(81bf) Management of Process Safety Barriers – A Methodology to Guarantee the Integrity of the Protection Barriers | AIChE

(81bf) Management of Process Safety Barriers – A Methodology to Guarantee the Integrity of the Protection Barriers



Throughout the years the attention at the issues that involves the Process Safety Management in the chemical and petrochemical industry has been constantly raised. Unfortunately, much of this improvement has been associated with the occurrence of great accidents. Since the Flixborough accident, in England, 1974, that the industry has been alerted about the importance of a good Management of Change.

In the same way, the Bhopal accident, in India, 1984, was the first alert to the industries about the importance of the mechanical integrity of equipments and its protection systems. This message, specifically, appear that wasn't completely understood until 2007, when the investigation report of the Texas City accident, appointed imperfections in the functioning of high level alarms that could be able to alert the operators about the operational deviations in the startup procedure that further caused the death of 13 people.

Since this last event, became evident the necessity of a systematic to guarantee the integrity of the process safety barriers throughout the time, in association with the level of risk that each barrier was design to protect. In other words, became evident the necessity to check if the maintenance strategy adopted to keep the integrity and the availability of a high pressure interlock of a water tank (without potential to lead to a process accident) should be the same maintenance strategy adopted to a high pressure interlock of a hydrocarbon vessel (with potential to cause fire and/or explosions).

A Braskem Internal Audit indicated that many of the existents process safety barriers could be potentially unavailable. In this evaluation, between others, it was verified if:

a) Maintenance plans (including calibration tasks) for each one of the barriers were in place and has been attended; and

b) Criticality classification of the barriers (that is responsible for define the maintenance strategy that will be put in place for each one of them) were defined and adjusted at its level of risk. The highest criticality level indicates the necessity of continuous monitoring and the maintenance preventive plan existence, on other hand, the lowest criticality level only indicates the necessity of corrective maintenances.

The results presented by the internal audit promoted many discussions inside the industrial areas, which led it to the elaboration of a methodology, whose objective is to guarantee the integrity and the availability of the process safety barriers that are associates to the scenarios of intermediated risk. This article has as objective to present this methodology, whose initial information were taken from the Process Risk Assessment (ex.: HAZOP and QRA) and the Process Safety Internal Audit Reports.

In a second step, a list of Process Safety Barriers was populated for each plant, and a set of Key Performance Indicators were defined by a multidiscipline team that involves Process Engineering, Process Safety Engineering, Maintenance and Reliability Engineering. Regularly the analysis of the Key Performance Indicators has been done by the team and presented to the Plant Managers. In summary, this methodology involves a systemic evaluation over the existing strategy that had been applied for the barriers at some years and the development of its functional tests.

The benefits of the mechanical integrity can't be directly measured when we are dealing with safety, but is clear that this work perfectly fits with the principles and objective of the PSM.

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