Molten material breakouts are a common cause of loss in primary metal occupancies. These spills may come from the melting vessel or from molten material handling equipment.
Refractory is very important and key in providing protection against molten metal breakouts. Refractory provides protection for molten metal in a way that automatic sprinklers provide protection for combustibles. Refractory failure of the melting unit is the most common cause of molten material spills. Refractory over time will wear out, due to metal and slag erosion, high temperature, improper sintering technique, improper installation procedures and other reasons. Improper charging techniques can damage the refractory. Dropping extra-large pieces into the furnace can crack the lining, creating a run-out situation during the melting procedure.
Bridging can also occur due to improper charging, causing the molten metal under the bridge to superheat beyond the refractory’s maximum temperature capability. Superheating under a bridge condition can result in a run out and cause a molten metal-water explosion.
Many melt shops use automated charging systems with conveyors that keep up with the melt rate of the furnace. Not keeping up the charge procedure with the melt rate can cause excessive temperature in the molten bath, resulting in erosion of the refractory and short life.
Perform frequent visual inspections of the furnace and conduct weekly-recorded thermal imaging to detect potential problem areas to prevent refractory failure. An alternative to weekly-recorded thermal imaging is the installation of an automated refractory monitoring system, which is preferred as it eliminates human error.
The recommendation for frequent visual inspection of the furnace and use of weekly thermal imaging is important.
Molten material breakouts can be contained with minimal loss if the proper safety measures are in place. Spill pits, protection of surrounding equipment and routine maintenance will help minimize loss potential.
The spill should be contained in an adequate dry basin; it should not damage critical equipment components such as:
a. electrical cables
b. fuel gas piping
c. oxygen piping
d. hydraulic oil piping
e. unprotected structural members
f. electrical and control room
g. surface water
Scrap metal radiation detection system should be provided at the truck and railcar scales and the scrap bucket or scrap convey.
Cooling water systems is integral to many processes in primary metal operations. Interruption of the flow or inadequate water quantities can lead to severe thermal over loading, and in some cases, catastrophic failure of the molten metal vessel. Automatic back up cooling water supply should be provided for safe shut-down.
Cooling water systems can also cause steam explosion and should be provided with differential pressure of flow monitors to detect leaks. Water pouring into a furnace will not, in itself, generate an explosion if it sits on top of the molten bath. The problem occurs when the furnace rocks or tilts for pouring of the molten metal. Water is trapped in the molten bath and immediately vaporized. The heat causes the water to partially dissociate into H2 and O2 resulting in a violent explosion. Facilities should have documented cooling water leak procedures.
Risk Logic can recommend and help develop preventive maintenance and property loss control programs at your facility. Please contact us to schedule a property survey at your facility by one of our molten metal specialists.