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Preparing for an Intrusive Inspection

Updated: May 3, 2021

This article was originally posted on Thursday May 2, 2019

Preparation is the key to a successful equipment inspection

In the refining and petrochemical industry, operating companies must maintain and operate their equipment with the goal of not only producing a product that is profitable, and safe all while ensuring that the equipment/asset stays compliant with ever-changing jurisdictional regulations and requirements. The cost to ensure equipment performs optimally comes in many shapes and forms. It takes teams of people that have distinct roles and responsibilities and all of them must be carefully coordinated, including planning, operations, inspections, and maintenance.

Taking a comprehensive view of the key elements required for intrusive inspections can help. The proper planning will enable the company to arrive at an agreed-upon scope. Even with the best planning any number of challenges can arise during the execution phase. In order to effectively plan an internal inspection during the normal run to maintain operations, planning should begin several months prior to removing the equipment from service. Preparation is the key to success,

Information Gathering

Start with the equipment folder or the inspection file to become familiar with the equipment. This will give you the tools you need to make informed decisions once you’re inside the equipment. Items to research in the inspection file should include (but aren’t limited to):

  • Metallurgy, corrosion allowance, original design thickness, etc.

  • Changes in corrosion rates

  • Inconsistent thickness monitoring data (e.g., growths, etc.)

  • Short remaining life

  • Inspection due date

  • Recommendations and reports from previous inspections

Review Damage Mechanisms and Corrosion Reports

Inspectors have huge responsibilities, and none are more important than analyzing the inspection data provided and using that information to help focus the inspection and implement the level of inspection that may be required. It’s important to have a good understanding of API 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry, and associate which damage mechanisms may affect the equipment being inspected and where it could possibly take place. Each section of API 571 consists of a description of the damage mechanism, a list of materials that are susceptible to that mechanism, guidelines for detection methods for that mechanism, and measures that can be taken to prevent or mitigate that mechanism. Review the inspection history to familiarize yourself with these damage mechanisms, previous findings that were not addressed during the previous inspection, and any conditions that could accelerate corrosion or erosion. This will help you determine if any findings need to be addressed immediately or if it can be deferred until the next T/A. The ability to know when to submit a repair recommendation and when to forecast the repair separates inexperienced inspectors from seasoned professionals. This is knowledge that is acquired over many years. Next, review corrosion monitoring reports to identify areas of accelerated corrosion at TMLs that can be visually inspected during the internal inspection. Compare the historical thickness data so you can identify areas of accelerated wall loss. This will give you clues as to where corrosion may be found internally. Review the Corrosion Control Document (CCD), if available, and look at the P&IDs to see what equipment is upstream, then review the inspection history for that equipment. A CCD incorporates knowledge of the unit operation, equipment inspection histories, and the damage mechanisms specific to the unit. The CCD is somewhat comparable to API 571, but the CCD only lists the damage mechanisms which are specific to the equipment you are inspecting, along with other important process information. By familiarizing yourself with the process information found in the CCD, you will have a better understanding of where to look and what to look for.

Gather Your Tools

To perform, investigate, and document the inspection, you’ll need a number of items:

  • Flashlight (two flashlights is preferable – one for backup in case batteries die, you drop one, or the flashlight otherwise fails on you)

  • Inspection hammer for tightness testing of tray bolts, internal flanges, etc.

  • Pit gauge, tape measure, and a ruler

  • Scraper

  • Camera to document internal conditions

  • Tally book for note taking

  • Markers (choose low-chloride markers for stainless steel alloys)

  • Inspection mirror for hard-to-get-to areas

Talk with the operations team

The operations team can give you incredibly helpful information. While you’re getting permitted, have a conversation with them and ask pertinent questions about operating temperatures, pressures, process upsets, operations reliability issues, leaks on the run, and so on. This can give you an insider’s view that the inspection department might not otherwise have access to. Finally, it’s time to perform the inspection! Be safe, and document everything you see. Remember, you are the eyes and ears of the owner and users. They rely on your report and your findings to make an informative decision before moving on to the next step in the inspection plan.

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