scope:

1.1 Scope

This standard provides procedures and design criteria for calculating the required wall thickness of new tubes for petroleum refinery heaters. These procedures are appropriate for designing tubes that will be used in both corrosive and noncorrosive services. These procedures have been developed specifically for the design of refinery and related process-fired heater tubes (direct-fired, heat-absorbing tubes within enclosures). These procedures are not intended to be used for the design of external piping.

This standard represents accepted engineering approaches based on up-to-date knowledge of the subject. The bases and sources of the procedures, particularly the design equations and stresses, are described in Sections 2 and 3.

Appendix A describes in detail the sources of the data used to develop the allowable stresses. Appendix B presents the derivations of the equations for corrosion fraction and temperature fraction. Appendix C describes a procedure for calculating the skin temperature of a heater tube. Appendix D describes limits for thermal stresses in heater tubes.

This standard does not include recommendations concerning tube retirement thickness, but Appendix E describes a technique for estimating the life that remains in a heater tube.