the beam with voltage, think horizontal and vertical in a TV.

You can center the beam on your material if your magnet is weak or too strong for the physical dimensions. Or if your filament is bent and the electrons go a little sideways. Or if a diode is blown in your high voltage power supply and AC gets into the beam and starts creating beam divergence problems and coronas.

You can put RF into a system to ionize gases to produce deposition on a surface. Mostly seen Silane and Oxygen to produce silicon dioxide to form an insulating layer. Must have a high current low Freq. burst to ignite a plasma, then a higher freq. lower current phase to actually produce the binding force between the two O2 and SiH4 (to produce SiO2). Byproducts can burn very nicely, and if O2 gets into the pump it can blow up reeeeaaaal good.

Or you can use RF to ionize a gas to propel it to a cathode surface to etch a material with whatever gas molecule you want. You can use a reactive gas, Chlorines or hexaflourides and the like, or great big molecules that hit with enough force to pound away at a surface like bead blasting. Argon works well.

Matching networks for RF are a necessity since vacuum chambers are just a great big capacitor that would end up burning out an RF generator in short order."


"My own personal example is thus. Upon seeing Irc's footer of "There is no magic, only science". I took this to assume he had no faith in a christian God. My patience was rewarded by his counter rant "wreck my Christian way of life". As with science life requires patience."

You would have to narrowly look at creation to assume God may not be the greatest scientist of all. It sounds like you are saying your assumption is one cannot believe in science and God in simultaneity. The words in my footer are quite clear. Magic is magic. Hocus pocus. Nothing exists which does not have a valid explanation, therefore by definition there is no magic. Anything perceived to be magic is merely a thing we do not understand. Yet. A large number of the worlds greatest scientists in history believed in God. However I imagine Faraday would have looked at my metal cutting beams of light as magic. I have no doubt being the scientist he was he would have worked until he understood what a laser was if he had the knowledge to do so. Also of course if he had the cool toys to play with we do today. I do not however think this added knowledge would have meant he could no longer believe in God assuming he believed in one before we gave him this new knowledge.

Belief in Science, belief in God. One has nothing to do with the other unless you are trapped within a limited perspective. I further find that without exception people with this limited perspective invariably base it upon the insights they have gained in life. Said insight always based upon the erroneous facts they heard from those who knew little about either subject i.e., God or science. As example the common misconception that to be christian implies one thinks the earth is only 6,000 years old. Or the devil made fossils to fool man into thinking it is older. I have heard it all and concluded that while most people claiming to be christian are quite ignorant, to be a 'scientist' and preconceive this implies all Christians are this ignorant shows them to be even more ignorant. After all the 'scientist' is supposed to be one. At least they claim to be a scientist. Much like a christian claims to be a christian. To me, these claims in no way prove to my satisfaction that either one is really 'either one'.

One cannot blame God if his children given free will choose to be stupid. This they did to themselves, whether a 'scientist', a 'christian', or 'both'.

I should point out however there is little use in renewing the God VS science debate as this is off topic and it seems has never gone very well anywhere on SCM.


[Edited on 2-9-2011 by IrC]

peach - 9-2-2011 at 03:52

Silane hey... :P

One hexachlorodisilane vaporiser and controller. That guy on the side looks in a bad way.

What are you planning to coat? By fusion, Farnsworth?




[Edited on 9-2-2011 by peach]

Regolith - 9-2-2011 at 04:00

I laughed "You do not seriously think the equipment I show or talk about is all there is?" no, otherwise I wouldn't have said "As a fellow scientist I conclude he must have a means of testing his own experiments".
You misread the tone of my post, in a roundabout way it was among other things to have you tell me, without directly asking, the scope of your project. I saw a very familiar looking vessel with the HV standoffs under your bell jar. Far from being critical of you there are very few of us who know what a farnsworth fusor is. Let alone made one. (I know thats not a fusor under the glass, or your a neutron loving alien)

I have for a time and perhaps again now that I have more knowledge. Tried carbon vapour deposition on a silicon substrate. At the time I was limited by the lack of (ran out of money) proper equipment and the expensive gases needed for the work. Now a russian team has discovered that ethanol and water in a 4/6 ratio is the perfect chemistry for depositing carbon onto a substrate. Wow russians found a use for Vodka, russians ? I was using a microwave beam to create my plasma rather than high voltage, different paths same destination. I imagine yours in operation would be much more visually impressive than mine, large glass jar as opposed to my tiny purple lit shielded quartz viewport. The intent is not to slam the carbon into the substrate but allow it to rain upon the surface with enough scavenging hydrogen to clean the unwanted material off.

"Only an idiot would put a video on You tube of his neutron beam experiment. I find living under the radar is the most intelligent way of existence. This does not preclude one from ever talking about anything they do."
I wholly agree there was a post in this board about someone wanting to tell the cops what he was doing for safety sake... yeah. That said, a neutron beam can be done quite safely and can be used in among other things (theoretical) reactors where there isn't sufficient neutron flux to start the chain reaction thus creating a very safe reactor that will stop if power is lost.

"It sounds like you are saying your assumption is one cannot believe in science and God in simultaneity." I find this curious my own words would show otherwise. Had I agreed and said great you don't believe in a God either. Then my thoughts would be clear. Instead my post shows that my patience was rewarded, hence joy. However this doesn't preclude the original error which may have been mine. I took it to be that YOU saw magic as religion, other boards I frequent these terms are intermixed. I read more into your words that I should have. Personally I believe science and God easily co-exist. Put bluntly the earth is millions of years old, dinosaurs roamed the earth at one point. God isn't going to find your keys for you, or save you from something stupid. He will one day judge my soul.

Edited for Peach. Irc is making his own optics. If we were active on the moon and/or had a helium3 source Farnsworth would be a household name. A fusor fed by the correct fuel would produce an alpha particle rather than a neutron. Allowing for that particle to be decelerated in a magnetic field like a transformer and thus have all the energy extracted. It's one of the running ideas of cold fusion.


[Edited on 9-2-2011 by Regolith]

IrC - 9-2-2011 at 10:05

Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971), my hero of all time. Well OK, Tesla is one also. His Tele (Philo's) may have had a crappy picture but it was first, and RCA's Z-man did steal it. Professor Hubert J. Farnsworth, known simply as Professor Farnsworth. I am certain this character was based upon the great Philo T.....

The jar was for experimenting with glow discharges and various shapes for electrostatic inertial confinement electrodes at higher pressures with say Argon and the like. Just to play with shapes of screen mesh electrodes, not to make death beams which pointed wherever they liked.

Peach you never cease to freak me out with the items you have laying around the house. I will never visit you now I have no doubt there is a Pu foil/Plexiglas stacked reactor in there somewhere.

In Job you read about God talking about playing with His pet Leviathan, which people take to be a Hippo as they do not carefully read the description of the tail. I am convinced it is a Super-Saurus, why not if you are God you can afford a really huge poodle right?

I came to the conclusion large mirrors for large lasers would always be out of financial reach, thus the need to try and build them. With a set beam current and a set amount of time you easily create quarter wave layers at the frequency in question, of course needing SiO2 layers of the proper thickness in between the metalized layers to build frequency selective dielectric mirrors.

Back in 1999 I was bouncing my ideas of carbon Bucky-balls vapor deposited to eliminate the need for silane off of G. Pat Flanagan, but one day I told him I was suspecting T. Beardon may be a quack and He got so pissed at me we never spoke again. Oh well. He was playing with lasers to make carbon Bucky-balls for some kind of health supplement or something or other. Sort of like the use for activated charcoal powder as a way to remove toxins from your digestive system only more high tech. I surmised He was thinking about microscopic 'cages' to contain bad free radicals thus safely transporting them out of the system. Being ever secretive I am not really sure if this was His thinking though.

The 1989 Loma Prieta earthquake aided my quest for MadSci as my brother lived 4 miles from the epicenter. The aftershocks for days made it impossible to sleep so he quit Intel and moved back to Phoenix, bringing me tons of stuff. His wife was tired of Him storing stuff around the house. Christmas! Yay!


[Edited on 2-9-2011 by IrC]

Regolith - 10-2-2011 at 02:00

MmmMmmmm Carbon 60, damn why can't you be a woman. I sense the start of a beautiful friendship. I'm stunned by the internal use of fullerenes as many nano particles are extremely bad for you (causes hemorrhage of the alveoli in your lungs) they would need to be purified to the Nth degree for safe human use. I've only read papers on them so it may be overstated, no practical personal use. However the idea of carbon nano particles stuck (forever) in me is not a good time.

Yeah peach, could you have some unshielded uranium or other radioisotope at your house so I have lots of warning before I get in the door that I should have pretty much a space suit on. Or just start a proper lab, seriously. You have the technology. I'm not sure of the market on your side of the pond though.

peach - 10-2-2011 at 04:27

I do know two people who work at a nuclear power plant, and one of them is the health and safety person there. I've been trying to slowly prise a pass out of him.

I was going mention Farnsworth from Futurama, and nanoparticles.

At university, I was lucky enough to feel up an MBE chamber, and then stole one of it's power supplies, before it was taken back. Molecular Beam Epitaxy is an example of where very high vacuum is a necessity to get continuous monoatomic layers and wires. The vacuum has to be so deep so as to produce a long mean free path in the molecular flow region, so the molecules from the gas furnace do not collide with a single other particle on their way there; to produce said 'beam' of molecules.

The researcher was in the middle of rewinding a directional coil, having forgotten to put a thermistor in and then burnt it out. I wandered into another, empty, research room and was perusing a large (taller and wider than my height) iron structure, with a tiny probe wobbling up and down in the centre, when another researcher literally appeared out of nowhere behind me and enthusiastically explained what was happening (it was a gradiometer measuring magnetic fields). In what was now becoming a reoccuring theme, it had been on fire the week before.

Epitaxy, for those wondering, means the new layer joins the substrate and adopts it's crystal lattice as opposed to it's own.

Some physicists at Manchester University, near me, won a noble prize for producing single sheets of graphite (graphene) and they have also been producing Hall sensors (the cheapo version of SQUIDs) using quantum wells. As the hall effect is 2D, having bulk silicon in the channel allows for the electrons to drift up and down, rather than going where they're supposed to for the sensor to work. The Hall sensors are much more sensitive as a result. I asked them for a couple and they sent me some. So I tried making a guitar pickup with them. It works! But there's a substantial hiss / rushing sound from the amplifier, which is thermal noise coming from the channel - intrinsic noise and noise that can't be cancelled by filters due to it being random.

A very interesting and exciting thing to me is that quantum wells / dots can be grow by colloidal synthesis in a chemistry lab, with glass and none of the special chambers or microfurnaces. The wells will produce laser / diode like emission spectrums, with extremely tight bandwidths. Better yet, they can theoretically reach a 100% level of quantum efficiency, zero losses, as they absorb the incoming light (as a spectrum, usually in the deep blue or UV) and re-emit the new, single line spectrum. That has important ramifications in countless different applications, like display technology, diode production and solar power - e.g. being able to easily harvest all of your UV and then dump it back out at the wavelength the cell will better absorb.

Another example would be data transmission. A single fibre optic can carry something like 460gb/s but (as with phone lines) the data needs multiplexing on different lines to fill up it's optical transmission band. Which means lots and lots of different wavelengths for each channel, all sitting closely side by side.

A neat property of this colloidal synthesis is that producing the emission band you want is as difficult as stopping the reaction at a specific time.

<iframe sandbox title="YouTube video player" width="640" height="510" src="http://www.youtube.com/embed/6Xm4LABNYzo" frameborder="0" allowfullscreen></iframe>

[Edited on 10-2-2011 by peach]

IrC - 10-2-2011 at 09:41

Flanagan was the one trying to make a medicine for radical cleansing. I was just communicating with Him on the various ideas of how to make the C60. I'm with you I do not think I would want to actually try it as a medicine. No idea how that idea went for Him I should Google a while to see.

I do know drinking activated charcoal in water is said to be a very good method for removing pathogens from the gastro-intestinal system. I have read that, unsure if it is safe or effective.

peach - 10-2-2011 at 09:55

It is also sold for taming those farts that make your co-workers want to wretch at the sight of you in the morning.

Think I'm kidding? Here's the start of the references <-----

Quote:

For those who need extra protection!

The Overpad-D is washable and reusable and many get several weeks of use out of the pad, depends on usage.

Price: $19.95


{edit}I particularly like the woman with a lab coat and board. She inspires confidence in me that, with Overpad-D, this truly will be the end of my smelly anus stinking the place up. Overpad-D is not compatible with fridge pumps, but activated carbon may be of use.

[Edited on 10-2-2011 by peach]

IrC - 10-2-2011 at 12:23

At least your topic made it back to gas, I mean vacuum, the absence of gas.

bfesser - 15-2-2011 at 14:28

Quote: Originally posted by Regolith  
The most badass glass mercury thermometer I have goes to 320C (I only have a couple left, try getting bubbles out of mercury when you have to take the glass to 350C to max it out and clear the bubbles).


Try dry ice/acetone to pull all the mercury down into the bulb. It's less risky (I'd argue, easier, too!) than heating.

bit of feedback

food - 18-2-2011 at 23:02

a bit of feedback

since my last post I've moved beyond filtration and done some vacuum distillations. The pump ran for many problem free hours. My concerns over heat have been steadily dwindling, and the last time I just directed a fan at it, which was just enough to have a temperature that I was ok with.

this thread has been very useful to me

not to mention that cutting and pasting the fridge compressor sub-assembly like this is so au courant, and very much in <a href="http://www.youtube.com/watch?v=4pimCdIwMPw">the spirit of the age</a>

peach - 20-2-2011 at 04:54

Liquid nitrogen - sans cryocooler

I decided to post this here rather than in the other thread, as information is becoming splattered.

There is a video of Patrick, a guy in Germany, liquefying nitrogen using compressors at home. This is the first time I've ever seen someone manage this, and I'm not counting the guy using a helium cryocooler, since that's designed to produce cryogenic temperatures anyway and he's just dropped it into place. Whereas Patrick has gone for a far more DIY and hands on approach that doesn't require bits of physics laboratory gear.

It is essentially a multistage freezer, with five separate stages as opposed to the one you find in a domestic freezer. Superfreezers use this setup, and the cold trap aonomus mentioned, but with less stages.

Each stage uses a different coolant to 'hop down' the temperature; one stage cools the next, and so on (a cascade).

He's using the following refrigerants in each loop;

R404A - An azeotropic blend of R125 (Pentafluoroethane), R133A (Chloro-2-trifluoro-1,1,1-ethane) and R134A (1,1,1,2-Tetrafluoroethane)
R170 with a mix of R1150 - This is ethane and thene respectively
R14 - Tetrafluoromethane
R50 - Methane
R728 - Nitrogen

Result, liquid nitrogen. DARN impressive hey? Click his videos and give him a thumbs up!

{Edit}I've just got another email from him and he's pointed me to a thread showing it being built

<iframe sandbox title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/uqU-d6-a5ws" frameborder="0" allowfullscreen></iframe>
<iframe sandbox title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/GHDZt1r4Ap8" frameborder="0" allowfullscreen></iframe>
<iframe sandbox title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/hhG5_xcGN18" frameborder="0" allowfullscreen></iframe>

[Edited on 20-2-2011 by peach]

aonomus - 20-2-2011 at 05:22

Impressive to see a series cascade built at home for cryogenic temperatures.... a gigantic autocascade would have been even more impressive though. Probably would have required a massive compressor and condenser though.

dann2 - 20-2-2011 at 06:28

The whole set up looks good and MAD

Book below about the liquifying gases.
May be useful

http://openlibrary.org/books/OL7140959M/Liquid_air_and_the_l...

There is another book (lost tech series by Lindsay Pub.) which I have. It may be available online.

Always wanted to do the 'smashing a motor tire into a thousand pieces' at home demonstration!

Dann2

smaerd - 4-3-2011 at 18:03

Well I'm bumping this thread because I FINALLY got my grubby hands on an old mini-refrigerator :D.

I haven't taken it apart yet, but its got a pretty interesting wiring. The compressor looks nice though :). Hopefully this little thing will last me many experiments/distillations/filtrations.

I'm sure I'll need some help figuring this thing out so I figured why not bump it in advance hehe...

Cheers again peach, your youtube videos and this thread help a shit-load.

peach - 6-3-2011 at 02:12

Remember to take a look at the wiring prior to taking the compressor out, and don't bin anything like the capacitors until it's working outside of the fridge.

smaerd - 6-3-2011 at 09:28

Good call, it's a mini-fridge and the schematic mentions nothing about a capacitor unless it's inside the pump box itself? It's kind of older and has been sitting for months in someone garage until given to me. So I'm assuming it's safely discharged if there is one.

The weird thing about this is the thermostat control seems to lead directly to the pump, and the main's cable does as well? Two green grounds are fixed to the bottom plate. Guess I'll try to figure this out another day, thanks for the tips though :D.

smaerd - 7-3-2011 at 09:01

Okay so the thing came pre-popped I was told. So I cut the copper tubing with a pipe cutter, and cut the opposite end(not the oil fueling line). Unbolted the bottom plate. Snipped the wire to the thermo-stat. Pulled out the thermostat.

Stripped the three wires(white, black, and green) on both ends of the thermostat wire. Reconnected the wires color coordinated and plugged it back in. The compressor gave no response? Wtf? The connections weren't soldered but were tightly wound and electrical taped.

The thing worked when I plugged it in originally(or atleast the compressor hummed)? The only thing I can even think is from the thermostat there was a little metal wire going from it to the ice-tray thing? Or did I kill this thing somehow?

edit:
Should I be 'over-riding' the thermostat entirely by connecting the white wire to the black wire on the thermo-stat wire? If I do this though then I'm not sure what to do with the ground.

[Edited on 7-3-2011 by smaerd]

smaerd - 7-3-2011 at 09:43

Well I connected the black wire to the white wire and completely left out the thermostat controller. The pump works again, it pulls air, it seems pretty weak but I'm sure it'll work perfectly :D. I'll bust out the solder gun, make this sucker official. FINALLY I have a vacuum pump, stupid water aspirator.

I might try to wire a little computer fan on-top of the pump to help keep the pump running cold. Hmmm, we'll see :).

[Edited on 7-3-2011 by smaerd]

peach - 7-3-2011 at 09:56

{edit}Chopped, since you've got it working in the time it took me to click reply :P{edit}

***I would stick to calling it the earth. Some people call it the safety ground, but the ground rail in a power supply is the thing that completes the circuit back to the power supply; it's designed to carry power when the circuit is on. The earth shouldn't have any voltage on it or current through it unless there's been a fault (usually the live touching the case). So I think terming one 'the ground' and the other 'the earth' is safer than using 'safety ground', because calling them both grounds is asking for confusion on something really important. The ground rail can sometimes be connected to earth (e.g. the neutral coming into your house is connected to earth), but the purpose of a ground rail and an earth are quite different. The neutral from the grid is there to carry power. The earth is there to carry faults.

[Edited on 7-3-2011 by peach]

smaerd - 7-3-2011 at 10:08

Makes complete sense :). Thanks for posting that naval electrical engineering training thing as well, very useful. Oh yea and thanks for making such a comprehensive thread with videos about all this.

Contrabasso - 18-3-2011 at 14:20

Anyone have a wiring diagram for a four wire fridge pump?

I have earth, neutral and two lives should I find a start or run capacitor from somewhere?

smaerd - 22-3-2011 at 13:37

Contrabasso does the one live lead to the thermo-stat? Mine did so I cut off the live from the thermostat and connected it directly to the live from the mains. I'm not sure if that helps you out any or not, I know nothing about these kinds of things.

However I did come up with kind of a cool idea to deal with the over-heating aspect of the pump. I'm thinking bend one of those 13-16 inch disposable pizza tin's to make sort of a bowl around the head of the compressor. Fill it with ice/water to cool the pump. The cool thing about this would be that it could double as a cooling bath for a solvent trap/filtering flask type set up. I'll post pictures if I ever get around to figuring out how to make my solvent trap/flask thing.

Contrabasso - 22-3-2011 at 13:46

Thanks for that S! I took the pump back to the breaker today and he fitted a lead and plug to it so I'm happy, it works nice and quietly.

Must get a huge buchner flask, and a moisture trap!

smaerd - 25-3-2011 at 07:19

Here's my little modification. It's not perfect I wish the little top container was bigger and had better thermal connectivity because of the concave shape of the compressor. Though it does touch maybe 4inchs^2 of surface area, which is okay for now until I find something better. It's PP5 so it should endure temp quite nicely just in-case. The tape is pretty ghetto but I couldn't think of anyway around it.

Anyhow how does this look :), keeps the pump cool and has a little solvent trap in-case anything escapes the receiving flask. Sorry the lab is a little messy.

Still need a means to empty the little container, maybe I'll find a spout in one of those old margarita mix containers or something.

DSCF0047.JPG - 143kB

smaerd - 15-4-2011 at 10:18

Well my pump took an unfortunate belly-full of water today :(.

So I used my aspirator to remove all the oil and water inside. Flushed with WD40 several times, and removed it via vacuum. Sprayed a little WD40 and is still runs but makes a lot of noise, so it probably needs R12 oil? Or is it likely totally f*$&ed?

So I flushed it out with R12 mineral oil, and now it faintly hums for maybe 30 seconds then there's a large click and an electrical spark going from something in the box to the ground :(. I think it's toast!:(

Well I tracked the spark it's going from the over-load to the ground. Not sure if the problem is the over-load or the relay, they see to be in perfect condition but obviously when the vac over-loaded from not being able to compress the water it must have blown something. It's just strange because it WAS running before I picked up the oil. Albeit loud but it was running.

Edit - nvm I don't want to win a darwin award. I think the problem is the Start Relay, wonder if there's a way around it...

[Edited on 15-4-2011 by smaerd]

smaerd - 15-4-2011 at 17:52

So I took apart the relay assuming that was the problem, some of the thermiser was oxidized so I scrubbed it with steel wool. Plugged it in no dice. Took apart the over-load, there was not a single sign of damage. So I am assuming the pump is stuck of struggling. Peachy any idea? :)

Picture attached below is the start-relay taken apart amazing how these things cost $40 a piece hahaha. The most expensive component in it can be ordered for 15 dollars...

DSCF0086.JPG - 141kB

GreenD - 17-4-2011 at 10:26

Thanks for the thread all - smaerd why do you need that anyways? I would assume for most of our purposes an on off switch is fine for everything...

smaerd - 17-4-2011 at 10:54

Well the thermiser sends power to the start prong until it heat's up then it changes it's conductivity to send it to the run prong. I guess you are right, an on-off switch should work but I need to find one that can handle those voltages. Assuming the problem is electrical and not mechanical at this point.

[Edited on 17-4-2011 by smaerd]

GreenD - 18-4-2011 at 15:46

Right now I just have mine as plug in - on, unplug - off.

Easy enough. Straight hardwired to an extension cord.

INORGANICUM - 8-4-2012 at 03:48

Hi, I had 2 questions to put to you scimad guys/gals.
1, (nothing to do with this post) Whats a "kewel"??

2, If I still have it and your still interested would you like to see an industrial freezer compressor cut open?
its almost dubble the hight of an ordinary compressor and maybe a tad rounder (oval though it is).
Also, is there any advice to a way of testing it b4 I dismantle a possably usefull lab itam b4 I take an angle grinder to it? inor

After a brief search & with many more places to look yet, I found 5 compressors, 3 oval 2 round.
The one round one is larger then all the rest but not the one im thinking of, is 23" round by 9" tall, I suspect its just a large freezer comp, as the one im thinking of is oval and heavy (a hulk of a compressor) and double the size as previously mentioned. IIRC INORE

[Edited on 19-04-1967 by INORGANICUM]

INORGANICUM - 8-4-2012 at 04:24

Quote: Originally posted by smaerd  
Here's my little modification. It's not perfect I wish the little top container was bigger and had better thermal connectivity because of the concave shape of the compressor. Though it does touch maybe 4inchs^2 of surface area, which is okay for now until I find something better. It's PP5 so it should endure temp quite nicely just in-case. The tape is pretty ghetto but I couldn't think of anyway around it.

Anyhow how does this look :), keeps the pump cool and has a little solvent trap in-case anything escapes the receiving flask. Sorry the lab is a little messy.

Still need a means to empty the little container, maybe I'll find a spout in one of those old margarita mix containers or something.


SMAERD, Can you get hold of some of that "Melt in the pot" coloured craft mould makeing rubber for candles to attach the top cooling chamber ? no worries about metal expanding/contracting and simple to use. just a thaught
IN ORE

mycotheologist - 8-12-2012 at 05:13

Petty all the videos are gone, I was gonna refrain from asking a question about fridge pumps. I'm gonna go to a recycling centre and find an old fridge but what kinda tools will I need to salvage the compressor? I don't wanna go there for nothing so I have to be prepared. Also, are there any other parts worth salvaging? I read something about the copper tubes at the back of the fridge which hold the freon. Should I salvage that too? I don't wanna leak freon into the atmosphere so I'll figure out a way to trap it instead.

[Edited on 8-12-2012 by mycotheologist]

watson.fawkes - 8-12-2012 at 07:59

Quote: Originally posted by mycotheologist  
I'm gonna go to a recycling centre and find an old fridge but what kinda tools will I need to salvage the compressor? I don't wanna go there for nothing so I have to be prepared.
[....]
I don't wanna leak freon into the atmosphere so I'll figure out a way to trap it instead.
You'll need mechanic tools to unbolt and unscrew everything. You'll need a large pair of shears or very-large gauge wire cutters to cut refrigerant lines. (I wouldn't recommend unsoldering or debrazing the lines in the field, when you don't know what's in there.) You'll need a container to drain the existing lubricant into and plenty of paper towels to wipe up the leaks and drips.

Now, if you want to capture the refrigerant, you've got more problems. You need a refrigerant reclamation pump, which is a vacuum pump with adequate gauges, valves, and plumbing. You need to power the pump, which likely means a battery and inverter. You need a tank to pump the refrigerant into. You need hoses for the pump and tank. And finally, you need a special piercing saddle tee to tap into the refrigerant line; you need to match the diameter of with that of the tubing, but there are only a few standard sizes.

mycotheologist - 8-12-2012 at 08:23

Looks like I better forget about capturing the refrigerant then. Do I have to cut the refrigerant lines to get the compressor or can I leave them alone? I don't have a car to carry my tools, its a 15 walk from the bus stop, I was thinking of just bringing one of these:

a screwdriver and a few other lightweight tools, will that be enough to get the compressor?

watson.fawkes - 8-12-2012 at 10:00

Quote: Originally posted by mycotheologist  
Do I have to cut the refrigerant lines to get the compressor or can I leave them alone? I don't have a car to carry my tools, its a 15 walk from the bus stop, I was thinking of just bringing one of these: [...] a screwdriver and a few other lightweight tools, will that be enough to get the compressor?
Yes, you have to cut the lines. There aren't connectors on them; they'll be soldered or brazed in. The picture of the vise pliers reminds me that there's a refrigeration service version of that tool that crimps lines shut; a few crimps and a half-bend on the innermost may allow you to recover refrigerant in the shop rather than in the field.

Get yourself a rolling toolbox or rolling cart to carry your things in if you're confined to walking. Wheeled luggage from the thrift store would work as well.

I can't say what tools you'll need exactly, not having seen the compressor. I'd take a ratchet wrench set and at least one adjustable wrench.

Fridge Compressor for Vacuum

Gargamel - 29-7-2013 at 12:32

Does anyone here use a fridge compressor for vacuum?

I just found that running a buchner with a vacuum cleaner is not the best solution. Not enough pressure.

Now salvaged an old Danfoss Model Tl4 from my neighbors fridge.

Do these things pull enough vacuum for our needs?


I also plan to get a small destilling equipment, that I could set under vacuum. Even if the vacuum is strong enough, I wonder how great the losses/leaks of "normal" equipment are, since the compressors flow rate is not so great.



How would I protect the compressor from aggressive vapours, is a washing flask sufficient?

And how about oil - if I ever refill that thing, is there some easily available substitute (motor oil....?)

Also it seems like some compressor oils are hygroscopic. Is that to an extent that running the machine in the air will cause problems rather quickly?

bfesser - 29-7-2013 at 14:12

Please <img src="./images/xpblue/top_search.gif" /> <a href="search.php?token=&srchtxt=compressor+vacuum&srchfield=body&srchuname=&f%5B%5D=all&srchfrom=0&filter_distinct=yes&sea rchsubmit=Search">Search</a> before starting new threads. And don't forget that there's an entire world of <a href="http://lmgtfy.com/?q=refrigerator+compressor+vacuum+pump" target="_blank">information</a> <img src="../scipics/_ext.png" /> outside of SM. ;)

[Edited on 30.7.13 by bfesser]

starman - 29-7-2013 at 22:57

Quote: Originally posted by bfesser  
Please <img src="./images/xpblue/top_search.gif" /> <a href="search.php?token=&srchtxt=compressor+vacuum&srchfield=body&srchuname=&f%5B%5D=all&srchfrom=0&filter_distinct=yes&sea rchsubmit=Search">Search</a> before starting new threads. And don't forget that there's an entire world of <a href="http://lmgtfy.com/?q=refrigerator+compressor+vacuum+pump" target="_blank">information</a> <img src="../scipics/_ext.png" /> outside of SM. ;)

[Edited on 30.7.13 by bfesser]


See this extensive thread by Peach for instance
Let this signal the end of the fridge pump questions!
As you can see this comes up a lot.Thats why search before ask.Saves pissing off the moderators.

[Edited on 30-7-2013 by starman]

Gargamel - 30-7-2013 at 07:08

Sorry, I know there's many information around, but sometimes you don't see the forest for all those trees...


I still have two questions/looking for experiences considering the flow rate...
If anyone has experience in using such a compressor for vakuum destillation, up to what size of destillery can such a thing approximately handle?


And considering the oil, has somebody ever tried to replace it?
It seems that the Danfoss compressors use a kind of oil that turns acidic when it comes in contact with the air.

What will hurt em more, having the oil turning acidic over time (or rather very quickly??) or running on "wrong" oil? Any experience?

edit:
It seems like that problematic oil is used with newer models. Mine was running on R12. So It seems like I don't have that problem. Any comment on that?

[Edited on 30-7-2013 by Gargamel]

soma - 24-12-2013 at 14:31

I'm getting "video doesn't exist" when I click on the videos at the beginning of this thread.

confused - 26-12-2013 at 02:39

same here, video doesn't exist

I Like Dots - 13-6-2014 at 07:11

I just salvaged a fridge pump from a mini-fridge. Water is distilling over at 45C so im pulling ~100mbar? I did not grease the joints, but the joints are only letting a very small amount of air through. All things considered I am happy with it. Perfect for vacuum filtration!

zenosx - 9-7-2014 at 18:02

Yes the video's at the beginning no longer exist? Fixing maybe?

Bert - 10-7-2014 at 04:21

I'd stumbled across this before- And wondered what the missing video might have contained.

*sigh*

http://youtu.be/jF4Ta1_-HUg

Don't know how many of these little buggers I've scrapped, should have saved a few!

maleic - 26-2-2015 at 00:06

Thanks for the funny video:D

Vacuum pumps from consumer products (compressor modifications)

RogueRose - 14-1-2016 at 05:47

I am in need of a vacuum that can pull a pretty high level of vacuum (ideally 24" Hg.) for an extended period of time (maybe 30 mins on - 10min off - repeat). I am capable of adding some kind of cooling to the compressor whether it is mearly a fan or enclosing the housing with a water jacket & running cold water through it - IDK what else may be possible.

I know fridges and freezers have compressors that will work for vacuums but are there other products that do as well? I would think maybe AC's and dehumidifiers may have something like this?

Anyone have any suggestion of other products?

Macom24guitar0 - 13-3-2016 at 16:11

Many years ago when I didn't stick to the theoretical side of the equations. I had to solve the same problem concerning both vacuum & water for condensers, steam distillations, clean ups, etc. Since my "Shop" had neither running H2O or drains I had a number of issues to deal with. First I had to study & grasp the Bernoulli principle then I ordered a small submersible pump picked up some 1/2"pvc and glued up a little loop that led from my pump at the bottom of a 7gal. pail up thru my bench down to my aspiration and back into the pail. This device was not powerful enough, but was ideal for the condenser, so it wasn't wasted time, I found a 1hp submersible and used 3/4" copper pipe, and a 25-30gal. drum for my new aspirator and it worked great when the water was cold, so I kept. Half dozen plastic milk jugs in the freezer and it sucked solvents thru the Buchner in seconds and allowed me to distill at temperatures that indicated a vacuum of 14torr. With the addition of a cold finger trap it was ideal for my limited horizons. It's an inexpensive, inconspicuous, and easily built solution.

XeonTheMGPony - 6-9-2016 at 07:57

Quote: Originally posted by RogueRose  
I am in need of a vacuum that can pull a pretty high level of vacuum (ideally 24" Hg.) for an extended period of time (maybe 30 mins on - 10min off - repeat). I am capable of adding some kind of cooling to the compressor whether it is mearly a fan or enclosing the housing with a water jacket & running cold water through it - IDK what else may be possible.

I know fridges and freezers have compressors that will work for vacuums but are there other products that do as well? I would think maybe AC's and dehumidifiers may have something like this?

Anyone have any suggestion of other products?


Not sure if relevant for you, but I'll answer it for others who view it:

A reciprocating compressor commonly used in fridges will easily do 25" of mercury sustained as long as it is running

To use it as a vacuum pump one simply needs to remove the oil and replace with 200sus Mineral oil, and provide some form of cooling, if lucky to have a unit with an oil cooler in it you're set! Other wise sanding down the bottom and soldering on a coil of copper tubing to flow water through will suffice to cool it!

You must make a vacuum trap to prevent fluids or solids to get into the gas stream, and a chemical absorber to keep acid vapors out of it.

Window air conditioners and newer dehumidifiers use rotary vane compressors, they will pull a deeper vacuum, but they will run hotter and oiling is a bit trickier to keep it running long term.

Deep freezer compressors are the best for using as a vacuum pump as they are designed with the rarefied gas atmosphere taken to account for the piston displacement, Old R-12 ones are even better of a find due to them all ready using a mineral oil (All though I do recommend switching to the heavier grade as it will improve operational life time and vacuum achieved!)

All ways have the R-12 properly recovered as it is very detrimental to the environment!

Now the discharge! You need to make an oil capture jar, this can be as simple as a jar with the pipe sticking into the lid and a hole for the exit to capture any oil mist, to a nice coalescent unit!

There is allot you can do to make advanced systems or a simple crude system to give a very good vacuum system.

Attachment: Oil cooling diagram 2.pdf (65kB)
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