Compliance
ASME Section VIII, Division 1.
The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section VIII, Division 1, is the design code of PlutoHX. These are the rules it applies, grouped by the part of the exchanger they cover.
What PlutoHX covers
The calculations of the design code.
- Detailed internal and external pressure calculations
- Maximum allowable working pressure (MAWP) determination
- Body flange design, with ASME PCC-1 (bolted flange joint assembly) calculations for assembly gasket stresses and assembly bolt stresses
- Tubesheet thickness calculations to Part UHX
- Nozzle reinforcement calculations
The rules, part by part
Where each rule applies.
| UG-27 | Shells under internal pressure |
|---|---|
| UG-28 to UG-30 | Shells and heads under external pressure |
| UG-32 | Formed heads: hemispherical, 2:1 ellipsoidal and torispherical |
| UG-34 | Flat heads and covers, such as the channel cover |
| UG-36 to UG-45 | Openings and their reinforcement |
|---|---|
| UG-37 | Reinforcement of the nozzle openings |
| Mandatory Appendix 2 | Bolted flanges, including the girth flanges of the exchanger |
|---|---|
| ASME PCC-1 | Used beside Appendix 2 for the assembly bolt stress and the gasket stress |
| Part UHX | UHX-12 for U-tube, UHX-13 for fixed tubesheet, and UHX-14 for floating tubesheet exchangers |
|---|
| UCS-66 | Minimum design metal temperature (MDMT) for carbon steels |
|---|---|
| UG-25 | Corrosion allowance |
| UW-11, UW-12 | Radiography and joint efficiency of welded joints |
| UW-20 | Tube-to-tubesheet welds |
| MAWP | Found from the thickness, for example with UG-27(c)(1) rearranged |
|---|---|
| UG-99(b) | The hydrostatic test pressure |
| Mandatory Appendix 46 | Lets a Division 1 vessel use Division 2 rules |
|---|---|
| See the Division 2 page. | |
MAWP and the hydrostatic test
From the plate chosen to the test pressure.
The maximum allowable working pressure (MAWP) is the top pressure the equipment may carry at its design temperature, as the code works it out. On the teaching shell of this site, a 1/2 in plate gives an MAWP of 313 psi in the corroded condition, a little above its design pressure of 300 psi.
UG-99(b) then sets the hydrostatic test at no less than 1.3 times the MAWP times the stress ratio, which comes to about 407 psi here.
Two factors in every thickness
Corrosion allowance and joint efficiency.
The corrosion allowance (UG-25) is extra thickness added to the calculated thickness, so that the part keeps its strength after the metal lost to corrosion or erosion over its life.
The joint efficiency E (UW-12) reflects the type of welded joint and how much of it is radiographed. The teaching examples use 0.85, for spot radiography.
Coming Winter 2026
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