(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:

Open Table
Make Compressor size Single strokes per minute Diameter of orifice
(in inches)
Air pressure maintained
(in pounds)
Westinghouse 912 120 1164 60
Westinghouse 11 100 316 60
Westinghouse 150 CFM 812 CC 100 932 60
Westinghouse 120 CFM 812 100 1564 60
New York 2a 120 532 60
New York 6a 100 1364 60
New York 5b 100 1564 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.


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