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|  MIL-C-52980B
3.26.6 Power takeoff. When a V-belt drive is used for the size 15-cfm and 25-cfm
compressors, the contractor shall furnish and install a power takeoff on the engine for driving the
compressor unit. The power takeoff shall consist essentially of a 4-bolt flange bolted to the
engine flywheel and a stub shaft or other device on which the drive pulley or clutch shall be
mounted. When a direct drive is used, a flexible coupling shall be installed between the engine
and compressor units. The nominal rating of the power takeoff shall be not less than 150 percent
of the rated horsepower of the engine.
3.26.7 Clutch. When specified for the 15- and 25-cfm size compressors (see 6.2), the engine
shall be equipped with a clutch. The clutch shall be accessible for adjustment, replacement of
parts, and lubrication (unless bearings with sealed-in lubrication are used). Adjustment of the
clutch shall not require special tools. The nominal rating of the clutch shall be not less than
150 percent of the maximum engine torque. The clutch operating lever shall be accessible to the
operator and labeled as to function and shall be provided with double-ended arrows showing the
direction of operation and labeled at each end to indicate the functional result (engage and
disengage) in accordance with MIL-STD-1472, 5.4.3.2.1.3 (see 3.7.2).
3.26.8 Pressure regulation. The compressor shall have an adjustable, pressure actuated
mechanical control of the head unloading type. The control shall be adjusted to stop
compression of air when the tank pressure has risen to 200 psig, +0 psig, -10 psig and to start
compression of air when the tank pressure has dropped to 175 psig + 10 psig. Means shall be
provided to prevent the engine from starting against tank pressure or cylinder head pressure.
3.26.8.1 Idle device. The size 15 and 25 compressor shall have a device to automatically
reduce the engine speed to idle speed when the compressor is unloaded. A manual control shall
be provided to by-pass the engine idle device.
3.27 Interchangeability. All parts having the same part number shall be functionally and
dimensionally interchangeable. Interchangeable parts are defined as two or more parts
possessing such functional and physical characteristics as to be equivalent in performance and
durability and capable of being exchanged one for the other without alteration of the parts
themselves or of adjoining parts, except for adjustment, and without selection for fits or
performance.
3.28 Workmanship. All parts, components and assemblies of the compressor including
castings, forgings, molded parts, stampings, bearings, seals, machined surfaces, and weld parts
shall be clean and free from sand, dirt, fins, pits, sprues, scales, or any damaging extraneous
material. The compressor shall be free of any defect that could impair its operation and
serviceability.
3.28.1 Fabrication. Steel and aluminum used in the fabrication of the compressors shall
provide original quality surface finish and shall be free from kinks and sharp bends. The
forming of the material shall be done by methods that will not cause damage to the metal.
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