Tutorial A - Create a typical piping system - CAESAR II - Reference Data

CAESAR II Applications Guide

Reference Data

This tutorial provides step-by-step instructions for defining a typical piping system, analyzing flexibility and stresses, and reporting results. This process includes:

The piping system you will model defines part of a refining process that moves crude from the bottom pump to a steam stripper unit. The end suction top discharge pump has a 10-inch suction nozzle and an 8-inch discharge nozzle. The 8-inch line runs through a check valve with a 6-inch bypass to a spring hanger support. The 8-inch line then runs over a hard support before entering the vertical vessel.

The boundaries of the system are the pump discharge nozzle (on the right) and the vessel nozzle (on the left). The pump nozzle is a satisfactory boundary because the movement of that point (as the pump heats up in operation) is known and easily calculated from the thermal strain between the pump nozzle and the base point. The vessel nozzle is an adequate boundary because of the known thermal growth of the vessel and the greater stiffness of the vessel with respect to the 8-inch pipe.

  • You can take an opposite approach by modeling the pipe ends to immovable points, such as the vessel foundation and the pump support (or base) point.

  • When you require a more accurate model for supporting structures, you can include structural steel in the model.

The check valve sits on top of the welding tee for the 6-inch bypass piping. The 6-inch line runs through a gate valve before reentering the 8-inch line through a second welding tee above the check valve. The total weight and length of this valve assembly is unknown. Because of this, the valve lengths and weights are pulled from the CAESAR II generic database.

The spring hanger above this valve assembly carries the deadweight and absorbs the thermal growth of the vertical pipe run. The hanger attaches to the elbow in line with the vertical pipe at the near end of the elbow. The hanger is quite sensitive to the weights used. The difference between the actual installed valve weights and modeled weights should be used to adjust the spring preload. In Tutorial B you will verify that the hot load on the spring is toward the center of the manufacturer's recommended spring working range to allow errors in load estimation. An appreciable change in these weights requires reanalysis of the system.

  • The weld point on the vertical run of the elbow is the near end and the horizontal run weld point is the far end.

  • The other end of the hanger attaches to available structure above the model. Because of the vertical thermal growth of the hanger attachment point, you cannot use a simple rod hanger.

  • The horizontal piping rests on an unspecified support at the far end of the next elbow. This support, modeled as a rigid nonlinear restraint acting on the pipe centerline, allows the piping to move upward but prevents downward motion.

Steps in this tutorial

  1. Review the piping system drawing

  2. Configure the software

  3. Define the first pipe element

  4. Define the vertical pipe run

  5. Define the horizontal pipe run

  6. Define the 6-inch bypass

  7. Review the piping input

  8. Check for errors

  9. Check the static load cases

  10. Run the static analysis

  11. Review the graphical analysis results

  12. Review the static output reports

  13. Conclusions