Flexibility Analysis of Refinery Piping System

Abstract

Piping systems in downstream refineries and process plants experience a great thermal strain due to the difference between ambient and operating temperatures of process and utility fluid flowing through them. This thermal growth causes thermal stresses which leads to failure in piping components like flange leakage, deflection in piping, fractures at nozzle juncture and other fatal errors in piping system. Therefore, these piping structures must be flexible enough to support their own weight and to absorb thermal growth developed.  To ensure this, a static flexiblility analysis will be performed by using an engineering tool called CAESAR II (Computer Aided Engineering Stress Analysis and Routing). Stress analysis ensures the flexibility in critical piping systems by maintaining the stresses below the allowable limits in compliance with piping codes like ASME B 31.3. Inputs like PandID, Isometric drawings, line list, material database, support standard documents etc. will be used to define the conditions of piping system and a variety of load cases like operational, sustained, occasional (wind, seismic) and expansion case etc., will be considered to qualify  the system in all possible cases. Piping supports like pipe shoe, guide, spring hanger, rod hanger, cantilever bracket are used to ensure proper support locations. This paper carries a detailed analysis on critical lines connected between process equipment’s to demonstrate the integrity and flexibility of the piping system. It also generates stress reports like nozzle loads and bending stresses which validates the design of high quality, timely and economic layout of refinery piping system. 

Keywords:  Piping Flexibility, Structural Integrity, Process Fluid, Isometrics, Load Cases