Aphid 17, 1914, THE COLLIERY GUARDIAN. 841 MULTI-STAGE AIR COMPRESSORS FOR DIESEL ENGINES. The development of the Diesel type of engine has induced Messrs. Reavell and Co. Limited, of Ipswich, to adapt their well-known three-stage compressors for use with this class of prime mover. The “ Reavell ” quadruples compressor, as originally constructed for Diesel work, has its four cylinders arranged, radially in a suitably shaped casing, the cylinders being disposed on the vertical and horizontal centre lines. The two horizontal cylinders are used for the first stage of compression, while the two cylinders on the vertical axis are used for the next two stages; the second stage being performed in the lower cylinder and the third stage in the top cylinder- The pistons are single-acting and of the trunk type, the high-pressure being fitted with a guide of a larger diameter than the piston. The crank disc and pin are usually attached directly to the shaft of the Diesel engine, or can be forged integrally with it, and is supplied Fig. 1.—Arrangement of Three-stage Quadruples Flat Base Compressor. pH jfSp IraBtfe Fig. 2.-—Section of Three-stage V-class by the engine builder. The air to be compressed passes freely into the interior of the crank case, from which it passes through the two low-pressure pistons by means of ports cut in each piston and in the gudgeon on each connecting rod. Each of the cylinder’s is bolted to the inner facing of the casing, and the outer body of the casing is provided with large covers to give ready access to each cylinder. The annular space between the inner and outer metal of the casing is completely filled with water and used as a water jacket. The air on its way from the first-stage cylinders passes through suitable pipe intercoolers to the blow-off vessel, or purge pot. From there it passes to the suction valve of the inter- mediate cylinder, and, after the second stage of compres- sion, is cooled in the tubular coil shown, and then passes to the second purge pot, from which it is admitted through a pipe to the suction valve of the high-pressure cylinder. On the next compression stroke it is then delivered through the final cooling coil shown, to the fitting on the casing to which the user attaches his delivery co - nection and pipe. The two purge pots referred to are each provided with a suitable relief valve, and with a blow-off or drain cock, from which moisture deposited during the compression of the air can be drained away. This drain cock on the first-stage “ purge pot ” is also used as a means of regulating the output of the com- pressor. The casing of the compressor is provided with a segmental facing, by which it is attached to a similar facing provided on the bedplate of the Diesel engine, as shown on fig. 1. One special feature of this machine is the great simplicity of overhaul, for by removing one bolt which attaches the crank-pin oiler to the end of the crank pin, the whole of the working parts can be readily withdrawn through the door in the.front of the crank case. The provision for this consists in providing suitable openings in the side of the piston and of the cylinder, so that when each piston in turn is at the extreme outer’ end of its stroke, the connecting rod with its gudgeon can be immediately withdrawn towards the crank-chamber Duplex Compressor. door. The pistons are so proportioned that they also can be readily withdrawn from the inside of the cylinder into the crank chamber. In later years a preference has been shown for- pro- viding a flat base on which the weight of the compressor can be carried, in addition to the segmental facing which is still retained for registration purposes, and fig. 1 shows this construction. The only modification it entails is that the purge pots, which are still of circular form, are placed in a position at right angles to their original position. The quadruplex land-type compressors are made in 16 sizes, with piston displacements ranging from 14’2 to 138 cubic feet per 100 revolutions. A demand has arisen for three-stage compressors for directly coupling to small Diesel engines, and for these the “V ” (or vertical) class three-stage compressor has been designed and patented. The feature in this com- pressor which calls for special comment is the construc- tion of the second stage or intermediate cylinder and its intercoolers. By suitably proportioning these it is possible to dispense altogether with inlet and outlet valves in the second-stage cylinder, making the tubular intercoolers, which convey the air from the low-pressure cylinder to the intermediate, and again from the inter- mediate to the high-pressure cylinder, a part of the intermediate cylinder itself. Apart from the simplicity of this construction it gives high efficiency, owing to the fact that the air in the second-stage cylinder is virtually compressed in the intercooler tubes as well as in the cylinder itself. The construction of this machine is clearly shown in fig. 2. A notable feature in this design is that the com- pressor correctly divides its total range of compression into three stages, whatever the delivery pressure may be ; consequently if air is required for lower pressures, i.e., manoeuvring or othei’ purposes, it can be taken by a T piece from the final delivery pipe of the machine, when, as long as the compressor is not at the same time delivering air at the full pressure for the Diesel engine itself, the compressor can be most efficiently run at the lower pressure desired instead of tapping off an air connection from the second stage. As in the quadruplex machines, the annular space in the easing forms a water jacket which completely immerses the cylinders with their valves, and also the intercooling tubes. The only valves which require examination are at the top of the machine, and consist of the first-stage delivery valves on the low-pressure Fig. 3.—V-class Compressor with Bearers. & 6 ---® cylinder, and the third-stage suction and delivery valves on the high-pressure cylinder. A suitable cover for giving rapid access to these valves is provided. The compressor is attached either by a segmental facing to the end of the bedplate, or to the engine bearers by feet on the casing, as shown by fig. 3, or by both methods. The working parts of the compressor are all readily removed through the crank case in accordance with the patented arrangement described for the three-stage quadruplex machine. There are 10 standard sizes in which this compressor is made, with piston displacements ranging from 2’51 to 22’5 cubic feet per 100 revolutions. The quadruplex and “ V ” class compressors are both supplied built upon bedplates with shafts and bearings for auxiliary purposes, and either for Diesel stations on land, or for marine work. All of the standard sizes are suitable for auxiliary purposes, but when specially high speeds are required suitable modifications are made to intercooler surfaces, &c., in accordance. They can be constructed with bedplates and pulleys for belt driving, or with extended bedplates for attachment to motors, or to steam or oil engines. Hull Coal Imports.—According to the official return of the Hull Corporation’s coal inspector, Mr. W. Herbert Truman, the quantity of coal imported into Hull during March was 511,452, of which 466,657 came by rail and 44,795 by river. The quantity imported in March 1913 was 577,136 tons. The total imported for the first quarter of the year was 1,539,882 tons, as against 1,802,520 in the corresponding period last year. Coastwise shipments in March reached 72,435 tons, whilst the total for the period January to March amounted to 223,892 tons. The exports for the month were 280,731, as against 377,760 in 1913, the aggregate for the quarter being 765,942 tons, as compared with 915,911 tons in the corresponding period last year.