Thread: Help With Air Compressor

Originally Posted by hitch

t has two identical dials one marked Tank and the other Outlet. I think I understand Tank but what does the Outlet dial tell me?

Tank is tank pressure, dial is pressure "dialed in" at outlet

It has two connection points so I guess two devices can be attached and used simultaneously?

The only simultaneous devices that can be driven with such small tanks are "air brushes"
The idea of two outlets is to have two devices hooked up but only use one at any one time. A 3HP belt drive with a 100 L tank is needed to drive most two devices simultaneously.

Anything else I should know about the efficient and safe use of a compressor.
To start with I have a finishing nailer, air gun and tyre inflater to be driven by it.

Make sure it has the right amount of oil in it and don't run it continuously or it will die.
Also completely vent the tanks after use every 4 or 5 uses to release the condensed water from the tanks to reduce rust development.

Thanks BobL, very helpful.

With regard to the outlet dial I guess the yellow knob near it is for setting the outlet pressure which I suppose could vary from tool to tool/application. Is that a major consideration or is there an average (sweet spot) to suit most applications? According to a label on the compressor it is rated at 130L/min free air ("under normal operating conditions" - whatever they are) and given it is a small capacity compressor, should I simply set it to max?

Originally Posted by BobL

The only simultaneous devices that can be driven with such small tanks are "air brushes"
The idea of two outlets is to have two devices hooked up but only use one at any one time. A 3HP belt drive with a 100 L tank is needed to drive most two devices simultaneously.

These outlets also make it easier in that you can have an oiler on one line and run the other dry.

This saves you from swapping hoses around if you're alternating between the two. eg. using the oiled line for a sander and the dry line for blowing down.

(In this case, both lines should be filtered to remove water, obviously! )

Originally Posted by hitch

With regard to the outlet dial I guess the yellow knob near it is for setting the outlet pressure which I suppose could vary from tool to tool/application. Is that a major consideration or is there an average (sweet spot) to suit most applications?

Most tools have a maximum rating and it should be dialed down to suit. When you buy your air-tools, if you keep an eye on their ratings you'll probably end up with just such a "sweet spot." But there's always some tools that you'll need to readjust for.

It's Murphy's Law, innit?

Originally Posted by hitch

Thanks BobL, very helpful.

With regard to the outlet dial I guess the yellow knob near it is for setting the outlet pressure which I suppose could vary from tool to tool/application. Is that a major consideration or is there an average (sweet spot) to suit most applications? According to a label on the compressor it is rated at 130L/min free air ("under normal operating conditions" - whatever they are) and given it is a small capacity compressor, should I simply set it to max?

Each air tool documentation usually states the operating pressure required, but pressure won't be a problem, FAD (free air delivery) could be a bigger problem for some tools. Most compressor labels overstate their FAD rating and some state the Pump rating (which is always more) instead of the FAD rating. With such a small tank you won't be able to drive any rotary air tools or normal spray paint unit for more than some 10's of seconds. Even if the FAD is 130 L/min that is almost certainly continuous and these compressors cannot be run continuously. So a more realistic FAD is half that or 65 L/min

Here is a list of air tools and the FAD required.
Air Tools and Air Consumption

To convert L/min to cuft/min divide by 28.3, so a 65L/min = ~2 cuft/min, enough to run a small nailer and pump up tyres but that's about it. Don't expect to be using a regular spray painter.

The yellow knob would be the pressure regulator control knob. On most regulators, the knob is pulled up/out to adjust and pushed down/in to lock the adjustment so that it does not change with vibration etc. Not familiar with your machine but if you cannot freely rotate the knob try pulling/lifting it. The knob normally moves about 3 mm to unlock.

With dual outlets, you could have one which is unregulated and has fluctuating pressure and another which is regulated and should maintain a constant user selected pressure, or you could have two regulated outlets.

If the system has one regulated and one unregulated outlet, then the unregulated one should only be used to connect a tyre inflator, blower nozzle, an external tank to increase the available storage capacity, or a bulk delivery line with remote regulator. Pressures at an unregulated outlet can reach 110 - 120PSI before the motor cuts out, and will fluctuate down to about 90PSI before it restarts. An unregulated outlet normally will not have an integral moisture trap to remove condensation.

Most air tools have a rated operating pressure of around 90PSI and operating at excessive pressure can damage seals etc creating problems. The major exceptions are spray guns, particularly HVLP types which frequently operate at about 30PSI, and often use a dedicated regulator at the tool inlet to compensate for pressure loss in the line. Like Bob above, I suspect that the unit will not safely source air for a full size spray gun, but it may cope with a touch up gun and should cope with an air brush.

With regard to draining the tank after use, there are two common drain points. There is normally a water trap incorporated into the regulator. These days these are commonly self draining through a valve that opens once the system pressure falls to about 15PSI, and closes when it increases above that level. These valves typically hiss while venting air and moisture. There should also be a screw plug at the lowest point of the tank to drain condensation that has settled in the tank. This needs to be partially unscrewed once the tank pressure has bled to near zero, then retightened once all moisture flow has ceased. Do not open this fitting while the tank is pressurised, there is a possibility of high pressure water ricochetting of the floor and hitting you in the face, or the screwfitting being ejected from the tank and lost or damaged.

Thanks Skew and BobL. Very good information. I don't have great expectations of this small compressor - it was a opportune purchase that came up at an auction I attended to purchase other things. It didn't cost much and I thought the portability a good feature and an opportunity to learn.

Thanks again

Austech is the company that supplies Scorpion, and HERE is a list of Tassie distributors.


Hope this helps.

Malb, thanks for your detailed response, very informative. Particularly good stuff re the pressure regulator control knob. I couldn't get it to turn so thought it was stuck/faulty and the current setting of 110psi would have to do for now.

I would like to try a spray finish on smallish items and have noticed that Scorpion have a gun that is about half the size of a full size gun that may be ok. This is another area about which I have almost zero knowledge and will keep your comments and others in mind as I look into it.

Always a great day when you learn something new.

Thanks

Thanks Yonnee for the references. I'll have a chat with the usually very helpful staff at Nubco Devonport when next I'm in town.

A friend uses this style with a 2HP 40l tank direct drive comp for small jobs and is happy with results. Listing info claims 8CFM air flow required, but that seems a bit steep.

There are also gravity feed styles available. This one clames 1-4 CFM air supply. Don't know anyone using one though.

Running with the reg set for 110PSI would be pointless for most things as that is about the motor cuttout point, after which the pressure will drop as you draw air. Be guided by tool instructions but 85 to 90 PSI is normally good, within the specs for most tools and just below the point where the motor cuts back in. Should be able to maintain pressure fairly well at that point if not overtaxed .

Thanks Malb.

I wondered about a gravity feed gun and still need to do the research. I'm retired and you know how it is - there just isn't enough hours in the day. Particularly so as I work to set up the new shed from scratch which is fun but I would rather be creating something. Also a new house with lots of landscaping work to be done to finish it off. Life's good and never a dull moment.

I have put a watch on the gravity feed gun in your post and it may be a cheep enough purchase to consider it research if I were to win the auction and it didn't work out.

Thanks again for your interest and valuable assistance

Ian

that compressor (if im not mistaken )is the twin tanked lightweight site job,its meant to run a frameing gun solo full time or two fixers full time.My poaching mate has one and while they are a great job they are not up to running a framer full time and motor gets very hot very quickly.Last job i used it on was with a t nailer on 8.00 mtrs of picket fence........ i went and got another compressor from the shed!

Hi Hitch,

the machine you bought looks like a fine piece of kit. Manoeuvrable, with a good type of oil lubricated Italian compressor unit, two stacked tanks (making a smaller footprint than one large one) and all the gauges and settings on top, together on one panel.

If you allow me, i'll continue in the European way (bar instead of psi). Systems this size are usually laid out for 10 bar max tank pressure. An automatic pressure sensitive switch starts the motor when the tank pressure drop below a set value (75 to 80% of max value) and stops the motor at max level. The compressor is connected to the tank through pressure tubing, with a one-way valve just before the tank. This valve prevents the tank pressure from bleeding away when the compressor is switched off. The pressure activated switch is also connected to the pressure tubing and has an additional bleed valve. When max pressure is reached, the membrane inside the switch box is pushed outward enough for a certain treshold value and trips both the switch and the bleed valve. The valve opens and releases the built-up pressure in the cylinder head and the pressure tubing up to the tank (with the tank's one-way valve preventing its emptying). This pressure release is necessary for the next start-up cycle. With the pressure still present in the cylinder head, the motor would not be able to start up. So at every switch-off, you hear this short and loud hiss of the cylinder head and pressure tubing being vented. 10 bar compressors usually switch on when the tank pressure drops below 8 bar. An 8 bar system switches on at approx. 6 bar.

You can calculate the yield of the compressor. Often the intake amount is mentioned (number of liters per minute drawn through the filter and the cylinder's inlet port), because it's a three digit number that looks impressive in the brochure. But this is not a very valuable statistic. When an amount of air is compressed to 10 bar, this means the volume of 10 liters is compressed into 1 liter. So, at an intake of 200 liters per minute, a 10 bar system would deliver 20 liters of 10-bar-air per minute. That's enough for car tyres, a blow-clean nozzle, a staple gun or a spray gun, but not nearly enough or air tools like wrenches, drills or hammer pistols. As stated in posts above, you need multi-HP systems with 500-1000 liters intake per minute for that.

There is a lot to be found on air consumption of various air driven tools on the web. Many air tools run on 6 bar, sprayguns use 1 to 3, airbrushes 0.5 to 2. Set on 0.5, you could even pressurise a beer vat and run a nice garden party "draw your own pint"system on it. The only disadvantage is the beer going flat sooner as wanted, because the air dilutes the carbondioxide in the beer. That's why there is CO2-gas on the beer taps, to keep the flavour intact. But 0.5 bar is the ideal pressure for a nice layer of foam on top (provided the beer is lager type), should you ever want to experiment.

The adjustable outlet valve is pushed down with a spring, which acts against the pressure coming from the tank. With the turning knob you set the compression of the spring. When turned tight, it pushes with a force equal to the counterforce of the tank pressure, so no air bleeds out. When turned "open" and with the spring loosened a bit, the difference between tank pressure and spring force determines how much pressure leaves the outlet. This makes for an accurate outlet pressure regulation between zero and full tank pressure. The gauge for the outlet pressure is the most important; this will tell you how much pressure is set for the intended tool or attachment. But the tank gauge is also nice, because it gives you the present status on the tank fill. E.g. when you decide to start an expensive spray job and you see the tank pressure drop below the switch-on setting during the job, you are warned that you may have forgotten to plug in the machine. Left with too little pressure, the spray gun will no longer vaporise the paint in a fine enough manner but will rather splatter droplets, ruining all your work. Not plugging the compressor in happened to me once, that's why i know the value of the tank gauge by experience.
As a last detail, pay attention to the extension hoses. When chosen too thin, the pressure drop after a few metres will be too much, especially with greedy air users like tools. Use a good quality reinforced hose with a generous gauge and also use those handy bajonet couplers. A moisture trap is advised, too; they keep condensed water droplets in the air from reaching the inner working of air tools or the delicate results of a spray gun!

And dont forget to drain the consendate from the tank now and then, to keep them from rusting from the inside. Bleed away the tank pressure down to approx 0.3 bar, then open the drain valve. Store the compressor without pressure and in drained condition, when you won't use it for some time. Check the lube oil level now and then.

Good luck and greetings!

gerhard

Thanks for your comments danielhobby. I will monitor the motor closely to see how hot it gets and how quickly. Probably consistent with other comment about its unsuitability for continuous operation.