2/20/2008 - Magic City Foundry

In the 1800's Birmingham was called "The Magic City" due to its extremely fast growth.  This growth was brought about by the iron and steel industries.  Today Birmingham is known for great hospitals, science, and technology, but the iron and steel industries still flourish. 

There are many weighing applications within the foundry world.  From incoming steel to outgoing cast iron parts, the most effective method of dealing with the material is through weighing.  In the metro area of Birmingham, Alabama, there are numerous foundries and foundry support companies with many materials to weigh.  One of the most hazardous and difficult applications is the pouring of molten metal.    

The melting of American steel is not an easy job.  It requires furnaces built to withstand over 6,500 degrees Fahrenheit.  Pouring liquid metal at temperatures over two thousand degrees Fahrenheit is dangerous, dirty work. 

Many foundries utilize crane scales when ladles of molten metal are moved.  This provision of weight information often utilizes wireless technology to keep operators away from the most severe temperature environments. This assumes that one has already poured the hot liquid before a measurement is necessary.  One Birmingham foundry recently brought this issue into question.

It has often been assumed that the pouring environment was too hazardous in which to operate weighing equipment.  The foundry in question is a world leader in the cast iron pipe market.  They are also leaders in technology.  Years ago they tried a railroad scale beneath the rail car that moves ladles of molten metal from the pour station to the waste removal station.  Before much time had passed the rail scale was rendered inoperable.  This was due in large part to the "splash" of sparks that explode from the ladle during pouring.

Experience is the best teacher.  This failure was discussed during early meetings between foundry engineers and personnel of Birmingham-Toledo, Inc. (BTI).  A smaller, local scale service company/scale distributor had installed the rail scale and was unable to keep it in working condition.  The initial reaction from BTI was to allow their superior technicians the opportunity to bring it back to working condition, but foundry engineers did not feel that it was worth the investment.  They were looking for fresh ideas.

A scale to weigh the rail car, ladle, and molten metal could possibly be protected from the heat, but it would be very difficult.  Additionally, the rail car would be "dead weight", or weight added to the system with no benefit regarding information purposes.  In order to weigh the application as accurately as possible, a scale needed to be directly under the ladle; however, temperature and sparks would never allow this.      

BTI proposed weigh modules installed within the structure of the rail car.  This would offer greater heat protection, as well as eliminating much of the dead weight.  The rail car modifications would have to be engineered carefully, as failure could mean loss of human lives.  Foundry engineers loved the idea, but asked BTI to engineer it, and moved on to their next issue: how would the scale be powered?

A 3D Image of one of the CAD drawings provided by BTI

The rail car axle, or "truck", with weigh modules mounted within the structure.

The rail car is powered electronically through a power cord reel.  The brushes within this reel would cause a great amount of interference, though.  This interference would affect the accuracy of the scale, at a minimum, possibly rendering it useless.  BTI proposed a battery-powered operation, and the customer was pleased. 

A good scale salesman always asks, "What would you like to do with the information?"  This question brought the next concern: where would the weight indicator be mounted?  In order to keep it safe, it would need to be enclosed in steel with kaolwool insulation.  Obviously, the weight readout would not be available visually.  How would the information be extracted? Again, the cord reel would cause a great amount of interference. 

BTI proposed a wireless system with the receiver and display mounted in the operator's office, above the operation.  The operator had been filling by sight for years.  Steam and white heat caused her to only be able to guess when the ladle was full.  Now, she would be able to see EXACTLY how much molten steel she had placed within the ladle. 

 The operator station.  Note the wireless receiver mounted on the wall next to the display.

The operator's window looks down on the rail car (the top of the car is barely visible).

Now, foundry engineers began to be excited.  If the operator knows EXACTLY how much she is filling, there should be no waste.  With no waste, how much money would be saved?  A conservative estimate was $1 million per year. 

The power problem raised its ugly head again, though.  A greater amount of power would be required for a wireless system.  The system would need to operate without interruption through an entire shift.  BTI proposed a marine battery within the weight indicator enclosure.  This would require a large enclosure, external charger, and back-up battery.  This would be a very small price to pay for such large potential savings.

Now, the engineers became a little greedy.  "If we have this weight information for the operator, how about the operators down the line who remove waste and add alloying elements?"  They could then know EXACTLY how much waste had been removed, and EXACTLY how much alloying element to add.  The result would be greater inventory control, better process control, and a much better alloy.  A better alloy would mean better parts, maybe even a price increase to their customers.

Wireless receivers and weight displays were added down the production line.  In addition, Mettler-Toledo's MTConnections software was utilized to input the information from the operator's display to her personal computer.  The gross, tare, and net weights, along with time and date, were sent to an Excel spreadsheet.  The company server accessed this spreadsheet and made it available for analysis.  

The alloy-add station with weight indicator, wireless receiver, and system HMI.

For the first time, the foundry is able to control their molten fill.  A ladle is placed onto the rail car, and the operator tares off the ladle weight.  She then begins the fill with a target weight in mind, dependent upon the day's requirements.  At the target weight, she stops the fill.  With the press of a key, the information is available to the next operator within the process, as well as to the front office.

The next operator removes the waste that has settled at the top of the molten metal.  The amount removed is recorded and analyzed by the front office before the ladle is moved along to the alloy additive station.  The perfect amount of the expensive, but immensely important, alloy is added to the molten metal.  Not only is the amount precise, but the front office can prove it.  A million dollars will be saved this year, and multiple millions will be made in increased prices in the future. 

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