Audit Vessel

File: PVE-5918, Last Updated: Aug 25 2014, By: LRB

The ASME Audit

PVEng has been involved in many ASME Audits, mostly for VIII-1. This sample shows the most common audit vessel, known in slang as a “Hartford Submarine” in honor of the Hartford Steam Boiler Inspection and Insurance Co. This is the type of vessel a shop builds when it has no vessels on order that it can use for an audit, or when it is first seeking ASME certification. Useful information about what is recommended for an audit can be found in:

ASME Boiler & Pressure Vessel Accreditation Guide For ASME Review Teams For Review Of Applicants For ASME Certificates Of Authorization (A, M, PP, S, E, V, HV, H, HLW, H (Cast Iron/Cast Aluminium), UD, UV, UV3, U, UM, U2, U3, RP, T, TD, TV) (guide)

From this document:

  • A review must cover a QC Manual and its implementation.
  • It is expected that fabrication functions be demonstrated using typical Code work. However they may be demonstrated using current work, a mock-up, or a combination of the two.

The above document also answers an often asked question – how do I demonstrate for more than one ASME stamp? Answer: Only one demonstration vessel is required, however more than one calculation set might be necessary:

For Applicants requesting multiple stamps, it is not necessary to have a demonstration item with design calculations for each Code Section. An item fabricated to any one of the requested Code Symbols may be used as the demonstration item. However, if the demonstration item is not to the most stringent Code requirements, the Applicant must provide additional calculations or another documentation package that contains Code calculations to the most stringent Code requirements and administrative documentation to sufficiently demonstrate compliance with all aspects of the company’s QCS.

This Audit Vessel

This vessel qualifies as a mock-up. The vessel, calculation set and drawings are simple. The materials are easy to source. The fabrication is easy. And the audit team has seen it before. However, we suggest that where practical, a real in-production vessel be used instead. If a mock-up is required, we can also design other vessel configurations that would be useful after the audit – such as vertical air receivers.

We can update the drawing and calculation set to the latest code and addenda if you want to use this vessel. (Do not use these out of date calculations for an audit!) We can also re-design the vessel changing size, materials, thicknesses and nozzle configurations as desired. Also commonly requested – update the design to demonstrate radiography.

Sample drawing of a standard pressure vessel for ASME audits.

Design Calcs

This vessel is calculated using the Design Calcs pressure vessel code calculation program. This is our favorite program for ASME audits. The printout is concise, easily readable and illustrated. Design Calcs provides the easiest to understand design report of any of the commercial code calculators. If requested, we can instead provide the calculations in the other code software we regularly use: Compress, PV Elite or our own in-house Excel spreadsheets.

Calculation Validation – Updated 2014

From the above referenced ASME document:

If computer calculations are to be used, the Applicant shall demonstrate that the computer program has the capability of producing acceptable calculations.

Over the many audits we have used any of the following:

  • Re-calculating the complete calculation set using hand calculations that show the same result. This is a lot of work.
  • Re-running the calculation set using another computer program that shows the same result. There are a variety of methods available within the code book to do things like calculate shells, also different programs show/hide different amounts of calculation results. It is not practical to get one program to exactly match the results from another, and they do not match line for line, number for number. The reviewer wants to be able to see the same formulas used by both and the same results. We no longer use this approach.
  • Re-running the calculation set using computer spreadsheets that shows the same result. Same comment as the previous method.
  • Re-running the calculation set using computer spreadsheets that provide the same result and providing hand calculation validation of the spreadsheets. When we were using this method, the spreadsheet validation was from our development files, and thus was not for the audit vessel, and did not validate the actual numbers used in the audit. Same problem as above. We do not use this method any more.
  • Providing a letter from the software vendor stating that the software release has been reviewed and is acceptable. This method has on occasion been rejected. We do not use this method any more.
  • Proving that the program used can provide the same results as Appendix L of the VIII-1 code book for a shell, a head and a nozzle. Appendix L does not exist any more, being moved to PTB-4 “ASME Section VIII – Division 1 Example Problem Manual”. This would not be a problem except that the auditor wants validation on the actual vessel being built. We do not use this method any more.
  • Providing no validation set at all, sometimes the validation is not requested. Many auditors will not ask for validation, however if they do, then providing the calculations becomes a rush job. Not recommended as this does not meet the requirements of the ASME guide. Once we understood where the requirement to provide validation calculations came form, we stopped using this method.

As of 2014, our current method is: run the code calculations in a computer program – (at this time we use Design Calcs for audit vessels but the actual program used does not matter). Run hand calculations to validate one head, the shell and one nozzle. We have had no issues with this approach. Recommended – see Hand Calculations for our take on how to prepare a successful set of validation calculations. The hand calculations should agree line for line, number for number with the calculation set, and they should reference back to the code book to show that appropriate formulas are being used.

SolidWorks

The drawing is created in SolidWorks. By default, we use SolidWorks to create vessel drawings unless AutoCAD is specified. The drawing provides all required information to order material and fabricate without referring to the calculation set – a standard in pressure vessel drawings. Solid modelling is a very useful tool in the design of vessels and other pressurized equipment.

Looking for Help?

Call us if you are looking for assistance on your next audit. We can provide a quote on the drawings, calculations and verification set. Sorry, we do not provide assistance in writing and implementing QC manuals.

Downloads (pdf format):

  • Audit Vessel Design Calculations These calculations are not to the latests code and addenda, contact us for a quote if you need up to date calculations for an audit.
  • Audit Vessel Drawing Likewise, this drawing needs to be updated to the latest code and addenda for an audit.