| Show straight line corliss compressor B by v H A W wainwright a in w r i g h t M E chicago t all engineers recognize in the corliss engine the most economical means of compressing air by steam power in the cross compound type one horse power may be produced on from 14 to 16 pounds of feed water per hour when running condensing or twenty to twenty three pounds non con densing but the price of the corliss unit appears large to many operators even in regions I 1 ions where the cost of the fuel saved would pay for the entire machine in hi a short time slide valve compressors are therefore often installed which require two to three times as much fuel to do the same work the development of an air compressor combining high steam economy with moderate price has advanced but slowly in some cases the principles of good mechanics have been distorted to the sacrifice of durability ease of action and mechanical efficiency in order to reduce construction costs in others various substitutes for the full corliss valve gear have been offered it is conceded that some of these compromise machines may fairly claim a certain degree of economy in operation and that when a testis test is made under ideal running conditions they make a good showing as compared with a corliss compressor the conditions of everyday every day operation however are not one time in a hundred like those prevailing in a test in the latter case the steam pressure air pres pressure sure and speed are all constant whereas in the former the fluctuation in any or all of these factors is likely to be extreme sometimes these extremes oppose one another sometimes they may be high or low together it is on account of this fluctuation that the corliss compressor co uses so much less coal in the course of a days run its valve gear brings the cutoff cut off in the high and low pressure steam cylinders under the automatic regulation tion of the governor there is no wire drawing of the steam nor is there throttling action at any time A new type A compressor has at last 1 een designed however which embodies the economy of the corliss cross compound type in a form which permits moderate price without the sacrifice of good engineering the credit for this achievement achieve ent belongs to mr S T nelson one of the mechanical engineers of the sullivan machinery company and the superintendent of its western factory at chicago the new machine known as the class WC is described as a tandem compound steam two stage air corliss straight line compressor to put it differently tandem compound steam cylinders with full fuli corliss valve gear on both have been attached to the flywheel fly wheel end of the standard sullivan two stage straight line compressor the high pressure steam cylinder occupying the same position as the single meyer valve cylinder of the WB 2 machine the photograph shows the arrangement design of steam cylinders the high pressure steam cylinder is of special design to make room for the corliss 2 1 in R aidi IT V straight line corliss air compressor valve bonnets and dash pots between the cylinder and fly wheels and in order to do this the steam chest is offset to one side the dash pots for closing the steam valves are set directly on the main frame and the motion rods for operating are longer back i bonnets are provided as usual and the fra frame m e is so designed that either one or all of the steam or exhaust valves may be removed without disturbing the valve setting the low pressure steam cylinder is attached to the end of the frame by means of rigid distance pieces the bottom feet of this cylinder are on the same level with the bottom of the main frame and its weight is supported by an extension of the foundation practically the same pattern is used for making this cylinder that is used for the sullivan cross compound corliss machines it embraces all of the regular valve gear usually furnished with the latter type of machine there are no adjustments between the flywheels fly wheels and the steam cylinders which require attention while the compressor is in operation the piston rod stuffing boxes are packed with fibrous metallic packing which needs only occasional care the main bearings and other parts which cannot be oiled by hand while running are lubricated by a system of pipes leading from a cluster of mounted at a convenient point so that the engineer can tell at a glance when one of them is empty me eccentrics for operating the valve gear on both the high pressure and low pressure steam cylinders are located on the crank pin on the outside of the flywheels fly wheels so that they are easily accessible the eccentrics rocker arms valve stems and all connections located between the flywheels fly wheels or between the main bearings on the WB 21 2 type are dispensed with in the class WC the governor pulley is all that is located on the shaft in their place the removal of these parts allows the use of two piston rods between the high and low pressure steam cylinders cylinder rs which are necessary in order to straddle the crank shaft which is kept in its original position in line with the cylinders steam regulation the governor is located on a separate mounting and with a combined speed and pressure regulator in appearance it is of the corliss fly ball type but it operates in unison with the pressure attachment either may also operate independently of the other when necessary the exhaust steam from the high pressure cylinder is carried around the outside of the cylinder barrel to the top by a passage cast with the cylinder and discharges into a covered receiver pipe extending bendin from the top of the high pressure to the top of the low pressure cylinder air efficiency from the standpoint of air efficiency this compressor takes the same high rank as the class WB 2 machine the inlet valves on both low and high pressure cylinders are of the semi rotary pattern positively driven by motion rods from an eccentric pin on the engine fly wheel the action of these valves permits the cylinder to fill itself completely at each stroke with air at the temperature of the atmosphere and there is no wire drawing or leakage the discharge valves are of the automatic type so arranged as to reduce clearance losses to a minimum they are removable by hand together with the valve seats so that the maintenance of a perfect fit is a simple matter the ideal of isothermal compression is approximated in these machines by means of unusually adequate cooling apparatus this consists of heavy water jackets on the air cylinders and an inter cooler of ample proportions containing copper water tubes across which the air must pass several times in its course from the intake to the discharge cylinder the class WC compressor is built very substantially being self con I 1 bained on its hea heavy vy frame and on the disi digi tance P pieces feces leces connecting the two steam cyl i inders these parts are sufficiently mas fa sive to sustain the low pressure cylinder of i themselves without the aid of foundations if such a necessity should arise the s straight craight t line type unites with its well known advantages of engineering excellence the features of low weight simplicity and minimum foundations as compared with duplex machines these qualities render it possible to sell these compressors at a comparatively ively low price to transport them readily and at small expense and to erect them without elaborate and costly preparations at the desired site they are built at present in sizes ranging from to 24 2450 5 0 cubic feet of free air per minute |
