Risk Management Professionals Hazard Operability Studies

The HAZOP Guideword method, used in conjunction with key process parameters (to define deviations from design or operations), prompts the Team to identify possible causes and potential consequences of deviations from anticipated design and operation configurations. For example, adding the guideword “NO” to the parameter “FLOW” to get the deviation "NO FLOW" would prompt the leader to ask the Team, "What causes could result in no flow in this node or line segment?" The potential hazard scenarios that include possible "Causes" and potential "Consequences" are documented in the report worksheets using the PHAPlus™ Software (data files compatible with MS Access2000). During the study session, the PHAPlus worksheets will be projected on a screen so that the entire Team, can view the information being documented. The possible "Safeguards" in place to reduce the risk associated with the specific cause/consequence scenario are then discussed and documented. For scenarios involving significant potential risk, “Recommendations" are documented if the Team believes they may further reduce risk or improve operability.

By design, the guideword approach often results in redundancies, because many possible "Cause/Consequence" scenarios can be identified from an evaluation of two or more deviations. As an example, a valve failing open might cause “MORE FLOW” in a line segment within the portion of the system being studied. Later in the study, as the PHA Team moves on to “HIGH PRESSURE,” they may determine that the same valve failing open would be a cause for “HIGH PRESSURE.” Thus, the valve failing open is a cause of both deviations. In such an instance, the “Cause/Consequence” scenario is fully developed and documented under the first deviation for which it is identified and the second deviation will refer back to the first scenario.

The specific steps of the HAZOP methodology used in the study are:

Choose a section of the system to study (node) and highlight it on the Piping and Instrumentation Diagrams (P&IDs).Apply a design or operations deviation (guide word + parameter) including the intention for the parameter.Identify possible causes of deviation from the intention.For credible causes, characterize the worst credible set of consequences.Identify existing safeguards.Qualitatively assess the scenario likelihood, severity, and risk (using a risk-ranking matrix).

If appropriate, identify meaningful recommendation(s) to address potential hazard or operability issues

This process is usually repeated for each deviation and node until the entire process has been analyzed.

The HAZOP technique is used to analyze, node-by-node, the specific process equipment. However, this technique may not document all the general safety issues that affect the health and safety of the workplace employee or local population. What-If/Checklists of additional issues are discussed throughout the study to ensure that these general topics are covered.