Read the following article.
ASHLAND oil tank failure
The background for the oil storage tank failure is as follows: the tank involved was a four million gallon circular tank which was built in 1940 for Ashland Oil Company in Cleveland, Ohio. Beginning in 1940, the tank was operated for many years in what was believed to have been heated oil service. It is unclear as to how many years the tank was not used, but in 1986 it was disassembled by cutting it apart into sections. Using oxy-acetylene torches the "old welds" were left in place as the tank was cut apart and the sections were moved to an Ashland Oil facility near Pittsburgh, Pennsylvania. Using shielded metal arc welding; tank was reassembled in 1987 and placed in a tank farm with many other similar tanks near the Monongahela River. When reassembled, tank joints were x-rayed and leak tested. Test results indicated that none of the welds need rework. The reassembled tank was 50 feet high and approximately 130 feet in diameter. A dike was built around the tank which will hold 150 percent of the tank capacity.
The tank was partly filled with diesel fuel in August 1987. On January 2, 1988, during its initial filling to capacity after reconstruction, the tank failed catastrophically creating a tidal wave of oil which sent nearly 4,000,000 gallons of diesel fuel into the Monongahela River causing a major environmental problem. The problem was so severe that the whole water supply for all of South Pittsburgh had to be shut down for two weeks. In addition to spilling thousands of gallons of oil in the river, the tidal wave of oil from the tank damaged other nearby tanks and structures as well. "A small, uncemented cinderblock shed about 120 feet distant had its walls literally swept away… leaving its roof lying neatly on the slab floor. "
Answer the following problems:
1. Decide what material composition was most probable used for the tank wall, document the properties of the material and then decide the most probable processing history for the manufacture and construction of the storage tank. Discuss these issues as the initial paragraph(s) of your report.
2. Compute the probable wall thickness of the tank.
3. If a 3/8” thick plate was used, compute the exact flaw size which caused the brittle failure of the tank.
4. Use your calculations as a basis for a one or two paragraph discussion of the tank failure.
5. By calculation and design assumptions, find out if any of the following materials can be used for this tank, given the (improbable) assumption that all manufacturing and joining problems are solvable for the particular material.
• The tank was 80% full of oil when it failed.
• Suppose that the crack was oriented vertically and ignore stresses in vertical direction.
• Disregard end effects when calculating the stress in the tank wall.
• The oil height above the crack at the time of fracture was 35 ft.
• Suppose a medium carbon steel has a KIC = 49 ksi?in.
Show all calculations.