Fire Protection in the Waste Management Industry
INTRODUCTION
Fire is an ever-present possibility at most waste management sites, not only because many wastes are readily combustible but they are often a target for arson attacks. Adequate controls should be in place to prevent fires and, should a fire occur, ensure that the risks to human health and the environment are minimised.
This document provides an overview of the different types of fire protection and detection systems available for use at waste management facilities.
In 2013 a total of 298 fires in waste plants were recorded, more than 5 per week.
Here are some statistics from one fire at a Smethwick plastics recycling plant in July 2013.
200 Fire fighters attended with a total of 6,000 man hours spent putting the fire out.
14 million litres of water was used.
19,000 tonnes of CO2 were released into the atmosphere.
6,000ft smoke plume could be seen up to 40 miles away.
3 days to put the fire out.
£6million cost.
FIREFIGHTING WATER SUPPLIES
The majority of waste industry fires are likely to be fought with water. Where a site entrance is located more than 90m from a public fire hydrant, additional private fire hydrants should be considered. A minimum output of 1,500l/min is usually recommended and fire authorities may require more depending on the amount of on-site combustible waste storage. The Environment Agency currently say that there should be sufficient water supplies available to manage a worst case scenario incident (e.g. all piles on site are on fire) and that a 300m2 pile of combustible material will normally require a water supply of at least 2,000 litres a minute for a minimum of 3 hours.
Hydrant standpipe and key ready for use
Hydrant cover removed
Alternatively, additional pumped water supplies with a minimum capacity water storage tank of 45,000 litres should be installed along with suitable fire hydrants.
WATER MONITORS / CANNONS
Water cannons can be either fixed or oscillating type and are usually connected into the sprinkler mains where available, or into a dedicated pumped supply if not. They can be either manually operated or have automatic control. Manually operated cannons are usually installed inside buildings protecting reception areas and bunkers, with automatic cannons installed to cover outdoor storage. Cannons can be linked into and operate on fire alarm activation, notably flame and video detection.
SPRINKLER SYSTEMS
Sprinkler protection is increasingly becoming an insurance requirement for waste processing facilities. Conventional sprinkler protection works on the principle that each head is designed to open independently of others in the building and discharge water onto a fire when a heat-sensitive fusible link or glass bulb gives way.
Typical sprinkler head
Deluge nozzle
Sprinkler head guards
System design varies but will typically be based on the following alternatives:
Wet pipe installation
In a wet pipe installation water is always present in the pipes supplying the sprinkler heads, and this type of sprinkler system is quick to react when a head opens in a fire scenario. These are the most common systems for use in buildings where there is no risk of freezing.
Dry pipe installation
The sprinkler pipes are charged with compressed air at all times and the water is held back by the control valve outside of the protected area. Should a sprinkler head open in a fire scenario, the drop in air pressure opens the valve and water flows into the pipework and onto the fire. Dry systems are slower to react compared to wet pipe but there is often no alternative in an unheated building.
Sprinkler control valve for a dry pipe system
Pre-action system
Like dry pipe systems the pipes are filled with air but water is only let into the pipes when a fire detection system also operates (e.g., smoke or flame detectors). As the fire detection responds faster than a typical sprinkler head, this reduces the time it will take for a dry pipe system to address the fire. Pre-action systems are often used where added reliability is needed to prevent a false sprinkler activation unless there is a real threat of fire, such as document stores, frozen food storage etc. but can also have application in an unheated waste facility where a dry pipe system is needed but the typical sprinkler response time needs to be reduced.
Deluge system
These are sprinkler systems where all the sprinkler heads/nozzles operate simultaneously and are generally used to provide local fire suppression for special hazards in industrial premises. This may be part of a larger conventional sprinkler system or a standalone installation. They are most commonly found protecting bulk flammable liquid storage. Foam is often introduced into the system to enhance its fire suppression capability. Deluge protection is also used for local fire suppression in waste management facilities to protect hazardous machinery such as shredders, and waste reception areas.
Bunkers in a reception area
Shredder protection
Deluge system valve station
Internally, deluge protection should be considered for spot fire suppression over shredders, balers etc., and external deluge protection may be needed for the building structure if there is excessive combustible storage located near to the property that cannot be avoided for operational reasons. Foam enhanced sprinkler protection may be appropriate for sites accepting high volumes of plastics or other highly combustible wastes. The use of foam as a wetting agent will also reduce the volume of water needed to fight a fire.
Manual deluge systems are usually installed on the walls around waste in reception and storage areas and also above shredders. These can also be automatic and connected to a suitable water supply. When automatic the system is linked into the fire alarm and is activated via area specific fire detection (usually aspirating or flame / video detectors).
Requirements for effective sprinkler coverage
Sprinkler protection should be installed throughout the facility at roof level, supported directly by the main building structure. The roof level system must be fully hydraulically calculated, and feature a network of piping designed to provide the design criteria set out by the type of goods and storage heights in the current occupancy. Although roof level systems should normally be of the wet type, waste recycling plants are rarely heated so it is common practice to tolerate slower-reacting dry pipe systems to prevent the installation freezing in sub-zero temperatures.
These are the typical design criteria used for a waste processing facility:
High Hazard Category III at roof level over ST1 type freestanding block storage to a maximum height of 3.8m.
Both roof and low level* dry pipe sprinkler systems designed to provide a minimum water discharge density of 12.5mm/min over 325m2 utilising 68oC upright 20mm, K factor 160 standard response sprinkler heads.
A maximum acceptable spacing of 9.0 m2 per sprinkler.
The design of the roof systems has to comprise terminal ranges with all piping and sprinklers as close to the roof as possible.
The maximum system size is 3.0 m3 (total volume of pipework) or successful end of line test within 60 seconds.
In practice however each sprinkler system would be designed specifically for the current or planned occupancy and fire load.
*Low level sprinkler protection will usually be needed in offices and below mezzanines, silos, plant and sorting machines. Sprinklers should also be installed under picking cabins where bunkers are located containing combustible waste, and below conveyors and walkways greater than 1m wide where combustible waste falls and collects.
These are typical low-level areas that would be shielded from roof level sprinkler coverage.
Standard – for insurer acceptance, sprinkler systems must be designed, installed, tested, commissioned and maintained strictly in accordance with an internationally recognised standard, such as:
LPC Rules for Automatic Sprinkler Installations 2009 Incorporating BS EN12845
FM Global Datasheet 2-0 Installation Guidelines for Automatic Sprinklers
NFPA 13
SMOKE VENTILATION
Smoke and heat exhaust ventilation systems are natural or powered systems used to remove smoke from a building, allowing low level escape routes to be kept clear and reducing property damage.
They comprise three main components:
Exhaust ventilators to remove the smoke
Smoke barriers to limit the spread of smoke while it remains in the building
Inlet ventilators to allow fresh air in to replace the smoky air removed by the exhaust ventilators.
Dampers and ductwork are often integrated into the scheme.
Smoke ventilation may have been recommended or required by the Fire Authority as an aid to firefighting within the building, but it is important to understand that when combined with sprinkler protection, sprinkler reaction time may be increased if the vents open first.
Standard – BS 7346 part 8:2013 Components for smoke control systems. Code of practice for planning, design, installation, commissioning and maintenance
FIRE DETECTION
There are many options available for fire detection systems. Those which may be applicable to waste management sites are:
Aspirating fire detection
Point detection
Flame, spark and video image detection
Linear heat detection
Standard – BS 5839 Part 1:2017 Fire detection and fire alarm systems for buildings. Code of practice for design, installation, commissioning and maintenance of systems in non-domestic premises
Aspirating fire detection
Aspirating smoke detection (aka HSSD – High Sensitivity Smoke Detection) continuously samples the air in the area being covered to provide the earliest possible warning of an impending fire hazard. This buys the critical time needed to investigate an alarm and initiate an appropriate response to prevent injury, property damage or business disruption.
The picture below illustrates a typical aspirating system. A series of plastic pipes run through the area being covered – usually at roof or ceiling level – and the air is sucked through holes in the pipes and directed down to analyser units which can detect minute smoke particles.
Analysers have multi-level warnings and a wide range of sensitivity that does not degrade or change over time, so even minute levels of smoke can be detected before a fire has time to escalate. Although historically prone to blockage or reduced sensitivity in the typically dusty atmosphere found in many waste facilities, recent technical developments have addressed this by for example improving the ability to discriminate between dust and smoke, or periodically blowing through pipework to eliminate dust build-up.
Aspirating system control panels, analyser units and detection pipework (in red)
Point detection
Point detectors provide the most common form of fire detection. There are principally two types employed – smoke or heat.
Smoke detectors are the more sensitive and are installed in any environment where smoke or steam would not normally be present. Heat detectors are installed in areas such as kitchens where smoke detectors would constantly false alarm during routine cooking. Sometimes the two types are combined into one unit to minimize false alarms.
Beam detection
An optical beam smoke detector is a device that uses a projected beam of light to detect smoke across large areas, typically as an indicator of fire. They are used to detect fires in buildings where standard point smoke detectors would either be uneconomical or restricted for use by the height of the building. Optical beam smoke detectors are often installed in warehouses as a cost-effective means of protecting large open spaces.
The detectors consist of at least one light transmitter and one receiver, which is photosensitive. In a fire, when smoke falls within the path of the beam detector, some of the light is absorbed or scattered by the smoke particles. This creates a decrease in the received signal, leading to an increase in optical obscuration i.e., transmittance of light across the beam path.
Optical beam smoke detector
Flame, spark and video image detectors
In waste facilities, fire may not produce much smoke initially and/or the smoke produced may take too long to reach ceiling mounted detectors in large open areas, so conventional smoke and heat detectors can be ineffective. There is also an issue with dust interfering with detection and causing false alarms.
The main requirements in waste facilities are to:
provide early indication of developing fire in reception areas and bunkers due to self-ignition
protect against fire and dust explosion in dust extraction systems and filters, conveying processes and shredder applications
Flame, spark and video image detectors have been developed to protect such facilities and are typically part of a system designed to detect, control and in many cases suppress or extinguish fires using CO2, foam or sprinklers. They are usually installed around reception and bunker areas and in or over plant and machinery to provide focused, local detection, although some types can also provide very effective long-range coverage. Flame detectors are often used in conjunction with other forms of fire detection to provide complete coverage. There are four main types of optical flame-sensing systems in use: ultraviolet (UV), ultraviolet/infrared (UV/IR), multispectrum infrared (MSIR) and video imaging using a charge-coupled device (CCD) sensor. These systems all work by detecting fire development within line of sight from radiant heat or recognizing the fire from a live image. Also, by utilizing CCD-based visual smoke and flame detection technology, some video systems can have the capability of enabling visual monitoring by operators and providing general security coverage.
Selection and siting of flame, spark and video image detectors is a complex process determined by an expert fire engineering evaluation of the environment and hazards being monitored, so it will not usually be possible for the Consultant to determine what type of detection would be the most appropriate. It is therefore crucial that the design and installation is undertaken by an approved contractor using equipment that has been tested to an appropriate standard. Currently there are no applicable UK standards but see below.
Flame detection
Spark detector installed into extract ducting.
Standard – for insurer acceptance, flame, spark and video detection must be designed, installed, tested, commissioned and maintained strictly in accordance with an internationally recognised standard, such as:
FM Approvals Standard 3620 – Radiant Energy-Sensing Fire Detectors for Automatic Fire Alarm Signaling
FM Approvals Standard 3232 – Video Image Fire Detectors for Automatic Fire Alarm Signaling
Linear heat detection
Linear heat detection cables are conventional heat detectors in a linear form. They sense heat anywhere along their length and are designed to be used in commercial and industrial applications.
Linear heat detection provides an early response to fire conditions or overheating of equipment, plant or the surrounding area.
Heat sensing cables can be used with or in place of conventional heat detectors, or where conventional heat detection is expensive or difficult to install and maintain. Typical application in a waste facility would be in sorting equipment or along a conveyor system.
FIXED FIRE SUPPRESSION SYSTEMS
Water mist
Water mist works by enveloping the fire with fine water droplets and breaking the cycle needed for combustion. The mist creates a large surface area of water droplets, increasing cooling and controlling the hazard.
By discharging water through special nozzles at high pressure, the mist reduces the amount of water used and the damage caused. Acting in a similar way to gaseous protection, water mist extinguishes fires in obstructed locations normally inaccessible to standard sprinkler systems. In addition, the technology is free from environmentally hazardous gases and potentially dangerous compressed gas.
Water mist is not a universal fire protection solution, and is most likely to be effective when utilised to protect enclosed plant and machinery rather than open spaces. Whole-building water mist protection is not currently supported.
Standard – BS 8489-1:2016: Fixed fire protection systems. Industrial and commercial watermist systems. Code of practice for design and installation.
Gaseous Fire Suppression
This is a term to describe the use of inert gases and chemical agents to extinguish a fire (also called Clean Agent Fire Suppression). While sprinklers provide excellent protection to most areas of a building, water can seriously damage vulnerable contents in areas containing plant control systems, computer rooms, communications equipment or data storage. Water ingress can cause as much damage as fire and can result in data loss and extended plant downtime, so the choice of fire suppression media in these areas is crucial and some form of gaseous extinguishant is normally employed.
There are four means used by the agents to extinguish a fire:
Reduction or isolation of fuel. No agents currently use this as the primary means of fire suppression.
Reduction of heat. Representative agents: Clean agent FS 49 C2 (NAF S 227, MH227, FM-200), Novec 1230, pentafluoroethane (NAF S125, ECARO-25).
Reduction or isolation of oxygen: Representative agents: Argonite / IG-55 (ProInert), CO2 carbon dioxide, IG-541 Inergen, and IG-100 (NN100).
Inhibiting the chain reaction of the above components. Representative agents: FE-13, 1,1,1,2,3,3,3-Heptafluoropropane, FE-25, haloalkanes, bromotrifluoromethane, trifluoroiodomethane, NAF P-IV, NAF S-III, NAF S 125, NAF S 227, and Triodide (Trifluoroiodomethane).
Typical application in waste management facilities would be to provide local fire suppression for:
PLC control cabinets for sorting plant and other complex machinery
Enclosed picking cabins
Mobile plant protection
A vehicle fire – typically involving loading shovels and other mobile plant in waste management operations – can result in machine loss or significant repair bills.
Vehicles and plant may be bespoke to the business, and often key items of plant perform a specific and crucial role. A fire on a vehicle or plant can heavily impact operations, causing widespread business interruption.
If mobile plant is working inside or close to a building there is a risk that a machine fire could spread, especially if flammable or combustible materials are being handled.
This exposure can be mitigated by having fire suppression fitted to the vehicle and this can often be incorporated by the manufacturer, otherwise retrofitted. Various types are available including wet and dry chemical and AFFF (Aqueous Film Forming Foam). This is increasingly becoming an insurer requirement for waste management operations.
Wet chemical fire suppression fitted to mobile plant
RECOMMENDED FURTHER READING:
WASTE 28 Reducing fire risk at waste management sites published by the Waste Industry Safety and Health (WISH) Forum, available at WASTE-28.pdf (wishforum.org.uk)
Fire prevention plans Version 2, March 2015 published by the Environment Agency.
BAFSA Information File BIF 25 Fire Suppression Systems for the Waste Management Industry
FIRE PROTECTION MATRIX FOR WASTE MANAGEMENT SITES
