Keeping a Record of Engine Speed in Blast Furnaces: The Recording Revolution Indicator

Posted By Richard Jefferson on 17 February 2015

Posted in The Vintage Machinery Almanac

The importance of keeping a continuous record of the speed of blast-furnace blowing engines on a chart has been the incentive for Messrs. Edward Brown & Son, Philadelphia, to devise a new recording revolution indicator. How well the instrument is adapted for this purpose is shown by the adjoining illustrations.

Fig. I is a photograph of a chart taken from a Brown recording revolution indicator in use on a blowing-engine at an Eastern Pennsylvania furnace. It will be noted that the number of revolutions per minute fluctuates several revolutions at times. The hour or minute at which the engine has been slowed down or stopped is clearly shown.

Fig. 2 is a record made at the Youngstown Steel Co. Ohio, on a blast furnace steam-blowing engine, and is a very fine chart, the number of revolutions having been kept within a quarter of a revolution except at stated intervals when the engine was stopped.

Fig. I, 2, 3, 4 - Speed Recorder Diagrams

Fig. 3 is a reproduction of a chart taken from erne of these instruments in use on a gas blowing-engine of a well-known type at the Park Gate Iron & Steel Co. England. It is evident that with the use of a gas blowing-engine the number of revolutions of the engine is subject to very sudden and great fluctuations. This is a feature that must be of considerable importance in the operation of blast furnaces with gas blowing-engines, for, according to the record illustrated, a fluctuation of as much as 10 revolutions per minute occurs at intervals of every few minutes except for a space of several hours, during which time the speed did not vary a revolution. It is difficult to give a reason for such a peculiar record unless the conditions in England are greatly different from those in the United States.

Fig. 4 is a photographic reproduction of a chart used on the recording revolution indicator on a gas blowing engine at a well-known German works. It has been necessary to make some slight changes in the design of the instrument to suit the conditions in Germany, but this has not affected the successful use of the recorder.


Fig. 5 - Speed Recorder

The recording revolution indicator itself, as illustrated in Fig. 5, is based on the law of centrifugal force, a body of mercury contained in a central chamber being thrown out into revolving arms  proportional to the speed at which the instrument is driven. A float resting on the mercury is suitably connected to a pen arm which marks the record on the chart. These instruments have heretofore been furnished with a chart 6 ½ inches in diameter, but the inventors are now manufacturing the instrument with an 8-inch chart, affording wide graduations.

Although the recording-revolution indicator has heretofore been chiefly used on blast-furnace engines, there is nothing to prevent its successful operation on all types of engines, machines, dynamos and motors where a record of the instantaneous speed is desirable. It becomes daily more evident that the best method of control over a large plant is with the aid of recording instruments, which give a true picture of all conditions of working at any moment.

Image Credit: Internet Archive Book Images