The Final Report on the Tragedy at the Medina County Fairgrounds

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A diagram from the Medina Sheriff's Office final report on the Case 110 explosion, detailing the progression of the crown sheet as it collapsed and then propelled itself in a downward fashion. The energy released from the explosion has been estimated at 330,000 foot-pounds.
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New Versus Old Stay Bolt Comparison: This diagram from the final report shows the level of corrosion found on the staybolts and the crown sheet of the Case 110 as compared to their appearance when new.
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This diagram shows the thinned crown sheet, reduced diameter staybolts, and how investigators theorize the crown sheet deformed and let loose from the staybolts.
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Investigators constructed this diagram to illustrate how staybolt thread engagement in the crown sheet decreases as the crown sheet thins.

Members of the steam hobby have been holding their collective breath since the tragic explosion of Cliff Kovicic’s Case 110 at the Medina County Fairgrounds on July 29, 2001. Initial reports on the precise cause of the explosion were confusing at best, and now, with the Oct. 5, 2001 release of the Medina County Sheriff’s final report, hope that any confusion surrounding the tragic accident would be laid to rest has been, in some measure, extinguished.

The Medina County Sheriff’s final report states its conclusion simply: “It is obvious from physical examination, photographs, and testing, along with computer generated stress analysis conducted on the stay bolts and crown sheet fastening points, that ninety plus years of corrosion and erosion had taken its toll on this boiler.” If Medina Sheriff Neil F. Hassinger was trying to quell further discussion on what caused the July 29 explosion with this statement, he doubtless failed to that end.

Primarily, this is because of strong sentiment in many circles that even a weak boiler, if properly tended and its water level kept up, will not fail in the cataclysmic fashion as experienced in Medina. This is not to suggest that anyone within the steam community would suggest in any way that any owner/operator should run a steam engine in less than a safe operating condition – the truth is quite the opposite. The steam community is universal in its embrace of the need for greater considerations of safety when operating steam engines and the attendant need for owners/operators to have their equipment properly tested and inspected to ensure its safe operation. What appears to be the greatest bone of contention is the idea that Kovicic’s Case 110, simply due to its age, was inherently unsafe at any operating pressure and that, by extension, all antique boilers are unsafe at any operating pressure.

More Details

While some sources have said that Kovicic’s Case 110 was of 1918 vintage (this date appears in the “General Details” section of the final report), serial number dating shows that engine number 20753 was constructed sometime between 1908 and 1909. This is also the date that appears through most of the final report, and it appears that any confusion surrounding the Case’s date of manufacture stems from dating the boiler number (9487) versus the engine number.

While the history of Kovicic’s Case 110 is not entirely clear, it is known is that Kovicic bought the tractor from Clarence (Junior) Christian, New Carlisle, Ohio, in August 1997. Christian had bought the unit at auction in Minnesota in 1993, had brought the tractor to Ohio, removed the engine to commence repair work, and, with the Case still disassembled, sold the unit to Kovicic in an “as is” condition.

Testimony given to investigators from the Medina County Sheriff’s Office fails to give a complete picture as to just what work Kovicic did to the Case 110 to get it operable. Kovicic did, over the course of three years, return the Case to operation, and testimony in the report suggests Kovicic knew the Case’s pressure gauge was reading light, showing about 25-30 psi low. Testing of the pressure gauge after the accident showed that it was consistently reading 25 psi low across a wide range of operation.

Additionally, post accident tests of the Case’s Kunkle safety release valve showed it failing to lift at 251.2 psi, even though it was preset to lift at 125 psi. It is suggested in the report that sand found in the guide area of the safety valve may have been the cause of its failure to operate properly. Deluca Test Equipment Inc. of Charlotte, N.C., tested the valve for investigators, and its report states that the 14-year-old safety valve had never been repaired or serviced. ASME codes call for a one year cycle for testing, inspecting and repairing safety valves. The Deluca report, while stating clearly that a root cause analysis was not complete, says “indications are the primary cause of the safety valve failure is sand in the guide area formed by the inside diameter of the guide or control ring and the outside diameter of the disc.” Where this sand came from is not known, but it has been suggested it was residue from sandblasting on the boiler during the Case’s refurbishment.

Further examination of the boiler found a total of six stay bolt heads that had been welded, and the report states that these welds had low penetration to the stay bolt heads and “contained porosity.” The report further notes that “the fusible plug bushing had been welded around the entire circumference.” Additionally, the report states the fusible plug “was intact and did not melt out.”

For investigators, these elements would appear to support a theory of sudden, catastrophic failure of the crown sheet. The report says that a combination of corrosion and erosion due to age, and excessive heat on the right front of the crown sheet (which the report says was exposed and had no water covering it, a condition caused by the tractor being positioned on a mild grade that placed its left rear down low) caused the crown sheet to fail. The report cites discoloration of the steel in the front part of the crown sheet as indicative of abnormally high heat. The fusible plug was located at the rear of the crown sheet, and investigators theorize it was covered with water while the forward part of the crown sheet was not, hence explaining the fusible plug’s failure to melt out.

It is unclear if any of the men on the Case that day were aware of impending disaster. However, in an interview with investigators, Kovicic’s daughter, Elizabeth Kovacic, said that just before the explosion one of the men, possibly her father, uttered an expletive, perhaps an indication he knew something was going wrong. Other witnesses interviewed claimed to have seen a combination of excessive steam releasing from the left rear of the Case 110 along with a change in the color of the smoke from the smokestack from dark to white. Investigators theorize the latter was an indication of stay bolt failure in the firebox, steam releasing into the smokestack turning the smoke white. The steam released from the left rear was apparently in response to an injector being opened by Dennis Jungbluth. On these two issues the report states: “The volume of steam in both areas exceeds what may be considered normal for engine operation in a static or near static condition, particularly the stack plume which is not in the form or image of engine exhaust on a warm summer day. The volume of steam and its density at the ash pan area exceeds the break exhaust of even a one-inch injector. The issuing steam and its characteristics supports the suggested theory of the initial crown sheet tear.”


What this tragic explosion will ultimately mean to the steam hobby is still unknown. Various sources report that insurance premiums for fairs and exhibitions are on the rise. As for the specter of lawsuits threatening to follow in the wake of Medina, to date it is unknown if any suits have been filed in the case. It will likely be a year before we know the full impact of the accident. One direct result of the accident, however, has been the introduction of legislation in Ohio to require boiler inspections for antique steam engines. Ohio presently does not require inspections of antique steam engines, which have been exempt from current boiler inspection laws in the state.

Ohio State Rep. Charles Calvert, R-Medina, introduced legislation on Aug. 21 that would amend the current boiler inspection laws and require the establishment of standards “for operating historical steam-powered tractors and testing operators of those tractors.” The bill, HB 344, was recently passed by that state’s house of representatives, and it specifically calls for an inspection and certification process for both the equipment and operators. It is likely that the tragedy in Medina will cause other states to review their inspection and certification process and, in the case of states with no inspection or certification, to likewise initiate standards for antique steam engines operating in their borders.

For those of us in the steam hobby, 2001 will be a year we will never forget. Owners and operators around the country have responded to Medina with a deepened appreciation for the importance of education and testing to keep the steam hobby safe. If the steam community’s resolve to work toward a secure, safe future, is any indication, the hobby of steam will stay with us as long as there are steam enthusiasts working to keep their engines in safe, operable condition for future generations to experience and enjoy, a proud reminder of our agricultural heritage.

From the Final Report: Causes of the Case Explosion

In the present case, the catastrophic event occurred due to crown sheet failure and the evidence point to the top, right front area of the firebox where the metal was found to be as thin as .085 inches. This failure most likely occurred due to a lack of sufficient water in this area to insulate the already structurally weakened stay bolts and sheet and over firing. When it further weakened, due to temperatures of 800° F to 900° F., it could no longer withstand the pressure of the steam above it. The pressure forced this area to pull and tear away, then exposed superheated water and steam in the boiler to the atmospheric pressure in the firebox. With this sudden reduction of pressure in the boiler, the superheated water flashed instantaneously and explosively into steam causing the catastrophic event which resulted in the release of approximately 330,000 foot-pounds of energy from the Case 110 steam traction engine, resulting in the deaths of five people and injury to forty-seven others.

The causes then are: Operator Error

1) Failing to thoroughly inspect an old boiler before firing it.
2) Failing to maintain and fully understand the importance of safety devices and practices.
2a) Apparent knowledge that the crown sheet had been welded in several places and not have a thorough and complete inspection done on it by a qualified and certified boiler inspector.
2b) Apparent knowledge that the steam pressure gauge was inaccurate and not replacing it.
2c) Apparent knowledge that the pressure relief valve did not lift at its set pressure of 125 psi and not repairing or replacing it.
2d) Not confirming the accuracy of the water gauge by using the try cocks frequently and making sure they are free of obstructions.
3) Driving the steel-wheeled 33,000 pound vehicle approximately 1.3 miles over concrete and asphalt, certainly further compromising the structural integrity of the boiler and its stay bolts due to intense vibration, that even though the boiler was mounted on springs, could not have been adequately dissipated.
4) Apparent over-firing and failure to maintain an adequate, constant water level.

The other cause of this then is: Structural Failure

Ninety plus years of erosion and corrosion did take its toll on this boiler and the lesson to be learned is to respect and understand the awesome energy contained in an antique steam traction engine boiler by all who own and operate them and that adequate methods must be established by which thorough and accurate inspections are conducted before they are fired. Present methods of sight inspection, ultrasound and X-ray may not be adequate enough to detect weaknesses at the very critical area where the stay bolt and the crown sheet fasten together and the boiler is under its greatest stress.

Richard Backus is editor of Iron-Men Album. Contact him at: 1503 SW 42nd St., Topeka, KS 66609-1265, (785) 274-4383, or e-mail:

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