Which kind of compressor is use into plasma cutters?

[Memmeddu]

Which kind of compressor is used into built in compressor plasma cutters?
Now that I'm looking to buy a plasma cutter I'm making research about .
So was thinking that maybe is better to me buy a built in compressor plasma cutter.
But they are more expensive and have lower duty cycle lower amperage
So what about hanging around a little compressor as the ones used in this machines?

 

[frank horton]

there's always a need for a decent compressor around the workshop, just get a get something u can just about lift into your van..that'll be big enough and of use for the other jobs you will find for it...........

 

[Memmeddu]

Can not found a compressor as the ones used into plasma cutter .
I think that they will be perfect for .
I don't have idea of how much out put may have one
I the specific my future plasma needs 180 litres minutes
Little 2hp 6litres compressor give 200 litres but is the input of air ,but if Einstein wasn't wrong is also the out put .
But I not sure maybe need to hack the pressure switch to start charging at 6bar to have a decent amount of air

 

[timgunn1962]

Most compressors will give a "displacement" figure. That is the amount of space displaced by the piston(s) in a minute.

There will be some dead space above the piston. Air will only flow out of the cylinder when the pressure above the piston is higher than the pressure in the receiver. Air will only flow into the cylinder when the pressure in the cylinder is less than atmospheric pressure. At zero receiver pressure, the output will pretty much equal the displacement.

As the receiver pressure goes up, the pressure of the compressed air left in the dead space above the piston will also become greater, so less of it will be transferred to the receiver. The trapped air will expand as the cylinder goes down, so the pressure in the cylinder will be less than atmospheric for a smaller proportion of the stroke, meaning that less air is drawn in.

Better compressors will usually quote FAD at pressure values as well. FAD is short for Free Air Delivered and is the volume of air you'd have if you allowed the air to expand to atmospheric pressure. It sounds like a con, but it saves a lot of calculation to standardise it like this, rather than quote the compressed air volume at a pressure.

http://www.aiedirect.co.uk/page9.html

The link is a spec for a 3HP compressor that I happen to know gives both a displacement figure (16 CFM/455 l/min) and an FAD at 7 bar/103 PSI figure (10.6 CFM/300 l/min). At pressure, it loses 1/3 of its throughput and I suspect it is pretty good compared to many other compressors. We use them at work because of their low speed (950 RPM all-iron pump) and relatively low noise level: on good A/V mounts, we get noise levels that mean we don't need to wear ear defenders when walking through the room (but would if we were staying in there with the compressor running for more than half-an-hour or so per working day). Efficiency and FAD were not really factors in the purchasing decision.

I am no expert on compressor design, but I'd expect it to take better design and tighter manufacturing tolerances to get the dead space down, and the FAD at pressure up, without risking the piston hitting the head. The more expensive piston compressors "generally seem" to give higher FAD at 7 bar than cheaper compressors of the same displacement. I've never really had an application for vane- or screw-compressors, so I can't comment on them.

If you use a compressor with an FAD at pressure that exceeds the needs of your plasma cutter, you'll be fine with a small receiver. If you have to use a compressor with a lower FAD at pressure than your plasma cutter needs, you'll need to keep stopping to let the receiver fill. In this case, a big receiver will let you run longer between stops than a little one.

Over here, a 3HP single-phase compressor is as big as we can run on a fused 13A UK domestic socket, so is really our sweet-spot. It's usually a good idea to have spare fuses handy and I always use 16A industrial plugs and sockets for them when I can.

If you need portable(ish), a direct-drive 3HP compressor on a 25-litre receiver would be as small as I'd want to go: something like the Abac Poleposition L30P

http://viewer.abacaircompressors.com/ABAC_PistonBinder_ProBooklet_v07/#page/10

It'll be horribly noisy (3000 RPM aluminium pump). We keep one or two at work as emergency spares because one guy on his own can throw one in a car, take it to site and get a plant back up and running until we can fix or replace a "real" compressor.

 

[Memmeddu]

I have a little 6,5 hp Lombardini petrol engine
I may search a pump that can be run by this engine
But much work is needed to
I need also a fuel tank ,and a little air tank ...

But if I will find one ready to start cheap may be my choice

 

[8ob]

I have a little 6,5 hp Lombardini petrol engine
I may search a pump that can be run by this engine
But much work is needed to
I need also a fuel tank ,and a little air tank ...

But if I will find one ready to start cheap may be my choice

I have a small electric start diesel compressor up for grabs, if you can find a big jiffy bag I may be able to post it

Its along the lines of this https://www.ebay.co.uk/p/Clarke-Sd2...ompressor-2085281/9013971524?iid=302584086927

Bob

 

[Memmeddu]

I have a small electric start diesel compressor up for grabs, if you can find a big jiffy bag I may be able to post it

Its along the lines of this https://www.ebay.co.uk/p/Clarke-Sd2...ompressor-2085281/9013971524?iid=302584086927

Bob

Its little bit big

 

[Morrisman]

My Rtech plasma cutter uses a surprising amount of air. I thought I could fill a small reservoir fastened on my welding/cutting trolley, and it might last a while, but no chance of that.
I have a small 6cfm compressor that I use for general shop air, good enough for the plasma cutter, but too small to run an air tool off for long.

 

[Memmeddu]

Ok so was checking the technical features of the model which I would like to buy , and I am very surprised ,it needs only 120 litres pour minute so essentially any little compressor may work maybe ,I think that will never hit the duty cycle
Now the question is how far is the input from the output
So if we have 200 litres imput ,how much out we can have?