Boiler explosion

There can be many different causes, such as failure of the safety valve, corrosion of critical parts of the boiler, or low water level.

The rapid release of steam and water can provide a very potent blast, and cause great damage to surrounding property or personnel.

[3] The rapidly expanding steam bubbles can also perform work by throwing large "slugs" of water inside the boiler in the direction of the opening, and at astonishing velocities.

A fast-moving mass of water carries a great deal of kinetic energy, and in collision with the shell of the boiler results in a violent destructive effect.

A several-ounce "slug" of water passing through a steam line at high velocity and striking a 90-degree elbow can instantly fracture a fitting that is otherwise capable of handling several times the normal static pressure.

This extreme form of water hammer propelled control rods, shield plugs, and the entire reactor vessel upward.

A later investigation concluded that the 26,000-pound (12,000 kg) vessel had jumped 9 feet 1 inch (2.77 m) and the upper control rod drive mechanisms had struck the ceiling of the reactor building prior to settling back into its original location.

[8] It was eventually found that this internal corrosion could be reduced by using plates of sufficient size so that no joints were situated below the water level.

Often referred to as "necking",[11] this type of corrosion can reduce the strength of the staybolts until they are incapable of supporting the firebox at normal pressure.

Grooving (deep, localized pitting) also occurs near the waterline, particularly in boilers that are fed with water that has not been de-aerated or treated with oxygen scavenging agents.

The air (which contains oxygen) collects in a layer near the surface of the water and greatly accelerates corrosion of the boiler plates in that area.

[14] This can occur when crossing the summit of the hill, as the water flows to the front part of the boiler and can expose the firebox crown sheet.

Poor operator training resulting in neglect or other mishandling of the boiler has been a frequent cause of explosions since the beginning of the industrial revolution.

[17]The stationary steam engines used to power machinery first came to prominence during the Industrial Revolution, and in the early days there were many boiler explosions from a variety of causes.

One of the first investigators of the problem was William Fairbairn, who helped establish the first insurance company dealing with the losses such explosions could cause.

When the [discharge] valve was suddenly opened at a pressure of 235 pounds [235 psi or 1,620 kPa] the boiler gave way, the iron being twisted and torn into fragments and thrown in all directions.

This was the cause of the Gettysburg Railroad firebox explosion[22] near Gardners, Pennsylvania, in 1995, where low water allowed the front of the crown sheet to overheat until the regular crown stays pulled through the sheet, releasing a great deal of steam and water under full boiler pressure into the firebox.

The first is the breakage of the boiler barrel itself, through weakness/damage or excessive internal pressure, resulting in sudden discharge of steam over a wide area.

The second type is the collapse of the firebox under steam pressure from the adjoining boiler, releasing flames and hot gases into the cab.

The other common cause of explosions was internal corrosion which weakened the boiler barrel so that it could not withstand normal operating pressure.

Dozens of explosions resulted, but were eliminated by 1900 by the adoption of butt joints, plus improved maintenance schedules and regular hydraulic testing.

The Pennsylvania was a side wheeler steamboat which suffered a boiler explosion in the Mississippi River and sank at Ship Island near Memphis, Tennessee, on 13 June 1858.

SS Ada Hancock, a small steamboat used to transfer passengers and cargo to and from the large coastal steamships that stopped in San Pedro Harbor in the early 1860s, suffered disaster when its boiler exploded violently in San Pedro Bay, the port of Los Angeles, near Wilmington, California, on 27 April 1863, killing twenty-six people and injuring many others of the fifty-three or more passengers on board.

The steamboat Sultana was destroyed in an explosion on 27 April 1865, resulting in the greatest maritime disaster in United States history.

[26][27] The boiler of Canada's PS Waubuno may have exploded on the ship's final voyage in 1879, though the cause of the sinking remains unknown.

An explosion could have occurred due to negligent upkeep or to contact with the cold water of Georgian Bay while foundering in a storm.

When the heat delivery is sufficiently rapid, a localized superheating can occur, resulting in a water hammer destroying the vessel.