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46 provide a path for the flow of water from inlet to outlet. 8. The discharge of water must be continuous. The oil discharge may be continuous or intermittent; but provision must be made to prevent the discharge of water from the oil outlet, and the means provided must not be adversely affected by the mo- tion of the ship in a seaway. 4. Oil broken into small globules (pseudo-emulsified) by passage through the pumps and pipes will not separ- ate by gravity unless the flow is perfectly steady. An efficient separ- ator will therefore have due provision for the prevention of eddying. The application of these ay ee will now be studied in more tail by reference to the various types of separator which have been evolved. (ATER OUTLET Fic. 13.—Tue “ STREAM-LINE’’ SEPARATOR. In the class in which a substantially horizontal flow has been adopted, an early invention of I. S. McDougall (designed for removing oil from boiler feed-water, and dated 1892) gave an extremely good lead to other designers. The oil-collecting chamber was suit- ably remote and distinct from the main flow, and the whole system was a closed one, and therefore suit- able for installation at any level in a ship. The oil was discharged by the intermittent operation of a hand valve, in conjunction with observation cocks at suitable levels as shown in Fig. 1. In 19038 J. Niclausse patented the arrangement shown in Fig. 2, which in general principle is seen to be analogous to that of McDougall, differ- ing in points of detail. In particular the greater accessibility of the oil- collecting portions to the main flow— making it certain that a proportion of water will sweep through the oil- collecting space, possibly carrying some oil into the water discharge— must be regarded as a retrogression. W. E. Lake’s patent of 1904 (prim- arily used for recovering lubricating oil which had become mixed with water) also embodied the same prin- i H..S. Hete-Suaw anp A. Bravt’s PATENT oF 1925. MARINE REVIEW ciples, except that the baffle plates were dispensed with. The oil-collect- ing chamber itself was suitably free from water current, but there was a probability of a proportion of the water sweeping around the area, A, indicated on Fig. 3, in the preliminary settling chamber and carrying oil away. More recently (1923) F. Pink has developed the apparatus now called the “Pirbright” separator, illustrated in Fig. 4, in which the features al- ready described have been combined with means for automatically with- drawing the recovered oil. By means of a float, designed to sink in oil but float in water, the oil discharge valve is opened when oil has ac- cumulated and closed before any water ean be discharged. Owing to the small margin of difference between the densities of oil and water, and the adhesive nature of the oil in which the valve operates, the float is made of considerable size, and op- erates the valve not directly (as shown in the diagram) but through a steam or other relay. The plants shown in Figs. 5 and 6, inventions of Mr. J. H. Palmer and Sir James McKechnie respectively, also come in the same broad class as those previously mentioned. In Palmer’s apparatus the main flow is horizontal, but the constraining of the main flow to rise near the oil-collect- ing space at A seems liable to cause oil to be entrained in the water dis- charge. McKechnie’s apparatus is generally similar, but arranged in the form of a spiral, so that the water takes a tortuous path and passes a multiplicity of baffles before being finally dis- charged. The length of path traversed is a good feature, although, of course, time is the main requirement for separation, and in a plant of given size for a given throughput the ar- rangement of a tortuous path in- creases the velocity of flow in the same proportion as the _ distance September, 1926 traveled, so that the time factor is unchanged. In addition to in which the flow horizontal, there are a consider- able number in which this 1s sacrificed in order to introduce some other feature held to be desirable. The “Conduit” separator Fig. 7, is typical of the principle of most of these. It consists of a very large U-tube with unequal legs, the oily, mixture being introduced at the top of the larger leg, in which the oil accumulates and from which it is withdrawn. The water passes down the larger leg and up the smaller, where it is discharged into an observa- tion tank, and thence overboard. The water and oil are discharged con- tinuously at suitable levels, the dif- ference between which depends on the density of the oil to be dealt with, and needs to. be adjusted to suit. This weir discharge provides some justifica- tion for the vertical flow, which is otherwise inferior in efficiency to a horizontal arrangement. Obviously the > greater the vertical length of the columns the greater the margin which can be allowed between the weir levels; hence the great height of the apparatus, which is otherwise purpose- less. Apart from the adjusting of the levels to suit varying grades of oil, the discharge is automatic, al- though the advantage appears to be offset by the unsuitability of an open- topped system for use in a seaway. The “Rocket” and “White-Comyn” separators, Figs. 8 and 9, follow the general principle of the “Conduit.” A more compact apparatus is produced by rearranging and duplicating the essential U-tube passages; but this introduces the disadvantage of a smaller margin between the weir levels, and the more delicate adjust- ments necessary are still more un- suitable for use in a Seaway. The “Fisher” separator, Fig. 10, is also similar to the “Conduit,” but with the provision of a spiral sur- face in the separation chamber up the underside of which the oil is supposed to creep into the oil-delivery space, with less chance of being carried for- ward by the water flow. The four separators last described use a vertical flow in order to in- troduce the weir discharge. For ship use, therefore, they must be carried above the water-line, since otherwise the discharged water must be re- pumped in order to pass it over- board. Two further vertical-flow arrange- ments may be mentioned, in which the weir discharge method is not used and the system is closed. the separators is substantially