Fig. 1. Ladle in operation at Gerdau Ameristeel in Petersburg, Va.


One of the obvious things to do to help with the cost of heat-treating equipment is to look for ways to cut out seemingly unnecessary parts of the design. Efficient insulation is all too often one of those items. Unfortunately for those operating the equipment, this is a short-term solution with potential long-term problems. In the end, cutting out the more efficient insulation serves to shorten equipment life, increase maintenance and energy costs, and increase the possibility of safety problems.

One company that recognizes the importance of using efficient insulation in equipment design is IMACRO, Inc. IMACRO offers refractory products, magnesium and aluminum sacrificial anodes, magnesium extrusions, strontium metal, specialty alloys and consulting services to the iron, steel, aluminum and other nonferrous metals and manufacturing industries. The company’s sales engineers are on a mission to help other companies discover the hidden savings that can be found in using the most efficient combination of insulation in their heating equipment.

While a facility operator may have too much to think about with daily operations – keeping people employed and servicing the customer – companies like IMACRO can come in and offer their expertise through assessments of existing equipment and propose solutions that take the guesswork out of insulation. By combining traditional refractory materials with a backup liner of microporous insulation, many companies are seeing their energy costs drop by up to 40%, depending on the equipment and application.

Microporous insulation is increasingly being used in many industries, including aluminum, steel, glass and furnace markets. With a maximum continuous-use temperature limit of 1832°F, it can be used alone for processes under this limit or as a backup to refractory for processes above it. The initial price of the insulation is typically considered high. Therefore, many facility operators immediately dismiss it as a possible choice. Upon closer investigation, however, the real benefits of using the material can be found. For the purpose of this article, a comparison of two ladles in operation at Gerdau Ameristeel in Petersburg, Va., is given (Fig. 1). One ladle has no insulation, and the other has an engineered solution including microporous insulation as a liner.

Overview of Process

Molten steel is processed at 2850-2900°F. The ladle metallurgical furnace (LMF) keeps the steel hot and is used to bring it to its desired chemistry during processing between the electric arc furnace (EAF) and the caster. Two ladles will be compared:

1. Ladle A is un-insulated.
2. Ladle B is lined (from inner to outer layer) with 6 inches of resin-bonded dolomite brick, ¾ inch of dry magnesite backfill, 3 inches of 60% alumina brick and 1⁄8 inch MICROTHERM Super G Hydrophobic Panel.

Fig. 2. Microporous liner (3 mm) installed in ladle

Finding the Cost Savings

Reduced Heat Loss = Energy Cost Savings
Reducing heat loss in the ladle results in lower energy costs, better control of processes and a more consistent final product. If refractory insulation is used with a microporous liner, a longer shell life can be expected because the shell does not overheat and eventually warp as it would if it was uninsulated. Comparing Ladle A to Ladle B, the energy cost savings comes from the reduced fuel consumption at the LMF. Over a one-year period – in the winter months – Ladle B used 15-16% less energy than Ladle A. In the summer months, the savings was 10-12%. Translated into average dollar savings, this is a way to save on production costs and remain competitive while not compromising the quality of product offered.

The energy savings equates to 4-6 kWh per ton of steel produced with a 120-ton ladle. Over a one- to two-year service life, the total energy savings for this LMF alone is at least five times the cost of the insulation package, including the microporous panels that are perceived as expensive.

Poor economic times mean that steel producers cannot run 24/7 as they have in better times, so ladles insulated with microporous panels help the steel shells and refractory materials handle the large thermal cycles from use temperatures to cold to use temperatures again during long production outages.

Increased Volume Capacity = Production Cost Savings
Microporous insulation is three to four times more efficient than conventional insulations, resulting in a reduced insulation requirement of one third to one quarter the thickness for the same performance. Adding insulation to a ladle obviously decreases the ladle volume capacity. The trade-off for a more energy-efficient ladle is a decrease in production. So, many steel plants will forgo the insulation in the ladle in order to keep production maximized. The often-unnoticed effects of this are increased energy costs, increased safety hazards and increased equipment replacement costs. The 3 mm microporous liner at Gerdau Ameristeel was chosen in part because the entire refractory lining is 75-100 times thicker. Therefore, adding insulation in the ladles has a minimum effect on volume. Figure 2 shows the 3-mm microporous liner installed.

Minimal microporous insulation thickness is also the case when insulating EAFs. Microporous insulation is also used in tundish applications to increase capacity and reduce heat loss from the molten steel. It replaces thicker, lower-performing insulation. For example, 5 mm of microporous insulation replaces 12.7 mm of ceramic fiberboard with improved performance and increased capacity.

In ladle applications where there is already insulation, insulating with a thinner microporous lining can result in increasing the volume capacity. This increase results in lower operating costs and higher production rates. In the current economy, the ability to produce more in less time also results in a savings in labor costs. Although the worker’s hours may be cut, the company can still offer employment and keep the skilled workforce until things turn around.

Future Energy Savings = Lower Costs
Very few high-temperature molten-metal applications use high-temperature insulation like Microtherm microporous insulation. They instead choose to either forgo any insulation in some equipment or to use a less-efficient, thicker, seemingly less-expensive insulation. In the end, either of these options can cost a company financially – through energy costs, lower product quality or loss of personnel due to accidents.

In today’s economy, it may be difficult to justify the cost of insulation, and it may be tempting to skip this seemingly unnecessary element of heating-equipment design. This is especially true in industries that don’t require insulation per code or where it has just become accepted so there is no way to reduce heat loss or shell temperatures. However, the company that chooses to invest in high-quality, efficient insulation will have a competitive edge. Lower energy costs could: save jobs while we as a nation get through this difficult financial time, improve the quality of your product, give your company a reputation for being the best even in this difficult market, help you keep your prices steady (and therefore help your customer and give you an edge over competition), improve the working conditions in your facility and much more. IH

For more information: Contact a technical sales representative at Microtherm, Inc., 3269 Regal Dr., Alcoa, TN 37701; tel: 865-681-0155; fax: 865-681-0016; e-mail: sales@microtherm.us; or Rob Doty, sales engineer, IMACRO, Inc.; e-mail: rdotyimacro@cs.com