This example guides you through the modeling techniques used in the analysis of jacketed piping systems. Where applicable, various alternatives are discussed that can benefit specific systems or problems.
The piping system to be analyzed is shown in the following figure. It consists of an 8-inch, schedule-40 crude oil line and a 12-inch, schedule-40 steam jacket. The section of piping from the pump to the valve is completely jacketed, while the section from the valve to the vessel has only the straight sections jacketed. This variation in the jacket is used to illustrate the two common types of jacketed systems. The core pipe is supported in the jacket using spiders. These spiders provide translational restraints in two directions, normal to the axis of the pipe. For this system, the spiders are located at each elbow weld line and in the straight runs such that the spider spacing does not exceed six feet. For this system, both the jacket and the core are low carbon steel.
In some systems, the jacket and the core consist of different materials. This condition must be modeled very carefully because the thermal growth in the core is different from the thermal growth of the jacket. Improper axial restraints in such a system can cause extremely large loads in the pipe.