Automatic Regulation

REGULATION, AUTOMATIC. Modern processing'is re quired in the production of most of the articles of clothing, food stuffs, and other items that are used in every day life. Processing requires proper conditions not only in workrooms but in the end less variety of boilers, ovens, furnaces, dryers, sterilizers and other types of apparatus. To insure the proper conditions the automatic regulation of temperature, pressure, humidity, timing, liquid level, flow, specific gravity of the substance being processed and speed of moving parts is of great importance. These eight conditions will be dealt with. Voltage (which must be regulated in many devices), current density (in electroplating, etc.) and other elec trical conditions are discussed under INSTRUMENTS, ELECTRICAL, and ELECTRICITY. No discussion is here given of the regulators, controllers or governors incorporated in engines, turbines, gen erators and other such machines, since these devices as con ceived, designed, built, sold, installed and maintained with the machines, belong to their machines and seldom can function on others.

Automatic regulation of the eight conditions listed above is, however, a science, and the proper application of standardized automatic regulators to improve products and effect economies is a prominent branch of engineering.

Development of Automatic Regulation.

For every in dustry it has been established that there is one best set of condi tions for operation and manufacture. Before the World War, in searching for this "one best way," workers were frequently re quired to watch indicators and manipulate valves and levers con stantly in order to maintain proper conditions, until a fairly suitable automatic device was purchased or painstakingly contrived. To day (1929) specialists may install the required automatic devices as soon as the particular requirements are known. One of the fac tors that have made this possible is the spread of knowledge of formerly secret processes. This has led to "professional divisions" within the larger engineering societies and to co-operative indus trial "institutes" and research bureaux. Competition between industries has also led to the exchange of formulae and data on automatic processes. Instrument-makers have pursued an increas ingly active policy of scientific research into processes, with two objectives : the development and standardization of classes and types of automatic regulators, based on industrial require ments; (2) the improvement and standardization of processes through methods worked out by their research staffs.

All these tendencies point to the need of an agency for the sys tematic utilization of scientific achievements. A central "insti tute" under the auspices of instrument makers may ultimately be developed. The progress of the last decade will undoubtedly be

eclipsed when manufacturers thus combine their research and present their united facilities to the instrument-using industries. For example, the standardization of bulbs, connections, protective sockets, thermocouples, charts, scales, ranges, etc., has been ini tiated in the United States, but as yet only on a small scale.

Types of Automatic Regulators.

All regulators require some form of power to operate a valve, damper, etc., in order to maintain the optimum condition.

Self-operating regulators requiring no auxiliary power are di rectly installed (i.e., on a steam line) and usually consist of a globe or balanced valve operated by a bellows ; the expansion of the bellows being obtained in temperature regulators by the dila tion or evaporation of a liquid in a sensitive bulb, and in pressure regulators by the pressure which is to be regulated. This group of devices includes thermostats and damper regulators.

Air-operated regulators are the most wide-spread in industrial process service. They utilize the ample and flexible power of compressed air, controlling its flow to an operative mechanism which usually embodies an elastic diaphragm. Pilot valves add ex treme sensitiveness to ample power, obviating the use of bellows— a small capsular or spiral spring or Bourdon tube being sufficient. (See Plate, figs. 6 and 7.) Electrically operated regulators function on the relay principle and actuate standardized electrical mechanisms. Heavy work may be performed through their agency but their on-and-off action pro duces the frequently objectionable "saw-tooth" record. On a tem perature application, for instance, the steam valve would "hunt" whereas air-operated regulators can provide exact throttling regu lation. (See Plate, fig. I.) Steam-operated regulators utilize the power of the steam which they control. They embody the sensitive bulb, capillary tube and capsular spring. This latter operates a pilot valve so located that the pressure above a steam diaphragm may be varied with respect to the pressure below it. Pressure fluctuations of the steam supply cannot destroy accuracy, for the differential principle is used. Valves up to 4 in. are successfully operated by diaphragms up to I I in. diameter. (See Plate, figs. 3 and 4.) Temperature Systems. Fixed Stem.—It is sometimes possible to use the "solid expansion" principle, and the sensitive member then consists of a bimetallic stem (or of a carbon or quartz rod within a metal tube) to which the instrument "head" with its graduated dial is directly attached. The great majority of appli cations, however, demand a remote bulb or thermocouple with either a closed system or an electrical system.