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Questions of the Week

Primatech posts weekly questions relating to various aspects of safety, security and risk on the home page of our website together with answers to provide visitors with the opportunity to test and improve their knowledge of these subjects. This page contains questions and answers that have appeared in previous weeks.

How can failure rates be determined for initiating events in LOPA?

Generic failure data can be used from references such as the book, "Initiating Events and IPLs in LOPA". However, site-specific failure rate data from individual facilities are preferable as they apply to actual operating conditions.

Is it acceptable for LOPA team leaders to pre-populate LOPA worksheets with entries for review by the team?

Usually, scenario information including causes, consequences, and safeguards is already established by the PHA team and that information can be transferred into LOPA worksheets prior to conducting the LOPA study. The initiating event frequency, enabler multipliers, and probability of failure on demand (PFD) values should be developed in conjunction with the LOPA team and not be pre-populated prior to the LOPA.

Should I have to use same PHA method for revalidation of a study that was used in the previous study?

If the earlier PHA is to be replaced, then a different method could be used. If the earlier PHA is being revised, a change from the previous PHA may not be practical. Changing methods will need to be justified but switching to a more sophisticated method would be easier to justify. However, the process safety regulations are performance-based so the choice is whatever is appropriate and justifiable.

Should safeguards be combined in the PHA worksheet when evaluating hazard scenarios during a PHA?

Although there are no specific regulatory requirements for listing safeguards individually in PHA worksheets, the best practice is to keep safeguards separate. A single cause may have multiple different consequences and the safeguards listed may not apply to every consequence. Thus, identifying applicable safeguards for individual consequences is difficult. Also, combining safeguards makes risk ranking and the identification of appropriate recommendations more difficult.

Of the four types of human failure (omission, commission, extraneous acts, and violations), which types are most likely to be overlooked by a PHA team?

Omission errors and commission errors are the easiest human failures to address because they are the most obvious. Procedures spell out specific actions to be taken and those actions either may not be performed or may be performed incorrectly.

Extraneous acts are more difficult to address because of the numerous possibilities outside those actions required. Credible violations of procedures are easier to envision, such as bypassing a nuisance alarm by an operator.

What is a competency management system (CMS)?

A management system that organizes and integrates all the activities needed to manage competency properly. It helps in ensuring competent performance by individuals and groups of people.

What is meant by process safety competency?

The ability to perform work activities to a relevant standard, as necessary to ensure process safety and prevent major accidents. Competency requires individuals to possess various attributes such as appropriate knowledge, skills, experience, behaviors and attitudes.

What is a safety culture assessment?

A survey to help an organization identify pervasive attitudes or beliefs regarding risk tolerance in the workplace. It is conducted to provide a basis for improving the safety culture.

Does a PHA scribe need to have a technical background?

Ideally, a scribe should be technically-oriented. They need a knowledge of processes in order to understand the discussions that occur during PHA studies. Also, they need to understand the process that is followed in performing a PHA study and be familiar with the technical terms and acronyms used. Sometimes, the role is filled by a junior engineer, although administrative personnel with appropriate experience also have acted successfully as scribes.

What is meant by safety culture?

Values, beliefs, perceptions and attitudes that shape behaviors exhibited towards safety within an organization. Put simply, factors that influence how people in an organization behave with respect to safety when no one is watching.

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