If you do beam-model pipe stress analysis with Caesar, chances are good that you sometimes lack access to a full-mesh FEA program for qualifying a trunnion support in the piping design. Non-FEA options are: the Kellogg Subject 3810 method (using an online spreadsheet of questionable origin), or the BS EN 13445 or ASME Code Case N-392-3 methods which are tedious to attempt under project deadlines.

Never seeming to have the right tool for this task, I constructed a trunnion qualification spreadsheet for myself (Excel 2007 Workbook .xlsx format) based on ASME Code Case N-392-3. It includes adjustments to stress indices for elbow-mounted trunnions based on the findings of EPRI TR-107453. (Report includes Code Case N-392-3. Contrary to its original end notes, TR-107453 is free to the public with no export control restrictions.)

Too many spreadsheets online are “black boxes.” Calculations are hidden and users must take on faith the accuracy of the final output. Here, all referenced equations and intermediate calculations are shown – “Show your work,” as math teachers say. The user may inspect (but not edit) the cell functions written to calculate them. Users enter basic pipe/trunnion dimensions and material properties, plus trunnion reaction loads from pipe stress program output. TRUNNION QUALIFICATION SHEET calculates whether the trunnion attachment is acceptable under Code Case N-392-3 (for tee-pattern run attachments) or as modified by EPRI for elbow mounting. Proper construction of the stress model and load selection remain the responsibility of a trained stress analyst.

ASME, EPRI and AWS gave me permissions (on file) to reference their sections in this spreadsheet. It is offered here to colleagues at no cost, and I invite feedback on errors and code interpretation. (See spreadsheet for email address.) As with any such tool, use with caution.

TRUNNION N392-3_R0