The explosion and resulting fire aboard the Sultana that occurred on April 27, 1865 remains the largest maritime disaster in U.S. History. We should honor the memory of those 1,700 plus lives lost.

The boilers on the Sultana were less than three years old, but were in horrible condition. The iron plates were burnt, one of the boilers had two repairs in two months and had already been re-tubed once. Although the inspection 15 days before the explosion indicated they were safe, they were not.

There were three primary reasons for the condition of the boilers and it was the combination of these that was the root cause of the tragedy.

• Material of Construction – The iron (Charcoal Hammered No. 1) used in construction was a poor quality iron. While it was the best available material of the day, it was not a suitable boiler material. This type of iron gets brittle when it is overheated and cooled repeatedly. By the late 1800’s, the textbooks noted that CH No. 1 iron was “not a suitable iron for boiler construction.”
• Water Treatment – These boilers had no water treatment and used water straight from the Mississippi River. The mud in the water settled on the plates and surfaces acting as an insulator between the water and the iron. This caused the iron to repeatedly overheat and burn. As noted, this iron gets brittle when it is overheated and cooled repeatedly.
• Boiler Design – The Sultana Boilers were a firetube design. They used 24 smaller flues instead of the traditional two larger flue design. This larger number of smaller tubes arranged closely together made the boilers hard to clean exacerbating the Mississippi River mud settling on the boiler bottom. This design proved to be incompatible with the material of construction and the water quality and these boiler designs were removed from the Mississippi river.

These points are supported by the testimony while accounting for what engineers did not know about explosions at the time. They match the statistics of boiler explosions of the time and the science of boiler explosion theory. These boilers were almost destined to explode and unfortunately, the boat was packed with those doomed passengers when they finally did.

The modern day benefit to this disaster is the inspection and insurance industry as well as codes such as the ASME Boiler and Pressure Vessel Code and the National Board Inspection Code.

• Part 1:  A story of greed, chaos and fire
• Part 2: How do boilers go boom?
• Part 3: Did careening cause the explosion?
• Part 4: Keeping the research simple

© 2016 The Hartford Steam Boiler Inspection and Insurance Company. All rights reserved. This article is intended for information purposes only.