Westinghouse engineers investigated and found that debris damage occurred only when the rods were new. To explain this, they theorized that the zirconium rods were oxidizing in the hot water surrounding them, developing a wear resistant exterior coating. This coating, formed gradually during operation, protected the rod from debris. In the period before the coating developed, however, the rods were vulnerable. To eliminate any chance of debris damage, CNFD needed to find a way to preheat the rods to achieve the protection of the oxidation effect before they were placed into reactors.

Finding A Heating Solution
Realizing that they needed a heating expert, Westinghouse contacted Lepel. "We were convinced that we needed an induction solution," Westinghouse engineer David Lambert commented. "It's the only viable heating method that offers the reliable temperature control and consistent, accurate heating that fit our design criteria." The decision to go with Lepel was also influenced by the team's perceptions of the company's technicians. "No one else," Lambert said, "knew as much about the possibilities of induction heating or heating in general."

Lepel Designs A Solution
Lepel began an aggressive schedule to design an efficient induction heating solution. Lepel needed to design a system that could heat as many as thirty-three fuel rods to the required specifications found in the testing stage. Because Westinghouse manufactures a wide variety of fuel rods, the system also had to be able to recognize and treat different types of rods in different ways.

To deal with the large quantity of rods, Lepel designed a long, oval, load coil with thirteen parallel mounted susceptors on two inch centers. The system was engineered to utilize three of these load coils, each heating eleven rods.

The heating coil, a water-cooled wound coil that surrounds the piece being heated, had to provide extraordinarily even heating. Since it would be inefficient to try to heat the fuel rods directly, due to the poor thermal conductivity of zirconium compared to steel, Lepel designed an alternative process. Lepel engineers placed a steel tube, or susceptor, between the heating coil and the tube and the tube heats the fuel rod, giving efficient, even heating for a consistent oxide coating.

Lepel's coils use an electromagnetic, non-contact, induction heating process to bring the rods to a specified temperature. Because of the precise nature of induction heating, the coils are able to keep the specific rod sections at a tightly controlled temperature for a specified time. As the induction process produces heat uniformly, there is little chance of distortion.

According to Don Blau, Lepel's lead Sales Engineer, the most challenging aspect of the job was to manufacture the three heating coils to perform to Westinghouse's demanding heating specifications. "We had to keep the temperature within a very narrow range," Blau said, "from tube to tube, batch to batch, and rod to rod. This is the kind of advanced application that is made possible by induction technology."

A Complete Success
Westinghouse has been pleased with the system's performance. "We keep it running around the clock, five to seven days a week," Lambert noted, "and after a year of operation, we haven't had any problems." Westinghouse has also been satisfied with the ongoing service they receive from Lepel. In short, the project was a complete success.

A low power module allows output to be reduced to less than 2% for a controlled cool down. Also available are solid-state and electromechanical switches to allow successive operations in two or more work positions.The LCG series comes in a NEMA-12 cabinet and operates at 30 kHz with no audible noise.

Model LCG
Specifications
Induction Heating Power Supply for Crystal Growing

Model	Output kW	Cabinet			Weight lbs	Input kVA	Water GPM
		W	H	L
LCG 25-30	25	28	32	25	300	31	4
LCG 50-30	50	36	65	30	800	60	7
LCG 75-30	75	36	65	30	950	92	14
LCG 100-30	100	36	65	30	950	120	14

New Applications

• Selective Heating of Brass Electrical Lugs
• Brazing 0.020" Dia. and 0.010" Dia. Wires End to End
• Bonding Golf CLub Shafts to Heads
• Brazing Jet Engine Sensors in Atmosphere
• Brazing Electron Gun in Atmosphere
• Soldering Detonating Device for Automotive Air Bags
• Heat Friction Plate for Removal of Alcohol
• Solder Brass Nuts to Copper Strips
• Continuing Heating of Bi-Metal Discs

Induction Heating for Heat Treating Applications
Induction heating can provide improved heat treated product quality through accurate control of power/temperature, repeatable part qualification or positioning, and consistent quenching. Typical heat treating processes such as hardening, tempering and selective annealing can utilize induction heating to take advantage of these properties. These three applications and important processing parameters for induction are considered below.

Hardening
Hardening steels requires austenitizing of the steel or raising the part temperature sufficiently to completely dissolve all carbide phases, thus forming a single austenitic phase. Metallurgical factors which determine the time and temperature required to completely austenitize the compound include composition or alloy content, prior microstructure and prior thermal mechanical processing (e.g. cold work, forging, machining, hardening and tempering). Induction can be used for either through or case hardening. In both applications, the rapid heating available with induction can reduce the austenitizing time from 1-1/2 hours, for typical furnace treatments, to several seconds. When through hardening, additional time is required to obtain a uniform temperature throughout the part. When case hardening, if the proper frequency, power density (kW/in2), heating time, and quench are selected, case depths ranging from 0.010" to 0.350" are achievable. Parameters that must be defined to select the proper equipment include the type of steel, the production rate (parts/hour), number of shifts/day, overall part dimensions, required hardness, maximum case depth and minimum case depth.

Tempering
Metallurgically, tempering involves heating a hardened material to a temperature less than that required to induce hardening. As the part temperature increases, diffusion of atoms increases, relieving internal stresses resulting from the volumetric changes associated with the hardening process. As the temperature is increased, the time required to achieve the same amount of diffusion can be drastically reduced. Induction tempering, therefore, can reduce the overall tempering time associated with typical extended time furnace cycles. Provided a furnace tempering cycle is known, the Grange-Baughman formula can be used to determine the tempering parameter (TP) and an equivalent short time, higher temperature, induction tempering cycle.

Annealing
Annealing is typically an extended thermal treatment performed to relieve internal stresses developed during prior thermal mechanical processing.Through proper coil and fixture design, induction heating can be used for selective annealing. Time cycles can be greatly reduced due to the rapid heating achievable with induction. Additionally, a temperature profile can be established along the workpiece providing the desired graded mechanical properties.

Induction heating is a viable and well demonstrated technology for heat treating steels and other metals. The improved temperatures uniformity obtainable through accurate and repeatable power and frequency control enables great gains in product quality versus the quality of parts obtained via conventional furnace treatments where thermal gradients of 500ºF may exist. Additionally, the rapid heating and higher efficiency of induction provide the opportunity to reduce operating expenses.