bushing type current transformers and as originally supplied were type B20-160-115J which were designed for capacitor switching. The generator transformer breaker for unit 2 failed during load-rejection tests on unit 2. The failure occurred on the C-phase pole and was apparently caused by a flashover or restrike. The Allis-Chalmers Co. repaired the damage as soon as possible. Later they removed all the resistor units from the ruptors of all breakers. They will put new resistor elements in the breakers when they complete tests on a new resistor design. The breakers are pneu-draulic operated.

The circuit breakers were erected under very adverse conditions under the direction of an Allis-Chalmers representative. The weather was cold and snow was plentiful. Erection proceeded quite well, however. The contractor used the A-frame on a truck to hoist the bushings into place. Oil was filtered into the breakers through a filter press which the contractor borrowed from Utah Power and Light Co. This machine was lighter and easier to handle than the Bureau filterpress. Final adjustments were then completed.

(0) 69-Kilovolt Oil Circuit Breaker.-- The breakers are rated as follows: 69 kilovolts; basic impulse level 350 kilovolts; continuous current rating 600 amperes; interrupting rating 1, 000, 000 kilovolt-amperes; rated interrupting time 5 cycles; control voltage 125 volts. The breaker is equipped with three wound-type current transformers with double secondaries. The breaker is type OGOR 80, and is pneumatically operated with vertical poles.

Erection was supervised by the manufacturer's representative who came here directly from Italy for this purpose. Since he was not very familiar with our language he had some difficulty in directing operations. As a result, one breaker pole was erroneously placed and had to be moved. The breaker assembled easily, except that there was some difficulty in connecting the control wiring owing to poor marking at the terminal blocks.

Other discrepancies and their correction were as follows:

(1) No indicating lamps were furnished; these were supplied by the project at no cost to the manufacturer.

(2) The fuses for the control circuits are of European manufacture and are not available locally, the manufacturer supplied a number of replacement fuses.

(3) The time meter for the compressor was not visible without removing the cover; a window was installed by project forces and the cost was backcharged to the manufacturer.

(4) The rubber mounting supports for the antipump relay were checked and cracked and were unserviceable; the manufacturer supplied new mounts which were installed by project forces.

(p) 14.4-Kilovolt Oil Circuit Breakers.--The breakers are rated as follows: 14.4 kilovolts; basic impulse level 110 kilovolts; continuous current rating 600 amperes; interrupting rating 250, 000 kilovolt-amperes; interrupting time 8 cycles; control voltage 125 volts direct current. Six bushing type current transformers were supplied with each breaker. The breaker has a spring-operated mechanism, with individual tanks for the poles.

The breakers were erected under the direction of a service engineer for Federal Pacific Electric Co. Erection consisted mainly of checking adjustments and filling the tanks with filtered oil.

(q) Power Supply for Piezometer Well.--An underground power cable was installed from the switchyard cable trench to the piezometer well. An additional breaker was purchased for the lighting panel in the switchyard to supply the feed. This provided a permanent power source for the well. As the original contract did not provide for this work, it was included in item 3 of order for changes No. 7. The excavation and backfill of the trench between the switchyard fence and the piezometer well was done by Palisades Contractors.

Tests were performed by Bureau personnel on the insulation of all control wiring on all apparatus. Wherever possible, ratio checks were made on all transformers. Dielectric tests were made on all insulating oil. Circuit breakers were checked in accordance with the tests outlined in the "Bureau Check List for Outdoor Power Circuit Breakers.

Some tests were omitted because of interference with the contractor's work. All test data are filed in the project office.

(r) Miscellaneous Fixtures.--Lighting fixtures were installed where indicated on the drawings. The original fixtures supplied by the contractor did not meet specification requirements and were replaced by the contractor.

Aluminum trench covers were placed on the cable trench in the switchyard. Cable trays were installed in the trench, and cable hooks were installed in the duct that runs from the powerhouse to the switchyard.

The installation of line tuning units, wave traps, and coupling capacitors is described under section 249.

253. Appurtenant Structures, Electrical Installation. The completion contractor was required to complete the electrical systems in the spillway gate structure, the spillway compressor house, the power tunnel intake structure, the outlet tunnel intake structure, the access road bridge, the outlet works valve control house, the penstock unwatering pump chamber, and air valve houses. Completion included the installation of all exposed conduit and all insulated wires and cables, and connecting wires and cable to all apparatus and fixtures. The contractor installed all lighting fixtures, wiring devices, and power outlet receptacles, as well as all power and lighting distribution panels, switches, and contactors. The contractor began installation work at the intake structures in October 1956, and most of the work was completed that fall. Work in the valve control house could not start until late summer of 1957 when the concrete for the structure was completed. The work was essentially completed that fall. Certain changes in installation were performed under orders for changes No. 5 and 6 and under a separate job order.

Tests on cable, wire, circuit breakers, contactors, and other electrical equipment were made by Bureau personnel. The data are on file in the project office.

254. Overhead Power and Control Cable Circuits Between Powerplant and Intake Structures. An overhead power and control cable circuit between the powerplant and the intake structures was installed by the completion contractor. The work consisted of furnishing and installing a self-supporting, three-conductor, No. 2/0 AWG aerial cable for a 3-phase 460-volt power circuit, and a self-supporting 12-conductor, aerial control cable. The cables were supported by cedar poles. The work included splicing connecting cable and installing lightning arresters. The completed installation provides power for the operation of all equipment at the intake structures, and remote control for the emergency closure of the fixed-wheel gates.

Since the contract stated specifically that no clearing was involved in the construction of the line, it was necessary to negotiate a price for clearing the few trees and brush along the right-of-way just above the dam. The work was performed by Palisades Contractors, the prime contractor, under a special job order. The crossarms on a pole belonging to Palisades Contractors were moved down the pole to remove interference between the contractor's 12.5-kilovolt distribution line to the intake structure and the new cable circuits. The work was performed by Union Electric Co., subcontractors to Anderson and Burke, who were electrical subcontractors for the completion contractor. The work was paid for under a purchase order.

The contractor employed a two- to five-man crew to perform the work. He began work the last part of June 1957, and the work was essentially completed by the middle of September. Insulation tests were made on the installed cable, and the test data are filed in the project office.

255. Factors Affecting Completion Contractor's Progress. (a) Weather.-Since most of the completion contractor's work was indoors, the weather did not influence his progress except for the problem of providing heat in the powerhouse. The cool working conditions undoubtedly slowed the work to some extent. The weather conditions for the contractor's work in the switchyard were very good except the last month before completion, when some rain and cold weather were prevalent.

(b) Labor.--The construction operations were plagued several times with labor difficulties. In 1956 two walkouts occurred which involved contractor's employees. On August 23 all crafts left the job for various reasons. Some crafts returned to work by August 28, and by August 31 all crafts had returned to the job. Electricians left the job at noon on December 17, but returned at day shift the following day.

On March 8, 1957, all crafts left the job on orders from the Building Trades Council representative. All crafts reported back for work March 13, 1957. On July 17, 1957, at 8 a. m. carpenters, millwrights, and machinists walked off the job. They resumed activities the following day.

The labor supply was plentiful; consequently, the contractor did not suffer from lack of workmen.

(c) Other. Findings of fact dated December 28, 1956, established a delay in completion of the work under paragraph 16(a), part (3), resulting primarily from the late receipt of Government-furnished materials. Findings of fact dated December 12, 1956, established that the delay resulting from the August 18, 1956, fire in the stator of generator unit 4 was due, insofar as this contractor was concerned, to unforeseeable causes beyond the control and without the fault or negligence of the contractor. The delay was therefore found to be excusable under the provisions of the contract.

B. Mechanical Equipment Installation (Specifications No. DC-3675)

256. Steel Tunnel Liners. (a) General.--The furnishing, fabrication, and installation of the steel tunnel liners for the power and outlet tunnels was performed under item 144 of specifications No. DC-3675 by Palisades Contractors. Palisades Contractors subcontracted the work to American Pipe and Construction Co., Portland, Oreg. The liners were installed from station 10+12 to station 17+32 in the outlet tunnel and from station 10+12 to station 16+52 in the power tunnel. A total of thirty-six 40foot "can" sections and two 16-foot can sections were fabricated and installed by the contractor. The field Mechanical Branch visually inspected all welds, qualified the welders, and witnessed production welding tests. Work was begun April 7, 1953, and was substantially completed on July 19, 1954. See figure 182 for general installation details.

(b) Fabrication.--Representatives of American Pipe arrived on the jobsite April 7, 1953, and within a few days a small crew began setting up yard facilities. Layout of the yard continued until early June 1953, when the first production tests were made.

As originally conceived, the yard consisted of two parallel straight-flow production lines beginning at the north end in the storage area and moving to the south end at 40-foot rolls. At the north end the 3/8-, 13/16-, or 1-inch-thick plate in either 8or 10-foot lengths was stored. Each plate had been shop rolled to a one-third arc of 26-foot inside-diameter circle. The first step in production was to move three plate sections into the first position where they were butted and tacked together and where internal spider supports were installed. The can section was then moved to a set of rolls where the longitudinal seams were automatically welded. Next the can was moved to a pedestal platform and placed with its axis vertical and the stiffener rings were tacked in place. Then two or three sections were moved onto a set of rolls where the stiffener rings were automatically welded, and the sections were tack welded together. The can section, either 16, 20, or 24 feet long, was then moved to a last set of rolls where additional cans were tacked on to form a 40-foot can, and all the girth seams were automatically welded. It was on this set of rolls that the contractor did his repair work, installed piezometer holes, grout holes, and the hauling dollies. During actual

NOTES

Liners to be made from steel plate except where

otherwise shown.

One power funnel liner required.

One outlet tunnel liner required.

SUBMITTED. RECOMMENDED. ∙Fitt· APPROVED.

DENVER, COLORADO. DECEMBER 3, 1981

456-D-36

production, the two flow lines were modified so that all automatic welding was done on the west line, and an additional set of 40-foot rolls was installed to facilitate welding repair and miscellaneous installation. Once a can was accepted and ready for hauling, it was transported to the switchyard area east of the powerhouse. There the required reinforcing steel curtain was placed around the can. Then the can was transported to either the power or outlet tunnel for installation.

American Pipe used a submerged-melt automatic shielded-arc welding process with a controlled-pressure melt backup for welding longitudinal and girth seams. This process used a Lincoln welder and a Linde welding head feeding 1/8- or 5/32-inchdiameter Oxweld No. 36 or Oxweld No. 40 filler rod submerged in Lincoln 840 grade melt on the face (inside) of the seam. The contractor used two different specially designed backup belts, one for the longitudinal and the other for the girth welds. The Longitudinal backup consisted of a steel channel trough with a canvas belt which held the weld flux. The backup trough was placed beneath the root of the seam and jacked into position so that the weld flux made contact along the entire seam. Air pressure was applied to the interim space between the trough shell and the canvas belt, which in turn exerted a backup pressure of the weld flux against the seam. By adjusting the air pressure, the backup pressure could be controlled to obtain a satisfactory root weld. The girth backup was a steel channel on which was mounted a continuous rubber trough belt which carried the flux. The backup was placed under the can and made contact with the root of the seam along the tangent. The backup pressure was regulated by adjusting the tension of the rubber belt. This backup arrangement did not prove satisfactory, because the backup pressure regulation was not sufficiently sensitive and its use often resulted in defective welds requiring considerable repair. All automatic welds were made from the face side only. The above process was used only for 3/8-inch-thick plate. For heavier plate, 13/16- and 1-inch thick, a continuous manual root pass was welded, eliminating the need for a backup belt, and then the face side was automatically welded using the same equipment as for the 3/8-inch plate. For stiffener plate fillet welds, American Pipe used a pair of Lincoln manual welders (commonly called "squirt guns") with a submerged arc. In welding longitudinal seams, the welding head traveled on a carriage across the stationary can. In welding girth seams, the welding head was mounted on a boom and was held stationary while the can and the backup belt revolved. In welding the stiffener rings, the squirt guns were mounted on rollers on top of the can and were held stationary while the can rotated.

American Pipe ran the first welding procedure test on June 2, 1953, and the first production weld on June 11. Only longitudinal welds were produced during June 1953, and, because of welder inexperience on the particular type of work, these were often inferior in that they had inadequate penetration or were lumpy and spongy at the root. These welds were chipped out to sound metal and repaired with manual welds. The first girth weld was produced on July 7, 1953. On that date, American Pipe changed from a one-shift, 8-hour day to two shifts, 8 hours each, 6 days per week, and then abandoned the second shift on July 10. The first 40-foot can section was fabricated and accepted on July 25, 1953, the second on August 2, and the third on August 14. Thereafter, until the end of the job, American Pipe fabricated an average of two 40-foot cans per week. From August 20 to November 8, 1953, American Pipe worked two shifts, 8 hours each, 6 and 7 days per week.

As welders gained experience and techniques were improved during the month of August 1953, very satisfactory longitudinal welds were produced. However, the girth welds still presented a problem. On November 6, 1953, American Pipe added a pneumatic pressure regulator on the girth seam backup belt which improved their welding technique and enabled them to produce welds with 100 percent penetration using their original welding process only. Investigation for porosity was then reduced to spot-chipping weld reinforcement every 3 feet.

On December 3, 1953, the last longitudinal weld was made, and crews began dismantling the yard. The last can section for the outlet tunnel was fabricated on December 16, and the last section for the power tunnel on December 19. All work ended December 20, 1953.

On April 1, 1954, American Pipe crews began returning to the project and resumed work on the tunnel liners. On April 19, the crews began operating on a twoshift basis, 8 hours per day, 5 days per week. On May 1, a third shift was started