Identifying Major Accident Hazards and Containing Hydrocarbons by Utilising Operational Knowledge Figure 1: Comparison Between Different Types of Safety


Process safety


Major accident hazards


Personal safety


Slips, trips and falls


Table 1: Process Hazard Review Guidewords


Internal explosion Reaction


Extreme pressure Extreme temperature Puncture


Excess loading


Long-term weakening Overfill Opening Leak


Figure 3: Missing Lock on Isolation Valve Increasing the Isolation Risk


Very unlikely


Possible Figure 2: The Need for Periodic Process Safety Reviews Continuous improvement


Process safety


performance Initial


learning phase


Changes in personnel Loss of knowledge Ageing equipment ‘Creeping’ change


Life of plant


safeguards. The experience of the team is used to identify current weaknesses, for example a level sensor on a safety-critical trip system that is known to regularly fail.


Recommendations for improvements are raised that are focused towards major accident hazards and known problem areas. These fall into the following generic categories, with a bias towards procedural changes rather than costly hardware changes:


• • • • •


Simple risk-reduction measures, e.g. fitting blank flanges to drain valves on hazardous lines.


Improvements to operating or maintenance procedures to ensure best practices are followed.


Improved inspection and testing of safety-critical equipment, e.g. vent lines on storage tanks liable to blockage.


New layers of protection for high-risk events to meet current company or international standards.


Research into poorly understood hazards, such as static control measures, or consequence modelling to determine the extent and severity of fires, explosions or toxic releases.


Plant tours are regularly made by the team leader accompanied by an experienced operator. This provides an opportunity to check the condition of safety-critical equipment in the field and confirm the status of measures stated at the team meetings. For example, a manual valve on the inlet line to an low pressure gas/condensate separator vessel was specified to be ‘locked open’ to prevent the


88


upstream line from being over-pressured and rupturing. It was found that the lock was missing from the valve, as shown in Figure 3, increasing the risk of the line being isolated in error. Most companies have a process safety risk matrix similar to the example in Figure 4. All of the identified events are located on the matrix using suitable word models and the judgement of the team guided by an experienced leader. The completed matrix showing the number of events at each risk level is a powerful toolto show the areas of concern. It allows for prioritisation of recommendations for improvements.


Implementing Improvements


Completing the PHR is the first stage of the improvement process and it is essential that the recommendations raised are then addressed promptly. Simple low-cost improvements should be implemented at the earliest opportunity to reduce risks and show a commitment to the improvement process. Technical assessments are then required to identify practical improvement options and carry out cost–benefit analyses. These are required to convert the recommendations into a series of specific actions with owners and completion dates.


The cost of making changes to an operational facility is higher than the cost of those made during the initial design stage. A common problem is making decisions on expenditure where the benefits are limited to reducing risks with no financial benefits. Events judged to be at high risk require urgent attention and changes to reduce such a risk should be made regardless of cost.


HYDROCARBON WORLD – VOLUME 5 ISSUE 2


Constant risk


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