The Project was initiated due to the oil and petrochemical industries’ recognition that the fire hazards associated with such tanks, although known to be relatively low, were insufficiently understood to be able to develop fully justified site specific fire response and risk reduction policies. Open top floating roof tanks, introduced to reduce evaporative losses of product to atmosphere, had always been recognised within the industry as having a relatively good fire incident record when compared to other types of facility. However, the associated risk had not been sufficiently quantified. It was also recognised that when a major incident occurred, such as a full surface fire due to ignition when the floating roof had sunk, control measures, mechanisms for incident escalation and consequential potential damage to life safety, the environment, business interruption and asset value were largely misunderstood.
Often the only information available was from organisations with a strong commercial interest in promoting one particular product or service.
It has thus been difficult for operators and legislative or statutory authorities to base risk reduction requirements on credible scenarios or proven effectiveness of mitigation measures.
When this situation is coupled with a general international recognition that the previous style of very prescriptive standards for fire protection has been shown to be inappropriate, it can be realised that there was a need to investigate, in depth, the fire risk associated with such facilities and develop a methodology by which a cost-effective, relevant and appropriate site-specific risk reduction policy could be determined.
(The 16 oil companies involved in the project are Agip, BP, Conoco, DEA, Elf, Exxon, MOL, Mobil, OMV, PetroFina, Repsol, Saudi Aramco, Shell, Total, Veba, WRG.)
The LASTFIRE Project objectives were stated as:
• To determine the current levels of risks associated with fires in large (greater than 40m diameter) open top floating roof storage tanks
• To establish recommended design and operational practice and to make this knowledge available throughout the industry
• To provide techniques to enable individual operators to determine their level of fire related risk and identify appropriate and cost effective risk reduction measures
• To identify the areas where a poor understanding contributes to the risk and, if necessary, to propose further work to overcome this.
A true Fire Hazard Management (FHM) approach to reducing fire associated risk to as low as is reasonably practicable was adopted during the project. This is in line with current regulatory trends towards preparation of “safety cases” whereby all aspects of risk mitigation including incident prevention are reviewed.
The Fire Hazard Management approach recognises that many factors can contribute to reducing risk (see Figure 1). All such factors were investigated during the LASTFIRE project. The methodology adopted was scenario based (see Figure 2).
From studies of incident histories and industry experience, the credible types of incident scenario were identified along with potential escalation consequences to life safety, the environment, business interruption, asset value or other issues such as public image or insurance costs. Next, all types of risk reduction measures were investigated and an assessment made of their contribution to risk reduction. The measures investigated included tank design features, operating practices, incident prevention measures, detection systems, fire protection systems and fire fighting techniques. In order to develop a site-specific Fire Hazard Management policy, it is also necessary to quantify incident probability and the cost of risk reduction measures. From this, an assessment can be made of the benefit provided by each risk reduction measure. The LASTFIRE project, therefore, not only investigated the contribution to risk reduction of each potential measure but also its cost so that a site operator could determine which measures were appropriate and beneficial for their particular situation.
The sponsoring oil companies’ Steering Group appointed an independent Project Co-ordinator, Resource Protection International, and the Working Group consisted of Resource Protection International, BP Engineering and Shell Research. Project deliverables were:
• Incident frequency survey report (a survey of the facilities owned and operated, worldwide, by the Steering Group companies, to establish the number of fire incidents within a large population of tanks thus allowing operators to understand current risk levels)
• Review of escalation mechanisms (including details of the causes of initial fire events, the mechanisms by which such fires can escalate, factors that affect escalation and the current ability to detect imminent escalation or to predict consequences)
• Risk reduction options review (a review to assess the effectiveness, efficiency and practicability of fire risk reduction measures for large open top floating roof storage tanks).
The risk reduction options discussed include both incident prevention and damage mitigation measures. All options discussed have been actually implemented or proposed for use on open top floating roof tanks at some stage.
The information provided in the document, which includes general design, installation and maintenance considerations for each option, is based on discussions and brainstorming meetings held at various locations internationally involving relevant specialist groups.
Firefighting foam review
As foam is currently considered to be the most effective firefighting agent for fighting large tank fires, a thorough review of the current state of knowledge and experience of foams was carried out and reported as part of the project. This document deals with the properties of finished foams and foam concentrates relevant to the scope of the project and how to evaluate them. As such, it should be read in conjunction with the Risk Reduction Options Review.
As part of the Fire Hazard Management philosophy adopted by the LASTFIRE project, a methodology was developed enabling a site-specific quantification and comparison to be made of the potential reduction in fire risk that can be achieved with different risk reduction options.
The methodology (see Figure 3) is based on a cost benefit analysis framework that involves an assessment of a site’s existing level of risk and the potential levels of risk reduction that can be achieved by implementing particular risk reduction measures. The methodology, described in the Risk Workbook, utilises the information reported in other LASTFIRE documents.
It is intended that this document provides a tool to help identify the most appropriate and cost effective risk mitigation options, which in itself should be one component of a co-ordinated Fire Hazard Management process. Thus, the Risk Workbook is essentially the main core document of the project into which all other documents have an input.
One of the major conclusions of the project was that policies for fire hazard management of large, open-top floating roof storage tanks should be based on a site-specific risk analysis incorporating cost-benefit analysis of potential risk reduction options. It is considered that, with good, pre-planned incident management, fires in such facilities should not represent a major risk to life safety or the environment and therefore further risk reduction measures should be based on their cost effectiveness. The Risk Workbook describes and gives examples of the methodology by which this cost-benefit analysis can be carried out.
Main project conclusions
The LASTFIRE project has, from a comprehensive and independent review of the risks associated with large, open-top floating roof tanks and associated risk reduction options, provided a methodology by which operators can select appropriate and justified measures to reduce fire related risk to as low as is reasonably practicable for such facilities.
In order to achieve a full understanding of the current state of knowledge and the methods by which risk reduction can be achieved, it is important to view all the project deliverables and recognise them as complementary documents.
However, some of the main conclusions and results are:
• Storage tank fires of the type under review should not represent a major risk to life safety or the environment provided the fire response is well managed to a pre-planned strategy
• Prescriptive requirements for provision of risk reduction options cannot be universally appropriate because each specific facility operates under different conditions
• The best practice regarding risk reduction in general and fire response specifically is to use a fire hazard management approach throughout the life cycle of the facility. This will result in a site-specific policy based on cost benefit analysis of risk reduction options
• The statistical analysis within the Steering Group members has shown that the fire incident probability and associated risk is relatively low
• Rimseal fires are the most likely fire scenario in open-top floating roof storage tanks. In well maintained tanks it is unlikely that rimseal fires will escalate to full surface fires. (Only one of the 55 rimseal events recorded in the Incident Survey escalated to a full surface fire.)
• Lightning is the most common source of ignition.
Correlations between rimseal fire frequency and thunderstorm frequency have been developed from the statistical analysis. Typical sample rimseal fire frequency for Northern Europe was found to be 1 x 10-3/tank -year.
The generic event frequencies for fires other than rimseal fires are as given in the following table:
A fire risk related tank inspection programme (and corrective action being taken on identification of a potential problem) is one of the most effective risk reduction measures.
The detail design of fire detection and protection systems is often inadequate due to the lack of operational experience and understanding within engineering design houses. Input should be sought from site-experienced fire professionals.
It is important to develop incident response strategies prior to an incident along with preplanning documentation, regular exercises and appropriate training for all responders.
It is clearly concluded that fire hazard management policies should be developed from a site specific analysis, but guidance is provided in the project deliverables on those measures which are most likely to be justified from the analysis.
Having identified one gap in knowledge as the lack of understanding of the way in which lightning causes incidents and the methods by which the associated risk can be reduced, a further phase of the project to investigate this was initiated. A specialist in lightning studies was used to consider the efficiency of lightning protection systems and potential for earthing and rimseal shunt improvements.
In addition, a training package on response tactics to fire events has been produced and given at various locations worldwide.
Finally, recognising the importance of firefighting foam in storage tank incidents a critical fire test aimed at this specific application has been developed. This has been used by several major oil companies as part of their foam concentrate evaluation and procurement process.
The LASTFIRE Update Project officially ended its initial phase in December 2008, and it has undoubtedly become the world’s recognised industry forum on all aspects of storage tank fire hazard management. It is now quoted regularly by legislators as a recognised source of reliable data and guidance. In addition, through research work, it has increased industry knowledge on boilovers, foam application, detection systems and tank operation.
In the next issue of IFJ, we look at the LASTFIRE project proposal for 2009 and beyond.