Pre-Planning for Molten Material Releases

Analysis of Industrial Fire World’s incident logs indicates a number of molten materials releases. These incidents are highly specialized and something that is rarely – if ever – discussed in firefighting schools.

Molten materials releases can include glass, steel, aluminum, other metals, sulfur or salt. Molten asphalt is excluded from this discussion because unlike the other products, it is combustible itself and is not hot enough to cause the kinds of damage addressed below (i.e. destroying steel).

Spills of these materials can be hot enough to damage steel columns and certainly to ignite any combustibles in the area. As an example, if a glass furnace, as would be found in a glass bottle plant, experiences a leak into the pit below the furnace, and if the supporting steel columns are not protected by refractory brick, the steel supports could fail and the entire furnace could collapse into the pit. The result would be a huge loss and extensive business interruption.

Likewise, a molten steel spill can sever hydraulic lines and ignite the fluid within. Needless to say, molten material is a severe personnel exposure hazard. The text Industrial Firefighting for Municipal Firefighters describes how spilled molten metal can ignite cable trays, which can shut down process controls and also spread the fire.

National Fire Protection Association (NFPA) codes and standards offer some guidance on these hazards. NFPA 484 references the word molten 58 times. NFPA 86, Standard for Ovens and Furnaces, addresses molten salt bath furnace hazards. Local fire and building codes offer little or no additional information. Insurance industry loss control standards or corporate procedures are the best sources of information.

References include:

• FM Global Data Sheet 7-25, Molten Steel Production
• FM Global Data Sheet 7-26, Glass Plants
• FM Global Data Sheet 7-33, High Temperature Molten Materials
• FM Global Data Sheet 7-64, Aluminum Industry
• XL GAPS Guideline 17.4.0, Steel Industry Abstract
• XL GAPS Guideline 17.4.1, Basic Oxygen Furnaces
• XL GAPS Guideline 17.13.0, Aluminum Industry Abstract
• XL GAPS Guidelines 17.22.1, Glass Melting Furnaces

According to NFPA Standard 655, Standard for Prevention of Sulfur Fires and Explosions, molten sulfur can release dissolved hydrogen sulfide which is both toxic and flammable. NFPA Standard 484, Standard for Combustible Metals, describes various reaction hazards with molten metals, including a thermite reaction between iron scale and molten metal.  

Sprinkler protection is typically excluded from molten material use areas because of the potential for a violent steam explosion which would throw molten material over a wide area. Fire protection water can even dissociate and release hydrogen. Water and molten aluminum reactions have been especially violent.

This means that combustible materials cannot be allowed in molten materials use areas. Hydraulic fluid should be avoided or else must be approved for use in these areas. Housekeeping (removal of residues) is needed because this residue can spread a fire even if no other combustibles are present.    

Each process has its own specific hazards. Our intent is to make you aware of the basic issues and hazards. It is critical to work with facility process experts. We have found that most facilities have the knowledge and experience to manage these incidents. Plant experts need to be a key part of the incident command system.

For example, in the glass industry, carefully controlled water application under the direction and supervision of plant specialist can help control leaks.

Needless to say, prevention is the best measure. During preplanning sessions, you should ask about refractory relining and thermographic monitoring. Refractory is a special type of brick that can withstand these high temperatures. Due to the extreme strain on the refractory, regular monitoring and replacement schedules need to be adhered to.

Likewise, some vessels have water cooling to deal with high temperatures involved and monitoring is needed to ensure that no water contacts the material or vice versa. Water must also be kept out of molten material containment pits. In the aluminum industry, for example, several precautions are taken to prevent any contact of molten aluminum and water.

As with all of the articles in this series, preplanning is the key to successful resolution of an incident.