Process Safety Tools LOPA, Quantitative and Qualitative Risk Assessment

Failure Mode & Effect Analysis is based on:
• How severe is the effect on the customer?
• How frequent is the cause likely to occur?
• How probable is detection of the cause?
• RPN = Risk priority number in order to rank concerns

• The Structured What-If Technique (SWIFT) is a systematic team-oriented technique for hazard identification.
• Developed to identify hazards in chemical process plants. It addresses systems and procedures at a high level.
• SWIFT considers deviations from normal operations identified by brainstorming, with questions beginning “What if…?” or “How could…?”. The brainstorming is supported by checklists to help avoid overlooking hazards.

FTA is a top-down approach for analysing pre-event failures with systems in development, beginning with the top event (the potential failure), then determining all the ways it can occur. Similarly, post-event failures can be analysed to find the root cause of the failure.

Event tree analysis (ETA) is an analysis technique for identifying and evaluating the sequence of events in a potential accident scenario following the occurrence of an initiating event
The objective of ETA is to determine whether the initiating event will develop into a serious accident or if the event is sufficiently controlled by the safety systems and procedures implemented in the system design.

Cause-consequence analysis [Nielson 1975] combines the hazard identification and quantification methodology of Fault Tree Analysis with Event Tree Analysis. The technique can be scheduled in six stages:
1) Select the event or type of accident
2) Identify the safety functions that influence the course of the incident resulting from the event
3) Develop the accident path resulting from the event (ETA Study)
4) Develop the initiating event and the safety function failure event to determine their basic causes (FTA Study)
5) Evaluate the accident sequence minimal cut sets
6) Document the results and detail possible recommendations

Investigates the hazards related to the maintenance of plant items. The technique can be used to identify hazards, or poor design leading to hazards, during the maintenance of the various plant items. With MOP study, each process item is analysed by asking the following questions:
– Can the equipment be properly isolated for maintenance?
– Can the equipment be properly drained for maintenance?
– Are there plans to deal with mechanical failure of equipment?
– Are there plans for critical spare parts to be available?

Task analysis is a systematic method for analysing a task in terms of its goals, operations and plans. The task is a set of operations/actions required to achieve a set goal.
This technique takes into consideration the following data:
– The general operating procedure including job descriptions, process diagrams, and operating manual.
– Output from a hazard review.
– Plant records.
– A number of interviews with people who have experience of the process and plant.
– Observations of the general operation of the plant.

Task Analysis tries also to address some relevant questions as:
– What actions do the operators perform?
– How do operators respond to different cues in the environment?
– What errors might be made and deviations caused in plant operations?
– How any errors might be recovered, or any deviations be controlled?
– How do operators plan their actions?

PHEA allows complex tasks to be analysed in detail. The technique applies hierarchical task analysis to split the complex tasks into component parts. Assesses the consequences of the hazards. The technique examines the consequences of the human errors if they occur within the process.
PHEA analyses the tasks systematically considering:
– Task type
– Error type
– Task description
– Consequences
– Recovery
– Error reduction strategy

Our professionals will also carry out other quantitative and qualitative techniques such as:
– Layer of Protection Analysis (LOPA) Study
– Consequential Modelling Study
– Checklists
– Safety Audit