This slide is moved by a valve piston in the usual way. The parts of the valve may be inspected and adjusted by removing the cover held by the two studs shown.
The outline engraving, Fig. [348], shows a cross-compound double acting vacuum pump, six-inch high pressure, nine-inch low pressure cylinders, by eight-inch stroke, and two air cylinders, ten-inch diameter by eight-inch stroke.
They are piped up to run either high or low pressure, also to run independently by manipulating the cocks, C, and D, as directed in the engraving showing arrangement of valves, Fig. [349], page 41.
Fig. 346.
These pipes are simple in design and run direct to the boiler for live steam and convey the exhaust to the atmosphere or condenser as desired. On a recent test at a fair rate of speed the capacity of this pump was shown to be equivalent to taking care of a triple expansion engine of 2,000 I. H. P. On a further test this same pump on a basis of 20 lbs. weight of steam per I. H. P. per hour demonstrated its ability to take care of 3,000 I. H. P. triple expansion engine.
The advantages claimed for this pump are briefly as follows:
Unusual light weight and compactness.
There being NO SUCTION VALVES, working-beams, rock shaft and bearings, beam-links, etc., this pump is simple.
It is economical in the use of steam, by reason of compounding the steam cylinders; also clearance loss is reduced to a minimum by the perfect regulation that is secured by the valve gear described. Full stroke at any and all speeds can be readily maintained.