Evaluation of Loads on High Temperature Condensate Tank Nozzles

We performed a structural evaluation of nozzle loads on elevated temperature condensate tanks, and recommended design changes if necessary.

A pump company manufactured six high temperature condensate receiving tank skids for one of its clients. The purpose of the evaluations was to ensure the structural integrity of each receiving tanks’ shell when subjected to external loads on the attached nozzles. Evaluation of the nozzles, flanges, and the tank support structure were not part of the work scope. A 0.0625 inch corrosion allowance on both the tanks’ shells and nozzles was taken into account in the evaluations.

Tank shells were evaluated using either hand calculations or finite element analysis. The hand calculations consisted of determining the stresses in the shell using the method described in the Welding Research Council Bulletin 107 “Local Stresses in Spherical and Cylindrical Shells due to External Loadings”. These calculations were performed using CodeCalc.

Finite element analyses of the receiving tanks were performed when the WRC 107 evaluation showed shell stresses requiring significant tank design modifications. The CodeCalc results determined that three of the tanks had to be further evaluated using FEA.

The receiving tanks are constructed of ASTM SA516 Grade 70 carbon steel, and the nozzles are SA53 Grade B carbon steel pipe. Material properties used in the finite element analyses were for 300 degrees F and are:

• Young’s Modulus: 27 x 10^6 psi
• Poisson’s Ratio: 0.3
• Density: 0.283 lb/in^3

The allowable stresses used in both the WRC 107 evaluation and the finite element analyses were taken from the ASME Boiler & Pressure Vessel Code.

The results of the finite element analyses showed that the original shell thickness was not sufficient for the nozzle loads, and that the
nozzle reinforcement plates would have to extend beyond typical dimensions. We thus designed larger thickness plates.

O’Donnell Consulting Performs Engineering Design and Analysis on Pumps, Valves, Vessels and other Process Equipment.