Vibration Improves Installation for Channel Furnace Inductors

Vibration Improves Installation for Channel Furnace Inductors

The Electric Vibration System, shown with a channel form and bushing mounted to the inductor. A temporary metal retainer is shown, too.

Installing dry vibratable refractory to optimal rammed density involves installing the material to a prescribed thickness, deairing it, compacting (tamping) and scratching (redistribution of compacted surface) it, and then repeating these steps. Frequently compaction is done via a manual electric vibration tamper or pneumatic vibrator, and as inductor designs changed and furnace sizes increased, installing the inductor refractory became simpler using form vibration of the inductor casings with an air-driven vibrator that attaches directly to the inductor case.

But, optimal installation relies on a consistent clean-air source to power the pneumatic vibrator. This compressed air must be "moisture free" to ensure maximum vibration, as moisture will dampen the vibration output. Dry compressed air is not always available.

This is one of the problems solved by the patented Allied Mineral Products' Electric Vibration System (EVS), which lowers labor costs and lessens installation variability, and time —— with no negative effects from any of the available compressed-air sources. Electrically powered, the EVS is a stronger and more durable method for installing dry vibratable refractories in channel furnace inductors.

The primary benefit is the ability to install refractory into the sidewalls of coreless induction furnaces and channel furnace inductors, without manually de-airing or "forking" the refractory material.

The EVS consists of an electric vibrator and vibrator control panel. A vibrator bracket can be welded directly to the inductor case, or a bolt-on bracket attachment can be used to attach the vibrator to the inductor case or loop form assembly.

The main component of the control panel is a variable-frequency drive (VFD). The VFD controls the output to the electric vibrator, which can be programmed to operate at various frequencies for selected amounts of time. Its digital display indicates vibrator operating status and drive output information. The VFD is available for low-voltage (200–240 V) and high-voltage (380–480 V) applications.

Consistent refractory installations are achieved because there is no concern that the compressor is supplying enough air pressure, because the system is powered by electricity. Fluctuating air pressures may result in less-than-optimal refractory density, which can shorten campaign life. Dirty or moist compressed air will degrade the internal components of pneumatic vibration equipment, which also can result in inferior refractory density.

The supply of electricity to the EVS is constant. The variable-frequency drive is accurate to 0.01 Hz, so the output of the vibrator will be exactly what is programmed into the unit.

Using EVS minimizes workers' physical involvement with the installation process. The refractory can be installed using bulk packaging lifted by cranes, and a large inductor case can be filled completely in under 10 minutes. The need for workers to de-air the refractory with a forking/de-airing tool is eliminated, too, reducing fatigue. The EVS performs the deairing function as part of the vibration process, so by using bulk packaging and eliminating forking the refractory can be installed two to three times faster than traditional installation techniques. And, the system can be programmed to automatically de-air and compact the refractory, so every installation will be completed in the same way every time.

In-plant operation of the EVS has shown it to be extremely versatile. It has been proven successful in large single- and double-loop inductors containing up to 3,500 kg (7,700 lb) of high-alumina or magnesia-based refractory, to small single-loop inductors containing 500 kg (1,100 lb). The operating procedure is no different even as inductor sizes vary, though the number of vibrator mounting locations will depend upon the size and geometry of the inductor case.

Foundries operating both coreless and channel induction furnaces will find that a single EVS will install refractory effectively in both designs, and it can be used to install various refractory compositions.

William M. Opatt is asst. business manager with Allied Mineral Products Inc., and David C. Williams is v.p.-technology with ASI International. Read the complete presentation.

TAGS: Materials
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