Special engineers may be assigned to act in any capacity for which they are qualified on steamers of one hundred tons and under. Inspectors may designate upon the certificate of any chief engineer the tonnage of the vessel on which he may act, and they may also designate any assistant engineer as special engineer on steamers of one hundred tons or under, and may restrict an engineer to a particular vessel. 3. Engineers on high-pressure steamers navigating rivers shall be designated as chief engineers (H. P.), assistant engineers (H. P.), and special engineers (H. P.). Assistant engineers may act as chief engineers on high-pressure steamers of one hundred tons burden and under, of the class and tonnage, or particular steamer for which the inspectors, after a thorough examination, may find them qualified. In all cases where an assistant engineer is permitted to act as first [chief] engineer, the inspectors shall state on the face of his certificate of license the class and tonnage of steamers, or the particular steamer, on which he may so act. 4. It shall be the duty of an engineer, when he assumes charge of the boilers and machinery of a steamer, to forthwith thoroughly examine the same, and if he finds any part thereof in bad condition, caused by neglect or inattention on the part of his predecessor, he shall immediately report the facts to the local inspectors of the dis trict, who shall thereupon investigate the matter, and if the former engineer has been culpably derelict of duty, they shall suspend or revoke his license. 5. No original license shall be issued to any person to act as engineer, except for special license on small pleasure steamers, who cannot read and write, or who has not served at least three years in the engineer's department of a steam-vessel, or as a regular machinist in a machine works; provided that any person who has served for a period of three years as a locomotive or a stationary engineer may be licensed to act as engineer on steam vessels after having had not less than one year's experience in the engineer's department of a steam vessel. CHANGES IN STEAMBOAT RULES. Amendments Made by the Supervising In- Section 5, rule 5, has been amended so that no person shall receive an original license as engineer who has not served at least three years in the engineer's department of a steam vessel, except locomotive and stationary engineers, and a regular steam engine machinist; and no person shall receive a license who is not able to determine the weight necessary to be placed on the lever of a safety-valve to withstand any given pressure of steam in a boiler. By section 18 the grade of an engineer or pilot shall not be raised during the term for which the license was granted except by consent of the board that granted the license. CHAPTER XII, TO FIND THE SIZES (DIAMETER) OF CYLINDERS FOR COMPOUND ENGINES-HORSE POWER TAKE for an example say: horse power = 100; initial pressure = 60 pounds (gauge); and piston speed 400 feet. First find the number of times the steam is expanded. Rule: Divide the absolute initial pressure by the terminal pressure. The quotient will be the number of times the steam is expanded. The area of the low pressure cylinder is the same as the area of the cylinder of a simple cylinder engine working under the same expansion: hence find the mean pressure as for a simple cylinder by the following rule : Find the hyperbolic logarithm for the number representing the expansion, to which add 1, and multiply the sum by the terminal pressure. = The product will be the mean pressure. The hyp. log. of 5 is 1.609, and 1.609 + 1 2.609, and 2.609 × 15 = 39 +, which is the mean pressure in pounds per square inch. The area of cylinder is found by the following rule: Multiply 33,000 by the number of horse power, and divide the product by the piston speed, multiplied by the mean pressure. The quotient will be the area of the cylinder in inches. Thus, 33000 X 100 400 X 39 of about 161⁄2". =211.5+, corresponds to a diameter The diameter of high pressure cylinder should be such as to equalize the maximum strains on the two pistons; in other words, the expansion should be the same in each cylinder. Hence, to find the area of high pressure cylinder: Divide the area of the low pressure cylinder by the square root of the number of times the steam is expanded. The quotient will be the area of the high pressure cylinder in inches. Thus, 2112 of about II. 94.5+, which corresponds to a diameter To find the point of cut-off in a high pressure cylinder: Divide the area of the high pressure cylinder by the area of the low pressure cylinder. The quotient will be the fraction of stroke which shouid be made before steam is cut off. 94.5 211.5 Thus, =.446+, which is the point of cut-off in the |