49. Q. How often should the air end of the compressor be oiled?
A. No fixed rule can be given as so much depends on the condition of the compressor, as well as the amount of work required; but in any case it should be used sparingly.
CROSS-COMPOUND COMPRESSOR
50. Q. What do Figures 4 and 5 represent?
A. These are diagramatic views of a cross-compound compressor.
51. Q. Why is this called a cross-compound compressor?
Fig. 4: Diagram of 8½" Cross-Compound Compressor.
High Pressure Steam (Low Pressure Air) Piston on Its Upward Stroke
A. Because both steam and air are compounded, that is, the steam is used the second time before it is exhausted to the atmosphere, while the air is compressed the second time before it is delivered to the main reservoir.