64. TURBINE DRAFT TUBE BULKHEAD GATES. (a) Description.-Twenty-four bulkhead are provided to seal the turbine draft tubes from the tailwater in the event that it is necessary to unwater the turbine units for inspection and maintenance of either equipment or structure. The 24 bulkhead gates and related equipment (fig. 149) were furnished under invitation No. DS-5341.

A gate having nominal dimensions of 12.42 feet wide by 15.95 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 10-ton gantry crane. An automatically engaging lifting frame is used for raising and lowering the gates.

The gates are normally stored in the upper portion of the gate slots. The gates are supported by latches so located that the lifting lug on the gate is just below the deck slot covers and is therefore 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.

Inasmuch as 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 the balanced head 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 of its seat, shearing the bolts which fasten 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 24 gates is 396,000 pounds.

(b) Design.-Maximum stresses are calculated on the basis of a dry draft tube and maximum tailwater surface, the maximum head being 78 feet. Under these conditions the combined stresses of the faceplate and beams are permitted to reach 24,000 pounds per square inch. Other stresses conform to the American Institute of Steel Construction.

65. DESCRIPTION. Glen Canyon Powerplant, which extends from wall to wall of the canyon and is located 400 feet downstream from the axis of the dam, is of the indoor type with a structural steel superstructure enclosed with concrete curtain walls (figs. 4, 150, and 151). The intermediate structure and substructure are reinforced concrete. The powerplant consists of a machine shop bay, a service bay, a control area and eight generating unit bays. Each unit bay contains a 125,000-kv.-a., 90-percent power factor, 13,800-volt, 150-r.p.m., 60-cycle, vertical-shaft, hydraulic-turbine-driven, alternating-current generator. Each generator is driven by a 155,500-horsepower hydraulic turbine operating at 150 revolutions per minute under an effective head of 450 feet. There are nine 345-kilovolt, single-phase, 100,000-kv.a. transformers and three 230-kilovolt, single-phase, 100,000-kv.-a. transformers located on a transformer deck downstream of the generating units. Each pair of generators is electrically paralleled, at generator voltage, and connected to one bank of three single-phase transformers, by means of an isolated phase bus, through generator-voltage circuit breakers.

Two 300-ton overhead traveling cranes are required to handle the rotor and other heavy pieces of equipment in the generating units and service bay. A 75-ton crane is provided in the machine shop.

The powerplant was designed to be built in two stages; namely, the first stage or prime construction work and the second stage or completion work.

66. POWERPLANT ARRANGEMENT. Figures 150 through 161 show the final powerplant arrangement as constructed. The powerplant is laid out in an L shape, with the longitudinal centerline of the units perpendicular to the canyon walls. Unit bay 1 is located against the west or right canyon wall. The units are numbered 1 through 8 toward the east or left canyon wall. The service bay is adjacent to unit bay 8 and extends to the left canyon wall. The machine shop bay is also against the left canyon wall and is adjacent to and downstream of the service bay. A control area is situated on top of the superstructure of unit bays 1 and 2. Access to the control area is by means of a stair and two elevators in the cable and elevator tower located on the right side of unit 1. Downstream of the machine shop bay is a large parking area and river outlet valve structure. Vehicular access to the powerplant is provided by taking the 20-foot-wide service road and tunnel located in the left canyon wall. The tunnel terminates at the powerplant parking area at elevation 3188.5.

There are two covered walkways from the dam to the powerplant. The right walkway is a structural steel bridge extending from a balcony on unit 1 to block 18 of the dam. The left abutment walkway is placed on the outlet pipes anchor block at elevation 3188.50 and connects block 6 in the dam with the powerplant at unit 8.

(a) Typical Generating Unit Bay. -Units 3 through 8 are shown on figure 150, while units 1 and 2 are shown on figures 160 and 161, respectively. A typical unit bay has a superstructure 65 feet wide in the longitudinal direction and 81 feet deep in the transverse direction (upstream-downstream direction). The generator floor and electrical galleries are at elevation 3168.50. A visitors' walkway or balcony is provided at elevation 3188.50 inside the superstructure wall on the downstream side of the units. A transformer and transfer deck is located at the same elevation outside the superstructure on the downstream side of the plant. The turbine gallery, governor gallery, and service gallery are at elevation 3153.50. The pipe gallery is located downstream at elevation 3138.50. The penstock gallery, unwatering gallery, and inspection galleries are at elevation 3124.75. The centerline of the distributor is at elevation 3140.00 and the invert of the draft tube is at elevation 3102.00. Units 2 through 8 are set on mass concrete.

The configuration of unit 1 is quite different from a typical unit bay. A cable and elevator tower with a large air-conditioned lobby and a curved balcony for visitors is located on the right side of unit 1. Downstream of the tower, a sewage treatment structure is placed on top of the substructure concrete and on the right side of the transformer deck. The base of the entire unit 1 structure sets on rock instead of mass concrete.

Unit 8 also varies from the typical unit bay. The visitors' balcony at elevation 3188.50 goes around the unit on the service bay side and is supported by columns. A concrete stairway is located on the upstream wall of unit 8 to provide access from the covered walkway down to the landscaped area at elevation 3157.0.

(b) Control Area. -The control area (figs. 156, 158, and 161) is a two-floor structure designed to allow adequate space for offices, visitor facilities, fallout protection, and the necessary control equipment for the powerplant. The lowest floor is at elevation 3244.24 and provides space for the control