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23. Outlet Works Electrical and Ventilation Systems. - (a) Electrical System.-The prime contractor was required to install in the outlet works valve house an electrical system for operating all power and lighting equipment at the dam. The equipment consists of a gasoline-engine generator set with distribution cabinets in the valve house and circuits leading to the points of use. Branch circuits lead to lighting system outlets in the valve house, the gate chamber, and the tunnel between these two structures, and to electrically operated equipment located in the valve house.

(b) Ventilation System. --A forced ventilation system is provided for the gate chamber and tunnel when it is required that men enter these structures for inspection or maintenance work. The ventilation system consists of a fan mounted on a wall bracket in the valve house, and 8-inch-diameter slip-joint duct leading from the fan in the valve house through the tunnel to the gate chamber, and a discharge head in the gate chamber. The pushbutton station for starting the fan is located in the valve house. The return air from the gate chamber flows through the tunnel to a louvered opening in the valve house wall, and then to the outdoors through the louvered opening. The ventilation system is designed to provide nine changes of air per hour to the gate chamber, and one change per hour for the combined tunnel and gate chamber.

The ducts were made of No. 20 U.S.S. gage copper-bearing galvanized sheets for corrosion resistance, and the other steel parts of the system were galvanized.

24. Welded Plate Steel Outlet Pipe. - (a) General. --A single 56-inch-diameter welded plate steel outlet pipe is provided for releasing water from the reservoir. The general layout and the details of the pipe are shown on figure 9. The water flows through a 6.5-foot-diameter concrete conduit buried in the dam to the gate chamber where it enters the steel outlet pipe. The steel flange at the upstream end of the pipe is bolted to the cast-iron liner of the high-pressure gate. In the horse shoe-shaped tunnel downstream from the gate chamber the steel pipe is supported on small concrete piers spaced 36 feet along the tunnel axis. At the downstream end the pipe is bifurcated by means of a wye into two 48-inch branches each of which is controlled by a 48-inch butterfly valve bolted to the steel flange of the pipe. The wye is completely embedded in the concrete of the valve house structure, which also serves as a pipe anchor.

An expansion joint located approximately midway between the gate chamber and the valve house takes up temperature movements of the pipe. The support rings of the pipe slide on self-lubricating bronze plates to reduce friction during temperature movements. The pipe can be drained through the butterfly valves. A 4-inch drain at the upstream end serves to drain the gate leakage when the pipe is unwatered for inspection and maintenance, and a 4-inch drain at the downstream end of the tunnel is used to release water left in the pocket formed by the wye which cannot be drained through the butterfly valves. Two 20-inch manholes provide access to the interior of the pipe for inspection and maintenance.

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The maximum static head at the centerline of the pipe will be 149 feet based on the maximum water surface elevation of 10, 042.0 in the reservoir. At this head the discharge through the outlet will be approximately 880 cubic feet per second with a maximum velocity of 51.5 feet per second in the pipe.

The specifications required that the steel for the pipe conform to any one of the following American Society for Testing Materials specifications:

(1) A.S.T.M. Designation A 7, "Tentative Specifications for Steel for Bridges, and Buildings," with carbon content not exceeding 0.30 percent.

(2) A.S.T.M. Designation A 283, "Tentative Specifications for Low and Intermediate Tensile Strength Carbon-Steel Plates of Structural Quality," grades B, C, or D.

(3) A.S.T.M. Designation A 285, "Tentative Specifications for Low and Intermediate Tensile Strength Carbon-Steel Plates of Flange and Firebox Qualities, " grades B or C.

Flanges, forged fittings, and drain valves were required to conform to A.S.T.M. Designation A 105, "Standard Specifications for Forged or Rolled-Steel Pipe Flanges, Forged Fittings, and Valves, and Parts for High-Temperature Service," with a maximum carbon content of 0.35 percent.

(6) Pipe Shell. --The design and construction of the outlet pipe conform to the requirements of the A.P.I. - A.S.M.E. Code for the "Design, Construction, Inspection, and Repair of Unfired Pressure Vessels for Petroleum Liquids and Gases," 1943 edition, unless otherwise noted. In order to provide adequate rigidity for fabrication and handling, and resistance to vibration and corrosion during operation, the pipe 'shell was made 5/16inch thick though a smaller thickness would have sufficed for resisting the stresses due to internal pressure and beam action. The pipe was fabricated in 36-foot erection lengths * with the field-girth joints located as shown on the drawings. The plate edges of the erection lengths were beveled for field welding. The field-girth joints are of the bell-andspigot type and designed so that all field welding in the tunnel can be done from the inside of the pipe. Individual pipe courses were rolled from single plates. The support rings were welded to the pipe shell with continuous fillet welds, and all longitudinal and circumferential joints were double welded. Radiographic inspection and stress relieving of the completed sections were not required, but each individual section, including the wye and the expansion joint, was given a hydrostatic pressure test of 100 pounds per square inch.

(c) Support Rings. --The support rings (fig. 9) slide on base plates grouted into recesses of the concrete piers, Bronze bearing plates with graphite composition inserts for self-lubrication are inserted between the bearing shoes of the support rings and the base plates to reduce friction during temperature movements of the pipe. Erection fixtures were provided to hold the base plates in contact with the bearing plates during the grouting operation.

(d) Wye. --The wye (fig. 9) was designed to resist the maximum operating head of 149 feet. This requirement was met by providing reinforcement in the form of a horseshoe beam and a circular ring around the pipe to which the ends of the horseshoe are attached by welding. The stresses in the reinforcement members, as designed, will not exceed the allowable stresses of the A.P.I. -A.S.M.E. Code under normal operating conditions, assuming that the wye will carry the entire load due to internal pressure without assistance from the surrounding concrete.

(e) Miscellaneous Metalwork. --The expansion joint. (fig. 9) has a single stuffing box. The packing consists of four rings of lubricated flax packing which will be compressed by a bolted gland ring to insure watertightness. The design is based on experience gained from the operation of similar expansion joints on previously built pipes.

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The design of the steel flanges and of the access manholes meet the requirements of the A.P.I.-A.S.M.E. Code. Commercial 150-pound sweep-type nozzles were specified for the drain connections.

(f) Painting. --Shop painting of the outlet pipe was not required except for those surfaces that will be inaccessible after assembly. These include the inner surfaces of the outer sleeves of the expansion joint and the packing gland, and the outer surfaces of the inner sleeve. These surfaces were cleaned and given three shop coats of CA-50 coal-tar paint.

25. 4- by 5-Foot High-Pressure Gate. - As previously noted, the valve chamber near the axis of Platoro Dam houses a 4- by 5-foot high-pressure gate (fig. 10). This gate is used only for emergency closure or to permit unwatering and necessary inspection and maintenance of the outlet pipe and butterfly valves. A semi-automatic gate hanger is suspended above the hydraulic cylinder of the emergency gate and is used to hold the gate in the wide open position.

The frames and bonnets of the gate and the sections of conduit lining and transitions are embedded in concrete, and the concrete is reinforced sufficiently to carry the water load. The top flange of the bonnet, the bonnet cover, and the circular end of the transitions were designed for a 200-foot head, as these parts are not embedded. Stresses and factors of safety for the various metals were allowed as follows:

Allowable stress, pounds per square


Factor of safety

Cast iron, class 25
Cast iron, class 40
Cast steel, class 2
Forged steel
High-tensile bronze
Bronze seats--bearing
Tin-base babbitt-bearing

5,000 8,000 12, 000 12,000 17,000

1, 100 3,500

The gate leaf was designed as a beam with a uniformly distributed load, for a maximum head of 250 feet. It is made of cast steel, class 2. The seats of the gate leaf are cast bronze, class C, of the following chemical composition:

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The seats on the downstream frame are cast bronze conforming to Federal specification QQ-B-691b, composition 6. The difference in the composition of the seats permits the use of bearing pressures up to 3,000 pounds per square inch without seizing, although the design stress was limited to 1, 100 pounds per square inch as previously noted.

There are air inlet connections on the downstream frame of the gate to which pipes are connected and extend above the floor of the gate chamber. A flanged bypass opening is provided for the gate on the right side of both the upstream and downstream frames. The bypass is for filling the outlet pipe when the emergency gate is closed, and prior to opening

The gate stem was designed to withstand the tensile load imposed when the gate leaf is raised and the compressive load when the leaf is lowered. For lowering and seating the gate leaf, the stem was designed as a column.

The gate is operated by a hydraulic cylinder hoist mounted on the bonnet cover. Ordinary motor lubricating oil, SAE 10 or Navy specification 2110, is used. The lifting capacity of the hoist is 110, 000 pounds. The size of the hoist was selected to provide the required lifting capacity with the oil pressure at 900 pounds per square inch.

The hydraulic system consists of an oil pump, motor, supply tank, four-way valve, regulating valve, pressure gage, and the necessary interconnecting piping. Typical operation consists of setting the four-way valve for "Raise" or "Lower" and starting the oil

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Upstream frame
Cost iron-Class 25

23 Piston ring

High quolity tin bronze
Downstream frome
Cost iron -Class 25

24 Stem

High tensile bronze
Cast iron -Class 40

25 Stem extension

Rolled bronze
Bonnet cover
Cast iron - Class 40

26 Locking key

5 Gate leof
See specifications

27 Key retainer

Gate sill
Cast iron - Class 40

28 Top leaf nut

Cast monganese bronze
Horizontal leaf seot
Class C bronze

29 Bottom leof nut

Cast mongonese bronze
8 Vertical leaf seot
Class" bronze

Cylinder gasket

Copper-holf hard
9 Bonnet seot
Class D bronze

31 f Oil pocking

See note 10 Horizontol frome seat Class D bronze

3237 Oil packing

See note
11 Vertical frame seat
Class D bronze

33 3 Water packing

See note
12 Leof recess cover
Bross plate

34 Pocking seat

Cost bronze
I coo screw
Rolled bronze

35 Packing gland

Cost bronze
1412 Cop screw
Rolled bronze

36 34 Packing seot

Cast bronze 15 13 "Stud with nut Bolt steel-Class"

37 3f Packing seat

Cost bronze
16 16" Stud with nut Bolt steel-Closs B

| 38 34 Pocking seat

Cost bronze
| 17 Stud with nut
See bonnet cover

39 Stud bolt

Bolt steel-Class 'A' 18 175+ Bolt with nut Bolt steel-Class "

40 "Stud bolt

Bolt steel - Class "A"
19. 31 'Top balt
Bolt steel - Cross "B"

41 Stud

Rolled bronze
20 Cylinder
Forged steel

42 13'Stud

Rolled bronze
21 Cylinder
Cost steel

43 Fillis ter head cop srew Rolled bronze
22 Piston
Cast iron - Class 30

44 Fillister head cop srew Rolled bronze

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Figure 10.--4- by 5-foot high-pressure gate.


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