Modern Gasworks Practice

EXHAUSTING MACHINERY 479 Pkessube Conditions throughout thb Appabatus Retorts .... Level-gauge. Hydraulic main | inch to 1 inch vaeuum. Exhauster inlet 4 inches vaeuum. „ outlet 30 „ pressure. Tar extractor, outlet 26 ,, „ Pressure thrown by tar extractor, 4 inches. Washers, outlet 24 „ „ „ „ washers 2 „ Serubbers, outlet 22 „ „ „ „ serubbers 2 „ Purifiers, outlet 9 ,, ,, „ » purifiers 13 „ Station meter, outlet 8-5 ,, „ „ „ meter 05 „ Holder, inlet and outlet . 8-5 „ „ „ ,> holder 8-5 „ 30 inohes From the above it will be seen that the forcing of the gas through the dry puri-fication material and the raising of the holder bell account for the greatest portion of the work which the exhauster has to perform against back-pressure. At times the physical condition of the purifying material may give rise to considerably in-creased pressure, when the offending vessel must be shut off, or a tier of oxide “slipped” by drawing the slides specially pro vided for this purpose. TYPES OF EXHAUSTERS lu considering the mechanical details of exhausters it is advisable to classify the various types under the following headings :— («) Reciprocating types. (b) Eotary types. (c) Steam jet types. (d) Turbo-exhausters and high-speed machines. Reciprocating machines operated on. the pump principle need be given no further notice as they are now obsolete. Rotary exhausters of various types are almost exclusively used at the present day, whilst the most recent development of the same principle is the turbo-exhauster. The first attempt to construct a practicable rotary exhauster was made by Beale in 1850, and this machine, with important modifications and refinements, has served as a model for the modern apparatus. About the same year G. Jones introduced a blower operating on the Roots’ principle, but for gasworks purposes the machine has not gained much favour in this country, aJthough in America it seems to be preferred. Some years later the Beale exhauster was much improved by Gwynne & Co., wlio introduced two overlapping blades instead of the single one originally employed. The Gwynne-Beale exhauster is shown in Fig. 289. The blades- pass through slots cut in the inner drum, which. is revolved from the source of power. The extreniities of the blades are provided with. steel-cased pins which are fitted into segments. The segments travel in grooves cast in the end covers of the drum, so that when th.e inner drum revolves the blades are drawn in and out, thus sucking in the gas from one port and discharging at the second. The main defect of this exhauster was the