Buying my first compressor...?

[The Z'eer]

I've read the FAQ's on compressors and decision has been made on what this tool will be used for. There's a few questions regarding the choice of compressor, perhaps someone might share a little knowledge on this area?

The main purpose will be for DIY automotive spray painting, I may use it to power certain air tools but not simultaneously. 240 volt single phase is the only power source available to me.

Firstly, Ideally I'd like to stick to a budget or really no more £300.00 for the unit, is this possible? Secondly, I'm guessing an HVLP gun would give the best results? As such a compressor with a high CFM of 15 is necessary?

Do I need a unit that has a tank of over 50 litres, if so why? What are the pro's and con's of an oil less vs oil using compressor? Can suitable water and oil filters be purchased to remove contaminating particles?

A newbie to this area, all help appreciated.

Thanks

 

[brianblock]

I'm no expert but I would suggest you need something like this

https://www.machinemart.co.uk/p/clarke-industrial-aircompressor-xev16100230v/

I don't think 50ltr would cut it, you need a volume of air to allow for surges in pressure as the pump fires in and out. Too small a tank and your pressure will fluctuate, bigger the better I'm afraid

There's a good article here to explain it all

http://www.sgs-engineering.com/help...buying-guide-which-compressor-should-i-order/

 

[douchecalamondaes]

I do similar to your description, air ratchets, a gravity feed spray gun, I got a second hand clarke industrial for pennies, 50L with an old twin piston compressor, if you are buying new, I would suggest that and of the v-twin 50litre machines that you see about-rated at 2.5hp would work jsut fine, aldi were doing them at one point.

the thing you haveto work out is will it keep up with your spray gun, most work at 20-40psi so the cfm needs to be adjusted for that if its stated at 8bar

 

[Masterofnothing]

I recently bought a 125l 10bar 3hp vtwin off a lad on facebook for 50 quid. its nearly twenty year old and built alot better than some of the new stuff these days, i filled it up to 10bar a left the shop one night, went back a few days later and still had over 9.5 bar in.

My point is if your going to buy one new i would look for a reputable brand not the cheapest one that meets the your spec as youll be disappointed. The displacement ratings manufacturers give is usually approx 30% less than stated. So if it stats 9cfm its more like 6. So if your tool requires 6cfm its and you want to use it for 5 mins its going to be on constantly on trying to keep up. Its like this with my shot blast cabinet but thats extremely thirsty! If the tank is only 50l its going to get used up pretty quick.

Oil free for any spraywork as the oil can contaminate paint an produce and awful finish, just get inline oilers for tools etc

 

[richie00boy]

Oil free compressors are generally small ones.
I've got a 50 litre 3hp and its fine for spraying with low pressure guns. Not much use for air tools though. But electric ones are generally decent, especially sanders tend to be better actually.

 

[stewart.d.campbell]

This is under £300 http://www.ukhs.tv/Workshop/Air-Compressors/Dakota-14-CFM-Air-Compressor

 

[Mee]

First you need to understand displacement, often manufacturers specify the pump displacement which is wrong but makes the machine look better than it is. You need the machines FAD or free air displacement which can often be around a third less than the pump displacement, the FAD is what the actual tank will give as air which is what you can use, and these differ as certain models may state 3HP with 15 CFM and give around 13/14 CFM as FAD while others may also be advertised as 3 HP with 15 CFM and only give 9/10 CFM as FAD.

Straight away you have a problem as a HVLP spray gun requiring 15 CFM is well above what the tank can give, you do have options, you can get guns which have interchangeable needles and a standard gun may come with a 1.8mm needle and requires 14 CFM of air, meanwhile it may have the options of a 1.4mm needle and a 1.2mm needle which require less air which may be inside your compressor FAD rating.

For spraying and air tools you need the largest capacity of stored air as possible, a 50L cylinder isn't going to deliver, the smallest I would use is 500L or the pump will constantly run and overheat without delivering the air required, you do have options and these are to get extra capacity by buying a scrap compressor, usually with a duff pump or motor and using the receiver, years ago I added a blanking cap to mine and removed it to connect a 1" hydraulic hose to connect to my large receiver and only plugged it in when required to give additional air capacity, and undoing it for normal use.

 

[armalites]

FAD is actually Free Air Delivery not Displacement.

Compressors are like audio amplifiers or 0-60 times the numbers don't always represent like for like performance.

In an ideal world get the biggest/most powerful one you can justify, you'd be hard pushed to find someone moaning that they have too much air available. Once you have a decent compressor you will be surprised how many time you use it. Air tools are great but you do need a decent air supply, I've met quite a few people in my time who say they don't rate air tools and then you find they have 25L direct drive compressor that would struggle with a few balloons.

 

[Mee]

Depends on which angle you come from, in engineering it is Free Air Displacement to be technically correct but often delivery is substituted, but hey, as long as the OP gets the gist of the subject instead of terminology then it doesn't really matter.

 

[armalites]

We are talking about compressors, FAD is Free Air Delivery, CFM displacement is a theoretical volume based on pump volume and speed.

http://www.airsupplies.co.uk/cfm-explained
http://www.engineeringtoolbox.com/rating-air-compressors-d_848.html

I've done a quick google(not extensive) and not found anywhere that describes FAD as Free Air Displacement

I take your point though with regard to the OP but terminology is important in this case, once we use the term displacement we are confusing the two measurements we adivising the OP not to confuse.

 

[The Z'eer]

I'm no expert but I would suggest you need something like this

https://www.machinemart.co.uk/p/clarke-industrial-aircompressor-xev16100230v/

I don't think 50ltr would cut it, you need a volume of air to allow for surges in pressure as the pump fires in and out. Too small a tank and your pressure will fluctuate, bigger the better I'm afraid

There's a good article here to explain it all

http://www.sgs-engineering.com/help...buying-guide-which-compressor-should-i-order/

That's great, thank you for the info I guess a unit with far greater sizwed tank really is needed then.

 

[The Z'eer]

I do similar to your description, air ratchets, a gravity feed spray gun, I got a second hand clarke industrial for pennies, 50L with an old twin piston compressor, if you are buying new, I would suggest that and of the v-twin 50litre machines that you see about-rated at 2.5hp would work jsut fine, aldi were doing them at one point.

the thing you haveto work out is will it keep up with your spray gun, most work at 20-40psi so the cfm needs to be adjusted for that if its stated at 8bar

Judging by the prices of a compressor that is 100 ltr and can supply 15 CFM or so I WILL be looking at second hand items.

 

[The Z'eer]

I recently bought a 125l 10bar 3hp vtwin off a lad on facebook for 50 quid. its nearly twenty year old and built alot better than some of the new stuff these days, i filled it up to 10bar a left the shop one night, went back a few days later and still had over 9.5 bar in.

My point is if your going to buy one new i would look for a reputable brand not the cheapest one that meets the your spec as youll be disappointed. The displacement ratings manufacturers give is usually approx 30% less than stated. So if it stats 9cfm its more like 6. So if your tool requires 6cfm its and you want to use it for 5 mins its going to be on constantly on trying to keep up. Its like this with my shot blast cabinet but thats extremely thirsty! If the tank is only 50l its going to get used up pretty quick.

Oil free for any spraywork as the oil can contaminate paint an produce and awful finish, just get inline oilers for tools etc

They don't make em' how they used to eh...nothing seems to last like it did. I doubt I'll be able to afford something which is new and has the capacity, and can supply the volume for three hundred. It'll be second hand I reckon. Thanks for the heads up on manufacturer's claims on supposed CFM. This is a little worrying since the 12-15 CFM machines second hand ain't that cheap, and from what I know already this really is required for HVLP spray gun.

 

[addjunkie]

To get your 15 cfm delivery... I suspect youll be talking about more juice than a 13 amp plug can supply.

3hp motors normally deliver roughly 10 cfm from my research....often needing a 16 amp supply. The figues quoted by manufactures are misleading, but in simple terms each cubic foot of air at the inlet is squashed down by about 33% to get it to 7.5 bar.

Hvlp high volume low pressure, where as the machines you describe as 7 or 8 bar which isnt low pressure. You can get hvlp spray set ups around the 300 mark, but these wouldnt run air tools

 

[The Z'eer]

This is under £300 http://www.ukhs.tv/Workshop/Air-Compressors/Dakota-14-CFM-Air-Compressor

I like the fact that the unit is mobile, that'll come in handy. However the Free Air Delivery or Displacement is not mentioned just Displacement at 14 CFM. Also, at 14 CFM is this just on the border of being capable of an HVLP gun? i.e to safely cover the application would a compressor of 16 CFM be more suitable?

 

[The Z'eer]

To get your 15 cfm delivery... I suspect youll be talking about more juice than a 13 amp plug can supply.

3hp motors normally deliver roughly 10 cfm from my research....often needing a 16 amp supply.

Yeah that could be so, and since it'll be used in a domestic property only single phase is available.

 

[Crater Creator]

I went with a Wolf Dakota 90 litre, with a converted 47kg propane cylinder hooked in as an additional air receiver. Works spray guns (and everything else I have thrown at it) no bother.

 

[addjunkie]

Yeah that could be so, and since it'll be used in a domestic property only single phase is available.

16 amp or 32 amp supplies would still be single phase, you would just need a specific supply with a round blue plug, from the correct breaker in your fuse board

 

[The Z'eer]

First you need to understand displacement, often manufacturers specify the pump displacement which is wrong but makes the machine look better than it is. You need the machines FAD or free air displacement which can often be around a third less than the pump displacement, the FAD is what the actual tank will give as air which is what you can use, and these differ as certain models may state 3HP with 15 CFM and give around 13/14 CFM as FAD while others may also be advertised as 3 HP with 15 CFM and only give 9/10 CFM as FAD.

Straight away you have a problem as a HVLP spray gun requiring 15 CFM is well above what the tank can give, you do have options, you can get guns which have interchangeable needles and a standard gun may come with a 1.8mm needle and requires 14 CFM of air, meanwhile it may have the options of a 1.4mm needle and a 1.2mm needle which require less air which may be inside your compressor FAD rating.

For spraying and air tools you need the largest capacity of stored air as possible, a 50L cylinder isn't going to deliver, the smallest I would use is 500L or the pump will constantly run and overheat without delivering the air required, you do have options and these are to get extra capacity by buying a scrap compressor, usually with a duff pump or motor and using the receiver, years ago I added a blanking cap to mine and removed it to connect a 1" hydraulic hose to connect to my large receiver and only plugged it in when required to give additional air capacity, and undoing it for normal use.

Thank you for the info there

Space might be an issue for 500 litres. Circa 100-200, I think I could accommodate that but 500 is a hell of lot, I've only regular domestic garage space. How long could I roughly spray for with a 100 litre tank? With respect to needle size, what happens if I was 1.2 mm? Obviously per second less paint is gonna dispensed, but could this cause problems? Time isn't an issue here.

 

[The Z'eer]

I went with a Wolf Dakota 90 litre, with a converted 47kg propane cylinder hooked in as an additional air receiver. Works spray guns (and everything else I have thrown at it) no bother.

Was the conversion easy to do? How many litres does a 47 kg cylinder hold? How long could you spray for with regular 90 litre tank?