Riley Industries, a U.K. based reseller of used and refurbished surface finishing plants and equipment, has secured a large order for the redesign, refurbishment and supply of DC rectifiers from a leading U.S. supplier of titanium castings to the aerospace industry. The rectifiers were redesigned for the anodic melting of titanium prior to it being poured into a mold, a process known as "skull casting." An electrode is hooked to the positive side of the power supply and inserted into a copper crucible, which is hooked to the negative side. The direct current produces an arc that initiates the melting process, which takes 12-15 minutes.

The project included four Westinghouse air-cooled, silicon diode transformer rectifiers, each with a 6000 amps/36 volts capacity. They were fitted with a new Thyristor control system, enabling them to work as one "master" and three "slave" units in parallel, delivering 0-24000 amps/0-36 volts of continuous power. In addition to the installation of new controls and general refurbishment, the rectifiers had to undergo a rigorous testing procedure at Riley Industries workshops prior to shipping to the U.S., the company reports. Other safety modifications made to the units included input isolators and contactors, current limiting chokes, voltage surge suppression and thermal overload relays.

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