JAN. 1911. 5 MODERN ELECTRICAL DOCK-EQUIPMENT, WITH SPECIAL REFERENCE TO ELECTRICALLY-OPERATED COAL-HOISTS. - BY MR. WALTER DIXON AND MR. GEORGE H. BASTER, Membeis, GLASGOW. OF - At the Summer Meeting of the Institution of Mechanical Engineers, held at Cardiff in July 1906, three Papers dealing with Coal Shipping and Dock Appliances were read. The general impression in these Papers, and particularly in the discussion thereon, appeared to be that hydraulic power was the only power sufficiently reliable for such appliances, and that Electricity, no matter what other fields it may enter, was certainly not suitable for dock equipments, particularly coaling-cranes and tips. A review of the history of what had already been done with electric power in docks may have justified such an impression, although as far back as 1903, Mr. Walter Pitt, in a Paper before the Institution of Civil Engineers, showed that electric jib-cranes compared very favourably on all points with those operated by hydraulics, quoting some figures obtained by Mr. Baxter, as a result of a comparison between a hydraulic crane and an electric crane at Downloaded from pme.sagepub.com at The University of Melbourne Libraries on June 5, 2016 6 ELECTRICAL DOCK-EQUIPMENT. JAX. 1911. Princes Dock, Glasgow. British Dock Engineers have confined themselves very largely to electric jib-cranes and capstans, which until recently were chiefly modifications of the hydraulic type, very little original design being employed, the electrical plant being simply applied to machines already designed. The authors fully appreciate all the merits of hydraulics, and that this form of power, having been thoroughly developed, is very safe and reliable, and, excepting where frost, moving ground or other natural objections arise, is, perhaps, under favourable conditions, not inferior to electric power. Where, however, in addition to reliability, economical working together with cleanliness and great flexibility is desirable, the inherent advantages of electricity at once become apparent, although it may not be possible to claim that one system is better than another for any particular case, as every equipment must depend on local and other considerations. Prior to recent electrical developments, there were undoubtedly cases in which hydraulics had a distinct preference over electricity, and, as an instance of this, reference may be made (as was done in the discussion on the Papers referred to above) to the difficulty of applying electricity to the shipment of coal either by cranes or by tips. This particular difficulty, however, has now been overcome, and notwithstanding the vast hydraulic equipments, electricity will occupy at least equally as important a place as hydraulic power in a11 future developments of docks. No doubt, in its early stages, the progress of electricity was considerably retarded by the absence of an entente eordinfe between mechanical and electrical engineers. Since the electrical and mechanical parts have received combined consideration, the past few years’ experience has proved that electrical plant is quite as reliable as hydraulic plant. Rothesay Dock, situated on the Clyde, and belonging to the Clyde Navigation Trustees, the general construction of which has already been described by Mr. W. M. Alston, Civil Engineer to the Trustees,* is designed essentially for dealing with the shipment of coal, and the import of iron ore, limestone, and other minerals. * Elzginesrilzg, 26 April 1907, p. 543. Downloaded from pme.sagepub.com at The University of Melbourne Libraries on June 5, 2016 JAN. 1911. ELECTRICAL DOCK-EQUIPMENT. 7 Hydraulic or Electric Power.-When considering the equipment of this new dock, the question naturally arose as to whether the appliances should be worked by hydraulic or electric power, the appliances at the other docks of the Trustees at Glasgow being operated either by steam or hydraulic power, with the exception of one crane at Princes Dock, which had been erected for the purpose of comparing the relative advantages of the two systems. The results obtained from this crane were so favourable that no doubt was left as to the advantage of dealing with the ordinary class of machines, such as cranes, capstans, etc., electrically. The proposed installation of several large coal-hoists, however, rendered the problem one which had not hitherto been faced. The mechanical difficulties in connection with such hoists had already been solved, but the difficulty of dealing electrically with the large amount of horse-power required in a very short period, together with the necessity of providing for rapid acceleration and retardation, and absolute control under all conditions, will be readily appreciated by those acquainted with electric plant, and the question as to whether such hoists could be designed to embody all the good qualities of hydraulic hoists, and, at the same time avoid their disadvantages, both as regards the hoists themselves and the power-station, had yet to be answered. It was at this stage recognized that the problem had developed into one which could not be adequately dealt with by the Mechanical Engineering Department without expert electrical advice, and Mr. Walter Dixon, joint author of this Paper, was appointed to collaborate with Mr. Baxter, Chief Mechanical Engineer to the Trustees, in the preparation of a scheme to embody the complete equipment of the dock. While two electrically-operated coal-hoists were atthat time in existence on the Continent, these being duplicates of each other, and a great step forward in what could be accomplished electrically, they were obviously impossible for dealing with the problem as now presented. It appeared to the authors, however, that, while the difficulties were great, they were not insurmountable, and, taking advantage of the latest electrical developments, they proceeded with the scheme, Downloaded from pme.sagepub.com at The University of Melbourne Libraries on June 5, 2016 8 ELECTRICAL DOCK-EQUIPMENT. JAN. 1911. which has resulted in the construction of two hoists. These have now been in operation for over three years, during which time they have given no trouble, and have more than fulfilled the duties expected from them. In fact,, so satisfactory have the results been that the two additional hoists now being erected will be, in all essentials, a repetition of t,he existing ones, differing only in some minor details. The dock equipment, while it may not be the largest insta,llation in this country, embodies so many novel features and new developments that the authors consider it will be of interest to record what has so far been done. The equipment is not yet completed, but sufficient time has elapsed since the commencement of working to speak with assurance as to what may be expected of it, and while complete records over thee or four years, which are not yet available, would undoubtedly be an advantage, it is hoped that the following particulars will not be without their value and influence on future dock-development schemes. From Fig. 1 it will be seen that the appliances already erected consist of two 32-ton coal-hoists ; eighteen 4-ton cranes ; twenty-seven 1-ton capstans ; two 18-foot tipping turntables ; two 5-ton pier-head capstans ; an underground distribution system, and an electric lighting installation, in addition to which two 32-ton coal-hoists and turntables, two 4i-ton trans- porters, three 4-ton cranes, and twelve capstans are in course of construction. Supply of Electrical Power.-Having resolved upon electricit,y as the motive power, it was necessary to decide whether the requisite energy should be obtained from an outside source, or generated in a power-station erected for the purpose at the dock. It is generally recognized that, where a reliable public power supply is available, it is desirable to take advantage of such a supply, and so obviate a considerable capital expenditure. In many cases, however, an objection arises to this course as the supply available is usually on the three-phase alternating-current system, which, while it may be satisfactorily employed, is not so suitable for dock purposes as direct current ; so that, if the best results are to be obtained, an Downloaded from pme.sagepub.com at The University of Melbourne Libraries on June 5, 2016 JAN. 1911. ELECTRICAL DOCK-EQUIPMENT. \\ Downloaded from pme.sagepub.com at The University of Melbourne Libraries on June 5, 2016 10 ELECTRICAL DOCK-EQUIPMENT. JAN. 1911. appreciable portion of the capital which might otherwise have been saved in dispensing with steam-raising and generating plant might have to be utilized for providing converting and transforming plant. Such a supply being available in close proximity to Rothesay Dock, the advisability of adopting it received due consideration, but the alternative of a separate generating-station was deemed to offer the best solution, it being found that power could be generated to better advantage and at a lower cost by plant specially designed for the purpose. The rates which are quoted at the present time by many of the public supply concerns are so reasonable that it is quite possible the requisite supply of energy may be economically obtained in this way, notwithstanding the first cost of and continual losses in the converting and transforming plant. The matter is one, however, which, in view of varying systems of charging for current, and the many subsidiary questions which arise, demands individual consideration in each ca.se. Generating Station.-The Generating Station, Fig. 2, Plate 1, a red-brick building, comprising boiler-house, engine-house, condenser- house and suita.ble store, also offices for the resident engineer and staff, is situated in a convenient central position on the North Quay of the Inner Basin. The Steam-raising Plant, Fig. 3, consists of two water-tube boilers, each capable of evaporating 12,5001b. of water per hour at a steam-pressure of 160 lb.