Handling the Heat of Weighing Foundry Ladles

Handling the Heat of Weighing Foundry Ladles

Crane scales in a foundry not only help to reduce costs and increase efficiency: They also increase safety by helping to prevent dangerous overloads.

The CFM A17 connects to any compressed-air system, creating suction by driving air through a venturi.

During melting, small, carefully calibrated amounts of metallurgical additives are poured into the molten metal as it waits in the ladle. Determining the exact quantities of these additives for each batch by weighing the ladles is one application for specialized crane scales in foundries.

Another common metalcasting application for crane scales is to determine the volume of metal in the ladle, to prevent waste or potential damage caused by excess molten material in the ladle.

Crane scales in a foundry not only help to reduce costs and increase efficiency: They also increase safety by helping to prevent dangerous overloads.

The heat in a foundry melt shop requires special designs for a crane scale to function reliably. The "hottest" task for a scale is weighing the ladle full of molten metal. If it contains molten steel, the temperature of the load will exceed 1,800°F, and the direct radiation of heat is a significant factor in the scale's performance. There is little chance for an extension cable to perform in such a setting, or even to survive. Usually, an extension cable is needed when using a remote readout, meaning that the crane should outfitted either with a large display integrated with the load cell; or, a remote, wireless (RF) indicator.

The former is not popular because there are critical times when reading the scale is essential, and rising smoke frequently obscures the display in a way that makes it impossible to read the weight. In these circumstances, the problem is solved by using a crane scale with wireless remote display.

A different problem is the effect of temperature increases inside the load cell, another effect of the high ambient temperatures. As with the other critical equipment used in foundries, these devices must be designed with enough insulation so that the internal temperature remains as low as possible. Crane scales are typically supplied with a heat shield, which is a partial solution as it delays the temperature increase within the load cell, where the RF transmitter and other electronic elements are located. This shield will delay the rise in internal temperature, but it will not prevent it.

One crane scale designed specifically for the high-temperature demands of metalcasting operations is the RON 2501 wireless device offered by RON Crane Scales (www.ron-crane-scales.com), which offer a temperature range of 14° to 175°F, and a unique, load-cell internal thermometer. The thermometer enables the user to know the temperature inside the load cell, which is essential information for optimal operator control of the ladle-weighing process.

"These are the only systems on the market that we've been able to find that withstand the high-temperature environments in foundries," confirms one veteran foundry operator. "We've been using them for at least the past five years. We recommend them to anyone looking for a crane scale that will work in these extreme environments."

Other design advantages of the RON Crane Scales line include alternate power-supply options (main or disposable, 1,500-hr batteries); RS-232 for communication with PC or printer; Integral data logger to record up to 6,000 data points, and present them as detailed reports with measurement time/date; a totalizer that displays the accumulated load; a 4-in. LED display; and set-point measurement.

Satisfied customers applaud the scales' safety advantages — "Having the wireless system has enabled us to safely monitor loads in our castings plant from a safe distance," reports one; as well as their simplicity — "One person can hook them up in a matter of minutes, and with the internal thermometers, it allows us to monitor the temperatures from quite a distance, to enable us to pull the load cell away from the heat for cool down periods. It takes out all the guess work," another states.

Pneumatically Driven Vacuums Need No Electricity
Vacuum power has many applications in a complex manufacturing operation, like a foundry, where dust and debris are unfortunately necessary to getting the real job done. Unfortunately, supplying the necessary power to operate a vacuum system is not always safe or convenient.

The solution may be a pneumatically driven vacuum, as introduced in two models by NilfiskAdvance America (www.nilfisk-advance.com). The CFM A15 and CFM A17 vacuums operate entirely without electricity, and still perform with all of the performance — suction, filtration, and durability — expected of an industrial-strength vacuum cleaner.

Both models connect to any compressed-air system and use air pressure driven through a venturi to create suction powerful enough to handle even large debris, as a sometimes occurs in these settings.

The CFM A15 is compact and maneuverable for working in confined spaces, or transporting to remote locations. The CFM A17 is larger, so it handles more demanding projects and provides a 26-gal tank. Because the venturi has no moving parts, it is a low-maintenance design element, well suited for continuous duty. (An explosion-proof model of the A17 is also available, with conductive wheels and non-sparking, conductive accessories.)

Both models have external filter shakers to prevent premature clogging. Both are available in stainless steel, and can be fitted with optional HEPA filters and various anti-static filters and accessories. "The CFM A15 and A17 give users cleaning performance in wet environments, in remote locations and in other areas where electricity either shouldn't be used or simply isn't available," according to a Nilfisk-Advance spokeswoman.

Beryllium-free Copper Alloys Now Available
Japan's Yamato Alloy Co. Ltd. has been manufacturing various copper alloys for more than 60 years, and after several years of R&D has developed two new copper alloys containing nickel, silicon, and chromium — but not beryllium. The two alloys, NC 25 and NC 50, are now offered to customers in North America.

Beryllium is a highly toxic light metal used as an alloy, particularly with copper, for applications that require electrical and thermal conductivity, high strength and hardness, and corrosion resistance, among other characteristics. Finding new alloys to replace effectively the ones containing beryllium has been a longstanding goal of many alloy manufacturers.

According to Yamato, the characteristics of NC 25 and NC 50 include high and uniform hardness, tensile strength, and yield strength, as well as high electrical conductivity. It claims NC 25 can replace beryllium-copper alloys that contain large amounts of beryllium, and is well suited for machine parts. It has high tensile strength of 1 giga Pascal (or 145 ksi).

NC 50 is said to have "excellent" electrical and thermal conductivity. Yamato particularly recommends NC 50 for manufacturing diecasting machine plunger tips, and the supplier states that one builder of diecasting machines has adopted it for this reason.

Among the specific advantages of NC 50 are:
• Wear resistance, contributing to long service life;
• Lubricity, saving on lubricant and maintenance costs;
• Material strength, improving the quality of cast products;
• Shorter holding time, improving productivity.

Yamato Alloy is supplying NC 25 and 50 to one of Japan's top automakers, while another has it under evaluation for its potential environmental advantages. It says automotive applications for the materials include moving engine parts and brake systems, where the hardness, conductivity, and wear-resistance are all critical advantages.

Techniques for Safer Ladle Weighing

There are techniques that the operator can use to improve a crane scale's performance during high heat exposure:

  • The distance between the load cell and the heat source should be a s greater as possible. If possible, the load cell should be installed above the crane hoist, to that the distance from the heat source is greater and the load cell is shielded better.
  • Whenever possible, the foundry ladle should be covered in order to decrease the ambient temperature and direct heat radiation.
  • Guard against molten metal droplets spraying the heat-shield jacket, and particularly from adhering to the jacket. Preventing this will avoid damage that can affecting the heat shield's capabilities.

For more information contact Yamato Alloy's U.S. offices via e-mail at [email protected], or call Tel. 773-592-6981.

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