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Keywords:

  • deferral;
  • mechanical integrity;
  • extension;
  • delay

Abstract

The days of “frequent” annual maintenance outages where mechanical integrity (MI) testing and inspections are performed are gone. The new reality of modern industrial gas and chemical plant operation includes increasing durations between scheduled maintenance down time that have sometimes reached 5 years and beyond. In addition, in the interest of keeping initial capital cost under control, there is constant pressure to restrict redundant architectures and systems intended to allow maintenance while running the plant.

Safety systems that have the potential for unrevealed failures lead to required plant down times to properly test and inspect those systems. Because our customers expect high reliability with long runs between maintenance outages it is prudent to design our facilities and MI plans to meet the agreed commercial strategy. However, unforeseen events can cause delays in maintenance outages and thus our window to complete mandatory MI activities. Air Products' process for reviewing the consequence and likelihood of these delays allows appropriate action to be taken to ensure continued safe operation while complying with customer needs to reschedule downtime windows to the greatest extent possible.

This article outlines the policy used to review and manage the effects of inspection and test delays on facility risk. The hazard review process is administered and documented through the company's existing management of change process. The review itself is handled using a team with diverse technical expertise that can uncover and address key factors affecting safety. Levels of approval are based on the expected length of the planned delay. Duration of the extension (planned delays) dictates the level of technical reviews and provides guidance as to whether qualitative or quantitative techniques are appropriate. In either case, mitigation techniques may be used to temporarily manage the increased level of risk associated with the inspection or test delay.

The implementation of this recommended process is challenging as the plant culture migrates from one of local decision and control to one of understanding the multidisciplinary safety impact these delays create. The preferred solution is always to find a way to perform the task as planned or by using alternate “on stream” inspection methods without requiring an extension review. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009