Driving change

ON AN historical basis, internationally, the installation of bus and coach engine fire suppression systems has not been a widespread mandatory requirement. The inclusion of such systems has until now been at the discretion of individual countries, local government transport bodies and individual vehicle operators. 

Furthermore, there has not been a common international approach to the fire extinguishing performance required of such systems that are installed for engine fire protection in the bus and coach sector.

In 2018 both of these issues, the mandatory need and the fire extinguishing performance, have now been addressed, as required by a countries membership of The United Nations Economic Commission for Europe (UNECE).

UNECE includes 56 countries, including those in Europe, but also countries in North America (Canada and United States), Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) and Western Asia (Israel).

The UNECE sets out norms, standards and conventions and included in that are matters relating to safety of public transport. It is in the specific area of buses and coaches that the UNECE have mandated changes moving forward in the Fire Safety provision that is included for the protection of the travelling public.

Legislative changes

It will become mandatory on certain new classes of buses and coaches to install a fire suppression system, complying with the requirements of UNECE Regulation No. 107, Revision 6, Amendment 5, Annex 13.

Only M2/M3 Class III vehicles are currently covered by the requirements for Fire Suppression under Reg.107.06, with the implementation date for new types being from 10 June 2018. It is anticipated that mandatory inclusion of fire suppression in other vehicle classes will follow.

The regulation details specific requirements, in order to achieve an approval from a ‘notified body’, for the fire extinguishing system in accordance with the regulations. There are two possible routes for manufacturers of such systems to achieve certification. The first is UNECE Regulation No. 107, Revision 6, Amendment 5, Annex 13 - Part 2. This includes for vehicle specific fire tests to be done in conjunction with a vehicle manufacturer. This then leads to a specific vehicle certification but would require re-testing for other vehicle types. 

Due to this fact, it is likely that the more generic Route 2 will be more practical for both vehicle and system manufacturers, but will also provide advantages of commonality for operators. The second route is UNECE Regulation No. 107, Revision 6, Amendment 5, Annex 13 – Part 1. This part of the regulation includes four distinct fire extinguishing performance tests, all related to different fire scenarios. The four fire tests have been adopted by UNECE from Test Method SP4912 developed by SP Research in Sweden. 

The fire tests examine the performance of a fire suppression system operating under a variety of conditions and fire loads. The tests also explore the ability of a system to deal with different fuel types and configurations. Factors assessed during the fire tests include: 

• Lowest operating temperature, some as low as -40⁰c;
• Air flow - Simulates moving vehicles and cooling fans;
• Hidden fires;
• Fuel types - Fibre Board, diesel oil, Heptane, engine oil; and
• Fuel configurations - Pool fires and spray Fires

Fire Test Rig 

The fire test rig used is prescribed in detail in the text of the regulations. The design includes mock-ups of all the key components and objects that might be found within typical engine compartments on buses and coaches, including: engine, exhaust manifold, muffler, exhaust and connector pipes, various significant obstructions and fan cylinder.

The rig has a gross volume of 4m³ and although generally enclosed on the perimeter, it does include other apertures, with a total area of 0.95m². 

The fire test programme simulates various conditions and fire scenarios within an engine compartment using combinations of fuel type, configuration and airflow to test the capabilities of a system to operate successfully under a variety of demanding conditions, when required to do so. Fire tests conducted include:

1. High load fire - Cylinder conditioned at lowest operating temperature, spray fire, no fan, two fibre boards, five pool fires of various sizes and locations;
2. Low load fire – With fan, five pool fires of various sizes and locations;
3. High load fire with fan – Spray fire, with fan, two fibre boards, four pool fires of various sizes and locations; and
4. Re-ignition test – Dripping oil on to pre-heated pipe, discharge system, time to re-ignition

Certification

Upon successful completion of the test programme, a report confirming compliance is written by the relevant fire test laboratory. However, compliance and certification of the system is only confirmed when a notified body has reviewed and approved the report, together with the manufacturers system documentation (System Manual). Upon successful review, a certificate is then issued by a notified body, authorised under the regulations. 

Certification is based on a datum system capable of extinguishing fires in a 4m³ gross volume fire test rig. The certification does allow for re-sizing of a system both in terms of the number of discharge nozzles, the mass of extinguishing agent and mass of the propellant gas container, if applicable. This extrapolation is controlled by formulas contained within the regulations and repeated in the manufacturers system manual, approved as part of the certification. 

Generally, due to the existence of an approved system manual, systems that comply with the regulations will be classed as pre-engineered. 

Suitable training by the system manufacturer will qualify approved companies to complete all the tasks to undertake risk assessment, design, specification, installation, service and maintenance activities related to such systems.

It will be the responsibility of the approved companies in collaboration with the bus or coach manufacturer, supplier or operator to carry out a full risk assessment for each vehicle class and accept full responsibility for the overall performance of the suppression system subsequently installed. The risk assessment must be documented and completed before installation of any system takes place.

Risk assessment

The risk assessment must highlight the high-risk areas of the engine enclosure to ensure protection is provided for these areas. Fire hazards to be taken into account in the analysis shall at least consist of the following:

• Components (e.g. exhaust pipe or exhaust manifold) whose surface may reach temperatures above the auto-ignition temperature for fluids, gases or substances that are present within the compartment;
• Electrical components and cables with a current or voltage high enough for an ignition to occur; and
• Hoses or containers with flammable liquid or gas (in particular, if those are pressurised)

To date, systems that have generally met the certification requirements of the regulations fall into two distinct categories of extinguishing agent – dry powder or water-based. Jactone manufactures a fully certified system in the first category under its Pneumatically Actuated Fire Suppression Systems (PAFSS) brand. 

PAFSS bus and coach systems provide protection inside the engine compartment and discharge at the heart of the fire, extinguishing quickly and preventing the fire from spreading. This can significantly reduce the risk of injury to personnel and vehicle losses, not to mention the operational disruption. 

The wider PAFSS range of systems, operate using two distinct principles. Direct systems, which offers both fire detection and system discharge take place via a pressurised detection tube. When this bursts due to fire the system actuates the cylinder valve to open and discharges the cylinder contents via the burst hole.

The second principle is indirect systems, which is when the pressurised detection tube only acts as a detector. System discharge is via separate pipe and nozzles.  The indirect principle is used in the PAFSS bus and coach fire suppression system. The system has the following distinct features, including several unique elements:

• 18 bar system pressure – Enhanced system pressure and gas propellant volume ensures ‘complete’ discharge under conditions of high vibration, compaction and low temperature, particularly present in vehicle applications. This is an absolutely vital characteristic in powder systems to avoid partial discharge;
• 6kg ABC high performance dry powder – Dry powder provides quick fire knockdown upon discharge and subsequent effective smothering action;
• Four discharge nozzles – High output and effective distribution within the engine space. A limited nozzle count aids several aspects of an installed system including ease of Installation, whether during OEM vehicle new build or retrofit and potential for reduced installation and on-going servicing costs;
• High performance pressurised detection tube – Specifically developed for automotive applications where zinc galvanised components are present. It’s also simple to install and requires no electrical signal to operate and provides effective system actuation; and
• UK manufactured pressure vessels – Enhanced external coating system, providing hostile environment protection and enables fine tuning of system capacities when scaling

Our system offers peace of mind for customers looking to specify a fully tested, approved and certified solution for fire protection of buses and coaches.

Craig Halford is managing director of Jactone Products Ltd. For more information, visit www.jactone.com