Better PSM Metrics

• By Tim Overton, Scott Berger
• Apr 15, 2008

The BP US Refineries Independent Safety Review Panel (“Baker Panel”) and the U.S. Chemical Safety and Hazard Investigation Board both recommended improved industry-wide process safety metrics in their final reports dealing with the 2005 explosion at the BP Texas City, Texas, refinery. This has also been a subject of frequent discussions among process safety organizations such as the Center for Chemical Process Safety (CCPS), as well as magazine articles and other forums.

Individual companies and some trade associations had defined metrics, but a standardized set of metrics used by the majority of companies and trade associations had not been implemented. In 2006, CCPS formed a committee to publish a guideline defining uniform metrics that could serve as a global standard. That committee has recently published recommendations for leading and lagging metrics of PSM performance at www.aiche.org/ccps/ metrics/index.aspx.

This article summarizes the recommendations and explains the utility of the metrics to better manage PSM. The ultimate objective of this committee is to complete a guideline book originally authorized by CCPS, so that additional information and guidance is available to individual companies on how to better use metrics to improve their process safety performance. The recently published document is intended to propose an industry-wide lagging metric and suggested leading and other metrics for individual companies’ consideration. The development of these industry-wide recommendations was led by CCPS in cooperation with numerous international chemical and petroleum trade associations, regulatory agencies, and other stakeholder organization

CCPS was established in 1985 by the American Institute of Chemical Engineers (AIChE) for the purpose of helping industry avoid or mitigate catastrophic chemical accidents. More than 100 corporate members around the world drive the activities of CCPS, which strongly recommends that companies around the globe adopt and implement these recommendations.

The Need for Metrics
Essential elements of any management system are a set of guiding measures to assist in shaping appropriate performance and a process against which you can measure performance. Therefore, to continuously improve process safety performance, it is essential that companies in the process industries implement effective management controls, including the adoption of leading and lagging process safety metrics. The key performance indicators and associated metrics should reflect the goals of the organization and indicate exemplary performance.

The CCPS document describes three types of metrics:

1. “Lagging” metrics: a retrospective set of metrics that are based on incidents that meet the threshold of severity that should be reported as part of the industrywide process safety metric.

2. “Leading” metrics: a forwardlooking set of metrics that indicate the performance of the key work processes, operating discipline, and/or layers of protection that prevent incidents.

3. “Near miss” and other internal lagging metrics: describing less-severe incidents (i.e., below the threshold for inclusion in the industry lagging metric) or unsafe conditions that activated one or more layers of protection. Although these events are actual events (i.e., a “lagging” metric), they are generally considered to be a good indicator of conditions that could ultimately lead to a severe incident.

Lagging Metrics
The CCPS document describes a set of definitions and metrics recommended as industry-wide lagging metrics. Lagging metrics allow for a company to determine trends and performance against pre-determined goals. While retrospective, they are valuable in allowing management to understand issues during their incipient stage, in the case of lagging metrics oriented toward smaller process safety incidents or near misses.

While companies may adopt a wide range of metrics oriented toward lesser incidents and benefit from documenting them, CCPS wanted to recommend a standard level of incidents, at a minimum, that balanced the benefits of standardized data collection while minimizing the burden on the whole of industry for the effort involved.

Process Safety Incident (PSI)
Essential to lagging metrics was the need for CCPS to define a process safety incident. This was possibly one of the more important aspects of the project, where strong collaboration between CCPS committee members, representatives from many trade associations, and external stakeholders was essential. For the purposes of the common industry-wide process safety lagging metrics, an incident is reported as a process safety incident if it meets all four of these criteria:

• Chemical or chemical process involvement
• Above minimum reporting threshold
• Location
• Acute release

Chemical or chemical process involvement
For an incident to satisfy the chemical or chemical process involvement criterion, a chemical or chemical process must have been directly involved in the damage caused. For this purpose, the term “process” is used broadly to include the equipment and technology needed for petrochemical production, including reactors, tanks, piping, boilers, cooling towers, refrigeration systems, etc. An incident with no direct chemical or process involvement (e.g., an office building fire, even if the office building is on a plant site) is not reportable.

An employee injury that occurs at a process location, but in which the process plays no direct part, is not reportable as a PSI (though it could be an OSHA reportable injury or another agency’s reportable injury).

Reporting thresholds
A release of material or energy from a chemical process qualifies as a threshold if it results in any of the three situations below:

1. An employee or contractor lost-time injury and/or fatality, or hospital admission and/or fatality of a third party (nonemployees/ contractor);

2. Fires or explosions resulting in $25,000 or more of direct cost to the company; or

3. An acute release of flammable, combustible, or toxic chemicals from the primary containment (i.e., vessel or pipe) greater than the chemical release threshold quantities described in Table 1 of the CCPS guidance (which includes hazardous material releases ranging from 5 to 2,000 kg, depending on hazard class), excluding releases to a properly designed and operating control device specifically designed for that event (e.g., flare, scrubber, or relief devices per API Standard 521 or equivalent).

For the purposes of applying these threshold values for “Flammable Gases/Vapors,” “Flammable Liquids,” and “Combustible Liquids,” the user may use either the definitions commonly used within the petroleum refining industry (based upon National Fire Protection Association, NFPA-30, definitions), the UN Dangerous Goods (Class 2, Div. 2.1 and Class 3), or the Harmonized System of Classification and Labeling of Chemicals (GHS), Chapters 2.2 and 2.6. These different methods classify materials in a similar manner; therefore, most flammable materials will fall into the same category regardless of the definitions used. Further information is provided in the CCPS document.

Lost-time injuries and fatality incidents
Lost-time injuries and fatality incidents that occur as a result of process-related loss of primary containment, fire, or explosion are those that fit into one of the following categories:
• Employee (lost time and/or fatality)
• Contractor and subcontractor (lost time and/or fatality)
• Third party (injury/illness resulting in hospital admission or fatality)

Location
Incident criteria were developed to limit the scope of the incidents documented from a physical location standpoint. An incident satisfies the location criteria if the incident occurs in production, distribution, storage, utilities, or pilot plants of a facility reporting metrics under these definitions. This includes tank farms, ancillary support areas (e.g., boiler houses and wastewater treatment plants), and distribution piping under control of the site.

All reportable incidents occurring at a location will be reported by the company that is responsible for operating that location. This applies to incidents that may occur in contractor work areas, as well as other incidents. At multi-party sites, the company that operates the unit where the incident initiated should record the incident and count it in its PSI metric.

Acute release
CCPS wanted to limit the events documented to a consistent criterion for time of the release. A “1-hour” rule applies for the purpose of the reporting under this metric—i.e., the release of material reaches or exceeds the reporting threshold in one hour or less. If a release does not exceed the TQ level over any one-hour period, it would not be treated as a PSI.

Process Safety Incident Severity
CCPS developed severity-level definitions for each consequence category for each process safety incident. This allows for a gradation of incident severity against standardized definitions. The criteria illustrate the comprehensive nature of the considerations for process safety incident consequences, with four levels ranging from minor to major and from issues including loss of reputation to loss of life.

The categories of incident consequences are safety/human health, fire or explosion (including overpressure), potential chemical impact, and community/ environment impact.

Rate Adjusted Metrics
Utilizing the definitions described above, a variety of rate-based metrics can be generated. These include:

A. Process Safety Total Incident Rate (PSTIR):

PSTIR =     Total PS incidents x 200,000                   
                  Total employee & contractor work hours

B. Process Safety Incident Severity Rate (PSISR) (i.e., severity-weighted process safety incident rate formula):

PSISR =    Total severity score for all PS incidents x 200,000
                  Total employee, contractor & subcontractor work hours

In determining this rate, 1 point is assigned for each Level 4 incident attribute, 3 points for each Level 3 attribute, 9 points for each Level 2 attribute, and 27 points for each Level 1 attribute, as shown in Figure 1. Theoretically, a PSI could be assigned a minimum of 1 point (i.e., the incident meets the attributes of a Level 4 incident in only one category) or a maximum of 108 points (i.e., the incident meets the attributes of a Level 1 incident in each of the four categories).

Leading Metrics
CCPS also published a number of potential leading metrics. If measured and monitored, data collected for leading metrics can give an early indication of deterioration in the effectiveness of these key safety systems and enable remedial action to be undertaken to restore the effectiveness of these key barriers before any loss-of-containment event takes place.

The safety systems for which leading metrics have been developed are:

• Maintenance of mechanical integrity;

• Action items follow-up;

• Management of change; and

• Process safety training and competency (and training competency assessment).

It is recommended that all companies adopt and implement leading process safety metrics around those four categories, plus “safety culture.” However, given the number of metrics defined, it may be impracticable to collect and report data for each category described in the CCPS document. Companies should identify which of these components are most important for ensuring the safety of their facilities and should select the most meaningful leading metrics from the examples provided. Other company-specific leading metrics may be defined, as well, if applicable.

These leading metrics recommendations will continue to be refined as the CCPS Metric Committee finalizes the Metric Guideline book in 2008. Enhancements or suggestions to these metrics are welcome.

References
1. CCPS, “Process Safety Leading and Lagging Metrics,” AIChE, New York, 2007.

This article originally appeared in the April 2008 issue of Occupational Health & Safety.