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Metal Casting Technologies : March 2011
46 www.metals.rala.com.au Back to the Checking an induction furnace before operation General hese are guidelines for checking induction furnaces before operation, especially newly installed units. There is no substitute for precautionary measures being undertaken prior to operations. A thorough checking out of the system is required after installation and prior to operation of the unit. If the system does not meet the specified standards, no attempt should be made to operate the unit until all faults have been corrected or defective parts replaced. The following check out procedures outline the steps to be followed prior to calling a Vendor's service engineer. It is important to recognize that most equipment is manufactured to operate at normal 440-460 volts, 3 phase, 50/60 cycle power systems. Higher power level furnaces are made to operate with a line voltage of 575 volts. Where the line voltage is 230 volts, 2,300 volts, or some other voltage, it will be necessary to supply a transformer (isolation or auto type) to step up or step down the voltage as required. These transformers are available from the Vendor. The supply voltage must be maintained within 5% below and 10% above the nominal rating. Should voltages be outside these levels, the power company should be contacted to change the appropriate taps on the transformers supplying this equipment. The equipment would have been furnished with a circuit breaker in the cabinet to comply with various codes. In most units, a hole must be cut into the enclosure to facilitate the connection of the proper size of conduit. Refer to the wiring diagram supplied with the furnace for cable and conduit size recommended. Cables and conduit of equivalent voltage and current ratings may be substituted as desired and in accordance with local electrical codes. Proper electrical service installation is ultimately the responsibility of the installation contractor. Warning: Some furnace units require a dedicated line isolation transformer. No other equipment whatsoever may be connected to the secondary of this transformer. Although the circuit breaker is provided in this equipment, the user should provide a means of protecting the incoming line. Note: The circuit breaker connection lugs will not necessarily accept all legal substitute cable. Be sure to check the compatibility of the circuit breaker connector before substituting cable sizes. Caution: Unless specified otherwise, disconnect incoming electrical power to all equipment until checking out procedures are completed. Electrical 1. Visually inspect all equipment for working condition or damage including: ● Meters ● Switches ● Wiring ● Cabinet door and hinge ● Loose hardware and fasteners ● Signs of water leakage 2. Circuit Breaker: Check for proper size. Check fuses (if installed ahead of unit electrical input) for proper service voltage and current rating. 3. Bus Bars: Should be fastened with non-magnetic material such as: ● Brass ● Silicon Bronze ● Aluminium Do not connect bus bars with magnetic materials (iron or steel) for operation above 150 Hz. Be sure that bus bars are adequately supported and secured against movement during operations. Joints in aluminium bus bars or joints between aluminium and copper bus bars, must be carefully made using Electrical Joint Compound according to the manufacturer's instructions. Water Cooling A.Shut off supply and drain valves to equipment. B. Pressurize the lines external to the melting system and check for leaks. Normal operating procedures General This section outlines the normal operating procedure for starting up a furnace system, for making heats, and for shutting down. Because systems vary greatly in type of installation, type of furnace, and type of cooling system, this section is made very general to cover most installations. Some operator procedures for abnormal conditions are suggested at the end of this section. However, each operator should review his own needs and develop specific emergency procedures based on his own unique installation and requirements. Daily starting-up 1. Turn the water on. 2. Inspect the lining and patch it as necessary. When the lining is correct, charge the furnace. Safety in induction furnace operations T By Prof. John H. D. Bautista, PEE, RMetE, MBA; Technical Consultant, Phil. Metalcasting Association., Inc. --PART1--