Fire hit The Torrington Company (USA) last Sunday morning, in a heat treat facility attached to the company's Standard Plant in Torrington, Connecticut.

Quick response by city firefighters confined the blaze to one area, further contained by fire break walls.

The company does not currently run a Sunday shift, so no employees were in the building at the time.

Torrington said in a statement, "We're grateful for such an excellent response by Torrington's fire and police personnel."

Fire reportedly began in an oil quench tank, although it is not yet known what sparked it.

Torrington's fire is a good reminder to every company running a heat treating operation to respect and monitor it closely. This is especially true for those employing batch-type furnaces with integral quench. The facility and the procedure, by its very nature, is volatile, often explosive and potentially deadly.

Quench tanks are large vats of coolant, kept at a specific temperature, for treating parts immediately after they are removed from the furnace heat area.

In the bearing industry, oil quenching is used because is behavior allows better thermal control over the cooling cycle, causes less distortion than other coolants, and stops oxidation from forming.

Standard quench oils generally have flash points between 270 and 560 degrees Fahrenheit, but the operating temperatures are held 150 degrees below the flash point. In a controlled atmosphere, quench oil temperature can be allowed to closely approach the flash point.

Contamination and degradation from use, however, strongly affect quench oil behavior and volatility. Low boiling point contaminants, such as water, reduce the oil's flash point and dramatically increase the risk of fire. For that reason, standard safety precautions generally do not allow quench oil contamination to go over 0.5%.

To cool the quench oil when a hot load from the heat treat oven is dropped into it, quench tanks are equipped with heat exchangers.

Many heat treat fires are caused by malfunctioning or leaky heat exchangers. Cooling tubes of water-cooled heat exchangers can crack, leaking water into the oil quench tank.

Because water is heavier than quench oil, some commingles with the oil, but most sinks to the bottom of the tank.

When hot parts fresh from the furnace are dropped into the water-contaminated quench oil, the water turns to steam, driving the oil up and out of the tank and often into the furnace chamber where a fire starts.

There are a wide variety of other potential causes for quench oil fires: inadequate ventilation, malfunctioning fire doors on the furnace, and improper furnace atmosphere, to name just a few.