Guest blog by David Hatch from Process Safety Integrity (PSI)
Don’t be alarmed – Understand the problem & undertake action
The UK Health & Safety Executive highlight that there is significant evidence to show that poorly designed alarm systems have contributed to major incidents and emphasize the need to provide accurate and timely detection and diagnostics to Operators.
Humans are a relatively weak protection measure and their role to prevent or mitigate hazardous events relies on an interaction with field and control room equipment to Detect (the problem), Diagnose (the cause) and Do (the right action) in response to an alarm.
Common vulnerabilities in this Hardware + Human relationship include (but are not limited to):
- Inappropriate or excessive alarms
- Inappropriate settings or priorities
- Insufficient training or guidance
- Insufficient time to respond
Operators who understand what has gone wrong and know what to do will be more effective. Therefore clear, consistent communication before and during alarm conditions is vital to minimize potential errors or omissions.
Abnormal Situation Management
Abnormal situations caused by process disturbance or plant distress can result in operations deviating from their normal state with potential effects on personnel, the environment and/or the asset.
Alarms are one of several potential protection layers and should direct the Operators attention towards conditions requiring timely assessment or action. Each alarm should alert, inform and guide, be useful and relevant to the Operator and should have a defined response.
Visualizing operations and abnormal situations with the bowtie method
A method that is becoming more widely used for visualizing normal operations, abnormal situations and how to manage them is the bowtie method. The bowtie method is a visualized way of doing risk assessments that enables you to get a good understanding of how your organization controls risks.
The graphical format provides a clear, concise framework to visualize complex risk & asset management information. It improves the understanding of people who design, maintain and operate the plant and represent hazards concisely and clearly to support decisions about alarms as appropriate protection measures.
The method facilitates the application of human factors and HMI design good practice and can dynamically represent alarms so that operators can quickly identify the cause of the problem, the highest priority consequence, and the appropriate response.
Bowties provide a framework for alarm management
The bowtie method can provide a framework to enhance key activities of a robust alarm management lifecycle:
- Identification: missing or unnecessary warnings
- Rationalization: appropriate priorities
- Design: optimise settings & response
- Operation: contextual response guidance
The effectiveness of these activities can be evaluated using advanced bowtie techniques such as plotting audit results and incident analysis onto bowtie diagrams:
- Maintenance planned alarm evaluation
- Monitoring unplanned alarm investigation
- Change impact assessment
For example, a simplified tank overfill scenario highlights the contribution that alarms make in the overall protection scheme (click to enhance picture):
An overview of the contribution that alarms make in the protection scheme, visualized in a bowtie diagram
This shows the potential causes of alarm initiation and gives a sense of the severity of the consequences and the relative urgency (taking into account other measures and escalation to/from the top event) to assist in justification, prioritization and settings. Duplicated, invalid/inappropriate or missing alarms are now more obvious and can be addressed.
Learn more about alarm management and bowties at the EEMUA 191 Seminar
David Hatch (CGE Consulting Partner – Process Safety Integrity) and Andy Geddes (PX Group) will be presenting “Bowtie analysis for alarm management” at the forthcoming EEMUA Seminar: Alarm systems and controls in Manchester on 12th July 2018 to showcase how bowties can provide the above-mentioned framework to execute & enhance the key activities.
The Engineering Equipment and Materials Users Association (EEMUA) publication EEMUA 191 is the international standard for alarm management and describes in detail the tools and techniques for various aspects of alarm management (e.g. rationalization, risk assessments, graphics design).
For more information; join David at the EEMUA 191 event or contact David directly.