Alan N. Beard

The influence of longitudinal ventilation systems on fires in tunnels

Abstract Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study investigating the influence of forced longitudinal ventilation on car fires, pool fires and heavy goods vehicle fires in tunnels. A Bayesian probabilistic approach is used to refine estimates, made by a panel of experts, with data from experimental fire tests in tunnels. Results are presented and the implications are discussed. The influence of longitudinal ventilation on heavy goods vehicle fires is predicted to be much larger than the experts’ estimates, causing a fire to grow ten times larger than if natural ventilation was used. The effect of ventilation on a pool fire in a tunnel depends on the size of the pool; the heat release rate of small pool fires may be reduced by forced ventilation, whereas it may be enlarged for large pool fires. The size of a car fire is not expected to be greatly affected by forced ventilation at low ventilation velocities.

Variation of heat release rate with forced longitudinal ventilation for vehicle fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper presents the results of a study using a Bayesian methodology to estimate the effect of forced longitudinal ventilation on heat release rate (HRR) for fires in tunnels. The behaviour of car and heavy goods vehicle (HGV) fires with a range of forced ventilation velocities is investigated. Results are presented and the implications are discussed. It has been found that forced ventilation has a great enhancing effect on the HRR of HGV fires, but has little effect on the HRR of car fires.

Fire models and design

Abstract Over the last 20 years there has been a great increase in the construction of computer-based models related to fire risk. Both probabilistic and deterministic models have been produced. Many existing models are in a state of development and new models are being created continually. However, how such models are to be efficaciously employed as part of the design process is far from clear and several problem areas have arisen. A context needs to be created within which fire models may play a part which is acceptable to society as a whole. The question emerges of ‘how may fire models relate to other knowledge and experience and form part of an integrated approach to design and regulation?’ Interalia the issues arise of: (a) How are the limitations and capabilities of a fire model, including the software, to be competently assessed? (b) What are the conditions under which one or more fire models may be employed in a real-world case in a way which is generally acceptable? These issues are discussed and some practical proposals are put forward.

Nonlinear dynamics of flashover in compartment fires

Flashover is a phenomenon whereby a room fire undergoes a rapid increase in size and intensity. Such a transition is suggestive of a nonlinear process. We therefore seek to apply modern geometrical and computational techniques of nonlinear dynamics to a simplified model of fire growth to investigate flashover and other instabilities occuring in compartment fires. We present here a simplified model of fire growth in a compartment and conduct a preliminary analysis of the dynamics exhibited, in terms of both transient simulations and quasi-steady evolution manifolds, for variations in controlling parameters.

Assessing safety management systems

Abstract Traditionally, both academe and practitioners have tended to address fire safety by focusing on technical aspects and looking for the immediate causes of fire incidents or accidents after they have taken place. More recently, organisations have focused on assessing the consequences of the fire risk inherent in their operations pro-actively. However, fire safety still tends to be addressed in isolation, though fire loss is an emergent property. An organisations emergent property results from the interrelated activities of people who design it, manage it and operate it. There is still a need for a systemic approach to understand the systemic nature of fire safety. This paper describes a fire safety management system (FSMS) model that aims to maintain fire risk within an acceptable range in an organisations operations in a coherent way. This systemic approach can be used as a diagnostic tool to assess the effectiveness of existing safety management systems (SMS). It is hoped that this approach will lead not only to more effective management of fire safety, but also to more effective management of safety, health and the environment for any organisation.

Limitations of computer models

The limitations of computer models in relation to fire risk are considered in very general terms. The vital importance of the appropriate use of a model and suitable interpretation of results is stressed. Further, the possible capacity of a model to assist in the gaining of qualitative insights is considered. Some general conclusions are drawn.

A systemic approach to fire safety management

Abstract A systemic approach has been adopted to construct a fire-safety management system (FSMS). It has been applied to the case of an oil and gas organisation, although the approach is general. Significant changes have taken place in fire safety management in the oil and gas industry over the last few years. However, fire safety still tends to be analysed in isolation, though fire loss is a result of the interaction of the parts that constitute an oil and gas organisation as a whole. Fire loss may be seen as a `systemic’ failure, not a result of a single cause. This paper proposes a FSMS for an oil and gas organisation. The approach aims to help to maintain fire risk within an acceptable range in an oil and gas organisations operations in a coherent way. It is hoped that this approach will lead not only to more effective management of fire safety in an oil and gas organisation, but also to more effective management of safety, health and the environment for any organisation.

Experimental and theoretical models of flashover

A comparison between experimental data and both the qualitative and quantitative nonlinear behavior predicted by a fire growth model is made for a model compartment (0·4 m cube). The predictions are in relatively good agreement with the data, and are consistent with the expected nonlinear behaviour and in particular the occurrence of flashover jumps.

A non-linear model of major fire spread in a tunnel

A non-linear model of fire in a tunnel, FIRE-SPRINT A1, is presented. It predicts the conditions for fire spread from one object to another within a tunnel which has longitudinal ventilation. It does this by identfying unstable states within the system and associating instability with the onset of fire spread. The particular case of spread from an initial fire to a heavy goods vehicle (HGV) within the Channel Tunnel is considered as an illustration. Thereby the thermo-physical and geometrical conditions leading to such a jump may be elucidated.

A Systemic Analysis of the Paddington Railway Accident

Abstract The Paddington railway collision may be regarded as the most serious railway accident on Britains railway system. The accident occurred on 5 October 1999. Thirty-one people were killed and many more were injured. An immediate and ‘direct’ cause of the collision was the fact that a train that belonged to Thames Trains had passed a signal at red and collided with a First Great Western High Speed Train at Ladbroke Grove Junction, near Paddington, London. Following this and several other accidents that have occurred since privatization of the railways (1994), there has been a large amount of public debate about safety management on the British railways. This article presents the results of a preliminary systemic analysis of the accident. The approach has been to compare the features of the Paddington railway accident with the characteristics of a railway systemic safety management system model, which has been constructed employing the concepts of systems. A number of discrepancies have come to light. Further analysis would be expected to reveal more. It is hoped that this systemic analysis will help to identify ‘learning points’, which are relevant for preventing accidents on the railways.