Steam " He must also, at the same time, pay a fee of £1, which will be applied in remunerating the Examiners. Notice will be given of the time at which the applicant is to attend to be examined; and if he passes, the result of the examination will be reported to the Board of Trade, and his Certificate of Competency will be issued or returned to him, as the case may be, with an indorsement as above mentioned, showing that he has "Passed in Steam." If he fails, no notice of the failure will be recorded on the Certificate, but no part of the fee will be returned. 17. Full directions as to the course of Examination in Steam, and the qualifications required of candidates, are contained in the instructions issued to Engineer Surveyors appointed as Examiners at the large Ports. Naval Department, Board of Trade, May, 1855. T. H. FARRER, Secretary. QUESTIONS. To be answered by Commanders of Steam Vessels, under examination in the practical use of the Steam Engine. Explain the nature and use of the principal valves and cocks connected with the boilers and engines, commencing with the boilers. BOILER VALVES AND COCKS. Safety valves-to control the pressure of steam, and to allow the steam to pass off, after it reaches the required pressure. Reverse or atmospheric valves-prevent the formation of vacuum, by allowing the air to pass into the boilers, and save them from collapsing, from external atmospheric pressure. Communication or stop valves,-for communication between the boilers or between boiler and engine, so that they can be shut off from each other if necessary. Feed valves,-regulate flow of water into boiler, and are fitted to the feed pipes to prevent the water from returning from the boilers. Kingston's valves,—are conical valves fitted in the ship's side, at the end of blow-off pipe, to enable the cocks to be taken out if required, and can be closed if necessary. Blow-off cocks,-for blowing supersalted water out of boiler into the sea; they are fitted at the bottom of the boilers. The water gauge cocks,-for showing the height of water in boiler, in case of accident to the glasses or cocks. The glass water gauge,-for showing the same more easily. Steam gauge,-shows the pressure of steam; it is a bent pipe containing mercury, which rises one inch to every increased pound of pressure. Hand pump for boilers,-for filling them when the engines are stopped, or before lighting fires. ENGINE VALVES AND COCKS Throttle valves, are fitted in steam pipe, for shutting off and regulating steam to the cylinders. Slide valve, to admit steam to give the necessary motion to piston by shutting off and admitting steam to the cylinder and condenser. Expansion valves,—are placed between the throttle and slide valves, for cutting off steam at any required part of the stroke, leaving the rest to be worked by expansion in the cylinder. Escape valves, for allowing the escape of water or too strong steam that may be in the cylinder. Blow-through valves,-for forming a vacuum in the cylinder on both sides of the piston, and in the condenser before starting. Foot valve, is at the bottom of air pump to prevent return of water into the condenser on the down stroke of the air pump bucket. Delivering valve,-prevents return of water from the hot well, it is at the top of the air pump. Air ритр bucket valve,-to allow the bucket to pass through the water in the air pump, after it has drawn it from the condenser, and before forcing it into the hot well: it opens in descending and closes in ascending. Injection valves and cocks, for regulating the flow or injection of water for condensing steam, the valve is fitted on the condenser, the cock on the ship's side. Bilge pump valves and cocks,-for pumping water out of bilge, the valves are fitted to the bilge pumps, and the cocks to the different bulkheads to be pumped from. Stop or sluice valves,-to discharge pipes, for preventing any sea water entering the discharge pipe. Jacket cocks, for escape of water from slide jacket of the cylinder before starting. The snifling valve,—allows a small quantity of air to enter the condenser and air pump, to prevent concussion of valves. BOILERS. Q.-If the safety valves were set fast, how would you relieve the pressure on the boilers, if steam was up and could not make its escape? A.—This will only occur to a dangerous extent, where the engines are at rest, and may be remedied by starting them at full speed if possible. If this cannot be done, open the blowthrough valves, and allow the steam to escape into the bilge; the blow-off cocks may also be opened, but care must be taken to feed the boiler by means of the donkey. U Q. How do you ascertaiu the saltness of the water in the boilers? A. By an instrument called the Salinometer. Q.-How would you manage to change the water in the boilers, if the blow-off cocks were set fast? A. By blowing off by the deck pump sea-cock, if there be one, or by taking the valves out of feed-pump. Q. -On examining the boilers, and they are found to be thin, what measures would you adopt to prevent accidents? A.-Reduce the pressure on safety valve. Q. How would you keep the boiler free from salt and incrustation? A. By blowing off frequently from the cocks at the bottom of the boiler, or by keeping the surface blow-off constantly open. Q. Is it requisite to have a hand-pump fitted to the boilers; if so, for what purpose? A. Yes; to fill boilers when steam is not up, or in case of accident to feed pump. Q.-Explain the use of the gauge-glasses and gauge-cocks, fitted on the boilers. A.-To show height of water in boiler; the former at a glance, the latter by opening them. Q. If the mercury was blown out of the steam-gauge by the pressure of steam in the boilers, what would you apprehend was the cause? A, That the steam was dangerously high. Q. What would you do to relieve the pressure of the boilers? A.-Open the furnace fire-doors, and shut the dampers and ease the safety-valves. Q-How would you water in the boilers? regulate the height or quantity of A-By allowing the water to rise from a little above the middle of the glass to near the top every watch. Q-When the steam is up, how is the feed applied to the boilers? A-By feed pump worked by engine, if in motion, otherwise by hand pump. Q-When it is not up, what is necessary to be done before the fires are lighted? A-Fill boilers. Q-When the engines are stopped, what precautions are necessary with regard to the water in the boilers? A-Keep the proper quantity of water in the boiler. A-When the water leaves the boiler with the steam. Q-How would you prevent it doing so? A-Reduce the pressure and keep the water low. Q-If the water in a boiler is suffered to get too low, what may be the consequence? A-The tubes or flues would be burnt. Q-What height should the water stand in a common boiler above the flues? A-About 10 inches. Q-What height should the water stand in a tubular boiler above the tubes? A-About 8 inches. Q-If any of the tubes were damaged by the fire, or leaky, what would you do, supposing you could not shift them? A-Plug up both ends firmly with some metallic substance. Q-If the water in a boiler is suffered to get too high, what might be the consequences? A-Water will pass out with the steam into the cylinder and perhaps knock the bottom out. Q-How would you know when the water in the boiler requires changing? A.-By testing it with the Salinometer. Q.-Explain the use of the thermometer and hydrometer? A. The thermometer measures the heat, and the hydrometer the density of the water. Having drawn off some water from the boiler, allow it to cool to the temperature for which the hydrometer was intended. The stem of the instrument being properly graduated will indicate the amount of salt in the water. ENGINES. Q-Explain the use of the cylinders. A.-To contain the steam while acting on or giving motion to the pistons. Q.-Explain the use of the air pump. A. To form a vacuum in the condenser and draw the exhausted steam from the cylinder. Q.-Explain the use of the condenser. A. For condensing the steam after leaving the cylinder. |