Throttle valve

“ It consists of two main parts—the pumps and the ram closing the throttle. The pumps, two in number, are worked alternately by some moving part of the engine, such as the air-pump lever. They inject water through a small pipe into a cylinder, the piston-rod of which operates a throttle valve in the main steam supply to the engines. At the bottom of this cylinder is a by-pass, or artificial leak, through which the water flows back to the pumps. The size of the flow through the by-pass is controlled by a screw adjustment. ”

“ A leaking slide valve is the cause of much loss of power, and waste of coal, and as the leakage mingles directly with the exhaust, it often remains unknown until it has thrown away a considerable quantity of fuel. It is best detected by blocking the engine with the piston at mid-stroke and opening the throttle valve slightly. If the cylinder drain cocks are now opened, the leaking steam that escapes into the cylinder will be seen issuing from the drains. ”

“ An adjustable valve stem Q passes through one side of the bent tube, the lower end being pointed and adapted to regulate the inflow of gasoline through the duct N, and into the U-shaped tube.
A throttle valve R is placed in the discharge end of the U-shaped tube, which is susceptible of regulation by means of a lever S. The diagram shows the gasoline within the U-shaped tube, so that it is on a level with the gasoline in the float chamber. ”

“ A. When you have from 25 to 40 lbs. of pressure open the throttle valve a little, allowing the cylinder cocks to be open also. Some steam will condense at first in the cold cylinder, and this water must be allowed to drain off. See that the crank is not on a dead center, and put on just enough steam to start the engine. As soon as it gets warmed up, and only dry steam appears at the cocks, close the cylinder cocks, open the throttle gradually till it is wide open, and wait for the engine to work up to its full speed. ”

“ Where this system is adopted, a throttle is also used, which enables the operator to regulate the quantity of mixture, and thus alter the power of the explosion. For example, when the maximum power is required, the throttle is open to the fullest, and the sparking advanced to the utmost that the engine will take.
(2) Exhaust-Valve Lifter.—This operates by preventing the exhaust valve from closing after the exhaust gases have escaped. When the exhaust valve is held fully up, no explosive charge is taken into the cylinder. ”

“ When the pump is stopped, pull the exhaust lever back, so the condensed steam from leak of throttle valve will not go into the pump. It is safer [Pg 96] also in cold weather to take off head of water end. Slight but constant lubrication adds much to the regular working of the pump. Be sure there are no leaks in the suction pipe, and when water is raised more than 10 feet, a foot valve should be put in. Compress the packings on piston rod as little as possible and yet prevent the escape of steam. ”

“ Keep the governor well lubricated with light oil, and keep the oil off the belt as much as possible. Governor valve should be carefully tested for tightness and freedom.
The throttle valve must be absolutely steam tight for a leaking valve is a dangerous proposition especially in stopping the 361engine. It is generally arranged so that it can be reground with pumice stone or crocus powder and oil. If the valve is of bronze or brass do not use emery or carborundum for the particles will become imbedded in the soft metal and put it in a worse condition than ever. ”

“ Then the secondary valve is suddenly thrown out of action, gives the leak full play, and causes the throttle to open quickly so that the steam may be cut off only for a moment. By the turning of a small milled screw-head a couple of inches in diameter the pace of 5,000 h.p. engines is as fully regulated as if a powerful brake were applied the moment they exceeded "the legal limit." ”

“ Pumping engines may be governed by allowing the pressure of water in the rising main to accumulate in a stand pipe or equivalent device until it stops the engine by excess of pressure. To prevent such an engine running away a catch is used, kept open by the pressure of water; when the pressure falls below a certain point the catch is released and closes the throttle valve.
Steam engines may also be safeguarded in the same way by a catch which is released and closes the throttle valve when the governor becomes fully expanded. ”

“ If the engine does not now commence its motion, it must be blown through again until it moves. If the engine be lightly loaded, or if there be no water in the pumps, the throttle valve must be kept nearly closed, and the top and exhaustion regulators must be opened only a very little way, else the engine will make its stroke with violence, and perhaps do mischief. If there is much unbalanced weight on the pump end, the plug which opens the steam valve must be so regulated, that the valve will only be opened very slightly ”

“ Throttle-valve, a valve [251] fixed in the steam-pipe of an engine, to which the governor is attached, to throttle or reduce the supply of steam to the cylinder. In some engines, as the locomotive, there is no governor motion, and the throttle-valve is consequently used by hand.
Waste-pit: a vertical pit or well, leading from the "overflow" on the embankment into the supply; or, in this case, the "waste culvert."
Drawer: the man employed to draw water from the reservoir by raising the "shuttle." ”

“ Two balls revolve around a spindle in such a way as to rise when the speed of the engine is high, and fall when it is low, and in rising and falling they open and close a valve similar to the throttle valve. The amount that the governor valve is opened or closed by the rise and fall of the governor balls is usually regulated by a thumb screw at the top or side, or by what is called a handle nut, which is usually held firm by a check nut directly over it, which should be screwed firm against the handle nut. ”

“ The regulation of the auxiliary valve is an adjustment that should be made only after the needle valve has been set properly for slow speeds of the motor. When this condition is obtained, the throttle should be opened and the further adjustment of the carburetor for high speeds of the motor should then be made through the auxiliary air valve. In other words, the needle valve should be set so that the motor runs properly at low speeds, while the adjustment of the auxiliary air valve should be made only to secure smooth operation at a high number of revolutions. ”

“ As the engine is almost invariably air-cooled, the skilful manipulation of these three levers is essential for satisfactory results. On a good level road when the engine may be working at a small fraction of its maximum power, the proportion of air mixed with the petrol vapour from the carburettor may be great, giving a “weak” mixture, yet one rich enough to be ignited in the cylinder. The throttle valve may be fully open and the spark advanced for high speed; the throttle partially closed and spark retarded for slow speed. ”

“ After the steam enters the throttle valve it passes through the front end of the valve, through the top of the boiler via the dry pipe (fig. 18) , through the front tube sheet, and then to the cylinders via the petticoat pipes. The throttle lever is a simple arrangement readily understood from the drawings. It has no latch and the throttle lever is held in any desired setting by the wingnut and quadrant shown in figure 18. The water level in the boiler is indicated by the three brass cocks located on the backhead. No gauge glass is used ”

“ The result is that the motor will begin to misfire and slow down as soon as it has attained any considerable speed. This is accounted for by the fact that at high speeds the increased suction will draw the particles of dust, etc., into the nozzle. By opening the valve needle half a turn and giving the throttle lever two or three quick pulls the dirt or sediment will often be drawn through, when the needle may be turned back to its original place. ”

“ A further control of the high speed jet is provided by the fuel metering valve operated by the carbureter throttle. This valve provides the maximum fuel feed to the "high speed" nozzle when the throttle is fully opened for high speeds and for quick "pick up." ”

“ The Throttle on an engine is the valve which allows the steam to enter or be shut off from the cylinder and should always be left wide open on a governor engine when running, as the governor regulates the quantity of steam required to run it at its proper speed and is much more economical. ”

“ Start engine as follows: After choke lever has been moved to normal open running position and engine is normally hot, correct adjustment of needle valve by turning needle valve down (to right) one notch at a time until mixture becomes so lean that engine misses, and is inclined to stop: then back out (to left) needle valve 5 to 10 notches, or until engine fires regularly with spark advanced and throttle closed (or as nearly closed as it can be set and still have engine running at idling speed) . ”

“ The steadiest running is probably given with [122] the throttle control, which diminishes the supply. On motor cars this method has practically ousted the "hit-and-miss" governed exhaust valve; but in stationary engines we more commonly find the speed controlled by robbing the mixture of the explosive gas in inverse proportion to the amount of the work required from the engine. ”

“ It is well at this time, while there is no load on the turbine, to be sure that the governor controls the machine with the throttle wide open. It might be that the main poppet valve has sustained some injury not evident on inspection, or was leaking badly. Should there be some such defect, steps should be taken to regrind the valve to its seat at the first opportunity.
On the larger machines an auxiliary oil pump is always furnished. This should be used before starting up, so as to establish the oil circulation before the turbine is revolved. ”

“ Under these conditions, then, it may be assumed that although the load on the test machine will vary, it cannot fall below 6000 kilowatts. Therefore, all that remains to be done to insure a perfectly steady load equal to the normal full load of the machine, or 6000 kilowatts, is to fix the main throttle or governing valve in such a position that the steam passing through at constant pressure is just capable of sustaining full speed under the load required. When this method is adopted, it is desirable to fix a simple hight-adjusting and locking mechanism to the governing-valve spindle. ”

“ Adjust throttle lever stop screw (fig. 43) as necessary to make engine idle at proper speed with throttle in fully closed position. Turning stop screw to the right makes engine idle faster. Turning stop screw to the left makes engine idle slower. Do not idle engine at the slowest possible speed, because an extremely slow idling adjustment causes hard engine starting. Changing idling speed with throttle stop screw is likely to change the low speed fuel mixture to some extent: therefore, it will be necessary to again check and correct the low speed needle valve adjustment (step (3) above) . ”

“ As the water is incompressible, slide valves must have neither lap nor lead, and piston valves are preferable to ordinary slide valves. To prevent injurious compression from exhaust valves closing too soon in rotative engines with a fixed stroke, small self-acting relief valves are fitted to the cylinder ends, opening outwards against the pressure into the valve chest. Imprisoned water can then escape without over-straining the machines. ”

“ All exhaust valves are operated by levers and push rods connected to a cam mechanism on the outside of the crank case. A single cam ring operates all of the valves except where a step-by-step compression is desired. The exhaust mechanism is provided with a simple device by which the closing of the exhaust valve may be delayed through any portion of the exhaust stroke, thus reducing the compression and adding to the facility of cranking. The motor is started with the compression entirely released in which condition it can be spun about its shaft with ease. ”

“ The bolt B has a very small hole bored through it from end to end. When the vacuum is broken slowly, the pressure falls in D as fast as in the pipe; but a sudden inrush of air causes the valve A to be pulled off its seat by the diaphragm C, as the vacuum in D has not been broken to any appreciable extent. Air then rushes into the train pipe through the valve. It is thus evident that the driver controls this valve as effectively as if it were on the engine. These "emergency" valves are sometimes fitted to every vehicle of a train. ”

“ The exhaust-valves are moved by an independent eccentric rod, which is itself moved by an eccentric set, as is usual with the Corliss and with other engines generally, at right angles with the crank. This engine, in consequence of the independence of the steam-eccentric, and of the contemporary movement of steam valve-motion and steam-piston, is capable of cutting off at any point from beginning to nearly the end of the stroke. The usual arrangement, by which steam and exhaust valves are moved by the same eccentric, only permits expansion with the range from the beginning to half-stroke. ”

“ It thus takes four strokes or two revolutions of the shaft to complete the Otto cycle, the cylinder being used alternately as a pump and a motor, and the engine, when working at full load, thus gives one impulse for every two revolutions. The valves, which are all of the conical-seated lift type, are four in number—charge inlet valve, gas inlet valve, igniting valve, and exhaust valve. The igniting valve is usually termed the timing valve, because it determines the time of the explosion. ”