The Aluminium Plant Safety Blog (APSB) found this story by happenstance. Most incidents that the APSB locate revolve around injuries, and death. This story does not. Without knowing any details other than what was written in the original newspaper article, here is the story:
A small molten aluminum spill occurred at the
end of February at an auto parts manufacturer in Tennessee forcing employees
out of the building, but no injuries were reported.
According to the local fire department chief the leak
occurred about 9:30 a.m. at the EXEDY America Corp. The company manufactures
parts for torque converters. One of their machines that melts aluminum to
fabricate parts malfunctioned and leaked molten aluminum in a 4-foot-by-4 foot
puddle.
"It was contained under the pot. Once
the power was secured to it and the heat source taken away, it began to cool
and sealed off the leak or spill," fire department chief said. "The
leak was close to the floor by a matter of inches. It was a slow leak, so there
were no injuries and nobody was splattered."
The chief said that as a precaution employees
were cleared from the building. "It was a little bit of excitement," fire
chief said. "The people who were on duty ended up shutting down that part
of the operation, and they went home for day."
Later
on the it was learned that the furnace holding the aluminum malfunctioned, and
the molten aluminium leaked onto the floor.
Experts
with the company were on scene to advise emergency responders on how to
properly handle the spill, which was allowed to cool for cleanup.
The
fire department was unsure of how much of the aluminum spilled, adding that it
was definitely not the capacity level of the furnace, which can hold 1,800
pounds.
Education, awareness, and response are three factors that may have contributed in EXEDY America Corp's plant not having a molten metal steam explosion.
The plant apparently had an effective education program that instructed their workers of the dangers of molten aluminium spills.
Experts at the facility gave advice immediately to the local fire department which they followed. That advice prevented the discharge of water on the molten aluminium. There was one incident that the APSB is aware of where a fire department unaware of the potential danger discharged water onto a dumpster fire that contained burning dross. The dross exploded resulting in the death of a fireman.
APSB makes the assumption that the plant had an approved safety pit coating (Wise Chem E-212-F and E-115) around the furnace and anywhere molten aluminium can come into contact with steel or concrete substrate to prevent an explosion from occurring.
There have several incidents this year where spilled molten aluminium has traveled into the pit below the furnace resulting in an explosion.
There have several incidents this year where spilled molten aluminium has traveled into the pit below the furnace resulting in an explosion.
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| An uncoated area 5cm x 5cm can be a source of a molten metal steam explosion. |
The workers decided to immediately notify their superiors. Who responded by ordering an evacuation and calling the fire department.
A molten aluminium steam explosion is not a rarity, but reality in our industry. Education, awareness, responsiveness as well as maintenance of the safety pit coating allows the plant to minimize the probability of an explosion from occurring. Repeat minimize not eliminate the probability of a molten aluminium steam explosion.
In the future the APSB will have posts about education, awareness, responsiveness, and maintenance of the safety pit coatings.
14 comments:
If the author of this blog does not understand why there was no explosion, read the report. It was a slow leak into a DRY pit. Therefor no steam explosion could occur. ALL furnace pits should be dry. If not, don't melt metal until it is dry. Therefore preventing the posibility of molten metal explosion due to the steam reaction.
Thank you for commenting. The article does not indicate if the pit was DRY or WET. Furnace pits should be kept dry and free from debris.
APSB has toured too many plants to count around the globe. The pit under the furnace is typically ignored during housekeeping. That has begun to change, all new construction now coat the pit under the furnace.
Molten metal (and slag) explosions are not the metal exploding, but a low boiling point liquid (or solid) underneath the metal explosively gasifying and throwing the metal in all directions. You can avoid these explosions by keeping all horizontal surfaces around the molten metal absolutely dry and free from debris. Water, oils, and plastics are the most common gasifying elements causing these explosions.
Drying floors and other horizontal surfaces is critical to worker safety around metal melting operations. Molten metal spills cannot always be avoided, but explosions can be prevented by good housekeeping.
Thank you for commenting! The APSB will have to politely disagree on several of your points, as well as agree of your several points too. The aluminium industry as whole recognizes three categories of explosions involving molten aluminium. Force 1, Force 2, Force 3. It is true that Force 1, Force 2 involve water under the molten aluminium. The water (typically room temperature) upon being covered with molten aluminium instantaneously becomes supersaturated steam and forces/throws the molten aluminium away. Distances can be in excess of 20 meters for a Force 2 explosion. Equipment damage and injuries can occur on Force 1, and Force 2 explosions.
Force 3 explosions are a result of a chemical reaction that occurs 2Al + 3H20 = Al2O3 + 3H2+ Energy. Force 3 explosions are simply horrific. The last Force 3 explosion that occurred 11 months ago in China. The Aluminium Plant Safety Blog will be posting videos and photos of that explosion which occurred when a dc casting billet table suffered a Force 3 explosion. Initially 3 workers were killed and 10 injured.
APSB agrees with your statement that horizontal surfaces should be free from debris. But, it is impractical/impossible for those areas to be also dry. Water is essential in the process of casting aluminium. Studies have shown that specific organic coatings (Wise Chem E-212-F and E-115) prevent molten aluminium steam explosions from occurring. Good housekeeping is essential. Over the past two weeks the APSB has toured a lot of cast houses on two continents and notice a wide variety of housekeeping in aluminium plants. Some facilities stressed good housekeeping, while others did not. Later this year the Aluminium Times magazine will have an article about the importance and practical benefits of good housekeeping in aluminium plants.
Very interesting ; one never stops learning in this industry........
To my knowledge, I may be incorect, moisture/water is required to cause an explosion of molton Aluminum
Thanks for the comment. You are correct moisture/water is required to cause a molten aluminium steam explosion. Moisture/water is easy to see (pool of water), as well as difficult to see (moisture in concrete). It is the moisture in concrete that causes problems.
For instance, charging recycled scrap ingots (RSI) or large master alloy ingots weighing more than 500 pounds into molten aluminium is usually unsafe. The drying practices used to dry aluminium sows may not completely remove the water of hydration from certain salts. It is not unheard of the salts finding their way to concrete surfaces. Then salts hygroscopically absorb moisture.
In travels around the globe, conditions of pits under furnaces vary. Some are excellent (free of debris, clean), others unfortunately are not. I was asked to give a safety presentation at facility last year and talked about the pit under the furnace. One of the attendees told me how a few months earlier a failure in the furnace lining resulted in the furnace pit being filled with molten metal. An explosion resulted. Most new construction projects coat the pit under the furnace with an approved safety pit coating (Wise Chem E-212-F or E-115). As I was told by an engineer, there is a small probability of the molten metal entering the pit under the furnace, but if it does there is a high probability of a catastrophe.
Although I am not familiar with the specific incident, the description sounds like a refractory leak, but, as there was not any water or other liquid in it's path, it just ran out onto the floor and stopped once the metal chilled enough it re-solidified.
It may sound odd at first, but with standard safety precautions, molten metal spills do not result in an explosion. The explosions you hear about isn't from a molten metal spill, but from some other introduced factor, usually water.
Two examples that may generate an explosion and why:
1. A furnace is full of molten metal and a furnace tender adds materials very cold or wet - In this case the charge materials could have trapped water or condensation. Adding, for example, rough charge material at 40 degrees with either condensation, trapped water (or ice), etc. will aid in submerging the water below the surface, and subject the water to 1300 degree (aluminum) to 3000 degree (steel) surrounding temperatures. The rapid heating of the water instantly converts to a gas with a far lighter density (<.04 lbs/ft3) than the metal surrounding it (Aluminum 168 lbs/ft3, Steel 492 lbs/ft3) ... In addition, the steam will expand to 1,700 times the volume thus will rise VERY rapidly to the surface.
2. A furnace full of molten metal begins to leak through the refractory lining - Although this rarely occurs (furnace operators should check and repair linings at least daily), it may occur. If the furnace is a coreless induction furnace, the bath is surrounded by copper water-containing tubes. If the bath leaks out past the refractory and the grout to the tubes, it may melt the tubes (as in the case of steel) or stress a weak spot (as in the case of aluminum or bronze). The result is similar to (1) above, but to a lesser degree (less surrounded metal) and for a longer duration depending on the leak.
In general, small spills occur every day in the pouring process on a regular basis, but, as water (or some other liquid) is not submerged into the middle of the molten metal, it simply cools down and is swept or chipped away. Foundries will also exercise great caution to make sure the operators are protected from sparks and small splatters through the use of protective gear such as spats, high temperature gloves, protective sleeves and jackets, as well as helmets and face shields.
I hope this helps to explain.
Thank you for your comments. The APSB agrees that with standard safety precautions, molten metal spills do not result in an explosion. But "standard safety precautions" vary by plant, by company, by country, etc. Having toured facilities around the globe every plant is different in regards to safety. After visiting 4 facilities in two continents over the past 10 days the APSB was surprised how different each facility was. The housekeeping for each plant was so different, that a column in the Aluminium Times about the importance and practical benefits of good housekeeping in aluminium plants will occur later this year.
Giving the total number of furnaces in foundries, it is rare when a furnace fails and an explosion results. As of now the APSB, we know of four furnaces that have failed over the past 6 months in foundries casting aluminium. That number would double or triple if other metal foundries were counted.
Proper personal protection equipment (PPE) is essential to minimize and/or eliminate molten metal burns. The Aluminium Plant Safety Blog has just posted a story about some students and professors who cheated death. Luckily they were wearing the proper PPE.
Please inform more about PPE.
From what I've seen running a foundry, I could speculate that some of the increases in furnace incidents potentially could be resulting of other changes that may be somewhat driven by the economy...
1. As energy prices have increased (in our area they've increased over 20%), it could be very tempting to consider shortening or eliminating steps to pre-heat pre-heating steps which would have dried materials.
2. As plants have been ramping back up since last year, the proper training and follow-thru on new hires may be incomplete (not to mention the lack of experience).
3. Other areas of changes in the interest of cost cutting may also yield problems. Ie. a foundry may consider reducing the refractory lining thickness to increase melt capacity and save on refractory... reducing a 4" lining to, for example, a 2" lining and increasing the potential of a spill in (2) in my previous post.
While PPE is very important, it does not substitute for proper training and a safe process.
Thanks for commenting. The APSB agrees with all of your comments, the increase in cost of energy can not be minimized.
Wearing the proper protective apparel and equipment when working near molten aluminum is extremely important in preventing injury to production workers. Sometimes it can mean the difference between life and death.
OSHA suggested minimum requirements are safety glasses, steel toed shoes, heat resistant molten metal resistant gloves, jackets, pants ( mainly cotton no polyester) When pouring metal or cleaning a furnace a face shield is recommended.
SOME PLANTS REQUIRE HARD HATS, SPATS OVER FEET AND LEGS, DUST MASK WHEN FLUXING, AND ALL ALUMINIZED CLOTHING.
This is a very timely discussion as these foundries and die casters get very busy now (some of them very quickly) sometimes the safety aspect of melting and holding aluminum get lost in the rush to get parts out the door.
APSB, I too have seen many different safety programs or lack there of all over the world and am sometimes appalled at what people are willing to do and put themselves in danger in the cast house or melt rooms around the world.
I give training session on cleaning and fluxing furnaces and safety is the very first thing on the agenda.
Thanks for commenting. The importance of proper personal protection equipment (PPE) can not be diminished. A few weeks ago a presentation at the 116th Metalcasting Congress (American Foundry Society) was given regarding molten aluminium steam explosions. The presenter mentioned in passing that the safety clothes worn in an aluminium foundry are not worn in a steel foundry. Surprisingly after the presentation the speaker got several questions about that.
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