Inspectioneering Journal

An Engineering Critical Assessment of a Service-Damaged Pressure Vessel

By Dr. John Bowker at Metals Technology Laboratories, CANMET, and Russell Orr at Metals Technologies Laboratories, CANMET. This article appears in the July/August 1995 issue of Inspectioneering Journal.

Petrochemical and energy utility industries require a methodology which will allow them and the governing regulatory authorities to make technical and financially sound decisions for the repair or replacement of pressure vessels which suffer damage during service. ECA (Engineering Critical Assessment) procedures, which are based on the principles of fracture mechanics, can be used to assess the risk of operation of a damaged vessel by predicting the amount of damage which can lead to premature failure, and thus determine the need for repair or replacement of the vessel. The total cost to repair or replace a damaged vessel can be high not only in terms of economics of repair but also that of loss of production and safety of workers and the public. Considerable savings can thus be realized if unscheduled shutdowns can be avoided. Valid ECA procedures would allow both the owners and insurance underwriters of pressure vessels to assess the integrity of the vessel, thereby avoiding costly and unnecessary repairs at the same time reducing the possibility of failure during service to an acceptable low level.

In Canada, a co-operative program between Metal Technology Laboratories of CANMET, a branch of Natural Resources Canada and a number of representative organizations from the petroleum, gas transmission and electrical utility industries, as listed in Table 1, was initiated to investigate the validity of ECA of a service damaged vessel. The vessel, a compressor knock-out drum, shown schematically in Fig 1, was selected as a typical example of pressure vessels being currently used in sour service in petrochemical plants. As input to the ECA, non-destructive inspection was performed in order to measure the length and depth of flaws in the pressure vessel, using magnetic particle inspection (MPI) and manual ultrasonic inspection. Two automated ultrasonic techniques were used in selected locations to provide additional data. Table 2 presents the depths of the major flaws. Based on the results of the initial MPI and manual ultrasonic inspection an area of the shell free of flaws was removed to provide test specimens for material property evaluation. A replacement patch was subsequently welded into the vessel. A hydrostatic burst test, monitored with acoustic emission, was carried out to confirm the assessment.

This content is available to registered users and subscribers

Register today to unlock this article for free.

Create your free account and get access to:

  • Unlock one premium article of your choosing per month
  • Exclusive online content, videos, and downloads
  • Insightful and actionable webinars
Interested in unlimited access? VIEW OUR SUBSCRIPTION OPTIONS

Current subscribers and registered users can log in now.

Comments and Discussion

There are no comments yet.

Add a Comment

Please log in or register to participate in comments and discussions.

Inspectioneering Journal

Explore over 20 years of articles written by our team of subject matter experts.

Company Directory

Find relevant products, services, and technologies.

Training Solutions

Improve your skills in key mechanical integrity subjects.

Case Studies

Learn from the experience of others in the industry.


Inspectioneering's index of mechanical integrity topics – built by you.

Industry News

Stay up-to-date with the latest inspection and asset integrity management news.


Read short articles and insights authored by industry experts.

Expert Interviews

Inspectioneering's archive of interviews with industry subject matter experts.

Event Calendar

Find upcoming conferences, training sessions, online events, and more.


Downloadable eBooks, Asset Intelligence Reports, checklists, white papers, and more.

Videos & Webinars

Watch educational and informative videos directly related to your profession.


Commonly used asset integrity management and inspection acronyms.