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Galvanized-Steel Conductors.



If galvanized-steel, star-section rod with copper-bronze couplings is used, the rod shall be three-fourths inch in diameter. The conductor shall be run as directly as possible on the building with no sharp bends or loops, and in such manner the rod shall be used, and end-to-end joints shall be carefully screwed together. Where branches are attached to the main conductor, Y-connectors shall be used so that bends of at least 2-foot radius may be formed with the laterals.

Copper-bronze or galvanized, malleable-iron screw fasteners or other fasteners of approved design shall be used. The fasteners shall be spaced not more than 4 feet apart, and screwed directly into wooden walls and roofs. Lead expansion shields shall be used for masonry and concrete walls.

Holes through the roof made by the fasteners shall be rendered watertight by means of elastic roof cement.

Star-section elevation rods shall be used with an inverted Y- or other approved connection to the main conductor. The diameter of the elevation rod shall be the same as the conductor.

Solid, copper, bayonet air terminal points screwed to the upper end of the elevation rod shall be used.

Air terminals shall be placed above ridges, gables, chimneys, and flat roofs, and shall be not less than 10 inches above the tops of chimneys, peaks, and pointed parts of the building.

Galvanized-iron tripod supports for the air terminals shall be furnished and installed and fastened to the roof with galvanized-iron screws, bolts, or expansion screws, as the case requires. When bolts are used, a lock nut shall be provided or the end of the bolt upset to prevent loss of nut.

Frost proofing Water Systems in Poultry Houses.

Poultry need a constant supply of drinking water for maximum egg production and proper growth.

Maintaining a constant water supply during cold weather is often difficult. Drinking vessels freeze; pipes may burst.

You can prevent the water in watering equipment from freezing by using electric warmers1. You can protect the pipes in a water supply system with electric heating cable. The cable may also be used to prevent the water in trough-type waterers from freezing.

Two general types of electric water-warming units for poultry watering equipment are available immersion and external. An immersion warmer heats the water directly; the heating element is placed in the water. An external warmer heats the container that holds the water.

Drinking fountains with built-in heating units are also available.

Selection.

Water warmers have the wattage stamped on them. This rating indicates the heating capacity. To obtain a warmer of the correct heating capacity, consider the size of the watering equipment, and plan to maintain the water temperature at not less than 40° F.

Tests have shown that immersion warmers are more efficient than external warmers. The heating capacity of an immersion warmer need not be as high as that of an exter­nal warmer to heat a given quantity of water.

For example, to prevent the water in a 14-quart bucket from freezing at 0° F, you need an immersion warmer rated at 50 watts or more. (An external heater of 75 watts or more would be needed.) To prevent the water in an 8-gallon fountain from freezing at 0° F, you need an external warmer of 150-watt capacity.

Insulating the drinking vessel reduces the heating requirement 20 to 40 per cent.

Operation.

Following are some general instructions for operating electric water warmers.

Install the convenient outlets for the warmers on a circuit separate from the lamps in the poultry house. During cold weather you may need to use the warmers in the daytime while the lamps are turned off. In mild weather the warmers will not be needed.

Water warmers are designed to operate on a specific voltage. Connect them to a power supply of the specified voltage. If the voltage is lower than that specified, the warmer will put out less heat than the rated heating capacity. If the voltage is more than that specified, the warmer will use more wattage.

Since the wattage rating is comparatively low it takes considerable time to heat the water. Therefore, operate the warmers continuously during cold weather. It is especially important to do this if the poultry house lights are turned on in the morning. A thermostat can be installed to turn on or shut off the power as the water becomes cold or warm. This reduces the cost of operation.

Electric Heating Cable.

Electric heating cable protects pipes3 in a water supply system against freezing even in the coldest weather. Its use save labor and may save expense. Pipes do not have to be drained when the temperature drops4 to freezing. Water does not have to be carried from other sources because of frozen pipes. There is no expense of replacing frozen pipes. Most impotent, poultry have a constant supply of drinking.

Several types of electric heating cable are available. Heating capacity of the cables ranges from 2.5 to 10 watts per foot. The type most frequently used has a heating capacity of 5 watts per foot.

Notes:

1electric warmer - электрообогрватель

2electric stock waterer – электрическая водонагревательная колонка

3pipe - трубопровод

4temperature drop – падение напряжения

 

Инженерно-технологический факультет.

Вариант №1.

IGNITION SYSTEMS.

There are two general types of ignition: the compression[69], and the spark[70] methods.

Compression ignition. The compression type utilizes the heat of compressed air to ignite the fuel as it is introduced to the com­bustion or precombustion chamber[71]. The temperature of this air may be as high as 1000 F and sometimes may be higher. If fuel was mixed with the air before compression, preignition would occur; that is, the mixture would ignite before the piston was in the most favorable position to receive the thrust of the expanding gases. This would not be desirable. Ignition is timed in the compression-ignition engine by timing the injection of the fuel. In an engine operating at a constant speed, the need for variance of the timing would not be present. The truck diesel engine, which must operate under a large range of speed conditions, must have a governor system which can control the injection[72] starting point and the injection period. In a cold engine, some trouble is usually experienced in bring­ing the compression temperature up to the ignition temperature of the fuel. To assist the process, glow plugs are sometimes used. These are operated electrically and are turned off when fuel igni­tion begins.

Most diesel (compression-ignition) engines utilize heavy-duty electrical starters, powered by 12 volts or more from storage batte­ries, or gasoline engines to turn the CI engine over fast enough to bring the temperature up to the ignition point. When the CI engine has reached temperatures that ignite the fuel, no further trouble is experienced with ignition. There are no wires[73], coils, and plugs to cause trouble. Some diesel engines under light load or at idle may cool sufficiently to produce poor ignition of the fuel. This condition is overcome as more fuel is burned under operating conditions.

The other ignition system, the spark type, is the one which is more complicated, and therefore it is the frequent cause of poor en­gine performance.

Spark Ignition. The purpose of the spark-ignition system is to deliver a perfectly timed surge of electricity across a spark-plug gap in each cylinder at the exact moment when explode the cylinder's charge of compressed gasoline and air with maximum power efficiency. The distinguishing feature of the SI (spark-ignition) engine is that there is a spark plug in the head. The plug projects into the combustion chamber. In most modern SI engines the gap of the plug remains fixed while the engine operates.

Considering the source of electric current, there are two of spark ignition. They are the battery-ignition and the magneto-ignition types. With the battery, current is produced by chemical reactions within the battery; with the magneto, currents are induced or created by rapidly moving coils or magnets.

Battery-ignition Types. There are two types of battery ignition according to the type of battery. At one time, dry-cell[74] batteries, such as are used in flashlights[75] today, were used to furnish the electric power. Four of these batteries fastened together in series would produce a force of 6 volts or more, until they began to deteriorate[76]. Once deterioration set in, the batteries had to be discarded. Storage batteries have almost entirely replaced the dry-cell batteries for ignition purposes. The storage battery can readily be charged while the engine is operating by means of an accessory called the generator.

Trends[77]. Magnetos are used on small one-cylinder engines powering motorboats and lawn mowers and on airplane engines and farm tractors. The above vehicles have little need for lights and therefore do not need a battery, and so magnetos have been retained. But as farm tractors have been designed to use battery conveniences, such as lights and starters, there has been a trend to use the same battery for ignition purposes. Also, there has been some trend away from magneto ignition because of the initial high cost and because of the difficulty in finding mechanics capable of servicing magnetos. As most automobile mechanics are familiar with battery-ignition systems found on trucks and cars, better ser­vice can be obtained with the battery system. The magneto and battery systems are almost identical in theory and operation. The main difference lies in the production of the current. The battery produces current and voltage by chemical action. The magneto produces current and voltage in one of two ways: either a coil rotates within a magnet, or a magnet rotates near a coil.

 

SPARK PLUG[78]

A spark plug (also, very rarely nowadays, in British English: a sparking plug) is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.

Spark plugs have an insulated[79] central electrode which is connected by a heavily insulated wire to an ignition coil or magneto[80] circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder.

Early patents for spark plugs included those by Nikola Tesla. Some historians have reported that Edmond Berger invented an early spark plug on February 2, 1839. Karl Benz is also credited with the invention. But only the invention of the first commercially viable high-voltage spark plug as part of a magneto-based ignition system by Robert Bosch's engineer Gottlob Honold in 1902 made possible the development of the internal combustion engine.

Reciprocating internal combustion engines can be divided into spark-ignition engines, which require spark plugs to initiate combustion, and compression-ignition engines (diesel engines), which compress the air and then inject diesel fuel into the heated compressed air mixture where it autoignites. Compression-ignition engines may use glow plugs to improve cold start characteristics.

Spark plugs may also be used in other applications such as furnaces where a combustible mixture should be ignited. In this case, they are sometimes referred to as flame igniters.

 

 

Вариант №2.





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