204. PENSTOCK FIXED-WHEEL GATES. The 13.96 by 22.45-foot fixed-wheel gates were furnished by Vereinigte Ostereichische Eisen und Stahlwerke Aktiengesell Schaft of Lenz-Donau, Austria, under invitation No. DS-5577. The frames and anchors were fabricated by Rockwell Engineering Co. under invitation No. DS-5469, and the hoists and stems by Pacific Coast Engineering under invitation No. DS-5601. The control cabinets were furnished by Auto-Control Laboratories under invitation No. (D) 190,638-A. The gates and related equipment were installed by the prime contractor under specifications No. DC-4825 (fig. 274).

Figure 274.-Gantry crane lowering 120-ton fixed-wheel gate into the tracks of penstock No. 8. P557-420-9711, April 20, 1964.

The fixed-wheel gates, hoist, and controls are located in the penstock trashrack structure of each of the eight penstocks and are used for emergency closures of the penstock and for maintenance purposes. The eight 13.96- by 22.45-foot fixed-wheel gates are installed on the upstream face of the dam. Each gate is connected through a series of intermediate stems to a hydraulic hoist located at the top of the trashrack structure. The control cabinets are installed adjacent to the hoist. Each fixed-wheel gate is a flat structural steel

assembly with brass-clad rubber seals mounted on the downstream skinplate. The seals prevent leakage by contacting seal seats embedded in the concrete on the downstream side of the gate slot. Wheels at each side of the gate bear on tracks, also embedded in the concrete on the downstream side of the gate slot. Guide rollers mounted on each side of the gate bear against guides embedded in the concrete of the gate slot. The nominal gate travel is 26 feet 5 inches.

The hoists are an oil-operated, cylinder type and are installed on the slope of the intake structure. The hoists are supported on steel support beams. Each hoist piston has packing and piston rings, is 30 inches in diameter and has a stroke of 26 feet 5 inches. A series of intermediate stems with an assembled length of 172 feet 9-3/4 inches connects the piston stem to the gate stem.

The fixed-wheel gates were assembled at the paint yard, approximately one-fourth of a mile from the left abutment of the dam. Two concrete pedestals were constructed for each gate and were placed in two lifts with 4- by 4- by 1/2-inch angle stubs embedded in the bottom lift. These stubs were capped with the plate accurately leveled and the second lift was then placed.

The gate body for penstock No. 8 was assembled first on the pedestals nearest the dam, and the remainder of the gates were assembled in reverse numerical order. Spaces between the various gates were sufficient to permit installation of the splice plates as well as the fixed wheels and their covers. Access to the upstream and downstream faces of the gate was obtained by use of easily assembled tubular scaffolds. Planks of sufficient length to reach from one scaffold to the next one provided access to the sides of the gate.

When the four sections comprising each gate were stacked and pinned together, a preliminary check of the seal bases for being "in plane" was made. It was not found necessary to change the position of any of the sections after thorough pinning and bolting. The connecting plates were installed, and after all bolting was accomplished, the gates were plumbed to within one-fourth inch of vertical. Stainless steel piano wire, 0.018 inch in diameter, was drawn taut over accurately machined triangular-shaped blocks by means of small turnbuckles. All measurements were made on the seal bases. These piano wires were also used to set the fixed wheels to the required projection.

Before the fixed wheels were installed and after the roller guide assemblies and seals were in place, the

wheel pockets were primed and given the necessary coats of CA-50 coal-tar paint. The paint was applied by brushing and was kept away from areas which would be in contact with the fixed-wheel assemblies. The fixed wheels were then installed and brought out to the proper relation to the piano wire mentioned above.

The prime contractor built a road from the paint yard to the rim of the canyon directly above the left abutment of the dam. A slide, consisting of two parallel runs of 36 140-pound I-beams, was anchored to the almost vertical canyon wall. A car was fabricated to keep the gates from rubbing while being lowered to the dam. The contractor fabricated a short gate stem for use while handling the gates. He also fabricated a short boom for the dragline and lifting beam for use by both cableways to left the 125-ton gates. The short stem was installed in gate No. 8, and the crane was positioned above the slide and used to lower the gate to the roadway of the dam.

The two cableways moved the gate to the upstream side of the dam, a distance of about 30 feet, where the 165-ton gantry crane could reach it. The short stem was removed and returned to the paint yard for use in gate No. 7. The regular stem for gate No. 8 was installed. The gate was picked up by the 165-ton gantry crane and set in block 7 gate structure above penstock No. 8. Seven intermediate sections of stem and the No. 8 hoist cylinder completed the installation. This procedure was repeated without mishap until all of the eight gate assemblies were completed.

The installation of the gate, the seven intermediate stems, and the hoist require about 10 hours with two to three men and an operator. The welding and other work required 20 working hours for the pipefitters to install the high-pressure oil. The first gate was placed in the gate structure on April 20, 1964, and the last gate was installed and fully tested on June 2, 1964.

The tests were begun in accordance with the appropriate operating drawings and instructions. However, the gate would not stop when the stop button was pressed and the throttle valve was one-fourth open. With this condition, the restoring feature would not operate.

A design engineer from the Denver office determined that valve C of the high-pressure oil piping needed a stronger spring, and new springs were obtained. The new, heavier springs corrected the faulty operation of the gates. However, two of the valve bodies were sensitive to the tightening of all the socket-head body bolts; i.e., one bolt if fully tightened

would render the plunger or spool inoperative. An 0.008-inch-thick shim in the joint under the bolt obviated this condition.

One of the checks made during the tests was to have an inspector, the contractor's chief of party, and a rodman enter the bellmouth, allow the gate to be closed, and use a feeler gage 1/32-inch thick to check the seals where daylight was observed. The feeler gage could be inserted between the rubber seals only on one gate. The most daylight appeared at the molded corners and not where the brass-bound rubber seals were placed.

The results obtained in the operational tests are as follows: Any of the eight gates will close in less than 2 minutes and 8 seconds; they will open in less than 20 minutes. While closing, they will stop in a distance of from 3 to 6 inches. The restoring feature cuts in when the gate settles about 11 inches.

In addition to the inadequate springs in valve C of the high-pressure oil piping, the makeup of the hanger stud assembly gave trouble when the hanger collar seized on the top of the piston and acted as a double nut while unscrewing the hanger stud. The lead plug was not positive enough to keep the collar stationary on the hanger stud. It was decided to install a 3/8- by 1-inch cup-point set screw in place of the plug. A 3/8-inch hole, 1/4 inch deep, was drilled into the hanger stud 5-3/8 inches from the end of the stud, the collar positioned, and the new set screw installed. This resulted in 4-7/8 inches of threads below the collar, which is the requirement. All eight hanger studs were modified in the above manner without further difficulties being experienced.

The workmanship on fabrication of the gate assemblies and on the erection and assembly of the gates was excellent.

205. STOPLOG GUIDES. The stoplog guides in the penstock trashrack structure were supplied by Bennett Industries of Peotone, III., under schedule 2 of invitation No. DS-5354, and were installed by Merritt-Chapman and Scott Corp., under specifications No. DC-4825.

Discrepancies in the assembled guide sections were discovered. The major error was that the ends of the cast iron guide sections were not in the same plane as the ends of the steel plate seat sections. This was contrary to the specifications and, if the guides were installed on the dam in this condition, tight joints could not have been obtained.

The first attempts to correct this discrepancy were started on September 6, 1962, with a vertical milling machine and an alinement table long enough to hold three complete guide sections fitted together. The first three sections after the ends had been machined were fitted together, checked and failed to meet the specified tolerances in the overall lengths and in the madeup joints. Further work with the equipment on hand failed to correct the fabrication errors.

The manufacturer brought in a heavier duty milling machine on September 24, 1962. Three guide sections machined on this new milling machine were fit together with all tolerances within the specified measurements. Corrective work on each of the 368 guide sections was completed on November 7, 1962. The general procedure used in the corrective work was as follows:

(1) For each guide section where the steel plate seat portion was shorter than the cast iron guide portion, weld was applied to the end for a buildup which equaled or exceeded the cast iron portion.

(2) Each section was placed on the milling machine and the end was machined normal to section. Where heavy cuts were made, a light finishing cut followed the heavier cut.

(3) Three consecutive sections after having been machined on each end, were fitted together on the alinement bench where each joint was measured with a feeler gage. The maximum acceptable gap was 0.004 inch.

(4) Two piano wires were stretched along the guide and the seat portions for a check of plumbness and straightness.

(5) After acceptance, the lower two of the sections were stockpiled. The upper section was then moved to the other end of the alinement table and was assembled to two more consecutive machined sections. This procedure was repeated for the remaining sections.

A crew averaging four men accomplished the corrective work. One man operated the milling machine; one man operated a forklift truck and carried sections to the milling machine, the alinement table, or stockpiles; one man assisted the machinist or assembled the machined sections; and one man applied weld buildup to the uncorrected sections. After the

corrective procedures were developed, these men did an excellent job considering the long hours and consecutive days of work.

Because of the sections being shortened in the corrective process, the installation of the sections required that the contractor insert stainless steel shims between some of the sections to make up the required distance. This was necessary since the anchor bolts had been installed in the mass concrete of the dam according to drawings. For accuracy of the placement of the guide sections, the sections were installed in blockouts and on the anchor bolts and then later concreted in place.

During installation, slotting of the splice plates was necessary at various locations due to either a misplacement of the embedded anchor bolts or in some cases due to the shortened sections before or after the addition of shims between the sections. No other unusual problems were experienced by the contractor during the installation of the guide sections.

206. DRAFT TUBE BULKHEAD GATES. Twenty-four 12.42-foot-wide by 15.95-foot-high bulkhead gates are provided for use in unwatering the eight turbine draft tubes. The gates are stored in slots, resting on latches, under the upper guide lug on each side of the gate. A lifting frame is provided for raising and lowering a gate with the 10-ton gantry crane. The bulkhead seats, gates, guides and frame were manufactured by the Ogden Iron Works of Ogden, Utah, under invitation No. DS-5341 and were installed on the downstream face of the powerplant by the prime contractor, Merritt-Chapman and Scott Corp., under specifications No. DC-4825.

An extra work order and an order for changes were executed during the life of the supply contract. Chain guides and pins were furnished with the bulkhead gate lifting frame for use in storage as extra work. Mill scale was removed from the structural surfaces of the steel to which the naval brass seats were secured and a coat of white lead and linseed oil was applied; and additional flathead steel cap screws and hexnuts were furnished for gates 4 and 5. The contractor also requested and was given permission to use naval brass in accordance with Composition 1, Federal Specifications QQ-n35, in lieu of that required in the specifications, and the use of flathead naval brass bolts instead of rivets on seat parts IL, IR and 2.

Timely delivery was was made in four separate shipments of six gates each and two separate shipments

of guides. Protection of the gates and guides was adequate during shipment and no unusual damage was incurred in transit. Shop painting of the metalwork was not required and all finished surfaces of ferrous metalwork were coated with a rust-preventative compound prior to shipment.

At the jobsite, the rust-preventative compound was removed, the surface prepared, and the gates and guides were painted with two coats of type IV red lead primer and two coats of phenolic-resin aluminum paint. The good paint system obtained was retained, because the installation contractor lowered the gates into place from the painting yard at the top of the canyon to the powerplant gate slots using the traveling cranes, or highlines, for convenience in handling and to avoid damage and paint repairs.

The close tolerances of 1/16 of an inch, plus or minus, top to bottom, required careful installation techniques by the contractor. After installation of the lower seal plate, the gate guides were rough assembled from top to bottom. Special templates were tack-welded to the lower seal plate on each side at the bottom, and steel frames were cantilevered from the concrete for the upper template. Three holes, just larger than No. 16 piano wire, were drilled in the templates for alinement, one each for the outside faces and one for the centerline of the inside of the slots for width and depth. Another set was drilled for the face of the lower steel frame. Piano wires were attached between the two templates using a device tensioned by a ratchet-type reel. Plates were set by precise surveying methods and were checked periodically.

During installation, it was found that the 1/2- by 2-inch naval brass flathead bolts, which secured the brass seal plates to the steel frames, were defective due to fractures, either at the body or head or in the threaded section between the head and the nut. About 15 percent of the bolts were found to be defective prior to installation, and further breakage discovered during erection amounted to about 20 percent of all bolts. As a result, all of the naval brass bolts were replaced with monel metal bolts. However, laboratory tests in Denver failed to confirm either that the bolts were defective or that they failed as a result of factory overtightening. The supplier was therefore not held responsible for the costs involved in replacing the bolts.

Other difficulties were experienced in installation due to insufficient depth in the concrete blockouts and improper location of anchor bolts. Minor difficulties were also experienced as a result of some of the guide sections being distorted or warped which required

special jack screws being made to spring the sections into position. Some warpage and twisting of the stationary gate seals and support frames was also noted. As the horizontal frame sections did not match the vertical sections at the top, the contractor jacked the upper frame section into place and welded at the assembly joints. Installation of the gates, seals, and guides was satisfactory and no difficulties were experienced during the testing and initial operation of the gates.

When the gates were placed in service for the first time, it was difficult to raise them due to a collection of sand, silt, and rubbish at the bottom of the gates, probably due to the testing and operation of the hollow-jet valves. The gates were freed with tube-introduced compressed air along the face of the gates. After the gates were raised for the first time, this waste material was flushed out and no further trouble was encountered.

207. RIVER OUTLETS. Nonpower drawdown of the reservoir is provided by four outlet pipes (figs. 109 and 110), each 8 feet in diameter and located 96 feet below the penstock elevation level. Although similar in construction to the penstocks, each major element of the installation differs in some respect. There are two trashrack structures for the four outlet pipes, each structure containing two pipes closely spaced at the same elevation. Upper closure is made by 96-inch ring-follower gates (fig. 275) inset some 50 feet inside the dam and by 10-1/3-foot square bulkhead gates seated in guides at the inlet face of the pipes. No stoplogs are provided for the river outlet intake structures. Embedded their length in concrete, the outlets discharge downstream from the powerplant through 96-inch hollow-jet valves.

Methods utilized for installation of the outlet pipes were essentially the same as those used for the penstocks. Being at the lower elevation of the two sets, horizontal pipe sections of outlets No. 1 and 2 (fig. 276) were first placed in block 6 of the dam and in the mass concrete downstream from the dam in February of 1961. Initial sections of outlets No. 3 and 4, which had intakes in block 5, were placed during the following month, and all sections extending downstream from the dam had been embedded by the end of July 1961. The four 8-foot-diameter pipes were positioned and welded as the blocks rose in elevation. Installation of the outlet pipes was completed in April 1962, when the bellmouth sections for outlets No. 3 and 4 were placed in block 5.

Figure 275.-General view of equipment used in testing of river outlet No. 4 at various flow conditions. Test station is located in the ring-follower gate chamber in dam block 5 at elevation 3387.5. P557-420-11016, May 24, 1965.

Figure 277 shows the outlet pipes partly embedded as of March 20, 1961.

208. RIVER OUTLET BULKHEAD GATES, GATE FRAMES, AND LIFTING FRAME. The bulkhead gate is a flat structural steel assembly with rubber seals mounted on the downstream skinplate. This gate was furnished by Johnson Machine Works, Inc., of Chariton, Iowa, on invitation No. DS-5493. The rubber seals of the gate contact the seal seats embedded in concrete on the upstream face of the dam around the bellmouth of the outlets. The seal seats were supplied by Fulton Shipyard, Antioch, Calif., under invitation No. DS-5370. The gate is closed, opened, and transported by the 165-ton gantry crane at the top of the dam. The crane raises and lowers the gate with a lifting frame which follows the gate guide slots and is coupled to the gate stem by a grapling hook. This lifting frame was supplied by Charles C. Steward Machine Co., of Birmingham, Ala., under

purchase order No. (D) 90,637-A. The bulkhead gate was received at Flagstaff, Ariz., on December 22, 1961, the embedded seal seats on February 2, 1961, and the lifting frame on August 14, 1963.

The bulkhead gate, embedded seal seats, and lifting frame were installed, erected, and assembled by the prime contractor. Installation of the seal seats and anchorage was performed in conjunction with the placement of the concrete. The work was substantially completed with the dry testing of the gate operating cycle in October 1963. The assembly of the bulkhead gate consisted of attaching rubber seals and clamp bars with the stainless bolts. Since the assembly work was performed by an experienced crew of millwrights, no difficulties were encountered during the assembly. The seal seats were placed on the anchor bolts in the blockouts and were adjusted to their proper position using templates and fine piano wire stretched tight for measuring control. The positions of the embedded frames and location of wire templates were determined by the contractor's survey crews. The contractor's survey crews were well qualified for this type of construction layout, and many of the alinement problems often associated with this type of installation did not develop.

209. RING-FOLLOWER GATES AND CONTROLS. The four 96-inch ring-follower gates