ASME PTB-7

Description / Abstract: This criteria document covers the development of the tubesheet (TS) design rules for the U-tube, Fixed, and Floating Head TS Heat Exchangers (HE) configurations contained in Part UHX of Section VIII Division 1, 2013 Edition. It applies also to Paragraph 4.18 of Section VIII, Division 2 which is entirely based on Part UHX.

The free body diagram of the HE, the equilibrium and compatibility equations, the solution of resulting differential equations and all intermediate steps are provided to show the derivation of:

• the deflection and the rotation at any radius of the TS,
• the bending and shear stress at any radius of the TS,
• the axial stresses in the tubes at any radius of the TS,
• the axial stretch force acting in the shell,
• the axial displacement of the shell.

The document provides the technical basis of the following items:

• the required loading case combinations,
• the acceptance criteria for each TS configuration, as applicable,
• the TS characteristics including the Effective Elastic Constants,
• the TS extended as a flange.

The following effects are in addition to the above basic items:

• the effect of different shell material or thickness adjacent to the TS,
• the effect of plasticity at TS-shell-channel joint,
• the effect of radial differential thermal expansion between the TS and integral shell and channel,
• the tubesheet calculated as a simply supported TS.