Faulty new compressor?

[Adam Wardlow]

Hi,

Recently purchased a compressor. It's the first one I have had, although I regularly use my dad's compressor which is a similar size with no problems for the stuff I generally do.

I am pretty certain there is something wrong with it. It's a 200L 3Hp piston model. 14 cfm displacement, 9 cfm free air delivered. It takes close to ten minutes to fill up from empty, and I have been trying to do some wire brushing using an air drill, and it can't even keep up with continuous drill use. The drill is a 5.5cfm model from SGS, and I have my regulator set at 90 psi. The compressor stops at 125 psi and starts at around 90psi, and takes roughly 2 minutes to top back up, with no load, but with the drill running, it just can't keep up and the pressure continues to drop.

Called the company and the engineer reckons my drill is too big, but I don't think 5.5cfm is particularly large? Pretty certain this compressor should be able to keep on top of that?

Does it sounds like the compressor may be at fault, or am I simply pushing it too hard with continuously running the drill?

Thanks in advance

 

[julianf]

Sounds like there is an issue to me.

 

[Seadog]

Do you know the air flow at rated pressure. It's common for compressor manufacturers, at least in the small "domestic size" market, to quote the swept volume per minute at atmospheric pressure.

 

[hotponyshoes]

I expect the drill uses 5.5cfm at 90psi.
If the compressor can only produce 9cfm at free rate it might struggle to keep up with that.

You will have to do some maths to work out if it should be able to cope or not. That will give you something to show to the engineer if it should be able to run it.

 

[Adam Wardlow]

Do you know the air flow at rated pressure. It's common for compressor manufacturers, at least in the small "domestic size" market, to quote the swept volume per minute at atmospheric pressure.

I don't I am afraid. I estimated the fill times based on 9 cfm, and assumed it took longer when I first started it when it arrived because the 9 cfm would not be constant at rated pressure. Using it for the first time this morning to wire brush something, and it's virtually unusable -- as I say, can't even keep up with a small drill.

 

[zzr1200]

Where did you buy the compressor from ???

And any photos of it available + data plate??

 

[Adam Wardlow]

Was bought from air-compressorsdirect. They don't seem to have it in stock any longer, but it is this model:


https://www.ebay.co.uk/itm/184159143182

 

[Cobbler]

Air tools tend to be rated at 25% use, so the air drill on continuous use could be taking about 20 cfm. I only found this out due to buying an air tool rated at 4cfm, looked at the leaflet inside & it stated rated at 4 at 25% 16 cfm continuous. When I looked into it, this is standard practice. This is fine for some tools like an air chisel or rattle gun that you use intermittently, but for a die grinder or such not so good.

Air tools are nice, but very inefficient, when it takes a 3 HP compressor to run a die grinder that the electric equivalent would be about 500 watts.

 

[MoreWellie]

I remember reading that you had to double the cfm of the tool to compare it to that of the compressor. It shouldn't be that way but I presume the compressor and tool people are both optimistic but unfortunately in different directions

Unless you have a lot of air available (your compressor spec is better than mine but still shy of what I consider a professional setup) I find that electric tools are better than air as they don't have to top up and, providing you buy decent ones, they can handle the continuous use

Edit: @Cobbler has a better explanation of why tool requirements and compressor output don't match

 

[hotponyshoes]

Is this a brand new compressor?
I'm sure there was something in the instructions for mine about running it in.
Something like fill with oil, leave the output valve open so it can't build up any pressure, run it for half an hour then check the oil again.
Maybe the piston rings need beding in or something?

 

[daleyd]

Have you checked things like belt tension, bolts on head are tight, no leaks ?? If you turn it in and don’t run anything does the pressure drop over say an hour?

 

[Adam Wardlow]

Hi all,

It is brand new. It does hold pressure with no load. After I plumbed in all my regulators etc, I left it for a few nights and I think my whole system may have lost a couple of PSI, so no major leaks. No squealing belts, and no sign of them slipping.

My father's compressor is a similar size (smaller tank actuall 150L), and I'd have no problems at all running his air drill for wire brushing something. Maybe as Cobbler says, the air tools I have just tinned up for are far hungrier than they state.

 

[daleyd]

Can you try your tools on your dads compressor?

 

[hotponyshoes]

The only difference the tank size will make is once it has charged up you will be able to run the tool for a bit longer until it kicks back in again.
As said above maybe try running your drill on his compressor to see that one handles it.

 

[Adam Wardlow]

I'll check my gear on his compressor in a few weeks when I am next there.

Tools aside though, pretty sure it shouldn't take 10 minutes to fill up from empty either.

 

[Al Strachan]

200ltr with 3hp and 10 mins. I have a 50ltr 3hp comp and it takes 2-3 mins from empty and its in good(ish) nick. sounds about right.

your quoted CFM is displacement. CFM FAD (free air delivery) is the figure thats comparable to the consumption of tools and it'll be less than 10 cfm .

i have a die grinder thats quoted as 7.6cfm, and my 3hp compressor (14cfm displacement) manages to maintain around 4 bar with continuous use which isnt great.

Worth checking you compressor over (finger over the inlets and you should get a nice suck/change in noise) but i think its just down to exaggeration in specs of DIY/cheaper tools.

 

[angellonewolf]

as above he just beat me to it

cheaper air tools generaly require more air than good quality

i got a blue point 1/2 inch and only a small compresser (actualy 2 one for blowing air as only very small tank i use most of the time the 2nd for bigger jobs spraying etc ) still the bigger one will only run the 1/2 inch gun for only 10/20 seconds the small one only 3/5 secs most of the time im working on bikes or a mower so even the small one normaly undoes the mower blade nuts that are hard to undo with a breaker bar as you have to hold the blade and then turn the nut

but i did use a cheapy 1/2 inch on the small and on my bigger one was eather a parkside or unnamed ebay special for the otherhalf father as he could not get it to run on his compresser only near done half a turn with my small and only a few seconds with the bigger

 

[daleyd]

Mines a 150l and probably takes a good 5-7 minutes from empty - never timed it but I can check

 

[daleyd]

Bit less than that for mine (150l) - it took just over 3 mins from empty so yours does sound a little excessive...

 

[dan treg]

if its a 200 lt tank which is about 7 ft3 and shuts of at about 120 psi then your getting air delivery of about 6 cfm . you can forget the hypothetical 14 cfm under load you will never see that . would say its about right especially as compressor specs are usually very optimistic . my compressor takes about 6 minutes but is two compressors chained together so your timings dont sound along way off to me