We freeze the design basis for the running example, a horizontal three-phase separator (1,800 mm ID x 6,000 mm T/T, SA-516 Gr 70), that the whole series designs.
Key numbers
| Max operating pressure | 13.0 barg |
| Design pressure (UG-21; margin = max(+10 %, +1.7 bar), rounded up) | 15.0 barg + full vacuum |
| Operating / PSV set | 86.7 % (below 90 %) |
| Static head, liquid-full | 0.177 bar, so 15.18 barg at the bottom |
| Design temperature (UG-20) | 120 °C |
| Allowable stress S (II-D Table 1A) | 138 MPa |
| MDMT | -29 °C |
| Corrosion allowance (UG-25) | 3.0 mm |
| Shell MAWP at top (preview) | 16.57 barg |
Generic example vessel. Confirm allowable stresses and clause letters against your own code edition.
