摘要:

The nature and extent of the deposits which occur on the heating surface of a boiler unit are variable in the extreme. The method of firing and the rate of combustion are open to choice. The completeness of combustion can be controlled to some degree, but the quantity and chemical constituents of the ash can seldom be forecast, and may vary widely.The form of fouling, and the effect on the different portions of the heating surface of the boiler unit, are examined.Development of the application of soot blowers from 1919 is discussed, and particularly the use of the single-nozzle blower. The design of the boiler to enable full use of the different types of soot blowers available is referred to, and mention is made of the effect on furnace walls, boiler tubes, and superheaters, economizer and air-heater surfaces. The future design and rating of boilers depend to a great extent on the development of the means of cleaning the heating surface.Reference is made to cleaning by water lancing and other means for, special cases.The importance of the availability of plant is emphasized.The essential features of power-operated mechanical soot blowers, with special reference to automatic operation, are outlined.The scope of use of the three main types of soot blowers is set out, as well as the essential features of their design.Points for consideration in the periods between individual soot-blowing operations and the extent of each blowing, are considered.A short history of the development of automatic soot blowers is drawn up, including a reference to a Patent Specification in 1920, and to a number of early designs of blowers and installations.The types of automatic soot blowers on the market are briefly described in Appendix (14.4), and a general indication of the trend of modern design of blowers, both electrically and hydraulically operated, is given.The object of the paper is to provide up-to-date information on a subject of general interest to users of large boiler units.

DOI:10.1049/ji-2.1942.0090

出版商:IEE    

年代:1942

数据来源: IET

摘要:

Simple Circuits are described whereby measurements of the crest value and time of duration of the transient voltages used in impulse testing may be made with a ballistic galvanometer.Both methods of measurement have been compared with the results obtained simultaneously by a high-speed cathode-ray oscillograph. The agreement in crest voltage was within 2%, even with voltages having a duration of the order of 10−7sec., and in time-lag was within 0.2 micro-sec. when the grid bias of the valve was suitably adjusted.The measurements are not critically dependent on the characteristics of the thermionic valves used in the circuit, and the range of voltages which may be measured can easily be extended by the use of suitable high-voltage resistors.The two circuits have been assembled conveniently into a general impulse-measuring equipment with mains-operated supplies for the valves. As an example of its use the time-lag curve of a 10-in, rod gap, obtained in a small fraction of the time necessary to do so by oscillographic methods, is reproduced.The paper concludes with a few measurements of the length of the front and tail of an impulse wave which have been made with the equipment.

DOI:10.1049/ji-2.1942.0092

出版商:IEE    

年代:1942

数据来源: IET

摘要:

The paper describes the construction of the two-element powder-filled cartridge fuse. Two recently introduced special features are described in detail, namely the provision for adapting the fuse for oil-immersion, and the striker-pin mechanism which ensures tripping on all three phases should only one fuse be blown. Discrimination in operation between fuses and other protective gear in circuit is discussed.Experiments are described which show the ability of powder to prevent corona formation on the fusible conductor. Transient voltages produced on fuse operation are important, and it is shown that a reduction in the magnitude of the transient can be obtained by changing the section of the fusible conductor in one or more places. A series of tests are described illustrating the behaviour of h.v. fuses on short-circuit in an ordinary 50-c./s. system. Typical oscillograms (ordinary and cathode ray) obtained during these tests are given. A test is also described which reproduces the operating conditions obtained when a rectifier backfires, and oscillograms are given showing the behaviour of the fuse when subjected to such a test. Fuses such as those described have been developed to have a rupturing capacity up to 1 000 MVA at 66 kv.The next section of the paper deals with the effect of these fuse developments on protection technique. It is suggested that H.R.C. fuses can be used (1) to improve fuse-switches; (2) as a back-up to safeguard old circuit-breakers in cases where the short-circuit burden has been increased; (3) in combination with a simple load-breaking switch, the switch dealing with small overloads only, all short-circuits and heavy overloads being taken care of by the fuse. A simple air-blast switch is described, suitable for use in the load-breaking switch and fuse combination.

DOI:10.1049/ji-2.1942.0094

出版商:IEE    

年代:1942

数据来源: IET

摘要:

An introductory paper on this subject is considered timely in view of the growing importance of electrically equipped excavators of the single-bucket type and of the lack of previously published information on the subject in theJournal.After describing their sphere of application and commenting on the increasing importance of electric drive, an explanation is given of the fundamental motions and structural limitations of these machines.A summary of the special service conditions precedes a discussion on electric drive methods for the two main groups of excavators, the “friction” type and the individual-drive machine where the application of the modern Ward-Leonard system with 3-coil dynamo and separately-excited motor is referred to in some detail.Main and auxiliary equipment is dealt with from the electrical and mechanical aspects: installation and wiring details are supplemented by illustrations of typical equipment layouts and wiring diagrams.Attention is drawn to certain special aspects of power supply and distribution to excavating projects, representative power consumption details being given.Concluding remarks discuss some possible future developments in electrical applications to this type of machinery.

DOI:10.1049/ji-2.1942.0096

出版商:IEE    

年代:1942

数据来源: IET

摘要:

Most of this paper is a commentary on present-day methods of carrying out industrial electrification installations rather than a detailed description of the work involved, as it is believed that such a description would be laborious and somewhat obvious. The latter part of the paper, however, does include brief descriptions of some of the more interesting installations recently carried out.

DOI:10.1049/ji-2.1942.0098

出版商:IEE    

年代:1942

数据来源: IET

摘要:

An experimental investigation of the eddy-current losses in cables when carrying alternating current at power frequencies has been carried out at the National Physical Laboratory. Measurements were made with single-phase current on two parallel cables of equal length, and of 1.4 sq. in. conductor section, forming “go and return”.Formulae are put forward for estimating the a.c. resistance of a cable from the design data, and these formulae are shown to give good agreement with the experimental figures.

DOI:10.1049/ji-2.1942.0105

出版商:IEE    

年代:1942

数据来源: IET