single 3/4-inch pipes lead from each manifold to terminal boxes embedded in concrete faces in the ring-follower gate chamber, the downstream face of the dam, or the discharge valve structure. The piezometer installation is shown on figure 124.

(c) Installation and Coating.-The outlet pipe sections were installed under the prime contract. Interior surfaces were coated with coal-tar primer and coal-tar enamel. Exterior embedded surfaces were not coated. Exterior surfaces exposed in the teetering section vaults were coated with phenolic-resin aluminum paint.

53. 96-INCH HOLLOW-JET VALVES AND CONTROLS. (a) Description. -Four 96 -inch hollow-jet valves and two sets of controls are provided at the discharge end of the river outlets to regulate the flow of water up to a maximum reservoir head of 536 feet. The hollow-jet valves were manufactured by Goslin-Birmingham Manufacturing Co., under invitation No. DS-5363. The controls were manufactured by the Rucker Co., under invitation No. DS-5503.

The hollow-jet valves and controls are located at the discharge end of the river outlets as shown on figures 125 and 126. A set of controls is located on a concrete platform above and between each pair of hollow-jet valves.

(1) Hollow-jet valve. -The hollow-jet valve is of cast and welded steel construction and consists basically of a circular body and movable concentric needle which forms an annular passage and seals in the entrance throat. The hollow-jet valve is hydraulically operated by a cylinder within the annular passage which is concentrically positioned by six radial splitters as shown on figure 126. The cylinder is 58 inches in diameter and the needle has a travel of 33-1/2 inches from fully open to fully closed position. As the valve is opened, water flows past the periphery of the needle in the shape of a cylindrical ring along the inside of the valve body. The splitters cut the ring into sectors and the water discharges from the valve in six separate jets. The estimated weight of each hollow-jet valve is 135,000 pounds.

(2) Controls.-Each control cabinet is of steel construction and encloses the control system for two hollow-jet valves. A cable-driven dial-type position indicator, for each hollow-jet valve, is located on the cabinet control panel to show the percentage of valve opening. Two 850-gallon oil tanks are located adjacent to the control cabinets.

An oil level gage is located on the side of each oil tank. The estimated weight of each control system is 7,300 pounds.

(b) Design.

(1) Hollow-jet valve.-The hollow-jet valve was designed to regulate the discharge from the 96-inch outlet pipes under any head up to 536 feet. The plunger capacity was based on the sliding friction of the plunger and packings, and the hydrostatic force from full reservoir head acting on the upstream face of the needle. V-type packings are provided to minimize leakage past the plunger. Stainless steel seats are provided on both the upstream body and the needle. Stainless steel cladding was used on the exterior surfaces of the plunger to prevent rusting.