TABLE OF CONTENTS Key Learning Objectives
What factors a process engineer must consider when setting specifications for a pressure vessel
How pressure vessels are designed and what determines the vessel wall thickness
How the ASME Boiler and Pressure Vessel Code is used in pressure vessel design
Why pressure safety valves are used and how to select, design and specify pressure relief systems
This chapter covers those aspects of the mechanical design of chemical plants that are of particular interest to chemical engineers. The main topic considered is the design of pressure vessels. The designs of storage tanks, heat exchanger tube sheets, and pressure-relief devices are also discussed briefly.
The chemical engineer will not usually be called on to undertake the detailed mechanical design of a pressure vessel. Vessel design is a specialized subject and will be carried out by mechanical engineers who are conversant with the current design codes and practices and methods of stress analysis. However, the chemical engineer will be responsible for developing and specifying the basic design information for a particular vessel, and therefore needs to have a general appreciation of pressure vessel design to work effectively with the specialist designer.
Another reason the process engineer must have an appreciation of methods of fabrication, design codes, and other constraints on pressure vessel design is that these constraints often dictate limits on the process conditions. Mechanical constraints can cause significant cost thresholds in design, for example, when a costlier grade of alloy is required above a certain temperature.
