Is there any reason not to charge a compressor upto 8bar?

Most likely your compressor was set at a cut off that is most efficient for the design of your compressor. If I remember correctly, 1 bar is just over

First, find out what your compressor is rated for. Second, for any given pressure that is demanded by your actual tools that you plug in, the most efficient compressor setting would be pressure just above that. Increasing pressure beyond that only wastes energy.

wrote: (clip) Has it been set to 7 intentionally, or is it normal to 'fine tune' it during its first few used? Any info would be appreciated. ^^^^^^^^^^^^^^^^ Certainly, besides the pressure switch (now set to 7 bar) it must have a pressure relief valve. As long as that is working properly, I don't think there is any danger.

compression

Jon,

If it's been sold in the UK it should bear a test plate stating the test pressure and the safe working pressure - or just conceiveable be provided with a certificate - though unlikely if sold into the 'hobby' market.

AWEM

really? when i'm blasting at 40psi, i can run a long time given a large tank between times the motor actually kicks on. if it was producing 45 psi in the tank, the motor would be running all the time.

regards, charlie

Aside from the differential, what's the formula for energy stored in a tank vs pressure? Proportional to the square of pressure maybe?

Best regards, Spehro Pefhany

If your compressor needed to run all the time to produce 40 PSI at your demand rate, you could not go above 40 PSI. Since you can go above 40 PSI, your motor would run intermittently.

I would expect it to be proportional to cube of pressure, since temperature of compressed air rises proportional to compression. That extra heat is fully wasted, unlike the (potential) mechanical energy of compressed air.

Yep, really. Have you ever noticed that many compressors give 2 different cfm ratings? One will be at a low pressure, and one will be at a higher pressure. The higher pressure always has a lower CFM.

Of course an air compressor motor uses a lot of electricity at start up, and less once it's up to speed, so that would have to be figured into the equation.

Dave, who has a 3000 psi compressor, and a booster for when that's not enough. :)

All depends upon the parts, and the design working pressure of each part. 12 bar (175 PSI) is not uncommon (usually with regulators on the outlets to drop to 6-7 bar (90-100 PSI) for working), but only if the compressor, tanks and all accessories are designed to take that - and your more sensible/cautious practitioner will prefer a system where all parts (perhaps excepting the compressor) are rated for a good deal more (say 20 bar/300 PSI) for some safety factor, with an over-pressure relief valve set above the working pressure and below the max safe rated pressure.

It sounds to me that you are getting pressure and volume mixed up. You could have a compressor that puts out 500 cubic feet a min. but not the power to compress more than 50psi. and you can have a compressor that puts out 300 # of pressure but just a .25 cubic feet a min. like those little compressors that run off your car battery for flats. Dick

If this is a single-stage one cylinder compressor, 7 BAR / ~100 PSI is a reasonable setting and will run most any tool you have. You can go slightly higher IF the pump and motor combination can handle the extra load, and the tank and plumbing are rated for it.

The manufacturer deliberately sets the pressure switch in the factory at a "safe" level slightly lower than the maximum the pump and motor assembly can attain, so they don't have to deal with failures brought on by excessive running time (as it labors to get that last pound) or motors overheating.

All pumps have a maximum pressure where you don't get any useful output, and for a small single stage, that's about it. If the motor doesn't overload and stall, the pump output drops off to nothing.

And they set the switch with a reasonable differential point of between 15 - 30 PSI (1 - 2 BAR) so it isn't starting and stopping constantly - you can damage the motor by starting it more than 6 to 10 times an hour, the start capacitor or winding can overheat.

If you need higher pressures on a regular basis, you have to go to a two-stage pump. They are good for 150 - 175 PSI.

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Call the manufacturer and ask them. I did so with a similar situation many years ago. The engineer that I finally got connected to asked for my telephone number and called me back to make certain that I was who I said I was, not some government official! He reminded me that the tank on my compressor was not ASME certified. But he then told me that it was fine to turn it up. I did that in about 1980 and have been using it that way ever since.

snipped-for-privacy@alcatel.co.uk wrote:

No, increasing tank pressure as much as possible (subject to the compressor's capabilities and the tank rating) will increase efficiency. This will be most noticeable if you use a "thirsty" tool in short bursts.

Yes, square - ignoring losses.