Thursday, March 24, 2022

Safety Message – Fires on passenger rolling stock

ONRSR is reminding rail transport operators (RTOs) about a range of risks, causes and controls associated with fires and explosions on passenger rolling stock.

Fires on Trains web

Fires on rolling stock can be deliberately lit, caused by rolling stock faults or started accidentally; RTOs should identify all possible causes.

Fires on rolling stock can result in catastrophic loss of life although this is not the case for the vast majority of fires on rolling stock due to the effectiveness of fire safety controls.

RTOs should continue to identify new potential safety controls and make an assessment as to whether they are reasonably practical to implement as well as reviewing their current operations to ensure that existing fire safety controls are in place and effective.

ONRSR’s investigations into fires on rolling stock have identified causes and contributing factors across the four areas listed below. While not exhaustive and given the range of operational environments within the Australian rail industry, the following causes, contributing factors and controls should be noted.

CAUSES AND CONTRIBUTING FACTORS

The causes of fires can be classified into organisational, technological, individual, and environmental factors.

1. Organisational factors e.g.

  • RTO has not equipped rolling stock with sufficient controls e.g. not equipped rolling stock with fire suppression systems or fire alarms, or these systems are insufficient for the size of the fire.
  • RTOs’ risk assessment procedures do not appropriately consider fires and controls available to minimise the risk of fires.
  • RTO has not investigated past minor fires and therefore potential learnings are not incorporated into practice.
  • RTO has not developed appropriate training for drivers and operational staff e.g. training and procedures do not cover emergency response to fires.
  • RTOs’ controls not effective e.g. ventilation or fire compartmentation controls not effective at preventing the spread of a fire, or public communication systems not effective or not fitted, leading to passengers being unable to evacuate/ escape or find refuge.
  • RTOs’ poor maintenance practices lead to fire ignition events occurring due to electrical or mechanical rolling stock faults.

2. Technological or equipment factors e.g.

  • Power sources, such as rolling stock powered by combustion engines or fitted with onboard energy storage systems, or combustion materials increasing the risk of a fire.
  • Rolling stock running capability impaired preventing rolling stock moving to a safe evacuation point.

3. Environmental factors e.g.

  • Lack of fire safety expertise leading to lack of appropriate fire safety standards or standards applied incorrectly.

4. Individual factors e.g.

  • Arson, explosion, or terrorist activities.
  • Misadventure or recklessness such as smoking or discarding a cigarette-end or match on trains or at stations.
  • Operational staff fail to detect or ignore fire alarms.

CONTROLS

While not exhaustive and given the range of operational environments within the Australian rail industry, the following controls should be noted. Operators must consider a range of factors, including the likelihood of the hazard and the degree of harm to determine what controls are reasonably practicable to implement (see the ONRSR Guideline – Meaning of duty to ensure safety so far as is reasonably practicable SFAIRP for more information).

The example controls listed here have been taken from AS7529.3:2014 “Australian Railway Rolling Stock- Fire Safety - Passenger”. RTOs should engage fire safety experts to determine which controls are appropriate for specific rolling stock as well as determining appropriate methods for demonstrating compliance to AS7529.3 or other fire safety standards. Fire safety experts should also be engaged to assess the impact of any proposed modification to rolling stock that may have an impact on fire safety.

Elimination:

While there appears to be few ways to eliminate fires on trains, there are several substitution and engineering controls that can minimise the risk.

Substitution:

Some of the substitution controls operators have employed to prevent or reduce the consequences of fires on rolling stock:

1. Fire load controls aim to reduce, remove, or prevent the accumulation of combustible material that can fuel fires on rolling stock. Combustible materials include fuel, oils, litter, luggage, dust, or debris that can contribute to large fires on rolling stock. Examples of controls to remove fire loads include:

  • Bins on rolling stock constructed with a self-closing lid and with a housing and lid material which is capable of providing at least 10 minutes fire resisting integrity.
  • Underframe equipment layout which, wherever practicable, avoid traps where debris such as litter or leaf matter can accumulate.
  • Heating Ventilation and Air Conditioning (HVAC) system ducting having access for cleaning to prevent the build-up of dust.

2. Ignition source controls are controls that remove or contain items that are potential sources of ignition. Many ignition sources exist on rolling stock: resistors, exhaust from combustion engines, and heating elements in HVAC systems. Examples of ignition source controls include:

  • Compartments that contain batteries which could release flammable gases under normal or fault conditions should be vented to the rolling stock exterior.
  • Suitable shielding to ensure that sparks from cast iron brake blocks, if fitted, do not pose an ignition risk to underframe mounted combustible component materials or locations on the underframe where litter, leaf matter, or other inflammable debris may accumulate.
  • The design and installation of high voltage equipment which ensures that ignition risks associated with arcing are minimised.
  • Equipment which has the potential to operate at high temperatures fitted with systems to ensure that over temperature conditions are detected and controlled to prevent fire generating conditions from occurring.

Engineering:

Some of the engineering controls operators have employed to prevent or reduce the consequences of fires on rolling stock:

1. Compartmentation controls are designed to inhibit the spread of fire on passenger rolling stock. By dividing rolling stock into a series of compartments limits the spread of fire and helps people evacuate, and emergency services with their rescue operations. Each compartment aims to form a barrier to combustion, smoke, heat and toxic gases. Examples of compartmentation controls include:

  • Rolling stock flooring assemblies that resist the spread of potential under floor fires to the passenger and crew compartments.
  • Reservoirs for flammable fluids designed to ensure that they do not drain their contents in the event of vehicle rollover.
  • Fire and smoke resisting inter-vehicle partitions providing train occupants with a place of relative safety on-board—especially important if there may be delays in evacuating passengers.

2. Fire suppression system controls include both fixed fire suppression systems and portable extinguishers carried on rolling stock:

  • Fixed fire extinguishing systems shall be fitted to areas of automatic, unstaffed passenger rolling stock which contain high power supply line and traction circuit equipment where a fire could develop unnoticed in a magnitude that could be hazardous to the rolling stock occupants.
  • Passenger rolling stock provided with an adequate number of suitably sized portable fire extinguishers compliant with AS/NZS 1841.

3. Ventilation controls: Under normal operating conditions, ventilation systems ensure fresh air is provided to passengers during fires, limiting oxygen to the fire and providing clean air to passengers. In the event of a fire, it should be possible for the driver or train crew to shut down air conditioning or ventilation systems to prevent the recirculation of smoke within passenger or crew compartments.

Administrative:

Some of the administrative controls operators have employed to prevent or reduce the consequences of fires on rolling stock:

1. Fire detection and alarm systems detect the presence of smoke, heat or fire. These controls should be located in passenger areas, where ignition sources are located - and, when alarms are activated, they:

  • are sufficiently audible to alert passengers and crew, even if they are asleep or in a noisy environment;
  • provide indications to train crew on what zone the alarm has been triggered or activated;
  • trigger fixed fire extinguishing systems;
  • shutdown ventilation and fuel supply systems (including fuel pumps) to remove the supply of oxygen and fuel to the fire.

2. Escape, evacuation and refuge system controls include:

  • Rolling stock fitted with sufficient emergency exits to ensure evacuation of all passengers and crew can occur rapidly once the rolling stock reaches a station and in a timeframe which is commensurate with the fire safety features of the rolling stock. The potential for exits to be blocked by fire should also be considered.
  • Running capability is the ability of traction and braking systems on rolling stock to continue to operate during a developing fire. This allows rolling stock to proceed to a safe place on the network to evacuate its occupants.
  • Signs and communication systems designed such that passengers can self-evacuate if the crew become incapacitated by smoke or fire.

3. Procedures and training controls include:

  • Procedures and training which familiarises rail safety workers with the specific rolling stock fire safety controls used by the RTO.
  • Training exercises conducted regularly to validate evacuation procedures.
  • Procedures which take into consideration alternative fire scenarios such as a loss of tractive power or train crew becoming incapacitated due to smoke or fire.
  • Procedures developed in consultation with local emergency services.

This information is provided as guidance only and may not be applicable to all rail transport operators.

Last updated: Mar 25, 2022, 4:19:06 PM