between 38 and 48 inches in diameter, an opening not less than 11 by 157 inches. 18. All wood-work or other ignitible substance, approaching within two inches of the boiler, shall be suitably sheathed with metal, so adjusted as to permit a free circulation of air between the sheathing and the ignitible surface. 19. All boilers shall have a clear space at the back and ends thereof of two feet opposite the back connection door. Slip joints in steam-pipes shall, in their working parts, when the steamer is to be employed in navigating salt water, be made of copper or composition. 20. There shall be fastened to each boiler a plate containing the name of the manufacturer of the material, the place where manufactured, the tensile strength, the name of the builder of the boiler, when and where built. 21. Every sea-going steamer carrying passengers shall be supplied with an auxiliary or donkey boiler of sufficient capacity to work the fire-pumps. 22. All steamers shall have inserted in their boilers plugs of Banca tin, at least one-half inch in diameter at the smallest end of the internal opening, in the following manner, to wit: Cylinder boilers with flues shall have one plug inserted in one flue of each boiler; and also one plug inserted in the shell of each boiler from the inside, immediately before the fire line, and not less than four feet from the forward end of the boilers. All fire-box boilers shall have one plug inserted in the crown of the back connection, or in the highest fire service of the boiler. All upright tubular boilers used for marine purposes shall have a fusible plug inserted in one of the tubes at a point at least two inches below the lower gauge-cock, and said plug may be placed in the upper head-sheet when deemed advisable by the local inspectors. All fusible plugs, unless otherwise provided, shall have an external diameter not less than that of a one-inch gas or steam pipe screw-tap, except when such plugs shall be used in the tubes of upright boilers, plugs may be used with an external diameter of not less than that of a three-eighths of an inch gas or steam pipe screw-tap, said plugs to conform in construction with plugs now authorized to be used by this Board; and it shall be the duty of the inspectors to see that these plugs are filled with Banca tin at each annual inspection. 23. All steamers having one or two boilers shall have three suitable gauge-cocks in each boiler. Those having three or more boilers in battery shall have three in each outside boiler and two in each remaining boiler in the battery; and the middle gauge-cocks in all boilers shall not be less than four inches above the top of the flues, tubes, or crown of the firebox. 24. Lever safety-valves to be attached to marine boilers shall have an area of not less than one square inch to two square feet of the gratesurface in the boiler, and the seats of all such safety-valves shall have an angle of inclination of 45 degrees to the centre line of their axis. The valves shall be so arranged that each boiler shall have one separate safety-valve, unless the arrangement is such as to preclude the possibility of shutting off the communication of any boiler with the safety-valve or valves employed. This arrangement shall also apply to lock-up safetyvalves when they are employed. Any spring-loaded safety-valves constructed so as to give an increased lift by the operation of steam, after being raised from their seats, or any spring-loaded safety-valve constructed in any other manner or so as to give an effective area equal to that of the aforementioned spring-loaded safetyvalve, may be used in lieu of the common lever-weighted valve on all boilers on steam vessels, and all such spring-loaded safety-valves shall be required to have an area of not less than one square inch to 3 square feet of grate-surface of the boiler, and each spring-loaded valve shall be supplied with a lever that will raise the valve from its seat a distance of not less than that equal to one-eighth the diameter of the valve-opening, and the seats of all such safety-valves shall have an angle of inclination to the centre-line of their axis of 45 degrees. But in no case shall any spring-loaded safetyvalve be used in lieu of the lever-weighted safety-valve, without first having been approved by the Board of Supervising Inspectors. The first paragraph of this section applies to valves constructed in material, workmanship, and principle according to the drawings for a safety-valve printed with these rules, and all common lever safety-valves to be hereafter applied to the boilers of steam vessels 'must be so constructed. When this construction of a safety-valve is applied to the boilers of steamers navigating rough waters, the link may be connected direct with the spindle of the valve: Provided, always, That the fulcrum or points upon which the lever rests are made of steel, knife or sharp edged, and hardened; in this case the short end of the lever should be attached directly to the valve-casing. In all cases the link requires but a slight movement, not exceeding one-eighth of an inch. DIRECTIONS TO ACCOMPANY DRAWINGS FOR THE SAFETY-VALVES REFERRED TO. (For drawings, see page 47, Proceedings of 1877, and page 28, Rules and Regulations of 1882.) All the points of bearing on lever must be in the same plane. The distance of the fulcrum must in no case be less than the diameter of the valve-opening. The length of the lever should not exceed the distance of the fulcrum multiplied by ten. The width of the bearings of the fulcrum must not be less than threefourths (3) of one inch. The length of the fulcrum-link should not be less than four inches. The lever and fulcrum-link must be made of wrought-iron or steel, and the knife-edged fulcrum points and bearings for the points must be made of steel and hardened. The valvė, valve-seat, and bushings for the stem or spindle must be made of composition (gun-metal) when the valve is intended to be attached to a boiler using salt water; but when the valve is to be attached to a boiler using fresh water, and generating steam of a high pressure, the parts named, with the exception of the bushings for the spindle, may be made of cast-iron. The valve must be guided by its spindle, both above and below the ground seat and above the lever, through supports either made of composition (gun-metal) or bushed with it. The spindle should fit loosely in the bearings or supports. When the valve is intended to be applied to the boilers of steamers navigating rough waters, the fulcrum-link may be connected directly with the spindle of the valve; providing, always, that the knife-edged fulcrum points are made of steel and hardened, and that the vertical movement of the valve is unobstructed by any lateral movement. In all cases the weight must be adjusted on the lever to the pressure of steam allowed in each case by a correct steam-gauge attached to the boiler. The weight must then be securely fastened in its position and the lever marked, for the purpose of facilitating the replacing of the weight should it be necessary to remove the same; and in no case shall a line or any other device be attached to the lever or weight except in such a manner as will enable the engineer to raise the valve from its seat. Donkey boilers used on all steam vessels for driving pumps, hoisting engines, electric lights, or other purposes, must be inspected the same as the main steam-boilers, and supplied with water and steam gauges, and the safety-valves must comply with the same regulations as the main boilers. The area of all openings in boilers and connections leading from boilers to safety-valves, both the lever and spring-loaded valves, used on marine boilers shall not be less than the area of the valve used in said safety-valve. 25. All steam-gauges heretofore in use on steamers shall be admissible by the inspectors, and other steam-gauges hereafter made, of equal merit, shall be allowed. 26. All boilers or sets of boilers shall have attached to them at least one gauge that will correctly indicate a pressure of steam equal to eighty per cent. of the hydrostatic pressure applied by the inspectors. 27. The appliances in use on steamers constructed prior to the 28th of February, 1872, for determining the height of water in the boilers shall be considered reliable low-water gauges. 28. There must be means provided in all boilers using the "low-water gauges," which are operated by means of a float inside the same, to prevent the float from getting into the steam-pipe. 29. In applying the hydrostatic test to boilers with a steam-chimney, the test-gauge should be applied to the "water-line" of such boilers. 30. All horizontal cylindrical boilers used on steamers navigating the waters flowing into the Gulf of Mexico shall be provided with a reliable. low-water gauge. 31. The hydrostatic test applied to the boilers of towing freight-boats on the Mississippi River and its tributaries shall be in the proportion of one hundred and fifty (150) pounds to one hundred pounds working steam pressure allowed; and the inspectors shall test all such boilers on said steamers for the amount of steam allowed. The above table gives the steam pressure allowed on boilers used on freight and towing steamers on Mississippi River and its tributaries, the standard pressure being 150 pounds for a boiler 42 inches diameter and .25 of an inch thick. To find the pressure required on other size boilers (not given in the above table), multiply 12,600 by the thickness and divide by the radius, or half the diameter. 33. All steam boilers made in conformity to the steamboat law in force at the time they were built-provided always that the boilers are in good condition-may be lawfully used on any steamer, provided they have not been used for other than marine purposes. 34. All holes cut through the bottom or bilge of a steam-vessel that are covered by a sea-valve or cocks, and secured to the skin of the vessel by bolts and connected to the engine and boilers by pipes shall be arranged 56 inches diameter. soqlu! 89 diameter 60 inches diameter. 42 inches diameter. 44 inches diameter. 46 inches diameter. |