longer life. Exposure tests are presently being conducted by the Corps of Engineers to determine longevity characteristics for polyvinyl chloride relative to rubber.

Styrofoam. This material, which is a polystyrene plastic, is being used in conjunction with concrete construction. It has been used as a filler material for concrete joints, particularly where new concrete is placed adjacent to existing concrete. It also has been used under concrete structures to control critical foundation pressures at specific locations.

OPERATING EQUIPMENT

POWER GENERATION

This

Turbine discharge measurements with radioactive tracers.-There is a need for a simple, expeditious method of making accurate measurements of turbine discharge in low-head hydroelectric powerplants. Discharge measurements are used for determining turbine efficiency and compliance with procurement contract performance requirements. At present, the only practicable method of making these measurements on low-head plants is by the use of current meters. method is laborious, time-consuming, and expensive and furthermore, has not been accepted in the United States as being capable of producing results of the required accuracy. Field studies are now being made to establish feasibility of measuring discharges by the use of radioactive tracers. This project is sponsored by the Atomic Energy Commission, Division of Isotope Development. Tests are being made on Corps of Engineers hydroelectric plant intallations as a cooperative investigation by the U.S. Geological Survey.

Teflon for hydraulic packing. In hydraulic turbines a packing box is required where the main shaft passes through the head cover. Because of is location, the packing box is not readily accessible and adjustments are not easily made. Teflon, a fluorocarbon resin developed by E. I. du Pont de Nemours & Co., is now being used by the Corps of Engineers for the packing material. It is more durable, has longer life, requires less adjustments and requires less lubrication than the asbestos braid type previously used for this application. The initial cost is greater than the asbestos type previously used but its longer life and less maintenance more than offsets the initial greater cost. Because of its superior characteristics as a packing material, Teflon is also used in the packing glands on the wicket gate stems and on the wicket gate servomotor shafts, and for Kaplan-type turbines, is used in the packing glands in the oil head. Teflon packing material is readily available and can be supplied by all of the turbine manufacturers.

High strength steel for hydraulic turbine spiral cases.-Hydraulic turbine spiral casings are manufactured of cast iron, cast steel, and steelplate. Generally large capacity medium head turbines have had steelplate spiral cases fabricated from low and intermediate strength plate field assembled by riveting and a relatively small percentage by welding. Field welding of spiral cases has generally been avoided by the Corps of Engineers due to the difficulty in obtaining adequate thermal stress relieving of field welded joints in accordance with the requirements of the ASME Code for Unfired Pressure Vessels. With the advent of high strength, heat treatable steel capable of providing high efficiency welded joints without the need for stress relief annealing, impetus has been given to the field assembly of spiral cases by welding. On large, medium to high head, turbines which would require spiral case thicknesses of 1%2

inches or more if built of ordinary steelplate, an economy may be effected by the use of these high strength weldable steels if a reduction in plate thickness can be made and still maintain the minimum thickness necessary for assembly purposes. Turbine manufacturers do not maintain erection forces for field assembly work and the field assembly is usually performed by the powerhouse contractor, with the assistance of erecting engineers supplied by the turbine manufacturer. The turbine manufacturer is therefore not directly responsible for the erection work. However, in cases where high strength steel is used for the spiral cases and field welding is permitted, the field erection of the spiral case is included under the turbine contract and the turbine manufacturer is then also responsible for this phase of the work. This high strength steel is produced by at least five of the leading steel producers.

Solid state electronic equipment.-Solid state construction which includes no electron tubes, mechanical relays, or moving parts is now commercially available from numerous manufacturers of powerplant annunciators, operation recorders, carrier current transmitters and receivers, supervisory control equipment, VHF and microwave radio equipment, and certain types of protective relays for power stations and transmission lines. Solid state equipment is smaller and lighter than conventional equipment and usually requires less maintenance. It is permitted to be furnished as an alternate to conventional construction wherever this construction is commercially available and operation of the equipment has demonstrated that its performance is reliable and satisfactory.

Grain-oriented silicon steel. This type of steel, containing 3.0 to 3.3 percent silicon, known under trade names of Hipersil, Corisil, and others, has very high permeability, low hysteresis loss, and excellent nonaging characteristics. It is extensively used in power transformers, motors, generators, and other electrical and electronic equipment, and has resulted in substantial reductions in core losses, increase in efficiency, and reduction in weight of the equipment. It is commercially available for use by all manufacturers.

INSULATING MATERIALS

"Butyl" compounds for electrical insulated wire. The insulating compounds for electrical wires and cables installed on most civil works projects must be resistant to heat, moisture, and ozone in addition to having adequate insulating characteristics. The search for better rubber and rubber-like insulating compounds that would have a service life approaching that of the project is a continuing one. The recent development of a synthetic rubberlike compound known as Butyl meets the above requirements for an electrical conductor insulation better than any compound developed to date, especially for the higher voltage applications (8,000 volts and above). It has excellent heat, moisture, and ozone resistant characteristics. Industry standards issued by the Insulated Power Cable Engineers Association (No. S-1981, 3d ed.) and the National Electrical Manufacturers Association (Pub. No. WC 3-1959) have been revised to include this type of insulation. Generally, it is more expensive than other types of synthetic rubber or oil-base rubber compounds more commonly used. Because of its superior characteristics, especially its ozone resistant

characteristics, this insulating compound is being specified in civil works procurements for insulated wire and cables for circuit-rated voltages of 8,000 volts and above. For applications below 8,000 volts, the superior characteristics of Butyl are not considered as essential and other synthetic rubber or oil-base compounds having satisfactory characteristics are permitted as an alternate to the Butyl insulating compound.

Epoxy resin for electrical machinery insulated windings. Many motors used on civil works hydraulic structures are exposed to extreme moisture conditions and special insulated windings and enclosed frames, with heating units inside the frames, are required to keep the windings dry. Epoxy resin insulating compounds have been recently developed which are particularly suitable for the above applications. The epoxy resin has high dielectric strength, is impervious to moisture and is fully resistant to attack by oils and solvents. It can be applied so that the stator windings including the end turns are fully encapsulated in a void-free homogeneous mass. The use of this epoxy material on motors used in camp locations allows the omission of the otherwise required winding heaters and the use of a less-expensive frame construction.

Mylar electrical insulating tapes.-Mylar, a polyester film, developed by E. I. du Pont de Nemours & Co., is a very versatile plastic material and is especially suitable as an electrical insulating material. It is highly resistant to moisture, resistant to solvent and chemical attack, has very high dielectric strength, has an operating temperature range of from 60° C. to 150° C., and has high tensile strength. These characteristics make it particularly applicable for insulating formed coils on electrical motors and generators. Because of the low moisture absorption of Mylar, general purpose motors insulated with it may be used under service conditions formerly requiring special motors. Mylar tape is also used as a binder in mica flake tapes used for insulating high voltage motors and generators. Because of its high tensile strength, the taped material can be wrapped tighter to the coils, thereby resulting in a more dense and more corona-free insulation. It is readily available and its use is competitively selected by electrical equipment manufacturers to meet specified operating conditions.

REGULATING WORKS FOR DAMS AND NAVIGATION LOCKS

High strength corrosion-resistant steel for gate wheels, rollers, and tracks. In the application of dam regulating gates which operate on wheels or rollers on vertical tracks, there sometimes occurs a combination of extremely high wheel or roller loading and an environment which is unusually corrosive to ferrous metals. Gate wheels, rollers, and tracks for service under these conditions require the use of metals which have a high degree of corrosion resistance, have high strength and hardness, adequate ductility, and which are capable of being heat treated with little or no distortion. These properties are supplied by the new precipitation-hardening, corrosion resisting, chromiumnickel steels. Furthermore, their weldability enhances their value as it permits these steels to be fabricated into forms which would not otherwise be practicable. This material is produced by at least two steel mills in the United States and is procured under Federal speci

fication QQ-S-763B entitled "Steel Bars, Shapes, and ForgingsCorrosion-Resisting Classes 322 and 322A.”

Teflon for bearing material.-In connection with the fish passage facilities in some of the Columbia River dams certain of the regulating gates rise and lower continuously in correspondence with the stage of the river downstream from the dam. The wheels on which the gates are mounted are submerged in the river water at all times. Operation of the gate is by its own buoyancy. Because of the low operating force, wheel bearings need to be as near frictionless as possible yet the use of antifriction bearings is economically impracticable in view of their high initial cost and the expense of maintenance and repair. Plain journal bearings with metal bushings do not have the lowfriction properties required and are short lived because it is not possible to provide them with adequate lubrication. The most satisfactory design has been found to be a journal bearing using a plastic bushing. The bushing material is a fluorocarbon plastic manufactured in the United States by E. I. du Pont de Nemours & Co., and marketed under the trade name "Teflon". This material is self-lubricating, has an extremely low coefficient of friction, has excellent load-carrying properties, and is practically unaffected by water.

PUMPING EQUIPMENT-HIGH-NICKEL METALS FOR CORROSION

RESISTANCE

High-nickel cast iron for corrosion resistance is now being specified for pumps to be used in a sea water environment. Due to the nature of the water, its low resistivity, the solids in suspension and the velocities involved, the pumps are subjected to a combination of corrosion and erosion to which these metals have been found to be unusually resistant. The tests conducted by the International Nickel Co., Inc., on pumps constructed of a high-nickel metal have shown that sea water has little effect on the metal and that years of satisfactory service can be expected. The metal is readily available from several sources and is covered by military specification No. MIL-G-858A. While this metal is slightly more expensive than the metal normally used in the construction of pumps, reduced operation and maintenance costs will more than offset the initial higher cost.