Industrial Valves

4Wall Thickness

4.1 Introduction

The bodies and bonnets of industrial valves are pressure‐containing parts that lead to leakage of valve internal fluid into the environment if they fail to function. It is essential to calculate and select the correct thickness for the body and bonnet to prevent mechanical failures. The American Society of Mechanical Engineers (ASME) B16.34, the standard for flanged, threaded, and welding end, covers various aspects of valves, including pressure‐temperature rating, dimensions, tolerances, materials, nondestructive examination requirements, testing, and marking. The valve body and bonnet thickness should meet the criteria set in ASME B16.34.

4.2 ASME B16.34 Minimum Wall Thickness Calculation

4.2.1 Conservation Approach (Mandatory Appendix A)

The minimum valve body thickness according to ASME B16.34, parameter t_m, is provided in both millimeters and inches. The minimum valve body thickness in ASME B16.34 depends on two valve parameters: internal diameter (parameter d) and the pressure class of the valve. Generally, the minimum valve wall thickness increases with the internal diameter and pressure class of the valve. The pressure classes, which are covered by ASME B16.34, are 150 (PN20), 300 (PN50), 600 (PN100), 900 (PN150), 1500 (PN250), 2500 (PN420), and 4500 (PN720). “PN” stands for pressure nominal. The internal diameter of a valve is the minimum diameter of fluid passage through the valve bore. Using Table 4.1 extracted from ASME B16.34, ...