Meena Rezkallah, P.Eng.
These codes and standards were written to establish minimum requirements for safe design and construction with very little reference to the physical routing of piping. However, the piping designer should be familiar with them as they apply to his or her work. There are a few specific references to physical piping design of safety relief valve arrangements:
The ASME Boiler and Pressure Code, Section I, Power Boilers, specifies that there is to be no intervening pipe, valves, or fittings between the safety relief valves and the vessel or piping to which they are attached. This means that they must be fitting-bound.
The ASME B31.1, Power Piping Code, Appendix II, Non-Mandatory Rules for the Design of Safety Valve Installation, provides guidelines for the physical arrangement of safety valve piping, the most significant being that the distance between the center line of the valve and the center line of the discharge elbow must not exceed 4 times the nominal pipe size of the relief valve outlet.
The Pipe Fabrication Institute has a series of engineering standards (ES) covering the fabrication, design, cleaning, and inspection of piping. Three of these standards, listed below, specifically relate to the physical piping design:
ES2, Method of Dimensioning Welded Assemblies
ES3, Linear Tolerances, Bending Radii, Minimum Tangents
ES7, Minimum Length and Spacing for Welded Nozzles
For piping and valve drawing symbols, refer to ANSI/ASME Y32.2.3, Graphical Symbols for Piping Fittings, Valves and Piping.
It is essential that designers read and understand applicable codes and standards prior to developing fabrication piping designs.