The background for the oil storage tank failure is as follows: the tank involved was a four million gallon circular tank that 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, the tank was reassembled in 1987 and placed in a tank farm with many other similar tanks near the Monongahela River. When reassembled, the tank joints were x-rayed and leak tested. Test results indicated that none of the welds required rework. The reassembled tank was 50 feet high and approximately 130 feet in diameter. A dike was built around the tank that would hold 150 percent of the tank capacity.
The tank was partially 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 that 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 entire water supply for all of South Pittsburgh had to be shutdown 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 questions:
1. Decide what material composition was most likely used for the tank wall, document the properties of the material and then decide the most likely processing history for the manufacture and construction of the storage tank. Discuss these issues as the initial paragraph(s) of your report.
2. Calculate the probable wall thickness of the tank.
3. If a 3/8" thick plate was used, calculate the exact flaw size that 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, determine if any of the following materials could be used for this tank, given the (improbable) assumption that all manufacturing and joining problems are solvable for the particular material.
Aluminum Oxide Glass