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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.

Why should I perform LOPA?

There are multiple reasons including:

  • Meet regulatory requirements or expectations
  • Comply with industry standards
  • Apply good industry practices
  • Avoid competitive disadvantages
  • Focus resources on the most important safeguards
  • Help manage liabilities from process risks

What information do I need to perform a LOPA study?

Four key pieces of information are needed:

  • Descriptions of hazard scenarios
  • Failure rate data for initiating event frequencies, IPL PFDs, and enabler multipliers
  • Estimates of severities of scenario consequences
  • Risk tolerance criteria for receptors of concern

Can operability be excluded from the scope of HAZOP studies?

Not easily. Often, operability scenarios cannot be recognized until much of the work of scenario identification has been completed.

Does a PHA scribe need to have a technical background?

Not necessarily, although it is advantageous. Scribes must be proficient with the means of recording studies, typically a software tool, and understand the technical terms used in PHA and to describe the process.

Does the geographical location of a facility affect the risk of the facility?

Yes, weather events that vary by location, such as flooding, tornadoes, hurricanes, and lightning, can cause process safety incidents.

How long should PHA documentation be kept?

OHSA's PSM standard requires that process hazard analyses, updates and revalidations, and documented resolutions of recommendations be retained for the life of the process.

Is it acceptable for a Revalidation PHA only to review scenarios for parts of the process that have changed?

No, a change in one part of the process could affect other parts of the process. The possible impact of changes should be evaluated across the entire process, not just the area where they were made. It is important to review every scenario in a PHA to ensure that any changes made do not have unrecognized consequences elsewhere in the process.

How does interconnection of utilities, steam, and electricity apply with regard to a covered process?

Utilities that serve a covered process are considered part of the process where they can have an impact on or affect a release of the highly hazardous chemical in the process. Utility system failure such as loss of instrument air, heating and cooling mediums, and electric power have been major causes of upset conditions in chemical processes. These utility systems are subject to all of the provisions of the PSM standard until such point where a failure in a component of a system can no longer affect a potential release of a covered chemical, or where the utility leaves the control of the employer.

Are railroad cars and tractor trailers containing more than the threshold quantity of a highly hazardous chemical and which remain in a facility for a period of time covered under 1910.119?

Commercial railroad tank cars and commercial tank motor vehicles (CTMVs) when remaining on a worksite and used to store threshold quantities or greater amounts of specified HHCs are covered by the PSM standard. They are covered by the PSM standard to the extent that they are not covered another regulatory authority. For example, the Hazardous Material Regulations of the Department of Transportation (DOT) (see 49 CFR Subchapter C and particularly, Part 177-Carriage by Public Highway) cover CTMVs. These DOT regulations cover cargo tank design, construction, maintenance (including repairs) and certain operations of CTMVs. Generally speaking if the cars are considered "in transit" by DOT, OSHA will defer jurisdiction to DOT.

Does OSHA require the use a risk matrix when conducting a PHA?

OSHA 1910.119 is a performance-oriented standard and does not require use of a risk matrix. However, in a letter of interpretation, OSHA suggested that the use of a risk matrix would meet the requirement in the standard that PHA address, "A qualitative evaluation of a range of the possible safety and health effects of failure of controls on employees in the workplace".