a normal downward thrust of 50, 000 pounds to force the gate closed; however, under normal operation, the gate will close by its own weight. The stems were designed to withstand a downward thrust of 175, 000 pounds.

The downpull for each gate was determined by laboratory studies. The maximum hoist load occurs when the gate is latched in the open position and has to be lifted for unlatching.

Allowable stresses used in the design of the hoist are based on a percentage of the yield point of the material: 33 percent of the yield was used for cast, rolled, and forged steel except that 25 percent of the yield was used for bolts; and 33 percent of the yield was used for cast or rolled bronze and brass.

Corrosion resisting steel was used for the piston stems to minimize the wear on the packing glands in the lower cylinder heads.

B. Outlet Works

66. 7.5- by 9.0-Foot Outlet Gates. - (a) Requirement.-- Eight outlets are located in the outlet works adjacent to the powerplant. Six of the outlets (outlets 1, 2, 5, 6, 7, and 8) are provided with two slide type gates in tandem and the other two (outlets 3 and 4) are provided with a ring-follower guard gate and a hollow-jet regulating valve. Outlets 1 through 6 are connected to the 26-foot outlet pipe and outlets 7 and 8 are connected to the 26-foot penstock. The outlet gates control the flow of water past the dam during certain periods when flow from power generation is not adequate to satisfy downstream commitments or when it is necessary to pass extra water to draw down the reservoir. Either of the two slide type gates in each of outlets 1, 2, 5, 6, and 8 is suitable for operation at intermediate openings to regulate flow. The upstream gate, however, is primarily a guard gate and will be used as a regulating gate only in case the downstream gate becomes inoperable. Use of the upstream gate for regulation will require removing the blind flange from the air inlet pipe to that gate.

(b) General Description.--The general arrangement and details of the 7.5- by 9.0foot gate installation are shown on figure 84. The gates were furnished under invitation No. DS-4073,

The rectangular gate opening is 7 feet 6 inches wide by 9 feet high. The rectangular leaf controls the flow of water through the opening in the body. During opening or closing, the leaf moves vertically 9 feet 3/4 inch and slides on mating bronze downstream seats on the leaf, body, and bonnet. The seats also act as seals when the leaf is in the closed position. Guides are provided to limit the lateral drift of the leaf. The gate body and bonnet are embedded in reinforced concrete with only the bonnet cover and hoist projecting above the gate operating floor in the outlet works control house. Grease is supplied to the seals with a portable pump through fittings located adjacent to the bonnet cover and a piping system to outlets in the body seats. Each gate is provided with a 6inch air inlet, but the air inlet for the upstream gate will normally be closed. Valves for venting air during filling of the outlet pipes are located in the side of the bonnet cover.

Each gate leaf is actuated by a 30-inch inside-diameter oil-hydraulic hoist mounted on the gate bonnet. The normal hoist stroke is 9 feet 3/4 inch to operate the gate. The piston is stopped at the top of its travel by contacting the upper cylinder head. At the bottom of the normal gate travel there is a clearance of 7/16 inch between the piston and the lower cylinder head to insure that the lower seal on the leaf contacts the seat on the body before the piston bottoms on the lower cylinder head. The gate may be held open in any position by blocking oil outflow from under the piston; however, if the gate is to remain fully open for a considerable length of time, a manually operated gate hanger provided in the upper cylinder head may be used to hold the gate leaf in the open position. A direct reading position indicator, attached to the side of each hoist cylinder, shows the position of the gate leaf.

The estimated weight of each complete gate is 127, 600 pounds. The estimated weight of each leaf and the parts moving with it is 32, 700 pounds.

(c) Design.--Four of the outlet gates are located in outlet pipes branching from the penstock and will be subjected to water hammer. In order to keep the gates similar,

all gates were designed for normal stresses with a total head of 346 feet, including approximately 100 feet of additional head due to water hammer. (See memorandum from H. A. Weidener to H. H. Sloane, D. C. Erickson, dated July 5, 1951, subject "Preliminary Speed and Water Hammer Studies-- Palisades Power Plant--Palisades Project," included as appendix E.) The cylinder and other control parts were designed for a maximum pressure of 2,000 pounds per square inch but should normally require not more than 1,500 pounds per square inch to operate the gates. At the normal operating pressure the hoist produces a net opening force of 954, 000 pounds and a closing force of 1, 060, 000 pounds on the leaf. The control and power unit was designed to open or close the gate in approximately 9 minutes with both pumps running. In case one pump is out of service, the gates may still be operated with the remaining pump but the operating time would be approximately 18 minutes.

Each gate leaf and bonnet cover is of cast steel designed for a head of 346 feet using 33 percent of the yield point in tension as the maximum allowable tensile or compressive stresses. The maximum allowable shear was limited to 0.6 of the allowable tensile stress. The wall thicknesses of the gate bodies, bonnets, and bottom body covers were determined by practicable casting thicknesses. These parts are embedded in concrete to carry the hydrostatic pressures. The piston stem is made of corrosion resisting steel to prevent the formation of rust and inhibit scale formation which would damage the chevron type stem packing. The stems and cylinders were designed for normal tensile and compressive stresses not to exceed either 40 percent of the yield point in tension or 25 percent of the ultimate tensile strength, whichever was the smaller. The shear stresses were limited to 0.6 of the allowable tensile stresses.

The leaf skinplate was designed as a rectangular plate supported by the ribs and loaded with the uniform hydrostatic pressure for the stresses due to bending in the vertical direction. For bending in the horizontal direction, the uniform hydrostatic load was considered to be carried by simple beams supported at the seats. The beams were considered to be composed of the skinplate as the upstream flange, the horizontal ribs as the webs, and the backplates between ribs as the downstream flanges. Various combinations of stresses were investigated.

The piston stem was designed as a column using the secant formula, and the maximum closing force of 1,060, 000 pounds was considered acting on the gross area. The stem tension was checked using the maximum opening force of 954, 000 pounds acting on the net root area of the threads.

67. 96-Inch Ring-Follower Gates. (a) Requirement.--Two of the eight outlet conduits (outlets 3 and 4) are provided with ring-follower gates which serve as guard and service gates for the 96-inch hollow-jet valves located at the downstream end of these two conduits. The gates normally operate under balanced conditions, but, in functioning as guard gates for the hollow-jet valves under emergency conditions, they must close with a full flow of water. The service function of the gates is to shut off the flow of water to the hollow-jet valves to permit maintenance or repair of the valves.

(b) General Description.--The general arrangement and details of the ring-follower gate installation are shown on figure 84. The gates were furnished under invitation No. DS-4200.

The nominal gate size is 96 inches. This dimension is the same as the inside diameter of the ring follower and of the conduit. When the gate is opened the ring follower forms a continuation of the conduit and provides a smooth water passage through the gate. Bronze seals on the leaf bulkhead and ring follower bear against mating bronze seats around the conduit opening and on the downstream side of the body. In the closed position, these surfaces seal the gate. Lateral bronze guides with shims are provided on the leaf bulkhead to center the leaf bulkhead on the seals. The gate is embedded in reinforced concrete, and only the bonnet cover and hoist project above the gate operating floor in the outlet works control house. A 2-inch bypass for balancing the downstream pressure with the hollow jet closed, and a 6-inch blowoff for silt or trash accumulations in the lower bonnet, are provided for each gate.

The gate leaf is actuated by a 20-inch inside-diameter oil-hydraulic hoist mounted on the gate bonnet. The normal travel for the gate and piston is 8 feet 6 inches. An additional one-fourth inch of overtravel is provided at the top of the piston travel to provide operating clearance for the automatic gate latch in the upper cylinder head. The gate latch

was designed to support 40, 000 pounds and will hold the leaf in the open position without maintaining oil pressure under the piston. A leaf position indicator mechanism is mounted above the bonnet cover on the hoist cylinder of each gate, where it can be seen from the control cabinet.

The estimated weight of each complete gate is 124, 000 pounds. The estimated weight of each leaf and the parts moving with it is 34, 000 pounds.

(c) Design.-- Each gate leaf bulkhead and bonnet cover was designed for a hydrostatic pressure of 125 pounds per square inch, a pressure slightly in excess of the total static head on the gates. Since the gates are in the outlet conduits, no allowance was made for water hammer. The cylinder and other control parts were designed for a maximum pressure of 2,000 pounds per square inch. At the normal operating pressure of 1,500 pounds per square inch, the hoist produces a net opening force of 405,000 pounds and a closing force of 471, 240 pounds on the leaf. The control and power unit was designed to open or close the gate in approximately 4 minutes with both pumps running. Approximately 8 minutes will be required to open or close the gate if only one pump is running.

Each gate leaf bulkhead, bonnet, and bonnet cover is made of cast steel designed for maximum allowable tensile and compressive stresses not to exceed 33 percent of the yield point in tension. The maximum allowable shear was limited to 0. 6 of the allowable tensile stress. The wall thicknesses of the gate bodies and lower bonnet covers were determined by practicable casting thicknesses. These parts are embedded in concrete to carry the hydrostatic pressures. The piston stem is made of corrosion resisting steel to inhibit the formation of scale and prevent rusting which would damage the chevron type stem packing. The stem and cylinder were designed for normal tensile and compressive stresses not to exceed either 40 percent of the yield point in tension or 25 percent of the ultimate tensile strength, whichever was the smaller. The shear stresses were limited to 0.6 of the allowable tensile stresses.

The leaf bulkhead skinplate was designed as a rectangular plate supported by the ribs and loaded with the design hydrostatic pressure for the stresses due to bending in the vertical direction. For bending in the horizontal direction, the hydrostatic design load was considered to be carried by simple beams supported at the lateral seats. The beams were considered to be composed of the skinplate as the downstream flanges, the horizontal ribs as the webs, and the backplate between ribs as the upstream flanges. Various combinations of stresses were investigated.

The piston stem was designed as a column using the secant formula, and the maximum closing force of 471, 240 pounds was considered acting on the gross area. The stem tension was checked using the maximum opening force of 405, 000 pounds acting on the net root area of the threads.

68. Controls for Ring- Follower and Outlet Gates. (a) Requirement.--An integrated control system is provided for the 7.5- by 9.0-foot outlet gates and the 96-inch ringfollower gates in the outlet works. As previously indicated, six of the outlets (outlets 1, 2, 5, 6, 7, and 8) have two outlet gates in tandem and the other two outlets (outlets 3 and 4) have a ring-follower gate in front of a hollow-jet valve. The controls are capable of operating any of the outlet gates under unbalanced conditions for use as regulating gates; however, the upstream outlet gates will be operated balanced and will be used as regulating gates only in case the downstream gates become inoperable. The ring-follower gates are normally operated under balanced conditions but may be required to close with a full flow of water in an emergency.

(b) General Description.--The general arrangement and details of the controls installation are shown on figures 85 and 86. The controls were furnished under invitation No. DS-4357.

A single oil tank and power cabinet unit with two high-pressure, rotary oil pumps and motors supplies oil for operating the 12 outlet gates and the two ring-follower gates. Each pair of outlet gates and each ring-follower gate is operated from an individual control cabinet. Oil for operation is supplied by a header connecting the tank, the power cabinet, and all control cabinets. Each control cabinet contains a pushbutton station for starting and stopping the oil pumps in the power cabinet, and a manually operated four-way valve for opening and closing each gate.