Compressed Air Flow Volumes for Various Sized Orifices

The values in the chart represent tested SCFM air flow through a round, sharp edged orifice. These test results are particular to pressure indicated.

In a plant, you will probably never come across a perfect, round, sharp edged orifice leak anywhere in your plant facility. Leaks occur in joints, couplings, slits or gashes in pipes and lines, and other types of fittings. Thus, the tables presented here can only be used as a guideline and actual leak values will be less than what are listed here. Real world examples, divide these numbers by two.

PSI Across Orifice	Orifice Diameter, in inches
	1/64	1/32	1/16	1/8	1/4	3/8	1/2	3/4	3/4	7/8	1
5	.062	.249	.993	3.97	15.9	35.7	63.5	99.3	143	195	254
7	.073	.293	1.17	4.68	18.7	42.2	75.0	117	168	260	300
9	.083	.331	1.32	5.30	21.2	47.7	84.7	132	191	260	339
12	.095	.379	1.52	6.07	24.3	54.6	97.0	152	218	297	388
15	.105	.420	1.68	6.72	26.9	60.5	108	168	242	329	430
20	.123	.491	1.96	7.86	31.4	70.7	126	196	283	385	503
25	.140	.562	2.25	8.98	35.9	80.9	144	225	323	440	575
30	.158	.633	2.53	10.1	40.5	91.1	162	253	365	496	648
35	.176	.703	2.81	11.3	45.0	101	180	281	405	551	720
40	.194	.774	3.10	12.4	49.6	112	198	310	446	607	793
45	.211	.845	3.38	13.5	54.1	122	216	338	487	662	865
50	.229	.916	3.66	14.7	58.6	132	235	366	528	718	938
60	.264	1.06	4.23	16.9	67.6	152	271	423	609	828	1082
70	.300	1.20	4.79	19.2	76.7	173	307	479	690	939	1227
80	.335	1.34	5.36	21.4	85.7	193	343	536	771	1050	1371
90	.370	1.48	5.92	23.7	94.8	213	379	592	853	1161	1516
100	.406	1.62	6.49	26.0	104	234	415	649	934	1272	1661
110	.441	1.76	7.05	28.2	113	254	452	705	1016	1383	1806
120	.476	1.91	7.62	30.5	122	274	488	762	1097	1494	1951
130	.494	1.98	7.90	31.6	126	284	503	790	1138	1549	2023
Values calculated based on dry air at atmospheric pressure of 14.7 psia, 70°F.

Common Air Leaks and Misapplication

1. Optical scanning equipment clean off - small blower will do just as good at a fraction of the cost
2. Air hoses - loose or frayed clamps
3. Air lances and fittings which are casualties of the fork trucks and other equipment
4. Large Computer and electrical rooms - pressurized to keep out dust - small blower effective at less cost
5. Conveyor belt cleaning - again, use a small blower
6. Cooling machinery bearings- use a fan
7. Worn cylinder packing, worn "O" rings in solenoid and control valves, faulty PR valves or broken diaphragms, bleed- off vent holes in valves

Characteristics of Leaks There are several important points to keep in mind with regard to leaks:

• Leaks are DYNAMIC - they are constantly reoccurring
• They cannot be fixed once and ignored
• It takes TIME to affect change
• Even with a consistent program leaks will reoccur

For additional information or assistance, contact Kelly Beiermann, Nebraska Public Power District.

Note: We encourage requests from Nebraska customers. Businesses outside of Nebraska will be directed to their utility for further information.

Source: Airometrix Mfg., Inc. 1999-2003