Air Compressor recommendation?

[Ed DuffnerParticipant @edduffner79357]

Hi everyone,

A while back my air compressor tank rusted through and I've tried to get some customer support from the company who sell/supply parts (out of warranty), but I think I'm being given the runaround by uninterested staff.

Anyway, they are now history as far as my custom is concerned and after selling some of my old guitar and fishing gear on Ebay I've been looking at getting a replacement compressor for air brushing, test running steam engine models and topping up the car tyres etc.

So, I wanted to ask a couple of questions.

1. Has anyone any experience of this type that are available on Ebay at the moment. They appear to be rebadged by quite a few companies/distributors. Are these quiet/noisy? when running? 82db apparently.

2. The silent type motor/compressor on my existing 9 litre unit is working ok and I wondered if I could swap that compressor unit over to the tank of one of these new compressors? It is exactly the same pressure rating, 8bar/115PSI. The only thing I am unsure of is the size of fitting for the inlet and outlet to the tank, can adapters be fitted?

My thought process is, a new 50-litre compressor with delivery cost is less than half the price of a replacement tank for my silent compressor. I would probably go for the 24-litre being even less expensive.

Sorry for the long read.

Thanks,
Ed.

 

Edited By Ed Duffner on 07/04/2016 17:45:37

[Ed DuffnerParticipant @edduffner79357]

[Bruno TaylorParticipant @brunotaylor21701]

I bought one a few months ago to air test a couple of minature steam engines. A 5" Boxhill 99% complete and a 3 1/2" gauge Maisie Chasis.

It worked fine but it is noisy. Also l got very little control of the pressure at the low volumes being used. I had the best results by using a globe valve as a regulator.

I bought an air blower type attachment to clean my lathe swarf but rarely use it as it blasts the swarf into even more innacessible places!

I have not used it for painting for which l have a baby elephant compressor also bought on ebay/amazon for my Badger air brush which works really well.

Hope it helps

Bruno

[KWILParticipant @kwil]

Generic type under many badges. I agree they are noisy, but you can barely hear it inside the house which is above the garage. I have not used it for paint as i have a small silent hydravane compressor for that purpose

[Ed DuffnerParticipant @edduffner79357]

Bruno, KWIL,

Thanks very much for your replies. I think I'll order one and see what can be done.

Ed.

[Brian HParticipant @brianh50089]

Found on ebay, there may be others, price £78

Air receiver, compressed air tank 50 litre price includes VAT

Edited By Brian Hutchings on 07/04/2016 19:54:09

[Old ElanParticipant @oldelan]

Posted by Bruno Taylor on 07/04/2016 18:31:20:

I bought an air blower type attachment to clean my lathe swarf but rarely use it as it blasts the swarf into even more innacessible places!

Bruno

I think I've been told not to do this especially without eye protection!

However, I am a beginner……

I understand that cubic feet per minute is more important than pressure depending on what you want the compressor to 'drive'.

[Ed DuffnerParticipant @edduffner79357]

Hi Brian,

Thank you for the link. That one is in Loughborough and a bit far for my old SAAB to go to pick it up, I'm in Bristol. I also looked at replacement tanks and most are collection only.

I've just placed the order for the one I linked to.

Ed.

[HughEParticipant @hughe]

Hi Ed

I use 50 ltr one similar to one you are looking at. Only problems i have had relate to starting. It does not like the cold and pops 13 amp fuses occasionally . I was advised to use a 16 amp mcb protected spur and fit a industrial plug (caravan type). I had one setup already for my welding kit so it was straight forward, no problems since.

Hugh

[Ed DuffnerParticipant @edduffner79357]

Thanks for the tip Hugh.

I used to be a sparky so I will have a close look at that to see if there are any potential issues, though I didn't have much involvement with motors.

Just adding the specs from Ebay for reference:

SPECIFICATION

• 230V/50HZ
• CAPACITY: 0. 11M3/MIN
• TANK CAPACITY = 24LTS
• PRESSURE: 115PSI (8 BAR)
• AIR DISPLACEMENT: 206L/MIN
• SPEED: 2850RPM
• CURRENT: 7. 5A
• INPUT POWER: 1500W
• OUTPUT POWER: 1050W
• WEIGHT: 24KG APPROX
• SOUND LEVEL: 82DBA
• OIL GRADE PUMP: SAE 5 W 50
• REQUIRED OIL QUANTITY (PUMP): APPROX. 0220
• 13 AMP PLUG FITTED/2 X WHEELS
• CE APPROVED

Ok, with a running current stated as 7.5A the start current will be approximately 7.5 * 1.8 = 13.5A, but the input power is 1500W which is equal to 6.25A.

6.25A * 1.8 = 11.25A starting current.

The 1.8 mutiplier is a rule of thumb constant for calculating the start current for inductive loads (e.g. motors, older fluorescent lights).

Ed.

[Ed DuffnerParticipant @edduffner79357]

It used to be possible to get motor fuses which allowed for an initial inrush current, but I don't know if they were ever available for a standard 13A 3-pin plug.

[Ed DuffnerParticipant @edduffner79357]

Just found some info regarding a similar scenario for a guy on an electricians forum and adding it here for reference.

Quote:

"Possibly the compressor is starting up with the motor under full pressure if the compressor is turned off at a plug rather than the machine itself.
If there is full receiver pressure on the pump as it starts it will be unable to turn and will stall out possibly blowing the fuse. Switching off at the machine normally operates a valve to release the pressure on the pump .

Either that or there is an internal wiring problem, but do make sure all external wiring connections are tight and check continuity."

So, we'll see what happens.

Ed.

[Nigel McBurney 1Participant @nigelmcburney1]

Regarding cleaning lathes with the airline,in my machine shop training one of the rules was no machine cleaning with an airline,it drives swarf and rubbish into the slide ways,and in those days goggles were used for riding motor bikes.

[Howard LewisParticipant @howardlewis46836]

Direct drive air compressors are noisy. Belt driven compressors are quieter, because the compressor runs at a lower speed. Diaphragm compressors are quietest of all, which is why Dentists use them to power their drills.

Mine are direct drive, one (Branded S I F) is claimed to have a 3hp motor, but starts and runs off a 13 Amp socket, without blowing the fuse.

Before putting it into use, I removed the plugs on the reservoir, and sprayed Waxoyl through it, to reduce the risk of rusting. (Catch 22? – NO, I used the HPC for this)

Another, the HPC with a smaller motor, capable of running off a 5 Amp supply, is still functioning happily after more than twenty years.

After use, I ALWAYS drain out the condensate, and leave the drain open. (Recommended by the supplier – a local compressed air equipment specialist). This means that the motors always start up on No Load, except when the pressure falls to the level where the pressure switch restarts the motor. The HPC has a valve on the compressor head to allow an unloaded start, even if the reservoir is pressurised.

At least, any moisture remaining after drain down has a chance to get away.

Don't be surprised if the drain stops after a while, and then restarts. (You are quite likely to see "steam" coming from the valve) As the air expands, it cools; often to the point where it freezes the condsensate. The big 200 Gallon (909 Litre) reservoir, in my bus garage, used to freeze repeatedly during drain down. We used to open the drain tap, and go for a cup of tea, while it spat lumps of ice around!

Both compressors have condensate filters fitted between between the outlet and the delivery connections for the flexible hoses. It is surprising how much water accumulates there during use, and needs to be drained out.

Howard

Must learn to check for typos BEFORE posting!

 

Edited By Howard Lewis on 08/04/2016 10:16:57

[Ian S CParticipant @iansc]

My compressor is home built, using a freezer compressor, the tank is mounted vertically with an automatic water trap/ drain, it's driven by a 1/2 hp 1450 rpm single phase motor, and is not too noisy.

Ian S C

[the artfull-codgerParticipant @theartfull-codger]

I don't know why but everyone [on various forums] seem obsessed with the tank size,which is fine to buy you a little more air but if the pumps not big enough but it takes longer to fill, as Howard says direct drive compressors are fast running & very noisy, I have a large tecalamit [3hp 2 stage] ex garage compressor for larger jobs but most of the time I use my home made one I built 45 yrs ago from a clayton dewandre air brake pump from a green goddess, mounted on a redundant gas bottle, it has seperators, cut-out & safety valve regulator & drain valve,it's sprayed cars, chiseled every bit of plaster from our old cottage,runs all my air tools & even ran a small double glazing plant for a few weeks, the only time it let me down was when a bit of swarf got into the oil feed pump & it melted the white metal from one of the big ends,[no shells straight onto the rod & cap]after a strip down I made a jig,re-poured the big end with some new & the old white metal, onto the myford faceplate to bore it out a tight fit, a scrape in with micrometer blue & back together & it's still going strong & that was 30 yrs ago. great bit of engineering [the air pump not me!!]

[John Stevenson 1Participant @johnstevenson1]

Try to run with a smallest tank as possible for what you want to use.

Having said that if you want to run a 1" air riveter forget the last statement

 

Compressed air is expensive to produce and wasteful and if you are filling tanks bigger than you need, only for it to leak out over time then it costs.

I run two hydravane compressors, each 12 or 15 cfm with both tanks linked so I reckon that's about 180 litres.

I only run one compressor at a time unless I need a lot of air which doesn't happen very often now as a lot of air tools have been replaced by electric.

For day to day running, blowing bits out, etc., I use a Bambi compressor which is far more economical and not very big at all.

So if you do use a lot of air think about two compressors, one large and one small and use what suits the job.

 

 

Edited By John Stevenson on 08/04/2016 13:22:06

[Clive FosterParticipant @clivefoster55965]

Back in the day we'd just "obtain" a calor gas bottle plumb it in and call it good. More than strong enough. I believe the design specifications are working pressure 240 psi, test pressure 480 psi, design burst pressure 960 psi. Can't see the lightweight tanks on small import compressors coming anything like close, ones I've seen barely look up to 150 psi test pressure. Especially after a few years of damp air accumulation. For something smaller I'd consider an air reservoir for a lorry or the air suspension on a modern 4 x 4. My P38 Range Rover runs 120 psi in the suspension and the tank looks a nice size for small compressor.

Looking at the specifications the motor is very inefficient, input power 1500 W, output power 1,000 watts. Doesn't give much confidence in its design. Will almost certainly produce a very large start up surge. Might be OK if blowing into an empty tank where the load from back pressure rises slowly but likely to be a problem if there is air in the tank and no decent unloading valve to let the thing run up to speed before it has to work for its living.

Found out the hard way about inefficient motors when I got a 3.5 HP (I think) cap start and capacitor run heavy duty one from Northern Tools to run a compressor. After killing several fuses and much jiggery pokering around with delayed shut unloading valves and the like I got it to run at about half design speed. But darn thing was a better heater than compressor which was when I finally checked the documentation. Specified output power was little more than 1/3 rd of the input power. I didn't know you could make a 240 V single phase squirrel cage motor that inefficient without it melting. After a good deal of leaning Northern Tools refunded my money.

Clive.

Edited By Clive Foster on 08/04/2016 15:32:59

[Ed DuffnerParticipant @edduffner79357]

Thanks guys,

I agree about not using the airline for cleaning up. In fact the only time I had the compressor in the workshop(shed) was when it got rusty so I need to find a new home for the next one.

There was a company I found about a year ago who were selling stainless tanks for about £45, couldn't believe it at the time and I can't find them now. I was skint at the time.

Ian S C and Clive Foster, did you or do you have to use any kind of special pipe connection for the inlet and oulet to the tank/cylinder? …and does that need PTFE or other thread tape or just a good sound thread with a brass gland of some sort?

JS, my use will be own light duty, I'm not planning on building anything Brunellian just yet Lol. That's an interesting concept having two compressor tanks cross linked.

Ed.

[Gordon WParticipant @gordonw]

I have an old sub-£100 pound one, still works and no leaks, replaced the pressure switch a couple of years ago and that's it. Also have a home made one- two cooking gas canisters welded together bottom to bottom. Pipe connecting the valves and a starter/ pressure switch fitted off another cheap compressor. Pump is an old lorry compressor. The motor is not really man enough for this so is a bit slow but quiet. BTW I did not make this.

[Ian S CParticipant @iansc]

My compressor is plumbed with ordinary 1/2" galvanized steel water pipe. The tank is a war surplus low pressure aircraft oxygen tank (probably from a Hudson bomber).

Ian S C

[Neil WyattModerator @neilwyatt]

Posted by Old Elan on 07/04/2016 19:55:23:

Posted by Bruno Taylor on 07/04/2016 18:31:20:

I bought an air blower type attachment to clean my lathe swarf but rarely use it as it blasts the swarf into even more innacessible places!

Bruno

I think I've been told not to do this especially without eye protection!

However, I am a beginner……

I understand that cubic feet per minute is more important than pressure depending on what you want the compressor to 'drive'.

ME carried a design by Peter Spenlove Spenlove for a blowgun with additional holes around the side that try to deflect any 'blown back' particles, but you should still use goggles.

Neil

[Author]

Posts