Adjustments. Timing of Fuel point of be ginning of fuel injection can be altered by adjusting the reach rod length. The clearance between the valve spring cap and dog is controlled by the adjusting set-screw on the roller lever d; this need not be more than Fuel valve body is water-cooled, and it is neces sary to use this cooling system when high-gravity fuel oil is burned. With heavy oils, around 24° &time, the water tends to chill the valve and lower its atomizing efficiency; the result is a decidedly smoky exhaust. It is advisable, with such oils, to discontinue the flow of water around the valve.
Needle valve seat requires the same attention as do all open-type valves. The shortening of the valve, due to regrinding, can be compensated for by screwing the valve out of the spring cap or dash-pot.
Fuel Check attention should be given to the fuel check valve while the plant is burning dirty oil. If the fuel be sulphurized to any extent, this valve will corrode and of course demand regrinding. Since the fuel is deposited in the atomizer during the compression stroke, the check works against a considerable pressure—from 250 to 400 lbs.; the sudden opening and closing of the valve in time hammer the seat. The check valve stem must be kept clean from corrosion since the spring is light and will not close the valve against any decided binding of the stem.
Injection injection air pressure is controlled by a governor-controlled valve, interposed between the low- and high-pressure air compressor cylinders. This is illustrated in Fig. 161.
Fulton Machine Co. Marine Diesel Fuel Valve.—Figure 132 illustrates the fuel valve of the Fulton Marine Diesel. It is along standard practice in closed-nozzle valves and is controlled by a rocker from the camshaft.
Nelseco Marine Diesel Fuel Diesel employs a closed-nozzle valve. The valve is located vertically in the cylinder head and is actuated by a rocker arrangement shown in Figs. 19 and 103.
Fuel Valves for Tar 133 and 134 illustrate fuel valves designed to use tar oil as the main charge and light oil for primary ignition.
Regrinding Fuel of the type of fuel valve, each, sooner or later, requires regrinding. In performing this pro cess, an engineer should be very miserly with the amount of grinding paste used. The best compound is one of powdered glass and vaseline, or emery flour and vaseline. Only a very small amount should be placed on the needle, being spread out evenly over the entire seating surface. The entire valve, with the exception of the spring,
should be assembled when grinding. This is to insure that the valve is aligned properly. It is unnecessary to secure more than a thin line contact at the seat—%4 inch in width is ample. After grinding, it is advisable to disassemble the entire valve and cage and wash very thoroughly with kerosene. This is to remove all emery particles.
New Needle the average plant can profitably purchase new needle valves from the engine builder.
Where a plant contains several engines, this valve cost is of some moment. Perfectly good valves can be made of drill rod or cold rolled steel with either a tool-steel or phosphor-bronze tip.
Lubrication of Valve Stem.—The valve stem gradually be comes coated with a thin layer of oil residue, this being more noticeable in non-cooled valves. To prevent binding of the stem, it should be constantly lubricated. A small amount of kerosene injected around the valve at least once every twenty-four hours will remove any residue.
Leaky Fuel Valves.—A leaky injection valve usually betrays its presence by causing the engine exhaust to be smoky. Leaky valves also allow the fuel charge to seep into the cylinder during the compression stroke and so produce violent preignitioft.
Incorrect Fuel Valve Timing.—If the valve opens too early, a sharp metallic click or pound will be heard in the cylinder. This is evidence of premature combustion. If the valve opens late, a dull thump or pound, quite like a pound due to loose pin bearing, can be heard. Furthermore, a smoky exhaust ordinarily ac companies this pounding.
Clogged Atomizer or Nozzle-tip Disk.—When either the atomizer or the disk at the end of the fuel valve, sometimes called the burner plate, is clogged, the exhaust is smoky.
Sticking Valve Stem.—When the fuel valve stem sticks in the open position, the exhaust will be smoky and the injection air gage will show a drop—with the open nozzle, the gage needle will show as much as a 75 per cent. pressure drop.
Fuel Valve Cooling Jacket Temperature.—The desirable tem perature, at which the discharge line from the fuel: valve water jacket should be carried, depends on the characteristics of the fuels. If the oil is heavy and viscous, the discharge should be around 160° Fahrenheit. With fuel oil of 28° Baum& and higher, 120° Fahrenheit is amply high since the valve must be cool to prevent gassing of the light oil.