Pressure Vessels and Piping Systems
What the exam tests
This domain tests ASME Section VIII Division 1 vessel rules, B31.1 power piping, MAWP, shell thickness, corrosion allowance, openings, relief devices, supports, expansion, and testing. You should be able to read a simple thickness calculation and explain why the result is rounded up.
Core rules
- For a cylindrical shell under internal pressure, the circumferential-stress formula is t = PR/(SE - 0.6P) + corrosion allowance.
- P is internal design pressure, R is inside radius, S is allowable stress, and E is joint efficiency. Use radius, not diameter.
- Openings need reinforcement; piping needs supports, anchors, guides, and expansion allowance so nozzle loads stay acceptable.
- Relief devices protect vessels and piping from overpressure; their set pressure and capacity must match the protected equipment.
Worked example
P = 150 psi, R = 24 in, S = 20,000 psi, E = 0.85, CA = 0.125 in. t = (150 x 24) / (20,000 x 0.85 - 0.6 x 150) + 0.125 = 3,600 / (17,000 - 90) + 0.125 = 0.213 + 0.125 = 0.338 in. A 3/8 in plate (0.375 in) is selected because commercial plate is not ordered to 0.338 in and the calculation is a minimum.
Traps
Do not substitute diameter for radius; do not omit joint efficiency or corrosion allowance; do not assume a relief valve set at MAWP is automatically adequate without capacity review; and do not ignore piping expansion forces at vessel nozzles.