Effect of temperature on failure of gas cylinders

A number of ammonia cylinders burst during open storage in a field in the month of June. The cause of failure was studied. No flaws in the cylinder material were detected. Under normal conditions, the tangential stress (5.4 kg/mm super(2)) in the cylinder is well below the yield strength (49 kg/mm super(2)). The tangential stress increases with the rise of temperature of the ammonia. As long as some vapor exists inside the cylinder, the liquid remains in equilibrium with the vapor, the cylinder pressure is equal to the vapor pressure of ammonia at that temperature, and the rise in tangential stress is insignificant (0.14 kg/mm super(2)/ degree C). However, as the temperature increases, the specific volume of the liquid ammonia inside the cylinder also increases. The cylinder is completely filled with liquid under certain conditions in accordance with the bulk thermal expansion of the liquid; under these conditions, the cylinder pressure rises sharply with increased temperature, causing a large rise in tangential stress (4.76 kg/mm super(2)/ degree C). Thus, an approximate 10 degree C temperature rise in a cylinder filled with liquid ammonia can lead to failure.