and is opened only for final unwatering of the spiral case and penstock. The drain header is provided with a bypass to the tailrace. This bypass is for the purpose of reducing high-velocity flow into the sump, in the event that a spiral case drain valve and the drain valve at the sump are both opened by mistake when the penstock is under pressure. A check valve in the bypass line prevents backflow from the tailrace to the sump. The unwatering sump pumps are normally controlled automatically by float switches, but may be controlled manually when desired. There are two independent provisions for high sump water level alarm.

Both the penstock and draft tube are provided with vents which will admit atmospheric air when unit is being unwatered.

(d) Transformer Oil Handling System.-The transformer oil handling system is designed to provide for receiving, storing, and purifying the oil and for transferring it to and from the transformers. The system provides for receiving oil, either from the transformers or from a new supply, at an unloading pit near the service bay entrance, and conveying it by gravity to an unfiltered oil storage tank. From the unfiltered storage tank the oil is processed through a purifier to the transformers or to a filtered oil tank where it can be maintained in readiness for use in the transformers. The purifier can process transformer oil at a rate of 1,200 gallons per hour and can be used either for purifying oil in storage or the oil in the transformers with the transformers in position. Oil in the filtered oil storage tank can be transferred to the transformers by a 50-g.p.m. oil transfer pump or by use of the purifier. To be drained or filled, a transformer must be moved into position near the oil unloading pit. An oil makeup line with connections near each transformer is provided to supply small quantities of makeup oil when needed by the transformers.

The normal design criteria for sizing oil pump and pipelines is to fill or drain a transformer in 3 hours or less, at a minimum design oil temperature of 40° F. The system design was based on estimates prior to the purchase of the transformers. Because the transformers were somewhat smaller than anticipated, the system has a capacity capable of draining or filling a transformer in approximately 2-1/2 hours.

Each transformer oil storage tank has a capacity of 10,000 gallons, which is adequate for storing one transformer volume of used oil and one transformer volume of clean oil. The maximum oil capacity of a transformer is approximately 7,650 gallons. Waste oil from the storage tanks can be disposed of by use of the purifier pump.

(e) Lubricating and Governor Oil Handling System.-The lubricating and governor oil handling system was designed to provide for handling, storing, and purifying the lubricating and governor oil in a manner similar to that described above for the transformer oil. The system capacity is based on the requirements for one generating unit. The combined volume of oil required for a generator, turbine, and governor is approximately 3,550 gallons. The oil storage tanks have a capacity of 4,000 gallons each. The transfer pump was sized for 30 gallons per minute. The purifier, which is used for both the transformer oil and the lubrication and governor oil, can process lubrication and governor oii at a rate of 600 gallons per hour. Clean oil is pumped from the filtered oil storage tank to the units, and dirty oil is conveyed by gravity from the units to the unfiltered oil storage tank.

The normal design criteria for sizing the pump and pipelines is to fill the largest sump or reservoir in 1 hour with oil at a minimum design temperature of 40° F. Because the generator thrust bearing oil reservoir was slightly larger than anticipated, the filling time for it will be approximately 1 hour and 10 minutes. Overflow lines connected to the drainpiping are provided to reduce the danger of accidental overfilling of the oil reservoirs.

(f) Service and Domestic Water System. -The design of the service and domestic water system provides for supply, treatment, and distribution of service and domestic water for the powerplant, dam, and visitor center, and for supply only to the city of Page, Ariz. The design was based on established design standards for domestic water for housing and community facilities, and the powerplant service water requirements. Required water quantities and facilities vere determined and the related pipelines, pumps, and storage tanks were sized to meet the present requirements and with reserve capacities to care for projected future demands.

The raw water supply is taken from the forebay and conveyed by gravity through a 12-inch pipeline to a pumping station in the powerplant. A 12-inch standby supply is provided from units 7 and 8 penstocks. The raw water supply passes through a strainer which removes any debris from the water.

The service and domestic water pumping station consists of four 920-g.p.m., centrifugal, multistage-type booster pumps, with a combined capacity of 3,000 gallons per minute, for supplying water to the city of Page, and two 100-g.p.m., turbine, can-type booster pumps for supplying the powerplant, dam, and visitor

center.

The water supply for the city of Page is pumped through a 12-inch pipeline to the Page filtration plant where it is processed and distributed by the city.

The service and domestic water for the powerplant, dam, and visitor center is chlorinated at the powerplant by a gas chlorinator which automatically injects the chlorine solution into the suction side of the two 100-g.p.m. booster pumps. The water is pumped to a 30,000-gallon storage tank located near the visitor center building. The booster pumps and chlorinator are automatically controlled by float switches in this tank.

The elevation of the 30,000-gallon storage tank provides sufficient water pressure for the facilities at the visitor center and dam. Water is conveyed from the storage tank by gravity to these areas and distributed to the various facilities.

Two 750-gallon storage tanks are provided in the dam for supplying service and domestic water to the powerplant distribution system. These tanks are located at an elevation suitable for supplying water by gravity at the proper pressure to the powerplant facilities. The water level in these tanks is controlled by a float-operated valve and the tanks can receive water either by gravity from the 30,000-gallon storage tank or directly from the 100-g.p.m. booster pumps in event the pumps are in operation when the tanks need filling. A standby water supply line to the storage tanks in the dam permitted filling these tanks by gravity from the forebay with unchlorinated water during initial powerplant operation prior to completion of the 30,000-gallon storage tank near the visitor center. This standby supply can also be used in the event of future emergencies. To permit servicing of the tanks in the dam, provisions were made for bypassing them by means of a pressure reducing valve connected between the high-pressure gravity supply from the storage tank near the visitor center and the powerplant distribution system.

System demands and facilities that can be isolated for service use only are small relative to the overall powerplant service and domestic water system requirements. For this reason, an economical design required servicing the powerplant auxiliary equipment from the treated water supply, thus permitting combining the service and domestic supplies into one system.

(g) Unit Cooling Water System. -The design of the generating equipment required the use of water as a

cooling medium for the transformers, generators, turbine and generator bearings, turbine packing box, and turbine wearing rings. Cooling is accomplished by means of oil-to-water heat exchangers for the transformers and the turbine and generator bearings. Primary cooling of the generators is accomplished by air-to-water heat exchangers. Cooling of the turbine packing box and wearing rings is by direct application of water, which also acts as a lubricant for these items. Cooling water for the wearing rings is required only when a unit is operating as a synchronous condenser with the water depressed below the runner. The heat exchangers were furnished by the equipment manufacturers as an integral part of the respective equipment.

accomplished by varying the amounts of cooling water that is recirculated. The cooling water supply is taken from the draft tube of each unit, passed through a strainer for debris removal, and pumped through the coolers. The water discharging from the coolers passes through an air-operated three-way diverting valve which routes the water in varying proportions to the pump suction for recirculation, or to the tailrace. The system will recirculate all, part, or none of the cooling water, depending on the signal conveyed to the diverting valve from the heat-sensing elements in the generator, to maintain substantially constant temperature in the generator. In event the control signal or operating air to the diverting valve is lost, the valve will go to the "full discharge to tailrace" position and provide maximum cooling and thus "fail safe" operation. A standby line connects the pump discharge of all eight units. In the event of pump failure at one unit, the remaining seven units can provide emergency cooling water, or a pump from another unit not in service can be utilized while the defective pump is being repaired. Pressure switches are installed in the system to prevent unit operation in the event of failure of the generator air cooler water supply system.

The cooling water for the transformers, bearings, packing box, and turbine wearing rings is taken from a common high-pressure connection at the spiral case of each unit. This water passes through a strainer for debris removal before being used in the cooling systems.

The design of the transformer cooling water system departs slightly from the unit concept, in that the cooling water is taken jointly from the two units which are served by a bank of three single-phase transformers. The supply provisions at each unit are similar in design, are connected in parallel, and each has a capacity adequate for supplying total transformer cooling in the event the other unit is shutdown with no cooling water available from its respective spiral case. The high-pressure cooling water supply at each unit is reduced to a low pressure suitable for the transformers by means of a pressure-reducing valve connected in series with two orifice plates. An identical standby pressure-reducing system is provided at each unit to permit servicing the pressure-reducing valves. The combined cooling water supply is piped to an elevation just below the transformer deck for distribution to the transformer heat exchangers. Each of the three transformers in one bank is equipped with two heat exchangers. One heat exchanger on each transformer is used for primary cooling and operates continually when a transformer is in service. The other heat exchanger operates intermittently in response to

additional cooling requirements as directed by a heat-sensing element within the transformer. Final distribution of water to the heat exchangers is accomplished by means of two headers. Each header supplies one heat exchanger on each of the three transformers. One header is used to supply water for primary cooling and the other is used for intermittent cooling. Solenoid valves installed in these supply headers control the flow of water to the heat exchangers. Discharge water from the heat exchangers is conveyed by gravity to the tailrace. The heat exchangers are provided with vents to prevent accumulation of air, to prevent build up of pressure, and to serve as vacuum breakers for the water discharge. Other safety features include a pressure relief valve, flow switches, over-pressure switches, and low-pressure switches.

Initial operation showed a need for the following principal modifications to the transformer cooling system:

(1) Replacement of oil-to-water and water-to-water differential pressure switches for the transformer coolers, with flow and water pressure switches.

(2) Increase in vent size to prevent intermittent negative pressure and surging at the cooling water discharge connection.

(3) Addition of bleed lines to offset leakage through the pressure regulators, with resultant "popping" of relief valves and water hammer in the piping, when a transformer bank is shutdown.

Proper adjustment of valves and control lines required considerable study and operational trial runs.

The high-pressure cooling water supply for the turbine and generator bearings, and the turbine packing box, is reduced to the desired pressure in a manner similar to that described above for the transformers. The water is piped to the bearings and packing box where final control is made by hand adjustment of valves. The discharge water from the bearing heat exchangers is piped to the tail race. Discharge from the packing box is conveyed by gravity to the powerplant drainage sump where it is collected and pumped to the tailrace. The unit bearing and packing box cooling water system utilizes a motor-operated valve for "On-Off" control.

The high-pressure water supply from the spiral case is piped directly to the turbine wearing rings to

provide cooling and lubrication when a unit is operating as a synchronous condenser. Control valves in the wearing ring cooling water supply are operated manually.

(h) Air Compressor Cooling Water System. -The air compressor cooling water system is shown schematically as a part of the piping diagram for the service and domestic water system (see fig. 192). This system was designed to automatically supply low-pressure cooling water in quantities as recommended by the air compressor manufacturers. A pressure-reducing valve reduces the plant service water from approximately 86 pounds per square inch to the required 20 pounds per square inch supply for the air compressors and aftercoolers. A bypass line, with a manually operated valve, is provided for emergency operation when the pressure-reducing valve is out of service. A pressure relief valve and a low-pressure switch installed in the low-pressure supply assures proper system pressure. Cooling water is automatically admitted to the compressors and aftercoolers by solenoid valves which open when any compressor is operated. The cooling water discharge drains by gravity to the powerplant drainage sump. Open sight flow tunnels are provided in the cooling water discharge lines for flow detection and to aid in flow adjustment. Final adjustment of cooling water flow is made manually by means of needle valves for each separate application.

(i) Fire Protection Water System. -The design of the fire protection water system supplies water to, and provides for, the following fire protection facilities:

(1) Thirty-two firehose cabinets located strategically throughout the powerplant. These cabinets are equipped with 1-1/2-inch firehose valves, adjustable pressure restricting valves, 75 feet of firehose, and spray nozzles adjustable from solid stream to fog. This equipment is suitable for

one-man use.

(2) Three 2-1/2-inch firehose valves, two located just inside the main doors at each end of the transformer deck, and one just inside the main door to the machine shop. Two-wheeled firehose carts with 250 feet of hose and fixed fog nozzles are provided for use with the 2-1/2-inch firenose valves. The primary purpose of this equipment is for use on or near the transformer deck, but it may be used in other areas within hose range. This equipment is designed for two-man operation.

(3) Automatic sprinkler systems for the oil storage and oil purifier rooms. These systems utilize

fusible-link sprinkler heads for automatic operation in event of fire in the oil rooms. Flow switches in the supply lines provide for alarm in event of fire at either location. In addition to alarm, the flow switch for the purifier room also starts a 5-minute timer. If not interrupted, the timer will initiate water shutoff and carbon dioxide discharge for the purifier room. Flow of water to the oil storage room will continue until shut off manually.

(4) Transformer water spray system. Each of the four banks of three transformers is provided with a fire protection water spray system. This system utilizes fixed spray nozzles for complete water spray coverage of the transformers. The "On-Off" control is by means of motor-operated valves, operated by pushbuttons at control stations just inside the doors at each end of the transformer deck.

The water supply for the fire protection system is taken from the high-pressure connection at each spiral case. A header interconnects the supply from each sprial case to assure an adequate supply of fire protection water at all times. However, due to the low pressure ratings available for the fusible-link sprinkler heads in the oil rooms, these systems are supplied from the service and domestic water system. A connection through a manually operated valve to the fire protection water system was provided for the oil storage room to insure against running out of water from the 1,500-gallon storage tank prior to installation of the 30,000-gallon storage tank. This connection should not need to be used after installation of the larger tank.

Blowoffs are provided on all dead-end firelines and on the main headers in the powerplant for periodic purging of the fire protection waterlines. The blowoffs in the oil rooms are also used for testing the sprinkler systems alarms and controls. During blowdown of the firelines in the oil purifier room, the electric controls for the purifier room carbon dioxide system must be turned off to prevent carbon dioxide discharge.

(j) Carbon Dioxide Fire Extinguishing Systems.-The carbon dioxide fire extinguishing systems are designed to provide automatic fire protection for the generators and oil purifier room. The design of the systems was based on guides established by the National Board of Fire Underwriters and Bureau guides. In accordance with these standards, the following quantities of high-pressure carbon dioxide were provided: