Inspectioneering Journal

Utilizing On-stream Inspection Techniques in the Petroleum/Petrochemical Industry in Lieu of Internal and Turnaround Inspections

By John Reynolds, Principal Consultant at Intertek, and Mark Bell, Senior Asset Integrity Consultant at Ethos Mechanical Integrity Solutions. This article appears in the May/June 1999 issue of Inspectioneering Journal.

This three-part article describes some of the advanced on-stream inspection (OSI) methods available for use in inspection of pressure equipment in the petroleum and petrochemical industry. These methods can be used, under the right circumstances, to supplement or in lieu of invasive and turnaround inspections, usually at much lower cost. Cost savings associated with using OSI techniques in lieu of internal inspections may include lower total inspection costs, lower turnaround costs, avoiding lost production opportunities, and avoiding vessel cleaning and decontamination costs. On-stream inspection also avoids the safety hazards associated with confined space entry of vessels. However, to achieve these savings and benefits, and still maintain high levels of pressure equipment integrity, the owner-user must understand the technologies in order to intelligently select, apply and interpret the results of these non- destructive evaluation (NDE) methods.

In part one of the article, we will cover some pitfalls and precautions when using OSI techniques in lieu of internal inspections. Parts 2 and 3 of the article provide some information on the main types of OSI techniques available, along with their advantages, disadvantages and relative costs.


There has been significant progress in recent years in commercially available NDE technologies for on-stream inspection (OSI), however, owner- users often do not fully understand many of these “black box” technologies. This lack of understanding can lead to misapplication, false confidence, high false call rates, wasted money, poor results, and other problems. When engineers and inspectors have the right knowledge and information to properly apply these advanced OSI methods, the cost savings and benefits can be considerable.

This three-part article briefly outlines some of the commercially available, OSI NDE technologies that field engineers and inspectors can use to inspect pressure equipment (vessels and piping) while it is still in service. Another important purpose is to highlight some of the important issues that must be addressed and pitfalls that need to be avoided. This three-part article is not meant to provide the reader with a lot of technical details about each methodology. Technical details are left for the many other papers on each specific OSI NDE method that are usually seen in the Inspectioneering Journal.

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