Case Study
Pressure Vessel Local Stress Review — Nozzle & Shell FEA
FEA Analysis — Pressure EquipmentConfidential Details Removed
Problem / Requirement
A horizontal pressure vessel in high-temperature hydrocarbon service was subject to piping system interface loads significantly higher than those assumed in the original design. The vessel's authorised inspector required a documented local stress review at all large-bore nozzle connections and at the saddle support pads before approving the revised piping isometric, with analysis traceable to ASME BPVC and WRC methodology.
Engineering Scope
Review of original vessel design documentation and identification of critical nozzle and support locations
Extraction of piping reaction loads at each nozzle from the piping stress analysis model
WRC 537 (combined loading) screening analysis for all nozzles to identify cases exceeding allowable limits
Detailed 3-D FEA of the three nozzles that exceeded WRC 537 screening limits, including weld geometry modelling
Stress linearisation through critical section paths to separate membrane and bending stress components
Saddle support contact and sliding analysis under thermal growth and operating weight combinations
Fatigue screening per ASME BPVC Section VIII Div. 2 Annex 5-B for cyclic nozzle load cases
Recommended pad reinforcement dimensions and revised weld detail for one non-compliant nozzle
Deliverables
WRC 537 Screening Analysis Spreadsheet — All NozzlesFEA Local Stress Report — Large-Bore Nozzles (×3)Saddle Support Contact Analysis ReportStress Linearisation Path Results SummaryFatigue Screening Assessment ReportNozzle Reinforcement Pad Detail Drawing (revised)Acceptance Criteria Compliance Matrix
Client Value Delivered
Inspector approval obtained on first submission, keeping the plant modification schedule on track
FEA identified that two of the three critical nozzles were acceptable without modification, limiting costly fabrication rework to one location
Reinforcement pad recommendation was sized to the minimum required, minimising added weight and weld heat input
Saddle analysis confirmed the existing support could accommodate thermal growth without anchor bolt overload
Fatigue screening cleared all cyclic load cases, removing the requirement for a full ASME Div.2 fatigue life calculation
Standards Referenced
ASME BPVC Sec. VIII Div.1ASME BPVC Sec. VIII Div.2 (Part 5 stress analysis)WRC Bulletin 537PD 5500 Annex GASME B31.3EN 13445-3 (reference)
Software Used
ANSYS Mechanical 2024 R1ANSYS WorkbenchPV Elite (Hexagon) — vessel baselineCOMPRESS (Codeware) — nozzle geometryCaesar II 2019 — piping load extractionMicrosoft Excel (WRC worksheets)
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