ExVeritas has a team of skilled engineers with a wealth of experience that can facilitate PHAs such as HAZOP, HAZID and LOPA reviews
HAZOP
A Hazard and Operability (HAZOP) study is used to review the design and operating procedures to identify any hazards or obstacles to operability which could arise.
Typically this is undertaken by reviewing a drawing, usually a piping and instrumentation diagram (P&ID), using a series of guide words and deviations of those words to assess how the piping can have problems regarding hazards – and therefore ‘risks’ – and operational (operability) issues. These can then be eliminated at a stage prior to the plant being built.
Applicable standards
- IEC 61882: Hazard and operability studies
- OSHA – Process Safety Management (PSM) standard (29 CFR 1910.119)
- CISHEC/8906/1000, CIA, Guide to Hazard and Operability Studies – Chemical Industry Association
HAZID
Similar to a HAZOP – A HAZID or Hazard Identification study is to identify potential high hazard events based on a top-down approach, define the severity of the hazards, record preventative measures in place and identify further measures as necessary based on likelihood of hazard occurrence to ensure that the risk can be reduced to a tolerable level.
This method considers a wide range of hazards and aspects of a project, including design intent, construction, operation, and decommissioning, it aims to uncover hazards that may not be obvious or that may have been overlooked in the early stages of a project.
Once a basic process is established and process flow diagrams (PFD’s) are available, but before piping and instrumentation diagrams (P&ID’s), the HAZID is most useful. This is especially important in highly complex projects where there may be a lot of interdependent systems and processes that need to be considered.
LOPA
Layer of Protection Analysis (LOPA) is a semi-quantitative technique and provides an ‘order of magnitude estimate of risk’. High risk scenarios identified during a HAZOP are assessed by the LOPA method.
The unmitigated severity for all identified hazardous events are reviewed, and the likelihood of their occurrence will be determined, taking into account existing independent protection layers and initiating events. Where deemed necessary, a safety instrumented function (SIF) shall be allocated with an appropriate safety integrity level (SIL).
Applicable standards
- BS EN 61508 and 61511
- OSHA – Process Safety Management (PSM) standard (29 CFR 1910.119)
- UK COMAH Regulations 4