Hyspeco

In Pounds per square inch

Word Formula:
PRESSURE = FORCE (POUNDS) / UNIT AREA (SQUARE INCHES)

Letter Formula:
P = F/A or psi = F/A

CYLINDER AREA

In square inches

Word Formula:
AREA = pi (3.1416) X RADIUS SQUARED (INCHES)

CYLINDER AIR CONSUMPTION

Per inch stroke, forward and return

The figures in the table below are generally used to size an air compressor to power the piston with the applicable bore. The figures are estimates only, and assume the standard rod size and a cycle where the cylinder stalls at the end of stroke momentarily and then immediately returns. Rod sizes will seldom effect the air consumption significantly. Stall force is assumed at 75% of maximum force available to the cylinder. To achieve normal speeds, the regulator needs to be set 25% above the stall pressure.

Table usage:

1) Determine the regulator setting in PSI and refer to that column.

2) Find the number in the table where the regulator PSI meets the cylinder bore.

3) Multiply this number by the stroke of the cylinder.

4) Multiply this number by the number of strokes (forward and reverse) that you will expect in 1 minute.

5) The resulting number is the Approximate SCFM for the application

Bore Dia.	60 PSI	70 PSI	80 PSI	90 PSI	100 PSI	110 PSI	120 PSI	130 PSI	140 PSI	150 PSI
1 1/2	.010	.011	.012	.013	.015	.017	.017	.018	.020	.021
2	.018	.020	.022	.025	.027	.031	.032	.034	.036	.039
2 1/2	.028	.032	.036	.040	.044	.049	.051	.055	.059	.063
3	.040	.046	.051	.050	.062	.070	.073	.078	.083	.089
3-1/4	.047	.053	.059	.065	.071	.081	.084	.090	.096	.103
4	.072	.081	.091	.100	.110	.125	.129	.139	.148	.158
5	.113	.128	.144	.159	.174	.197	.204	.219	.234	.250
6	.162	.184	.205	.227	.249	.282	.292	.314	.335	.357
8	.291	.330	.369	.408	.447	.507	.525	.564	.603	.642
10	.455	.516	.576	.638	.699	.792	.820	.881	.942	1.00
12	.656	.744	.832	.919	1.01	1.14	1.18	1.27	1.36	1.45
14	.891	1.01	1.13	1.25	1.37	1.55	1.61	1.73	1.85	1.96

Cv Factors

Flow Factors for air valves

Air valves are often rated by using a Cv factor supplied by the manufacturer. This system for rating valves is a very misunderstood rating system, so let's try to take the mystery out of it. The Cv factor is found by a calculation that states that the flow of a valve is equal to the square root of the differential pressure of the valve times the square root of the total of the inlet and outlet pressure of the valve times 0.6875 when the flow factor is 1.00. There, that should clear everything up for you ? okay, maybe not. The Cv factor, in terms that I can understand, is a description of how easily air can flow through a valve. It's a good sign as to how effective a valve can be, and it gives you a good indication of which valve to use in a given application. The higher the Cv factor, the less pressure the valve will use, and the more pressure available to do work at the application. Be aware that the differential pressures that the Cv factor is figured at, the temperature that the testing is done at, and the fluid used in the tests can effect the outcome. Often you will find that manufacturers can manipulate the Cv factor of their valves by altering these parameters, so read the fine print!