As explained in Chapter 4, under the heading Distinction Between Boiler Proper Piping and Boiler External Piping, Section I rules for the design of boiler proper piping are somewhat limited. They actually cover the design of pipe for internal or external pressure only. More extensive rules are provided in B31.1, Power Piping Code, applicable to the design of boiler external piping. Those rules cover, in addition to pressure, many other loads that piping might be subject to, such as mechanical loads that may be developed due to thermal expansion and contraction of the piping, impact loading, gravity loads, and seismic...