passes through the guide bearing, and a removable and renewable split stainless steel sleeve is provided where the shaft passes through the packing box in the head cover. The turbine guide bearing is a babbitt-lined plate steel shell made in two sections to permit dismantling. The bearing is self-lubricated by means of an oil reservoir surrounding the bearing. The welded plate steel head cover and discharge ring are each made in one piece. The discharge ring and bottom ring are made integral. The bearing housing is welded plate steel construction with the cover and bottom pieces each made in two parts for ease in handling. It supports the gate shifting ring and turbine guide bearing. A carbon seal packing box, with two carbon rings and one resin packing ring, is mounted on the head cover where the main shaft passes through. The box is arranged so that the carbon seal rings, backup pieces, and garter springs can be replaced without disturbing the guide bearing. Connections are provided for water and grease lubrication. Packing boxes are also provided where the wicket gate stems pass through the head cover. Removable and renewable wearing rings are provided where there are close running clearances between the runner and the stationary parts of the turbine. The wearing rings are made of chromium stainless steel, and, in addition, each of the stationary wearing rings at the runner seal clearances has two chromium steel inserts. The turbine is furnished with 20 cast chromium steel wicket gates to control the supply of water to the runner. Each gate stem has three bronze-bushed guide bearings, one located in the bottom ring and the other two in the head cover--one below and the other above the packing box. Forced grease lubrication is applied independently to each of the gate stem bearings. A shear pin is provided between each gate link and gate hub lever. The pin is designed to withstand the maximum normal operating forces, but will break in either the opening or closing direction in case one or more of the gates becomes blocked. The mechanism is designed so that failure of one shear pin will not cause progressive failure of adjacent pins. The gates may be adjusted independently by means of a turnbuckle-type link between each gate lever and the shifting ring. The turbine gate operating mechanism of each unit is powered by two oil-pressure, doubleacting, hydraulic servomotors having a total displacement of 10,990 cubic inches, a design piston stroke of 10.391 inches for full gate travel, and a cylinder diameter of 26-1/16 inches. The servomotors have a combined rated capacity of 202,000 foot-pounds at the minimum oil pressure of 220 pounds per square inch available at the pistons and are designed to move the wicket gates a full opening or closing stroke in 5 seconds under the maximum head, including water hammer, on the turbine of 1,075 feet with this minimum oil pressure. An automatic mechanical gate lock is provided on one of the servomotors to secure the gates in the closed position upon shutdown of the unit. The gate lock is operated by oil pressure through the governor gate lock control valve. An interlock switch is provided to prevent starting the unit until the automatic gate lock is in the unlocked position. At heads above rated head, the output of the turbine can be limited to the rated output of the generator by an adjustable stop nut on one servomotor piston rod. The gates may be held in either the open or closed positions against maximum oil pressure by means of the manual operating arrangement provided on the automatic gate locking device. A horseshoe-shaped mechanical stop is also provided which will lock the gates in the closed position. A depressor system is provided for lowering the water level in the draft tube below the bottom of the runner when the unit is being motored on the line. The unit should never be motored unless the penstock butterfly valve is open and the spiral casing is full of water. Wicket gates leakage water is needed to cool the runner seals; otherwise they will heat up and the runner may seize. The depressor system consists of a main control mounted on the main control board, two pilot-operated 4-inch valves, two 2-inch solenoid valves, two float-operated switches for controlling the compressed air supply, and control switches operated by adjustable cams on the restoring mechanism in the governor actuator cabinet. One of the 4-inch valves opens initially to admit compressed air through the turbine head cover for lowering the water level, and one 2-inch valve admits sufficient air through the shaft and runner snorkel to maintain the established water level below the runner. The other 4-inch valve is automatically opened to exhaust air to the atmosphere upon initiation of a shutdown while the unit is being motored. This permits the water level to rise so that its braking effect on the runner can be utilized to stop the unit. The 4-inch air vent valve is also controlled by means of a cam-operated switch in the governor. Initially the cam is designed and set to open the air vent valve from 0 to 15 percent gate. Cams can be cut to open the valve at any desired range of gate positions in addition to the 0 to 15 percent range. The other 2-inch valve admits atmospheric air below the runner at certain gate openings to improve operation of the unit if required. Opening of this valve is controlled by a cam-operated switch in the governor which is set initially to open the valve from 0.5 to 0.6 gate. Cams can be cut to open this valve over any desired portion of the full gate operating range. 208. Governors. (a) General Description. --The governors for regulating the speed of the turbines are of the oil-pressure, cabinet-actuator type with electrically driven speed-sensitive elements. The normal operating oil pressure will vary between 270 and 300 pounds per square inch. The portion of the governor system subject to pressure is designed to withstand 300 pounds per square inch. The governors were designed and furnished by the Pelton Division of Baldwin-Lima-Hamilton Corp., in accordance with the requirements of invitation No. DS-5466. A stationary 20-c. f. m., 375-p. s. i. air compressor, with connecting piping, is provided to add air to the pressure tanks of the governor system. The governors are rated at 202,000 foot-pounds which is the combined capacity of the servomotors of the turbine. The servomotors are designed to operate the turbine gates through a complete closing or opening stroke in 5 seconds with a minimum effective oil pressure of 220 pounds per square inch at the pistons. Stop nuts are provided in the main distributing valve in the governor that can be adjusted to limit the rate of movement of the turbine gates for a full gate closing or opening stroke in from 5 to 15 seconds. Invitation No. DS-5466 describes the controls, indicators, airbrake valve, shutdown mechanism, automatic turbine gate lock, and all special devices furnished with the governor. (b) Remote Governor Control and Indicators.--In addition to the controls and indicators located on the governors, the following devices for remote control and indication of the governor of each unit are mounted on the switchboard in the control room of Clear Creek Powerplant: (1) Gate-limit control. --Control for motor operating the gate limit. (Also at Keswick Powerplant.) (2) Gate-position and gate-limit indicator.--Electrically operated dual indication of gate position and gate limit. (3) Speed-changer control. --Control for motor operating the speed adjustment. (Also at Keswick Powerplant.) (4) Speed-changer-adjustment indicator. --Speed-changer control functions as indicated to show speed adjustment setting. (Also at Keswick Powerplant.) (5) Speed-droop-adjustment mechanism. --Control for motor operating the speed-droop adjustment. (Also at Keswick Powerplant.) (6) Speed-droop-adjustment indicator. --Speed-droop-adjustment mechanism functions as indicator. (7) Draft tube water-level depressor control. (8) Electrically operated tachometer, to indicate the speed of the turbine. (This indicator was furnished under separate contract from the tachometer on the actuator but is connected to the same rectifier-resistor pack furnished by Pelton.) (9) Complete shutdown mechanism. --Electrical control to stop a unit manually or automatically when necessary. 4. Turbine and Governor Unit Auxiliaries 209. Generator and Turbine Bearing Lubrication. (a) Generator Bearings.--The generator thrust and upper guide bearings have the same oil reservoir and are entirely independent of the lubrication system of the lower guide bearing. All bearings are self-lubricating. In addition to the normal lubricating system, a high-pressure lubricating system is furnished to establish an oil film between the thrust bearing surfaces prior to starting and to maintain the oil film during shutdown. The high-pressure system is self-contained, including a motor-driven high-pressure oil pump, a piping system to introduce the oil between the bearing surfaces, and pressure gages and a pressure relay. (b) Turbine Guide Bearing.--The babbitt-lined turbine guide bearing is self-lubricated from an oil reservoir surrounding the bearing. The bearing system is designed so that the temperature of the bearing or the oil should not exceed 60° C. under continuous operation. Cooling water coils and electric heaters are located in the reservoir to control the temperature of the lubricating oil. The oil reservoir has a capacity of 320 gallons. An oil transfer pump, rated 15 gallons per minute at 70 pounds per square inch pressure, is provided in the pump alcove to pump the oil back to the station-service oil storage tank. (c) Other Turbine Bearings. --A centralized lubricating system is provided for lubricating the gate stem bearings, gate operating ring, servomotor connections, and gate linkages. 210. Unit Cooling Systems. (a) Generator Air Cooling Water.--An automatically controlled cooling water system is provided for cooling the air in the generator housing. The system consists of a pumping unit, a diaphragm-operated, three-way diverting valve along with an indicating pneumatic control thermometer and a pneumatic valve positioner. A 1,300-g. p. m., 115-foot-head, centrifugal pump in the unwatering gallery takes water from the tailrace through a 10-inch valve and twin strainer and pumps it through an 8-inch header to the generator air coolers. A 6-inch, three-way diverting valve in the return line from the coolers proportions the quantity of water to be recirculated and the quantity to be discharged to tailwater. A pneumatic control thermometer, with its sensing bulb in the air discharge from one of the generator air coolers, is located on the unit control panel. It indicates the desired valve position by varying air pressure between 3 and 15 pounds per square inch. A valve positioner, on the diverting valve, positions the valve in accordance with the indicated desired valve position. The valve, with positioner, has a definite position for a given pressure, and the valve position, between the two extremes, is also proportional to the air pressure between 3 and 15 pounds per square inch. One emergency cooling water supply pumping unit is provided for the two generating units. Valves are provided for manual control of this source of supply. A 1/2-inch header, with automatic air-vacuum valves in branch lines from the top of each air cooler, is provided to prevent the accumulation of air in the generator air cooling water system. (b) Unit Bearing Cooling Water. --The normal unit bearing cooling water is supplied from the turbine spiral casing through a 6-inch plug valve, twin strainer, and a 2-1/2-inch motor-operated valve. A pilotoperated pressure regulating valve reduces spiral case water pressure to a safe value. A pressure-relief valve set to discharge at a pressure of 60 pounds per square inch is provided for additional protection. Cooling water from this source is supplied to the generator thrust and upper guide bearings, generator lower guide bearing, turbine guide bearing, and turbine packing box. The approximate flows for each unit are 150 gallons per minute to the generator thrust and upper guide bearings, 6 gallons per minute to the generator lower guide bearing, 55 gallons per minute to the turbine guide bearing, and 20 gallons per minute to the turbine packing box. An emergency cooling water supply for the unit bearings is obtained from the station fire-protection system. A connection is provided in this system for runner seal cooling water should operating experience indicate that this is necessary. 211. Generator Airbrakes and Jacks. Each generator is equipped with air-operated brakes of sufficient capacity to bring the generator and turbine to a stop from one-half normal operating speed within 5 minutes after the brakes are applied. The brakes are also designed to serve as hydraulic jacks to lift the generator rotor a sufficient distance to provide for removal or adjustment of the thrust bearings. A hand-operated double-plunger pump supplies the oil pressure for jacking. 212. Auxiliary and Service Facilities. (a) Description of Drainage System. --The unwatering system in the powerplant consists of the pumps, piping and valves necessary to completely unwater each penstock, turbine casing, and draft tube for inspection or repairs. The combined drainage and unwatering sump has an area of approximately 370 square feet. Two sump pumps, each having a capacity of 3,250 gallons per minute at a total head of 50 feet are provided to remove the incoming water. Float controls are set to give each pump an operating range of 6 feet variation of water level in the sump. The settings for the float controls are stepped to give a total operating range of 9 feet in water level in the sump, with provisions for manually alternating the sequence of the two pumps. A manually operated 1-1/4- by 2-inch scavenging eductor is provided for complete unwatering of the sump. Special chilling drains from the oil storage and purifier rooms are also provided. (b) Flap Gates.--Two 24-inch flap gates are located in the downstream wall of rooms 207 and 208 at elevation 1209.00. These valves are for emergency use only and are designed to open and reduce the possibility of flooding the generator floor in case the lower galleries should become flooded. They are protected by 24-inch butterfly valves inside the powerhouse. These are normally kept open unless the flap valves leak excessively when tailwater is high at times of flood. (c) Governor and Lubricating Oil Service System. --Separate oil storage and oil transfer facilities are provided for handling the total amount of governor and lubricating oil contained in the governor system and bearing oil reservoirs of one complete generating unit. The same purifier used for purifying the transformer oil is used for the governor and lubricating oil system, and when used on this system, the rate of purifying should be reduced to approximately 300 gallons per hour. One purifier unit is provided for use at Trinity, Clear Creek, and Spring Creek Powerplants. The flexible metallic hoses common to both the transformer and governor lubricating oil systems should be thoroughly cleaned by flushing clean oil through them when changing from one type of oil to the other. The system is designed with separate supply and return headers, flushing connections, filtered and unfiltered storage tanks of identical capacity, and a transfer pump having a capacity of 30 gallons per minute at 100 pounds per square inch discharge pressure. The supply line to any piece of equipment should be thoroughly cleaned by flushing at operating velocity just prior to filling or adding filtered or clean oil. In establishing the size of pipes in the system, the minimum temperature of the oil to be handled was considered to be 50° F. and its viscosity at that temperature approximately 2,000 seconds Saybolt. (d) Transformer Oil System.--Oil storage facilities are provided for handling the amount of transformer oil in the largest transformer installed at the powerplant. The transformers may be brought into the powerhouse for servicing or may be serviced in place. Oil filling and drain connections are provided on the transformer deck and in the powerhouse in the service area. The system is designed so that unfiltered oil cannot enter the filtered lines. Separate supply and return headers and separate filtered and unfiltered oil storage tanks of equal capacity are provided. The transfer pump handles filtered oil only, and the return flow from equipment to unfiltered storage is by gravity. The supply line to the transformer should be thoroughly cleaned by flushing at operating velocity just prior to filling or adding filtered or clean oil. No pressure tank is provided in the system. The transfer pump, for transformer oil, has a capacity of 60 gallons per minute to permit filling the largest transformer in approximately 3 hours; and a discharge pressure of 100 pounds per square inch so that standard weight pipe, 150-pound fittings, and 125-pound valves can be used in the piping system. A portable oil purifier with a capacity of 600 gallons per hour is provided for use at Trinity, Clear Creek, and Spring Creek Powerplants. This purifier will dehydrate the transformer oil required for one transformer in approximately 19 hours. In establishing the size of pipes in the system, and also the oil purifier capacity, the minimum temperature of the oil to be handled was considered to be 40° F. and its viscosity at that temperature 200 seconds Saybolt. (e) Compressed Air System. --Compressed air is provided for the operation of the generator airbrakes, air tools, grease pump, sewage ejector, draft tube water-level depressor system, and governor pressure tanks; and for miscellaneous air service requirements. |