Abstract
Three-dimensional finite element analyses were performed on closed-ended thick-walled cylinders with a radial cross bore under internal pressure. The aim of this study was to determine the behaviour of the hoop stress as well as to establish the optimal Stress Concentration Factors (SCF). Cylinders of thickness ratios of 3.0 down to 1.4 with cross bore size ratios (cross bore to main bore ratio) ranging from 0.1 to 1.0 were studied. The maximum hoop stress was found to increase with the increase in the cross bore size. Amongst the five different circular radial cross bore size ratios studied, the smallest cross bore size ratio of 0.1, gave the lowest hoop stress while the highest stress occurred with a cross bore size of 1.0. Moreover, the lowest SCF occurred in the smallest cross bore size ratio of 0.1 at a thickness ratio of 2.25 with a SCF magnitude of 2.836. This SCF magnitude indicated a reduction of pressure-carrying capacity of 64.7% in comparison to a similar plain cylinder without a cross bore.
Highlights
Majority of industrial processes use various types of high-pressure vessels such as boilers, air receivers, heat exchangers, tanks, towers, condensers, reactors etc. in their operation
It was observed that the hoop stress increases with the increase in the cross bore size. This increase in the hoop stress was more pronounced in the cylinders with small thickness ratios, K = 1.4 and 1.5
Amongst the five cross bore sizes studied, the smallest cross bore size ratio of 0.1 gave the lowest magnitude of Stress Concentration Factors (SCF) of 2.836 at K = 2.25. This SCF magnitude indicated a reduction of pressure-carrying capacity by 64.7% in comparison to a similar plain cylinder without a cross bore
Summary
Majority of industrial processes use various types of high-pressure vessels such as boilers, air receivers, heat exchangers, tanks, towers, condensers, reactors etc. in their operation. Failure of high-pressure vessels does occur, being the source of approximately 24.4% of the total industrial accidents in these industries (Nabhani, Ladokun, and Askari, 2012) These failures have resulted in loss of human life, damage of property, environmental pollution, and in some instances, lead to the emergency evacuation of residents living in the surrounding areas (Nabhani et al 2012). These codes only give sets of wall thicknesses and their corresponding hoop stresses that are below the allowable working stresses without any detailed stress analysis (Kihiu, 2002) This practice has led to the use of high safety factors in pressure vessel design ranging from 2 to 20 (Masu, 1997). It is likely that a more detailed stress analysis will obviate the need for autofrettage, with the accompanying reduction in the manufacturing cost
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