December 2017

Environment and Safety

Address damage mechanism reviews in a process hazard analysis

Performing damage mechanism reviews (DMRs) to determine credible degradation modes and susceptibilities of processing equipment has become an important step in developing effective mechanical integrity plans in the refining, chemical processing and related industries.

Performing damage mechanism reviews (DMRs) to determine credible degradation modes and susceptibilities of processing equipment has become an important step in developing effective mechanical integrity plans in the refining, chemical processing and related industries.

DMRs aid in formulating inspection plans to mitigate risk from loss of containment and/or unplanned outages, and are the subject of the corresponding API Recommended Practice (RP) 571. Additionally, the California Occupational Safety and Health Administration (Cal/OSHA) has revised its regulation for Process Safety Management (PSM) for petroleum refineries (Cal/OSHA PSM regulation), which became effective on October 1, 2017.1 The revised Cal/OSHA PSM regulation requires that (1) DMRs be performed, and (2) process hazard analyses (PHAs) address DMR reports that are applicable to the process unit being analyzed.

A refinery PHA team that is subject to this regulation must now review the results of and/or consult with individuals with expertise in damage mechanisms when performing the review of applicable DMR reports. To help address this requirement, the primary PHA methodology [e.g., hazard and operability study (HAZOP), what-if, etc.] can be supplemented with a checklist to help the PHA team identify DMR issues that might be applicable to the process unit.

New DMR requirements

In 2012, the California Interagency Working Group on Refinery Safety was formed as a response to recent refinery and process industry accidents to examine ways to improve public and worker safety at petroleum refineries. The objective of the group was to identify means of improving both refinery and agency performances with regard to pinpointing regulatory gaps, areas of overlap and areas in need of improved coordination. The Interagency Group published its findings in February 2014 in the report, “Improving public and worker safety at oil refineries.”

FIG. 1. Results of a DMR should be considered when implementing other related PSM elements.
FIG. 1. Results of a DMR should be considered when implementing other related PSM elements.

This study resulted in changes to the accident prevention and process safety requirements, as they apply to refineries in California. The proposed changes to the Cal/OSHA PSM regulation became effective on October 1, 2017.

Requiring the performance of a DMR is one of the new elements in the Cal/OSHA PSM regulation. In addition, the results of a DMR should be a consideration when implementing several other related PSM elements, as shown in FIG. 1. While many companies already conduct damage mechanism assessments and DMRs—and have done so for quite some time—this is the first instance in which specific regulations have addressed this topic as an explicit requirement of a PSM program.

DMR definition

The Cal/OSHA PSM regulation defines a damage mechanism as a mechanical, chemical, physical or other process that results in equipment degradation.

A DMR is an analysis process designed to determine credible damage mechanism susceptibilities of fixed equipment. Such equipment includes process vessels, heat exchangers, process piping, storage tanks and process heaters. The analysis process is performed circuit-by-circuit by a multidisciplinary team that typically includes operations, maintenance, mechanical, materials and inspection personnel. The results from a DMR can be used to formulate inspection plans to mitigate the risk of a loss of containment and/or unplanned outages.

DMR process

What are the regulatory agencies’ expectations as to what should occur in a DMR? One expectation is gaining a better understanding of the process/operating conditions and the potential resulting damage mechanisms. A DMR is often needed to establish and maintain a robust mechanical integrity program.2,3,4,5,6

Understanding damage mechanisms is important for several reasons, including:

  • Selecting appropriate equipment inspection intervals/due dates, locations and techniques
  • Making decisions (e.g., modifications to a process, materials selection, monitoring frequencies) that can help eliminate or reduce the probability of a specific damage mechanism
  • Determining the types of failures that could occur.
FIG. 2. Activities during the DMR process.
FIG. 2. Activities during the DMR process.

FIG. 2 illustrates the typical activities carried out during the DMR process, including conducting, documenting and subsequently using the results from a DMR. To understand the new Cal/OSHA PSM regulation, refiners should assess their own previous experience with the DMR process, as well as consider industry-wide processes, applicable standards, codes and practices, as they relate to mechanical integrity.

Applying the results of a DMR in a PHA

According to the Cal/OSHA PSM regulation, a PHA conducted to meet that regulation now requires consultation with personnel with expertise in damage mechanisms during PHA meeting sessions. The DMR report serves as additional process safety information for reference during the PHA.

To address this requirement, the primary PHA methodology (e.g., HAZOP and/or what-if analysis) may be supplemented with a DMR-specific checklist to help the PHA team identify hazardous scenarios, while considering the results of any DMR report(s) applicable to the process unit.

The checklist discussion during a PHA can serve as an effective transfer of knowledge of unit-specific damage mechanisms to unit personnel. It should be noted that some damage mechanisms may be identified using the primary hazard evaluation technique (HAZOP and/or what-if analysis) during the PHA. However, supplementing the primary hazard evaluation with a specific checklist allows the PHA team to address damage mechanisms in a systematic fashion to confirm more in-depth coverage than that afforded by the primary analysis techniques alone.

The checklist approach also helps the PHA team discuss the contents of the DMR report that has been prepared for the process unit, and communicate how the damage mechanisms are being managed by the mechanical integrity group for the process unit. The checklist can also guide the discussion of hazards and potential major incidents associated with any identified damage mechanisms.

Checklist contents

The contents of the checklist include a set of questions that allows the PHA team to confirm that the DMR requirements of Cal/OSHA’s regulation (as they apply to the PHA element) are met, together with questions that deal with the specific damage mechanisms known to occur in petroleum refineries. The questions are related to specific types of damage mechanisms (e.g., high temperature, low-temperature corrosion and stress corrosion cracking, external damage and mechanical damage, among others) and include questions developed from industry standards, as well as incidents related to mechanical integrity issues.2,7,8

The checklist in TABLE 1 was created to include topic-specific items and questions to help a PHA team leader elicit responses from the team. The purpose of the questions is to allow a PHA team to brainstorm and discuss the DMR that has been prepared for the process unit being analyzed, as well as to confirm that the report was prepared to include damage mechanisms applicable for all potential operating modes (e.g., normal startup and shutdown). This scenario is similar to a PHA team using a facility siting checklist in a PHA to help identify any facility siting issues, while considering the results of any separate facility siting study report conducted for the process unit (per API RP 752 and/or API RP 753).9,10

Potential responses to the questions could include an acknowledgement that the PHA team understands which specific damage mechanisms may be present in the process unit, and a discussion of how the damage mechanisms are managed (i.e., inspection programs, defined integrity operating windows, etc.). If a corrosion mechanism listed in the checklist is not present in the process unit being analyzed, the team can respond by indicating that it is not applicable.

The checklist discussion may also help identify other damage mechanisms that may not have been identified during preparation of the DMR report that could occur from a process parameter deviation (e.g., flow, temperature, pressure). The discussion can also verify whether mechanical integrity plans are robust and have taken into consideration any process changes identified by the PHA team.

Supporting the PHA framework

A PHA team can use this checklist approach to help efficiently identify DMR issues. These issues include:

  • Identifying and demonstrating that known corrosion and damage mechanisms are understood and controlled
  • Ensuring that a DMR report appropriately documents applicable damage mechanisms to the process unit
  • Confirming that a DMR would be performed for incident investigations where a damage mechanism is identified as a contributing factor.

Although conducting DMRs and incorporating their results into PHAs and other elements of a PSM framework are not required by most regulatory agencies, state regulators in California require them for refineries. As the petroleum industry continues to recognize the value of conducting and documenting DMRs (per guidance in API RP 571) to enhance mechanical integrity programs and mitigate the risk of loss of containment events, the results of these DMRs11 can provide additional relevant information for assisting PHA review teams in identifying potential hazardous scenarios for processes. HP

NOTES

This article was adapted from the technical paper, “Effectively addressing the results of damage mechanism reviews in a process hazard analysis: A checklist approach,” which was presented at AIChE’s 13th Global Congress on Process Safety in March 2017. For more information, and to receive a copy of the full checklist, visit ABS-Group.com/knowledge-center/Insights.

LITERATURE CITED

  1. Title 8, Div. 1, Chapter 4, Subchapter 7, General Industry Safety Orders Group 16, “Control of hazardous substances Article 109, Hazardous substances and processes, §5189.1,” Process Safety Management for Petroleum Refineries (proposed regulation), filed with the Secretary of State on July 27, 2017.
  2. “Materials resistant to sulfide stress cracking in corrosive petroleum refining environments,” National Association of Corrosion Engineers (NACE) Standard MR0103-2003, Houston, Texas.
  3. “Pressure vessel inspection code: In-service inspection, rating, repair and alteration,” API 510, 10th Ed., May 2014.
  4. “Piping inspection code: In-service inspection, repair and alteration of piping systems,” API 570, 4th Ed., February 2016.
  5. “Risk-based inspection,” API RP 580, 3rd Ed., February 2016.
  6. “Risk-based inspection methodology,” API RP 581, 3rd Ed., April 2016.
  7. “Corrosion control documents, downstream segment,” American Petroleum Institute (API) Recommended Practice 970, proposed 1st Ed., March 2016.
  8. “Course 110: Process hazard analysis leadership training, mechanical integrity issues checklist,” ABSG Consulting Inc. (ABS Group).
  9. “Management of hazards associated with location of process plant permanent buildings,” API RP 752, 3rd Ed., December 2009.
  10. “Management of hazards associated with location of process plant portable buildings,” API RP 753, 1st Ed., June 2007.
  11. “Damage mechanisms affecting fixed equipment in the refining industry, downstream segment,” API Recommended Practice 571, 2nd Ed., April 2011.

The Authors

Related Articles

From the Archive

Comments

Comments

{{ error }}
{{ comment.comment.Name }} • {{ comment.timeAgo }}
{{ comment.comment.Text }}