BB-7 Illinois Class Propulsion
The speed guarantee was 16 knots per hour, to be maintained successfully for four consecutive hours, successfully for four consecutive hours, during which period the air pressure in the fire rooms was not to exceed an average of one inch of water; the vessel to be weighted to a mean draught of 23 feet 6 inches. No premium for speed in excess of that required by the contract was provided for, but a penalty was inflicted at the rate of $25,000 per 1/4 knot between 16 and 15-1/2 knots, and $50,000 per 1/4 knot between 15-1/2 and 15 knots, but if the speed should fall below 15 knots it was optional with the Secretary of the Navy to reject the vessel or accept her at a reduced price. The weight of the machinery was limited to 1,130 tons, which weight included main engines, boilers and appurtenances, distilling apparatus, tools in workshop, and water in boilers, condensers, pumps, pipes and stern tubes, but did not include turret machinery, capstan, windlass, steering gear or winches. The penalty for over weight was $500 per ton up to 5 per cent., beyond which an additional $10,000 was to be attached.
The official speed trial for the Illinois took place off the New England coast, between Cape Ann and Cape Porpoise, on the I2th of June, 1901, and consisted of two runs over a measured course 33 nautical miles in length. The average speed for the two runs, after correction for tidal observations, was 17.449 knots. The weather conditions were favorable. There was an abundance of steam, and the passover valves on the first and second receivers were partly open during the greater part of the trial. The coal was New River, of excellent quality.
There were two sets of triple-expansion, twin- screw engines, each in a separate water-tight compartment, besides some So odd auxiliary engines. There were eight cylindrical boilers. The smoke pipes are two in number, and and uniquely stood abreast of each other.
Each engine is fitted with a double-disc, balanced, stop and throttle valve, worked by a lever and adjusted by a screw stem and hand wheel from the working platform. The main steam pipes are of copper, and where above g\ inches in internal diameter are strengthened with steel bands spaced 6 inches between centers. In the starboard engine room there is a 50-gallon distributing oil tank for supplying the oil manifolds of both engines. This tank is supplied from the main tanks by a Worth- ington duplex steam pump, and by a hand pump, and can be used as either a pressure or a gravity tank.
The main pistons are steel castings, dished, and are each fitted with two packing rings and a follower. The piston rods are of forged nickel-steel, oil tempered, and hollow; a screw plug is fitted and riveted over at the upper end. The connecting rods, with their caps and bolts, are of forged nickel-steel, oil tempered ; the rods have a 4-inch axial hole bored through their entire length. The body of the crosshead is forged on the end of the piston rod, and a manganese-bronze slipper, whose sliding faces are fitted with white metal, is bolted to its under side. The crosshead guides are of cast iron, and are made hollow for the circulation of water to keep them cool. At the top they are bolted to lugs cast on the cylinder casings, and at the bottom to forged-steel cross bars, secured to the engine columns.
The backing guides are also of cast iron, and are bolted to flanges provided for that purpose on the go-ahead guides. The eccentrics are of cast iron. Each backing eccentric is securely keyed on the shaft, and each go-ahead eccentric is secured to the corresponding backing one by through bolts in slotted holes. The eccentric straps are of composition, faced with white metal, and the eccentric rods of forged steel.
The propeller shafts are fitted with a composition casing from inboard of the stern-tube stuffing box to the propeller hub. The propeller shaft is in two sections connected by an outboard sleeve coupling fitted near the after end of the stern tube, and protected by a watertight covering. The thrust bearings are of the horseshoe pattern ; the pedestals are of cast iron, the ends and side walls forming an oil trough ; at each end there is a bearing, lined with white metal, for taking the weight of the shaft. The horseshoes are eleven in number, and are of cast steel, faced with white metal, and fitted with oil cups and holes for the distribution of oil to the bearings. At each end of the bearing there is a divided stuffing box and gland to prevent the escape of the oil. The pedestal is bolted to a cast-iron sole plate, fitted with wrought- iron wedges at each end of the pedestal for adjusting the bearings fore and aft.
There are two main condensers, one for each engine ; the shells are of wrought-steel plate, with an angle iron riveted around each end forming a flange for securing the water chests. The water chests and tube sheets are of composition. The circulating water passes through the tubes. Baffle, circulating and tube-supporting plates are fitted. There are by-pass valves in the water chests to allow the water from the circulating pumps to pass directly overboard.
For each engine there is a Worthington twin-cylinder, vertical, single-acting air pump. The steam cylinders are placed directly over the pump cylinders, the pump rods and piston rods forming a continuous length. The pumps are connected by means of a beam which is pivoted at its center, and from which beam the valve motion is actuated. The beam receives its motion through links swinging from crossheads on the pump and piston rods. The pump valves are each made of three flat discs of rolled manganese-bronze.
There are eight single-ended boilers of the horizontal, return, fire-tube type, all of steel. The shells are of one course of four plates, the top heads being curved to a radius of 3 feet 4 inches. The longitudinal joints of the shells are treble riveted with double-butt straps. The joints in furnaces and combustion chambers are single riveted. There are two combustion chambers in each boiler. The tops of the combustion chambers are braced by girders. The combustion chambers are stayed to each other and to the shell by screw stays screwed into both plates and fitted with nuts, the nuts being set up on beveled wishers where stays do not come square with the plates. Each furnace is in one piece and corrugated, riveted to flanges of front head and flanged and riveted to combustion-chamber plates. The grate bars are of cast iron, and those at the sides are made to fit the corrugations. The bridge walls are of cast iron, and extend to the back of the combustion chambers. Each boiler has circulating plates fitted at each side of each nest of tubes. Each boiler is bolted to angle irons which are riveted to the saddles. The boilers are bolted rigidly to the angle iron of outboard saddles, but the inboard angle irons have oval holes to allow for expansion.
The closed fire room system of forced draft is used. The air is supplied by eight Sturtevant blowers, two in each fire room. The fans are driven by two-cylinder vertical, simple, enclosed engines with cranks at 180 degrees.
There are thirty-two coal bunkers with a total capacity of 1,270 tons at 43 cubic feet to the ton. They are distributed as follows: Ten on the berth deck with a capacity of 224 tons, eight on the splinter deck with a capacity of 115 tons, and fourteen in the hold with a capacity of 931 tons. They are filled from either the upper or the main deck through portable chutes and trunks fitted between decks. The trunks have shunt doors fitted at the tops where they pass through the bunkers on the berth deck, and vertical doors at the bottom, for passing the coal from the upper to the lower bunkers. Armored shutters are fitted in the trunks where they pass through the protective deck. Trolley rails and buckets are fitted fore and aft in the hold bunkers, with portable sections in the wake of watertight doors, for the transportation of the coal.
Escape doors are fitted to all the bunkers on the berth deck open on the main deck (circular plates), those on the splinter deck to ammunition passage (swinging doors), and those in the hold to deck of ammunition passage (circular plates). Steam fire-extinguishing pipes are fitted to all the bunkers and holds. Over the vertical watertight sliding doors of the hold bunkers are fitted screen doors, in the shape of a hood, designed to take the weight of the coal from the watertight doors, so that they may be easily closed at any time.
There are two ash chutes on each side fitted inside the vessel. The upper ends of the chutes extend above the main deck, where hoppers are formed inside, and so arranged that the fire-main pressure may be used to clear the chute. Trolley ways for carrying the ash buckets are fitted under the deck beams above, leading from the ash hoists to the chutes.
The main drain pipe is of galvanized steel, 14 inches in diameter, and runs from the forward boiler rooms along the port side of the center-line bulkhead above the inner bottom to the engine rooms, having branches connecting it with the starboard compartments. It is fitted with stop check valves in each boiler and engine room, all worked from the berth deck. The suction pipes leading from the valves in the boiler rooms do not dip into drainage wells, but have their mouths located as low down as practicable and covered with coarse strainers. The main drain pipe leads to the main circulating pumps, and is also provided with connections to the principal steam pumps other than the main feed pumps and water service pumps.
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