Air consumption

1. Calculate the displacement of each cylinder (pi x r² x stroke) - this is probably best done by converting mm to ft at this stage, to avoid confusion with the units later on.

2. Calculate the average number of powered strokes per minute. If operation is infrequent, average over an hour, or even 8 hours.

3. Minimum required cfm (at working pressure) is (number of strokes/minute) x (displacement per cylinder). Add a safety margin - how much you add is down to your judgement, or advice from someone who has had experience with similar systems.

4. If operation comes in bursts, with periods of inactivity between, you must size for the cfm required during the active period - the size of the receiver comes into this.

Or, contact three or four pneumatics suppliers (or one trusted one), give them the details, and ask them to work it out for you. If you don't know the suppliers well (or they have not been reliably recommended), you can usually say that the required figure is more-or-less the average of the two or three closest answers. Be suspicious of any answer which is much larger or smaller than the others.

If you do use a supplier's recommendation, make sure you've given them all the facts in writing, and get their offer in writing, before you buy. It will put you in a much stronger position if you install the system & find you're running out of air!

DON'T FOR GET TO FIGURE THE VOLUME OF AIR IN THE FLOW LINES BETWEEN THE AIR VALVE AND THE AIR ACTUATOR.

That is volume that must be filled each cycle and can be a lot on poorly designed applications.

Had a customer call once about low operating pressure after 5 minutes of running his assembly line. The machine builder had figured the amount of air to run the cylinders but had not figured how much air it took to fill the lines between the valves and the cylinders.

Unfortunately the valves were mounted on columns along the line and tubing was neatly fabricated to take the air from valve to actuator at distances of up to 25'. The air to fill and exhaust the lines between the valves and cylinders actualy required more compressor volume than it took to run the cylinders.

They had to run a second 2.5" air line to run the line. It had over 120 air cylinder operatins.

If at all possible, ALWAYS MOUNT AIR VALVES AT THE CYLINDERS OR OTHER ACTUATORS. The air to fill the lines to the valves may be longer but that air does'nt exhust every cycle like the lines between the Valves and Cylinders.

It may be moer trouble up front to build the circuit this way, BUT, the old saying, "Pay Me Now or Pay Me Later" always works when supplying air to cylinders.

Buy the calculator available less than $5.00 from :

http://www.about-air-compressors.com/cylinder-calculator.html

As per "About air compressors.com".

The formula to use to determine the area of a circle is:

Pi x r2 or 3.14 x the radius squared

We'll use a 2.5" bore air cylinder for demonstration purposes. A 2.5" bore cylinder will have: 3.14 x r2(1.25 x 1.25) or, 4.90 square inches of surface area on the piston face.

Using this same 2.5" bore cylinder, let's make the stroke 10". That means that this cylinder 'holds' 4.9 x 10, or 49 cubic inches of compressed air.

If we extend and retract this cylinder - one cycle - that's 98 cubic inches of air we'll need for one extension and one retraction.

98 cubic inches of air x 10 complete cycles per minute = 980 cubic inches of air consumed per minute

A cubic foot of compressed air has 1,728 cubic inches in it, therefore:

980 cu inches divided by 1728 = .6 cubic feet of air.

Now work on yourself. Please thank About air compressors.com

depends on the cycling rate, and the size of your tank.

calculating capacity of air compressor:-

1.find out the speed of compressor

2.calculate the volume of cylinder: stroke lenght x cross section area of cylinder=volume (nm3)

3.calculate the nm3/hrs= volume / hrs=nm3/hrs or cfm

thanks

r.c.mandal

C.E.(INDIA)

Hi:

Please note that ussually the Compressors makers, refer the capacity of compressors in terms of Nm3, so you need to specify this value and your delivery pressure.