SIP Compressor problem

Hi, first post on this excellent site, I've been lurking for ages but now need to ask a question.
Recently I bought a SIP compressor it was almost new, virtually unused, model number Model Number 06262, 3.0 hp, 13 CFM, FAD 8.5 CFM and a 150 litre air receiver. The trouble is it's not supplying as much air as I expected, perhaps I was expecting to much? If I empty the receiver completely it take about 7 minutes to reach the cut of at 10 BAR.
I have the air regulated at 80psi but it struggles to run a (cheap) 3inch cut off tool for any length of time. Does this sound about right or is there something amiss with the compressor. Are there any ways to check the efficiency to see if it's working like it should.
The compressor was bought to help me do up a very rusty Hillman Imp, I intended to use the 3" cutoff, die grinder and possibly DA Sander but it's not looking possible at the moment.

Any help gratefully received.

Mike

Seemed a long time to fill, but it's a big tank. I did some calcs - others please comment if I'm wrong - I'm as confused as everyone else about compressor specs.

The tank is 150L which is about 5.3 cubic feet. The cut off is 10 bar so you need to get 10 times that much air in - thats 53 cubic feet. At 13cfm that ought to take about 4 minutes.

Hold on a minute you say - the 13cfm thing is a bit of a lie to do with selling compressors and charging when there's no pressure in the tank. If I can only run about 8.5cfm FAD at a sensible pressure then there can't be any more getting into the tank otherwise it would blow up. 8.5cfm would give you 6 minutes fill. So sounds like the compressor is close to right.

Air tools on the other hand - they tend to be rated optimistically and on FAD. Do you know the cfm rating of the air tools? Some are more suited to actually being used than others. Cheap ones are generally suited to being sold on eBay with no concern for the unsuspecting buyer. Especially when they are sold as "pro" (read 30cfm min).

Could you define the problem with running the cut off tool more clearly ?

Thanks for the quick replies

Malcolm, the 3" cut off tool is rated at 4CFM it's a Machine Mart Clark, so I thought the compressor would handle that fine

Tigler, the cutoff tool runs at full power for a while but the compressor cannot maintain 80psi and the performance drops off, it doesn't rev so high and due to the lack of power the cutting jams. I'll go out to the workshop and see how long it takes till the compressor drops below 80psi from a full tank tomorrow.

Thanks

Mike

We have exactly the same compressor, and had the same problem.

The factory fitted regulator screwed into the tank strangles the compressors output.
We took the cheapo regulator out and piped it straight into a fixed system in the workshop. Theres a reg/water trap etc further down the line. We used a Norgren one, which is much better quality.

The compressor itself is fine, quite powerful. It runs plasmas, spray gun, etc with no problems.

I found the answer on here. Theres probably a bit more information lurking somewhere.

Welderpaul, if it's that simple that'll be great. I'll try a new regulator next week and let you know how I get on, many thanks

Mike

That time to fill sounds about right, my Clarke with the same spec takes about the same time.

As they say above get a better reg, mine has 1/2 inch BSP ports, and try to site the reg as near to your work as possible, that way the pipework is at the higher pressure, allowing greater airflow.

M@tt on here had the same problem
http://www.mig-welding.co.uk/forum/showthread.php?t=12961

Gentlemen a quick update..... I didn't have much time to mess about with the compressor today but I did try the cut off tool again, starting with the receiver full I ran the tool non-stop with no load, the pressure gauge for the receiver (not the regulator) droppedfairly quickly until the compressor kicked in at 110psi then continued to drop (slower) when it reached 50psi then I gave up.
I would have thought the compressor should manage to keep the cut off tool running and maintain pressure. I'm still gonna try and borrow another regulator to see what happens.

Thanks again

Mike

cutoff tools tend to use a lot of air .more than manafacturers seem to state just the same as 4inch air grinders

yoshie said:

I'm still gonna try and borrow another regulator to see what happens.

Click to expand...

what do you hope to achieve with another regulator?, yours sounds to be working fine as the tool is using more air then the compressor can produce and the regulator is not restricting it.

and as you may imagine with cheap air tools not a lot of money and time will be used in their design so they may not be as effecient as a more expensive tool.

I have a similar compressor just with a smaller tank. It will cope with spraying and run my air shears, nailer or nut runner but I have a die grinder which is similar to a cut off tool in design and it totally outpaces the pump's ability to cope running at 90psi which is it's design pressure according to the instructions.

Hmmm, well I tried to see if the problem was the cheap air tool, I borrowed a Mac cut off and timed the difference between the tools.
Clarke cheepie from 150psi to 110 (where the compressor kicks in) 25 seconds, I kept it running until 75psi - 1min 30 sec
Mac tool was the same within a couple of seconds, so what did this prove (if anything) perhaps a more expensive tool isn't necessarily any better on the usage of air, my compressor isn't man enough and my neighbours are quite tolerant.

So where do we go from here?? I have another compressor it's a 2hp Campbell Hausfield model number VT2721, not sure of the spec of the pump but I guess its about 5CFM FAD. Would it be possible to it possible to use these in tandem to give sufficient air supply. As I'm short of room for 2 compressors in the garage could I just use the pump & motor of the second connected to the 150litre tank of the SIP compressor. Most important.... would this be safe!!

Thanks in advance

Mike

yoshie said:

......... Would it be possible to it possible to use these in tandem to give sufficient air supply. As I'm short of room for 2 compressors in the garage could I just use the pump & motor of the second connected to the 150litre tank of the SIP compressor. Most important.... would this be safe!!

Thanks in advance

Mike

Click to expand...

Yes.

You could fit a non-return valve between the output of the 2nd unit and the tank, before the regulator and plumb in a second pressure switch to control the 2nd compressor. Set them at slightly different pressures so they don't switch at the same time to avoid surges on the mains.

Have a look here http://www.mig-welding.co.uk/spray-painting.htm

Just a thought but have you checked the tension of the belts, and is the air filter clean.

eil, Checked the belts and the filter it seems it's just not up to the job pretty disappointing really.

rtbcomp, I plan to use the two compressors to get the extra ooomph I need, you mention fitting a one way valve but I've searched the net but cant find one it would need to be 1/2"BSP any suggestions where I will get one, is it necessary?

Cheers

Mike

Have a look in the Links Forum, Compressed Air thread, Airline Components post, a few suggestions there. One way valves are also known as check valves and non-return valves.