Engineering’Failures’–Lessons’in’Professional’Ethics’–ACase’Study ... ·...

Engineering Failures – Lessons in Professional Ethics – A Case Study

Outline of Presenta;on

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²  Basis for Professional Ethics ²  Laws RelaDng to Engineering Work ²  A Case Study -‐ Pipe Break Due to Relief Valve Cha6er ²  Summary of the Ethical Lessons for Engineers ²  Unexpected Technical Lessons for Engineers ²  Q&A period.


Basis for Professional Ethics

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²  The Ontario Professional Engineers Act h6p://www.ontario.ca/laws/statute/90p28

²  RegulaDon 941 -‐ Code of Ethics h6p://www.ontario.ca/laws/regulaDon/900941

²  PEO Professional Engineering PracDce Guidelines h6p://peo.on.ca/index.php/ci_id/22127/la_id/1.htm

²  Other PEO Guidelines are available as a free download at: h6p://peo.on.ca/index.php/ci_id/1834/la_id/1.htm


Laws Rela;ng to Engineering Work

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²  Ontario acts and associated regulaDons, visit: h6p://www.e-‐laws.gov.on.ca

²  Federal acts and associated regulaDons, visit: h6p://laws-‐lois.jusDce.gc.ca/eng/acts/

²  These are the laws that are more likely to get you into serious trouble if you don’t know your obligaDons. All are available as a free download.

²  Also remember that some of these laws require certain industry standards to be followed (eg: ASME piping and pressure vessel code, CSA electrical wiring code, etc.)

Engineering Failures – Lessons in Professional Ethics – A Case Study 5

Pipe Break Due to Relief Valve ChaEer


Power Plant Bleed Condenser


Pipe break occurred at elbow.


²  What happened ? ² Bleed condenser relief valve opens and cha6ers

causing inlet pipe high vibraDon. ² Relief valve inlet pipe breaks at elbow resulDng

in a small reactor loss of coolant accident. ² Operators correctly respond to cool reactor and

contain spill within containment. ² 4 reactors shut down -‐ 3 for 3 months pending

root cause invesDgaDon, 1 for 12 months unDl repairs completed.



²  What errors were made ? ² Design engineer located relief valve in the

wrong place -‐ too close to reactor face for periodic tesDng – radiaDon fields too high there.

² ConstrucDon engineer relocated relief valve – modified installaDon was dynamically unstable – asked for drawings to be reissued “as-‐built”.

² Design engineer did not check as-‐built drawings for compliance with ASME code’s dynamic stability requirements – assumed construcDon engineer had done so.



²  How Did the Errors Happen ? ² No procedural requirement for design engineer

approval of construcDon engineer’s “as-‐built” changes.

² ConstrucDon engineer not familiar with ASME code requirements for relief valve dynamic stability.

²  Inadequate supervisory review of ASME Boiler and Pressure Vessel Code -‐ SecDon III design changes.



²  What are the Ethical Issues Involved ? ² ConstrucDon engineer performed design work

he/she was not qualified to do and did not consult qualified engineer.

² Design engineer did not retain design responsibility for his/her own system – reissued but did not check as-‐built drawing.

²  IneffecDve supervisory review and approval of safety criDcal engineering work.



²  What were the safety and economic impacts of the errors ? ² Fortunately no one was hurt. ² Fortunately no radiaDon was released to the

environment – the spill was in the reactor building which is part of the radiological containment structures.

² The total repair and replacement power costs for the 4 unit outages was of the order of $100,000,000.



Summary of Ethical Lessons for Engineers

² Engineers should only do independent work where they are fully competent to do so.

² Engineers who are not yet fully competent should get help from more experienced engineers who are competent in the work that is being done.

² Engineers should review changes made to their work by others and confirm all codes and standards have been met.

² Supervising engineers must ensure effecDve independent review of safety criDcal engineering work either directly or by commissioning a competent senior engineer to do the independent review.


Unexpected Technical Lessons for Engineers

²  During the accident invesDgaDon and the associated computer modeling, simulaDon studies and laboratory validaDon tesDng we discovered two important design aspects of safety valves that manufacturers and uDliDes were not aware of.

²  Safety relief valves that have to handle 2-‐phase flow (eg: liquid and vapour in equilibrium) may NOT have a tradiDonal safety valve characterisDc and can fail to re-‐close at the reset pressure – this was an important discovery for toxic, flammable and radioacDve fluids. Laboratory tesDng at the idenDcal plant condiDons is essenDal if valve re-‐closure at the reset pressure is a safety requirement !

²  Safety relief valves cycle safely rather than cha6er destrucDvely if the natural frequency of the valves and the hydraulic natural frequency of the piping are sufficiently separated – this is the criDcal factor to prevent cha6er, NOT the distance between the safety relief valve and the vessel that the valve protects !


Unexpected Technical Lessons for Engineers


Ques;ons ?

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Notes: OSPE seminars can be downloaded at: hEp://www.ospe.on.ca/?page=pres_lib#peo Would you like to become a member of OSPE? Visit: hEp://www.ospe.on.ca/?page=JOIN University Engineering Students can join OSPE for free !

www.ospe.on.ca

4950 Yonge Street, Suite 502, Toronto ON M2N 6K1 Tel: 416-223-9961 • Toll Free: 1-866-763-1654

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