The allowable unit design stresses used for the butterfly valve and controls were based on the yield point and ultimate tensile strength of the material. The smaller of the following tensile stresses was used:

The compressive and bearing stresses are the same as tensile stresses. The shear stresses are 0.6 of the tensile stresses, and the tensile stress for plate steel cylinder of the operating unit is 15,000 pounds per square inch.

123. Turbine Draft Tube Bulkhead Gates. (a) Requirement. --Six bulkhead gates are required to seal the turbine draft tubes from the tailwater in the event it is necessary to unwater the turbine units for inspection and maintenance of either equipment or structure.

(b) General Description. --The six bulkhead gates and related equipment were furnished under invitation No. (D) H-33, 422-A.

A gate having nominal dimensions of 8.92 feet wide by 10.5 feet high is available for each of the draft tube openings. The gates and lifting frame operate in steel guides embedded vertically in the concrete structure.

The gates are raised and lowered by means of a 4-ton electric hoist which operates on a monorail over the gate slots. An automatically engaging lifting beam is used for raising and lowering the gates.

The gates are normally stored in the upper portion of the gate guide slots. The gates are supported by latches so located that the lifting lug on the gate is just below the deck covers and therefore is easily accessible from the deck. The latches consist of hinged bars which will automatically engage the gate guide lugs during the raising cycle and may be laid back out of the path of the gate guide lugs to allow the gate to lower.

The gates must be raised and lowered only under balanced head conditions. A filling valve is incorporated in the gate lifting stem of each gate for the purpose of creating balanced head conditions prior to raising the gates. In the event that high-pressure penstock water is unintentionally admitted to the turbine and draft tube while the gates are in place, a gate will blow off its seat, shearing the bolts fastening the lower guide lugs to each side of the gate. The top guide lugs are rigidly fixed to the gate, enabling the gate to swing out in the event that the lower guide lugs shear. The estimated weight of the six gates is 31,800 pounds.

(c) Design. --Maximum stresses were calculated on the basis of a dry draft tube and a maximum tailwater surface, the maximum head being 38 feet. Under these conditions, the combined stress of the faceplate and beams was permitted to reach 24, 000 pounds per square inch. Other stresses conformed to the Standards of the American Institute of Steel Construction.

(d) Similarity of Gates at All Powerplants. --The gates furnished at Trinity, Clear Creek, and Spring Creek Powerplants are all similar in appearance and design but differ in size. The gate operation is essentially the same for all powerplants.

The following tabulation compares the bulkhead gates at the three powerplants:

124. Generators. (a) Ratings and Characteristics. -- Each of the two generators is rated 55, 555 kilovoltamperes, 90 percent power factor, 3-phase, 60 cycles, 13,800 volts, and 200 revolutions per minute. The generator rating and capacity were selected to match the turbine output at 426-foot head and full turbine gate output of 85,000 horsepower. The alternate turbine runner for 334-foot head and full turbine gate output is rated 70, 000 horsepower.

2

The power factor of the generators was selected on the basis of supplying the required kilovoltamperes to the power system. The generator voltage of 13, 800 volts was selected on the basis of being the most economical from an overall cost comparison and using equipment of standard manufacture.

Short-circuit ratio, reactance, and characteristics which are normal for generators of this type and rating were specified. The generators were designed to withstand a runaway speed of 400 revolutions per minute, which was determined by the manufacturer as the speed the unit could attain under no-load conditions with maximum head on the turbine and full gate opening. The calculated excitation characteristics for the generators are shown on figure 104.

An efficiency of 97.30 percent at 100 percent rated output was guaranteed by the manufacturer. It was specified that the price of the generators would be reduced by $1, 110 per generator for each 0.01 percent that the actual efficiency, as determined by test, is less than the warranted efficiency at 100 percent rated output and 90 percent power factor.

The following technical data on characteristics of the generators were calculated by the manufacturer: (1) Losses in kilowatts at 90 percent power factor:

3000

STATOR - AMPERES

2000 O

(3) The resistance of the armature windings at 75° C. is 0.00903 ohm per phase.

The resistance of the field winding at 75° C. is 0.338 ohm.

(4) The deviation factor of wave form is 10 percent.

(5) The direct-axis synchronous reactance (Xa) is 102 percent.

The quadrature-axis synchronous reactance (Xq) is 66 percent.

(6) The direct-axis, rated-current, transient reactance (X'du) is 33 percent.
(7) The direct-axis, rated-voltage, transient reactance (X'q) is 30 percent.
(8) The direct-axis, rated-voltage subtransient reactance (X"d) is 22 percent.
The quadrature-axis, rated-voltage subtransient reactance (X"q) is 26.5 percent.
(9) The zero sequence reactance (X) is 8.4 percent.

(10) The negative sequence reactance (X2) is 24. 2 percent.

(11) The negative sequence resistance (r2) is 1.4 percent.

(12) The short-circuit ratio is 1.15.

(13) The direct-axis, open-circuit time constant is 4. 56 seconds.

(14) The direct-axis, short-circuit time constant is 1.50 seconds.

(15) The initial, root-mean-square, symmetrical, 3-phase, short-circuit current is 10, 580 amperes.

(16) The initial, root-mean-square, symmetrical, single-phase, shortcircuit current is 8, 720 amperes.

(17) The initial, root-mean-square, symmetrical, phase-to-neutral, shortcircuit current is 12, 780 amperes.

(18) The sustained, root-mean-square, 3-phase, short-circuit current is 2, 670 amperes.

(19) The sustained, root-mean-square, single-phase, short-circuit current is 3, 670 amperes.

(20) The sustained, root-mean-square, phase-to-neutral, short-circuit current is 5, 960 amperes.

with initial field current as required for rated voltage at rated speed and open circuit

(21) The maximum value of no-load, balanced, telephone-interference factor is 50. (22) The maximum value of no-load, residual, telephone-interference factor is 30.

(23) The calculated regulation, in percent of rated voltage, is 27.5 at 0.90 power factor.

(24) The field current and nominal collector-ring voltage required for rated kilowatt output (50, 000) at rated voltage (13,800) and power factor (0.90) are 784 amperes and 286 volts, respectively.

(25) The field current at 57, 500-kilowatt output at 14, 490 volts and 0.90 power factor is 886 amperes.

(26) Characteristics curves, see figure 104.

(27) The approximate maximum operating temperature at rated load for:

Armature winding (by embedded detector) is 100° C.

Field winding (by resistance) is 100° C.
Collector rings (by thermometer) is 105° C.
Cores and mechanical parts is 90° C.

(28) The maximum line charging capacity without the generator becoming completely self-excited, when operating at rated voltage, rated frequency, and zero power factor is 48, 888 kilovolt-amperes.

(29) The burden on voltage regulator potential circuit, per phase, at 115 volts is 400 volt-amperes, 1.0 power factor. The burden on voltage regulator current circuit at 5 amperes is 300 volt-amperes, 0.7 power factor.

(30) The test voltage to be used for induced dielectric test is 6,000 volts per turn.

(31) The integrated product capability, It, is 40.

(32) The moment of inertia of the rotating parts (WR2) of one generator and exciter, in pounds at

a radius of 1 foot, is 17,842,000.

(33) The amount that the rotor must be raised to dismantle the bearings is 0.25 inch.

(34) The quantity of oil, for one generator, required to fill:

The thrust bearing and upper guide bearing is 1, 105 gallons.

The lower guide bearing is 180 gallons.

(35) The approximate quantity of water, for one generator operating at 115 percent rated kilovoltamperes, at 25° C. required to cool:

The surface coolers is 1, 200 gallons per minute, at 1.63 pounds per square inch.

The thrust and upper guide bearing is 80 gallons per minute, at 1.95 pounds per square inch.

The lower guide bearing is 6 gallons per minute, at 1.95 pounds per square inch.

(36) The net volume of air within the housing and ducts of one generator, for which carbon dioxide for fire protection must be provided, is 11, 500 cubic feet.

(37) The weight of:

One complete generator, including direct-connected exciter, is 802, 630 pounds.
Rotating parts, including exciter, is 402, 350 pounds.

Heaviest individual part as disassembled for shipment (shaft and rotor) is 86, 300 pounds.

The total weight of the heaviest part that must be lifted by crane during assembly or disassembly (shaft and rotor) is 379, 600 pounds.

(b) Construction Details. --The two generators were manufactured under invitation No. DS-5422 by General Electric Co. Each generator is a vertical-shaft synchronous machine with a thrust bearing and a guide bearing above the rotor and a guide bearing below the rotor. The thrust bearing supports the entire weight of the rotating parts of the generator, exciter, and turbine. The upper bearing bracket supports the thrust bearing and its load as well as the stationary parts of the exciter and transmits this entire load to the stator frame. The stator frame is supported on a concrete foundation by six foundation caps. Each cap will support a vertical load of 182, 250 pounds and a maximum tangential force of 181, 000 pounds based on short-circuit conditions.

The lower guide bearings and the combination airbrakes and lifting jacks are supported by the lower bearing bracket. The lower bearing bracket is supported by four soleplates, each of which will support a vertical load of 126, 050 pounds during jacking.

The thrust bearing is made by the General Electric Co. and consists of eight babbitted stationary segments and a cast-iron runner. The cast-iron runner is secured to the rotor shaft by means of the thrust collar and the stationary shoes are mounted on a flexible support of precompressed springs. The thrust bearings and guide bearings are insulated to prevent circulating currents from passing through the bearing surfaces. Test terminals are provided for use in connection with testing of the bearing insulation. The upper guide bearing and thrust bearing are located in one oil reservoir and the lower guide bearing in another oil reservoir. Heat from the bearings is removed by water-cooled cooling coils provided in both oil reservoirs. The bearings are self-lubricated except during starting or stopping operations when highpressure oil is forced between the bearing surfaces of the thrust bearing to help maintain an oil film.

Devices for the following purposes are furnished with each generator:

For indication on the generator instrument panel:

(1) Thrust and upper guide bearing oil temperature.

(2) Lower guide bearing oil temperature.

(3) Cooling air temperature.

(4) Thrust and upper guide bearing cooling water supply pressure.

(5) Lower guide bearing cooling water supply pressure.

(6) Main cooling water supply header pressure.

For indication at the apparatus:

(1) Cooling water supply temperature located in the main cooling water supply header for bearings and coolers.

(2) Cooling water return temperature located in the water outlet from each surface cooler.

(3) Thrust and upper guide bearing water return temperature located in thrust and upper guide bearing water outlet.

(4) Lower guide bearing water return temperature located in lower guide bearing water outlet. (5) Oil level sight gage at each reservoir.

The following devices are furnished with the generator for remote operation of alarm for excessive temperature or loss of pressure, control of bearing cooling water, and starting control interlock:

(1) One thrust bearing oil level float switch for low- and high-level alarm and starting interlock.
(2) Two temperature devices in the thrust bearing metal.

(3) One temperature device in the upper guide bearing metal.
(4) One temperature device in the lower guide bearing metal.

(5) One temperature device at each surface cooler (six in all).

(6) One temperature device in the thrust and upper guide bearing oil reservoir.

(7) One temperature device in the lower guide bearing oil reservoir.

(8) One pressure device in the main cooling water supply header (pressure failure).

(9) One pressure device in the main cooling water supply header (normal operating pressure) for starting control interlock.

The following resistance temperature detectors are furnished for detection at the apparatus and remote indication:

(1) Thrust bearing--two detectors.

(2) Upper guide bearing--one detector.

(3) Lower guide bearing--one detector.

(4) Armature winding--12 detectors.

(5) Generator ambient temperature--one detector.

An enclosed cooling system complete with metal housing, air passages, and six water-cooled heat exchangers spaced around the periphery of the stator is provided for each generator. Radial blades attached to the upper and lower ends of rim segments on the rotor spider serve as blowers for the generator. The cooling system with one heat exchanger out of service should maintain a satisfactory air temperature when the generator is operated at rated output. The water requirement for the heat exchangers is 1,200 gallons per minute. A small rotor fan with radial blades is installed under the main exciter for circulating cooling air through the exciter.

The housings are practically airtight to insure effective operation of the automatic carbon dioxide fire-extinguishing system. A pressure relief door is provided on the side of each generator housing for relief of excessive carbon dioxide pressure. Each generator is equipped with two independent ring headers supported near the stator winding and above the rotor, one for the initial discharge and one for delayed discharge from the high-pressure carbon dioxide gas supply. The initial header has one nozzle located above each cooler to discharge the carbon dioxide into the airstream entering the generator. The delayed header has four nozzles spaced around the stator frame and discharging into the area above the stator. A thermoswitch is located in the hot-air passage ahead of each cooler. The thermoswitches are of the single-pole, fixed-temperature, self-resetting tubular-shell type rated at 0.5 ampere and designed to close a 125-volt, direct-current, ungrounded circuit when the surrounding air reaches a temperature of 185° F., thereby