Material Number List of parts-One valve [See illustration, p. 99] Description Semisteel. Semisteel and bronze... 1 Packing clamp.. Needle... 8 9 Nozzle seat. Mild steel.. Bronze.. ----do .do.. ....do.. .do. Brass. Steel.. Bronze.. Semisteel. Bolt steel, class "A," Bolt steel, class A". Rolled bronze. Bolt steel, class “A”. ...do.. ...do.. do.. Bolt steel, class “C”. Standard forged steel. Garlock No. 99 or equal, inch square. Steel... do.. Cast steel. Garlock No. 99 or equal, 3 inch square. Rubber.. do... 20 feet long. 24 feet long. 1 8 1 3 1 16 9 gate chamber about 155 feet above its outlet. The inlet to the tunnel is protected by a trash rack structure having 5% by 6 inch trash bars placed 6 inches, center to center. Two 48-inch balanced needle valves are placed in a concrete valve house at the outlet. end of the tunnel, and the valves are each connected to the emergency gates by a 54-inch diameter riveted plate steel pipe made of 3-inch steel plates, with all rivets countersunk on the inside, and all joints made with outside straps, thus making a smooth interior, a vital necessity where velocities may be from 35 to 45 feet per second. The layout of the outlet works is shown in the accompanying illustration. The maximum required discharge of irrigation water is 800 second-feet, and each of the two 48-inch needle valves will deliver practically this amount with a full reservoir. Under test one valve discharged 640 second-feet under a net head at the inlet to the valve of 90 feet. The maximum static head on the outlet, from the center line of the valves to the maximum reservoir water level, is 138.6 feet. Emergency gates.-The emergency gates are 4 by 4 feet in size with gate leaf designed for 140-foot head, using a 15-inch hoist cylinder. The concrete plug is properly reinforced to withstand full reservoir pressure inside the conduits and heavily keyed into the rock, with ample provision for draining and weeping the gate chamber. A simple form of air valve is attached to the air vent for the gates, con8 sisting of a metal flap inside the valve case, hanging free normally when air is flowing inward but swinging against an inclined seat when under water pressure. The gates are equipped with automatic gate hangers 36 and signal lights for remote operation from the valve house. 1 See note. 2 20 rings. NOTE.- Furnish one each of parts 67-69-70, and 71 for each item of contract regardless of the number of valves specified. NEEDLE-VALVE OUTLET Typical needle-valve outlets are those installed at McKay and Gibson Dams, representing two entirely different plans. OUTLET WORKS-MCKAY DAM At McKay Dam the tunnel used for diversion during construction is also used as the reservoir outlet. In this case the entire tunnel, 705 feet in length, is lined with concrete, with the concrete plug and emergency Balanced valves.-The balanced valves are installed. in a concrete structure, which has a large passageway around the foundations leading from the tunnel, to allow escape of water without destroying the structure in case of a break in the pipe line. The valves are controlled from a control stand on the floor above, the control being of the cylinder sleeve type. The control of these valves has proven very satisfactory and it is possible to regulate the discharge within 10 second-foot increments. A gantry crane is provided for easy dismantling of the valves for maintenance and repairs. A motor-operated triplex pump and the emergency gate control pipe system is installed on the upper floor of the valve house. A statement of costs for the outlet works is included in the descriptive article on McKay Dam, p. 53. GIBSON DAM The outlet works in Gibson Dam, which is of the massive concrete type, are shown in the accompanying illustration. In this case the conduits are 72 inches . diameter, and are designed to withstand full reservoir pressure with a generous allowance for deterioration by corrosion. The inlets are of the bell-mouth type and are protected by trash racks built up of % by 6 inch trash bars on 6-inch centers. At the downstream face of the dam, where the stresses are high, to compensate for the space taken up by the conduits, the concrete is heavily reinforced with T-rails. The emergency gates are embedded in concrete at the downstream face of the dam, and the needle valves are attached directly to the downstream frames of the gates. The needle valves are 60-inch valves of the internal differential needle type, to operate under a maximum head from the center line of the outlet to the outlet to the maximum reservoir water surface of 163.5 feet. A mast jib crane is provided for handling the heavy parts of valves during installation and operation. The emergency gates are 5 by 5 feet in size, designed for an operating head of 162 feet, with cast-steel gate leaf and 21-inch hoist cylinder. There is no electric power available, and the triplex pump used for operating the gates is driven by a gasoline engine. STONY GORGE DAM The outlet works at Stony Gorge Dam are shown in the accompanying illustration. This design is inserted principally to illustrate a different application, covering installation in a dam of the buttressed type with face slab of reinforced concrete. The outlet consists of two 31⁄2 by 32 feet high-pressure emergency gates, designed for a head of 140 feet, with a 12-inch hoist cylinder, to operate under a head of 98 feet, embedded in mass concrete at the water face of the dam. Regulation of the discharge is by two 42-inch balanced valves similar to those used at McKay Dam, connected to the emergency gates by 50-inch riveted plate steel pipes. The emergency gates are operated by a direct motor-driven triplex pump. Power for operating the pump and gate hoists, and for lights, is furnished by a small hydraulic turbine and 25-kilowatt generator, with a 125-volt storage battery for stand-by service. OWYHEE DAM There are three sets of high-pressure outlets in Owyhee dam, as shown in the sections of the dam in the illustration on page 86. Power outlet. The power outlet, at elevation 2,569.83, operating under 100-foot head, consists of two 5 by 6 foot high-pressure gates, properly protected by a trash rack, with 72-inch circular cast-iron conduits extending through the dam and terminating in a tunnel in the rock below. These outlets are for future power development, and when the power plant is constructed the 72-inch conduits will be extended to the turbines. Regulating outlet.-The regulating outlet, shown in the illustration on page 89, is at elevation 2,469.83, operating under 200-foot head, and consists of three 4 by 4 foot gates, designed for 250-feet head, with 18inch hoist cylinders, embedded in the dam near the water face, with three 48-inch internal differential needle valves installed in a reinforced structure on the downstream face of the dam. The valves are connected to the gates by 57-inch cast-iron conduits designed to withstand full reservoir head, with a liberal allowance for deterioration. The valve house is provided with a massive curved concrete roof for protection in case water should overtop the dam. Sluicing outlet. The sluicing outlet is at elevation 2,370, with the gates installed under 300-feet head, but the hoist cylinders provide capacity for operation under only 125-foot head. The layout of this outlet is shown in the illustration on page 88. Because of the unusually high head under which these gates are installed, and the fact that the lower 250 feet of water in the reservoir is dead storage, it was considered advisable to install the gates, 4 by 5 feet in size, in tandem, using the upper gates for protection of the lower, or service gates. The conduits below the gates are 60inch cast-iron pipes. |