Finite Element (FEA) Analysis on a Heater Vessel

We performed Finite Element Analysis (FEA) on a Heater Vessel to determine the structural integrity of its bolted flat heads.

Due to the complexity of the vessel bolted flat heads, the ASME Section VIII, Division 1 formulas could not be used to accurately account for the gussets and staybolts connecting the flat heads to the liquor boxes. Therefore, the finite element method was used to accurately simulate the structural responses of the vessel when subjected to operating pressures.

A detailed three-dimensional model of the entire vessel was constructed, including tubesheets, tubes, liquor boxes, bolted flat heads and gussets reinforcing the liquor box flanges. Tubesheets, shell, heads and connecting flanges were modeled with 3-D solid elements. In addition, head reinforcement plates and dividing plates were modeled with shell elements.

Equivalent material properties were used for the perforated areas of the tubesheets. Tubes, staybolts, and flange bolts were simulated with beam elements having the appropriate geometrical and material properties. Each flat head was connected to a liquor box only by the flange bolt and staybolts allowing the divider plates to separate from the flat heads. For stresses in the perforated areas of the tubesheet, a ligament efficiency was calculated.

A review of the stresses in the vessel shows that the stresses are higher in the bottom flathead, liquor box, and tubesheet in comparison to the stresses in the same components in the upper portion of the vessel. Stresses in the staybolts and shell/head flange bolts were found to meet the ASME Section VIII, Div. 1 requirements.

O’Donnell Consulting Engineers Performs (Thermal, Stress, Vibration and Fatigue) FEA Analysis on Components including Heat Exchangers, Piping and Vessels.