49 C.F.R. § 230.71
Orifice testing of compressors
(a) Frequency of testing. The compressor or compressors shall be tested for capacity by orifice test as often as conditions may require, but not less frequently than once every 92 service days.
(b) Orifice testing criteria. (1) Compressors in common use, as listed in the following table, shall have orifice test criteria as follows:
| Make | Compressor size | Single strokes per minute | Diameter of orifice (in inches) | Air pressure maintained (in pounds) |
|---|---|---|---|---|
| Westinghouse | 91⁄2 | 120 | 11⁄64 | 60 |
| Westinghouse | 11 | 100 | 3⁄16 | 60 |
| Westinghouse | 150 CFM 81⁄2 CC | 100 | 9⁄32 | 60 |
| Westinghouse | 120 CFM 81⁄2 | 100 | 15⁄64 | 60 |
| New York | 2a | 120 | 5⁄32 | 60 |
| New York | 6a | 100 | 13⁄64 | 60 |
| New York | 5b | 100 | 15⁄64 | 60 |
| Note: This table shall be used for altitudes to and including 1,000 feet. For altitudes over 1,000 feet the speed of compressor may be increased 5 single strokes per minute for each 1,000 feet increase in altitude. | ||||
(2) For compressors not listed in the table in paragraph (b)(1) of this section, the air pressure to be maintained shall be no less than 80 percent of the manufacturer's rated capacity for the compressor.