radiation. By using the dry process at 216 deg. the process kettle loses heat only through radiation in amount equal to about 5 boiler h. p. and through condensate form the drain equal to about 61⁄2 boiler h. p., the loss through the vent with automatic regulation being negligible. It is questionable how the 61⁄2 boiler h. p. escaping from the drain may be utilized. It might be returned to the boiler as feed if provision were made to eliminate impurities. An exhaust steam feedwater heater is added, by means of which 26 boiler h. p. is recovered, but as the exhaust steam is in excess of the requirements for preheating the feed water, some of that available from the engine is lost through the vent. It is very possible that this excess of steam should be recovered in one of the steam-using units; for example, if a process kettle were designed with sufficiently large steam pipes and openings, exhaust steam could be used in it, or this exhaust steam could be used in a vacuum pan. There are a number of such possibilities.

GENERAL CONSIDERATION.

45. Having now taken up in more or less detail the various familiar steam-using units in the canning factory, the writer would conclude with a few remarks of general application. Economy in steam means three thingsincreasing efficiency of units, eliminating all avoidable wastes, and utilizing all other wastes of heat as by-products. The first two can only be accomplished through measurement-it is necessary to know how much steam is used and wasted. The packing house should be properly equipped with measuring instruments for this purpose. The familiar and little appreciated pressure gage is almost a stranger in the packing house, and yet a judicious use of this instrument will disclose much valuable information as to how steam is being used or abused. To find out how low the steam pressure is on some units whose inefficiency or lack of capacity has been ascribed to other causes and inspired futile remedies, will open the eyes of the superintendent. Next, when we eliminate wastes, we must eliminate all wastes, and not tolerate any just because we have been accustomed to seeing them and know that they are difficult to avoid. Wherever steam shows in the atmosphere is represents a waste, whether the steam comes from the jacket of a kettle, the vent of a process retort, the flue from an exhaust box or heater or scalder, or from any cause whatsoever. We have no right to discharge steam into the atmosphere, even if it is exhaust steam. We have no right to radiate heat to the atmosphere which might be caved by non-heat-conducting protection, and such wastes, it is necessary to say, are wantonly committed in the packing house. No steam-using units the writer has seen in such houses make the slightest provision against loss of heat by radiation. This is not only a waste of coal, but a waste of human energy, since the operators cannot work efficiently in the torrid heat usually prevailing and aggravated by radiation from steam-using units. The packer objects on the ground of expense, but he should remember that each square foot of surface with steam behind it radiates to the atmosphere in ten hours an amount of heat requiring the burning of one pound of present-day coal, and then, upon calculating what this aggregates to, will he realize that it is not a question of the expense of installing pipe coverings and other similar devices, but the expense of not doing so.

46. Finally, the question of how to utilize by-product heat requires careful study. In each factory the problem may be different, and in each it may be a separate case of proportioning the units to fit into each other. Feedwater heaters, traps, low-pressure heaters-all should be considered. Even the water used for cooling the cans, which carries away all of the useful heat transmitted, as previously defined, may be made to render up some of the heat it has removed.

WATER AND STEAM PROCESS.

When processing in a retort with water and steam, close bottom outlet and fill retort half full of water; bring to a boil; shut off steam and place crates; then handle same as with steam, of course keeping bottom outlet closed.

TESTING GOODS.

Self-registering can-testing thermometers are valuable aids in determining when goods have reached the sterilization point, and are especially valuable for dry-packed corn, which should be tested, if not every batch, at least several times a day. When testing articles packed in either brine or syrup, remember that the thermometer marks the temperature of the surrounding liquid and not the internal temperature of the fruit or vegetable; consequently, good judgment is required in reducing process time, particularly so when goods are cooled, as they always should be, after processing. It is advised that frequent tests be made of the temperature attained during processing, and probably the best and most economical device yet placed on the market is the Self-Registering, Sterilizing Thermometer. These thermometers are fitted to metal caps (as shown on page 54) which are soldered to the regular tin cans, and may be used almost indefinitely by replacing the tins which may become bent, misshapen or rusted from constant use. Cut cans frequently, noting cook, color, weight and general appearance of goods.

PROCESSING GLASS.

Glass jars are used principally for high-grade products—jams, preserves, jellies, etc.-and are best processed in water at 212 degrees or in steam at a temperature not much in excess of this point. During cold weather temper all glassware before filling, and it is customary to fill with hot liquid instead of exhausting, though they may be exhausted in hot water or steam, but preferably the latter at about 175° F. After making closure, place in water of about same temperature as contents of package; bring very slowly to a boil; take time; when process time expires, turn off steam and allow the water in kettle to cool about to 189 degrees before removing jars. Be careful not to expose the hot jars to a current of cold air, as this will cause excessive breakage. Under favorable conditions a loss of less than 1 per cent. may be expected from breakage in processing and cooling glass goods. Glass may be processed in steam in an ordinary steam exhaust box, or in an extra long continuous steam exhaust box run at the proper speed. Bring the heat up very slowly and cool very slowly

STERILIZATION-IMPORTANCE OF PROPER PROCESSING. (Reprinted from THE CANNING TRADE, Issue of January 20, 1911.)

Note.-In this article the terms "retort" and kettle" are used synonymously since the subject deals with the treatment of canned foods in closed vessels under pressure.

Assuming that all who are engaged in the canning business are familiar with the basic principles of processing, this article will deal only with the methods by which processing can be made an easier and surer operation by the use of modern and up-to-date appliances that make automatic the operations on which scientific processing depends and which cannot be perfectly carried on while relying altogether on manual labor and human intelligence.

If a constant boiler pressure could be maintained at all times and a perfect steam circulation be produced in the kettles a careful processor could, by constant attention, hold the kettles at a fairly uniform temperature. But since these two ideal conditions are rarely found in a canning plant, what can be done to improve them?

Owing to the variable demands for steam pressure, it is almost, if not utterly, impossible to keep a steady boiler pressure, but the conditions in the boiler-room can be improved by employing a first-class engineer and modern power plant equipment.

Circulation in the ketles.-If processing altogether with steam, good circulation is assured by placing a vent in the cover so that a steady stream of steam escapes when the kettle is closed and under pressure. The thermometer pocket should also have a vent to insure perfect circulation around the thermometer bulb, otherwise the instrument cannot give true indications of the temperature existing inside of the kettle.

If cooking in a closed kettle with water heated by live steam, obtaining perfect circulation is more difficult than where dry steam only is used.

In order to produce a uniform pack, it stands to reason that every can in every batch must be exposed to the same temperature for the full cooking period. If this is not done, some of the cans will be either over-cooked or under-cooked. If undercooked, "swells" will result, because the bacteria, which are always present in food of any kind, have not been destroyed; if over-cooked, the goods will either be discolored or lose their firmness and cannot be classed as first quality or standards.

To obtain this uniform temperature then, in waterbath process, it is essential that the best possible circulation be produced and maintained, and this can be accomplished by the use of a simple but effectual circulating system, which is illustrated by Fig. 1.

By means of the three circulating pipes "D" and the suction created by the force of the steam passing through the jet "C," a rapid circulation takes place, which causes the water in the kettle to flow out the circulating pipes at "A" and into the kettle again at "B." As a result of this constant passage and repassage of the water through a kettle, the water is thoroughly mixed and the cans are sure to be exposed to the same temperature, regardless of their location in the kettle. The use of "telltale" can-testing thermometers placed in cans in different parts of the crates will give positive information regarding the temperature to which the goods have been exposed, because each thermometer will register the maximum temperature to which its particular can has been subjected during the cook.

The next step is to control the flow of steam into the retort so that a constant temperature may be maintained. When this is done, by having a man pass up and down the line of kettles, watching the thermometers and adjusting the hand valve according as the temperature has increased or de

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creased, the same risks are taken which would be assumed in a boiler plant if, instead of placing safety valves on the boiler, the engineer was wholly depended on to hold the pressure at the right point by constantly watching the gauge.

You may employ the best processor obtainable, but since he is human, you run grave risks so long as you depend entirely on his endurance to do this work for you. During the busy season he is often obliged to work night as well as day, and he cannot give the attention to his work that he ought.

To overcome this difficulty and to reduce to a minimum all chances of loss due to improper control of the steam entering the retort, there exist various automatic or mechanical processing devices.

Two systems of automatic retort control are in use. One, known as the individual retort control, and the other known as the battery control. The former requires that every kettle or retort have its own individual regulator, thus making each regulator independent of every other. The battery control consists of but a single regulator, which is equipped to control the entire battery as a unit. It will be seen, therefore, that in cooking different kinds of goods at various temperatures in the different kettles of a battery, the regulator for battery control cannot be used and the individual regulator is essential.

Aside from this, if the regulator for battery control is in operation and anything goes wrong which requires shutting down the regulator, the whole battery is without the use of automatic service.

If, however, the kettles are equipped with individual regulators and it is found necessary to cut off one of the devices, the only kettle affected will be the one whose regulator is shut down. This kettle can then be operated by hand and the others will continue to run automatically.