October, 1934
I K D U S T K I A L A N D E N G I N E E 1%1 N G C A E M I S T R Y
1027
FIGURE 10. RECORDS OF KILNA N D FEEDER SPEEDS IN CEMENT MIM, Kiln eposd ia ~oouiatelyfallowed by the feeder, giving uniform loading of the kiln snd makiox it possible to obtain B uniform product; twin metem on the board reoord the weed of kilns nnd the respective feeders.
tion between the gun and boiler departments, and the adoption of a biJnuS deduction for shooting helow 950 pounds have eliminated this wasteful practice. AfEAsUREMENT OF THE TIME ELEMENT THROUOH MEASUREMENT OF SPEED There are many processes where the time element OS the process can be ascertained most conveniently through the measurement of speed which, in turn, is casy to record continuously through electrical means. Such a record not only has the advantage of indicating the exact speed a t which the equipment was operated at all times hut of showing at a glance the timeoi occurrenceanddurationoS any shutdounsor delays. In the manufacture of cement the time required for any portion of the charge t.o pass through the kiln depends upon the kiln speed. By taking simultaneous records ol kiln speed and feeder speed, one la.rge eastern cement mill u w able to increase its clinker output 30 per cent. This was donc solely through accurate control of the time factor, properly coordinating slurry speed t.o kiln speed, and this in turn to comhustion conditions (Figure 10). Another instance where specd measurement and control are OS extreme importance is in the operation of paper machines. Here the speed must be absolutely constant to p r o vent costly breakages OS the paper web and yet must be as high as possible in order to ohtain the maximum output from the extremely costly machinery. A plant in Oregon installed a 234-inch newsprint mill designed for operation at a maximum speed of 700 feet per minute. Frequent and expensive breakages of the paper web prevented satisfactory operation a t any speed over 500 Sect per minute; thus production was reduced to ahout 70 per cent of that which should have been possihle from the machine. A carefully coordinated study of the speed and rmwer conditions, made through tlie use of elect,ricalrecording instruments, so reduced the trouble that csentually it wm found possihle to speed the machine up to 1000 feet per minute; this increased the output 40 per cent above that which the machine manufacturer himse!f had considered the maximurn,
esses described above and for completely different typos of applications. Once it is learned that a graphic instrument can furnish useful data when applied to a certain process, the only question to decide is the simple one OS economics: How soon will the instrument pay for itself? An analysis of a great variety OS applications ha shown that the cost of owning and using a graphic instrument vi11 range hetwen 10 and 25 cents per 24-hour day. This includes not only the cost of charts, ink, and necessary maintenance or occasional repairs, hot also depreciation and interest on the investment. In considering instrumentation in general, it is natural to compare the continuously reconling type with simpler and less expensive indicating instruments. To visualize the scope oE both types, it is necessary to hear in mind that the only time the indicating instrument has any value is during . the instant when an operator is looking at it; Sor the rest of the time, no matter how valiiable its story, i t is lost. Contrast this with the permanent recording instrument which works 24 hours a day. The graphic instrument never rests; it records every minor detail, every unsuspected change; it obtains the facta just as completely and accurately during times of stress, when things have gone wrong and the operators are too busy correcting trouble to read meters, as it does when everything is progressing smoothly. Best of all, i t puts all these facts down in permanent forin so that they can he studied on the following shift, the folloning day, or the following year, and in the one form which appeals most directly to the brain-a two-dimensional graphic chart. R ~ c m v ~A nw u t 6. ISM.
AnnENnnM. Anather sentence should have been added to footnote 2, page 753, of my article on “Critical Temperatures in Silicate Glasses” I m . ENQ.CXEM.,25, 74855 (1933)J. The : “These electrical conductivity measureer a fellowship at Purdue University under , and the viscosity dat,a on the by Lillie (9). Lark-IIorovitz and Bahcock have represented these data by the formula:
INSTALLATION AND OPERATION OF GRAPHICINSTRUMENTS Obviouslv there are manv other Dossihie uses of these instruments, both Sor purposes similar to thosr chemical proc-
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J. T.LIT~WTON
