Effect of Piping Loads on Vessel Support and Foundation Design

Abstract

It is a common challenge for pressure vessel and foundation engineers to determine the effects of piping loads on the foundation and vessel support design and to find out the appropriate design method to be used. Pressure Vessel Codes specify loadings to be considered in the vessel design but limited guidance is provided on the application of piping loads when designing vessel supports. Consideration of piping loads in the design of vessel supports and foundation is left to the engineer’s judgment. Vessel supports are typically designed to withstand the operating weight of the vessel, seismic and wind loading. Pressure vessel literatures provide well-established methodologies in considering these loads in the design of vessel supports. Civil engineering literature, such as the American Society of Civil Engineers (ASCE) Wind Loads for Petrochemical and Other Industrial Facilities [11] or the ASCE Guidelines for Seismic Evaluation and Design of Petrochemical Facilities [17], provide well documented procedures and guidelines for evaluating wind and seismic loads. However, there is limited literature on how to account for external loads from attached piping. Typical major project schedules have vessels and their supports/foundations designed well before the development of the piping design that provides calculated actual nozzle and piping loads on the vessel. This paper reviews the type of piping loads, how the piping loads are translated to the vessel support/foundation and provides a proposal for simplified approach analysis on how to apply these piping loads in the design of the vessel support/foundation. There might be cases where the piping loads will cancel out, but that may not always be the case. Ignoring and not considering nozzle loads in the support design/foundation may not be appropriate for all vessels. The intent of this paper is to also make the Vessel Engineer aware of ways to reduce these loads and to encourage communication with Stress Engineers in regards to flexibilities and other factors used to calculate nozzle/piping loads. In most cases, the vessel shell and nozzles are considered as rigid anchors in the piping stress analysis. By using the proper flexibility at nozzle junctions and the global vessel flexibility, the effect of piping loads in the design of the vessel support can be reduced. There is little or no industry guideline on how to include loads due to the thermal expansion or contraction of piping. Since the thermal loads and calculation of flexibility are the least understood part of the analysis, this paper provides background including examples of how these loads and flexibilities can be calculated. In short, the intent of the paper is to provide a better understanding of how piping loads are translated to the vessel support and to provide some design guidelines that are not readily available in current literature and are not clearly specified in the industry codes or standards.