Coordinated approach to the dangers of fire

Afire in a single plant area can cause long downtimes for the whole production process, so fire protection measures for panel factories demand complete system solutions to provide best protection for each process area, while also functioning as an integrated network.

Based on years of experience in the wood industry, Minimax says it offers such tailor-made and certified fire protection concepts from a single source.

The following overview describes the various types of extinguishing systems and their areas of application within wood based material plants.

Given that it is never sufficient to use one type alone, a variety of systems must be combined and if all are supplied by one source, it is logical that their components will be better coordinated, providing higher standards of service.

For water-based systems, the core of every extinguishing water supply on industrial premises is an optimal fire extinguishing pump system, with a water reservoir and all necessary accessories to meet the specific requirements of the application.

All factory premises have underground piping networks connected to the extinguishing water supply. In addition to supplying the water extinguishing system and internal hydrant systems, these networks are also connected to the hydrants located outside the building.

Sprinkler systems are able to identify a fire, raise an alarm and fight the fire during its initial stages: the heat of a fire causes the glass bulbs on the nearest sprinkler to burst, releasing a fine spray of water from a deflector plate over the source of the fire. The system is designed so that water is only sprayed onto the burning area. In wood based panel factories, sprinklers are used to protect the whole building – in warehouses, production halls and even in office areas. Depending on the specific fire risk and structural conditions, a wide range of sprinkler types are available.

In order to protect objects or machines with a high risk of fire, and where a fire may spread extremely rapidly, deluge systems are considered an optimal solution.

In contrast to sprinkler systems, deluge systems are fitted with open extinguishing nozzles and are automatically activated via detectors: If a fire is detected, water is immediately released from all nozzles and is sprayed over the whole extinguishing area. Typical areas of application are the protection of cyclones, filters, screens, silos, bunkers, forming machines, mechanical conveyor systems and transformers.

For foam-based systems, in conjunction with the appropriate activation mechanism via sprinklers or automatic call points, Minimax foam extinguishers provide protection for hydraulic and thermal oil pump areas. In contrast to pure water, foam is ideal for extinguishing flammable liquids.

Extinguishing foam is a highly effective extinguishing agent generated by the combination of water, foam concentrate and oxygen, which uses a range of different extinguishing effects such as cooling, suffocating, separating, covering, absorbing and suppressing. Either individually or together, this ensures rapid extinguishing.

With Minifog PressProtect, Minimax offers a solution based on modern low-pressure water mist technology, specifically designed to protect continuous or multi-opening presses in the production of wood based panels. The company says the VdS and FM Globally-approved Minifog protection concept has been fitted to almost 200 presses worldwide. (The VdS Schadenverhütung GmbH is one of Germany’s leading independent testing institutions for fire protection and security, while FM Global is a leading commercial insurance company that offers worldwide industrial and commercial product certification and testing services).

Special Minifog impulse nozzles are arranged along, and even in, the press to protect at-risk areas and minimise water use. The extinguishing water is finely sprayed via the impulse nozzles. The surfaces, and hence the contact surfaces for heat transfer, are thereby increased and the water’s cooling capacity optimised.

In addition, large amounts of steam are created by the rapid vapourisation of the small water droplets in the area of the flame, hindering the supply of oxygen to the fire and resulting in a suffocation effect. This has proved to be an effective combination that can control and extinguish a fire in seconds.

The arrangement of nozzles, and the droplet size, ensure that the source of the fire is reached, even against influences from heat convection or air flow.

The extinguishing areas include the high-fire-risk areas of the press inlet and outlet, as well as the press centre, upper and lower heat tunnels and thermal oil distribution trenches.

The press pit poses another hazardous area, especially in multi-opening presses, as oil pipes, hydraulic and thermal oil units are located below the press, where leakages and material gather. In order to handle these risks and to shorten the extinguishing time, the press pit should be protected as a separate extinguishing area by a foam system.

The fire protection concept in and around a press can be completed by an extinguishing system for the fume extraction system and cable trays, which run in close proximity to the press.

Extinguishing fires with gas is another system which is available. Systems with gaseous extinguishing agents, such as Minimax Argotec systems, offer the advantage of residue-free fire fighting without damaging sensitive electrical equipment. As a result of this, operational downtimes after a fire are kept to a minimum. The operating principle of this type of device focuses on the displacement of oxygen: once the concentration is reduced below the specific value required for burning, the fire is quickly smothered.

In wood based panel factories, extinguishing systems using carbon dioxide are generally chosen to protect unmanned switch and power rooms, while systems with argon are predominantly selected for staffed control rooms. Given that these gases spread three dimensionally in a room, they are ideal for combating areas with difficult access.

Spark extinguishing
Minimax spark extinguishing systems for pneumatic conveying and suction systems automatically identify and extinguish sparks and hot particles before any potential source of ignition is carried to high-risk downstream equipment.

The VdS and FM-approved combined fire detection and spark extinguishing system, FMZ 5000 Reflex, not only identifies fire potentials, but also activates the extinguishing process as a rapid reflex response – just two milliseconds lie between detection and solenoid valve activation.

Spark detectors with varying degrees of sensitivity – and for various temperature ranges – are available for the immediate activation of the downstream valve units with patented flat jet nozzles.

The self-closing flat spray nozzles create a fan-shaped mist covering the complete cross-section just downstream from the nozzle’s injection point. This ensures that even short pipe connections, such as those found between ventilators and filters, or in drop chutes, can be protected optimally. A special version of the detector and automatic extinguishing unit (which can also be supplied as a retrofit for existing installations) is available for use in Ex Dust areas in accordance with AtEx 94/9/EC. (The ATEX directive consists of two directives describing what equipment and work environment is allowed in an area with an explosive atmosphere). An air flushing device for the visual detector is also available when employed in extremely dirty areas.

Hand-held devices
In order to complete the extinguishing technology, a series of fire extinguishers and wall-mounted hydrants must be installed throughout the premises. These units are ideal for tackling small fires in their initial stages. It is also important to ensure that the right type of extinguishing unit is available, depending on the fire risk at hand: for instance, fire extinguishers or mobile extinguishers with carbon dioxide are available for areas with electrical risks. For areas in which a risk of oil fires exists, such as in power plants, special foam/water wall hydrants are available.

Fire detection
During the production of wood based panels, highly-flammable material is transported to, and stored in, closed silos or bunkers.

With Silo Protect, Minimax says it has developed an active smoke aspiration system capable of detecting even the smallest smouldering fire long before the temperature detector could activate the alarm: the system continuously takes air samples from the silo or bunker area. These samples are then tested for carbon monoxide and smoke particle content. If these exceed one of the three programmable concentration values, an alarm will sound and the activation of an extinguishing system via the FMZ 5000 fire detection control panel is possible.

The fire detection control panel is the core unit of the active fire protection in a wood based panel factory and represents the interface to the process control technology. This unit collects and registers all fire alarms and monitors readings from all the smoke, heat and spark detectors and extinguishers distributed throughout the premises. The panel is also responsible for controlling the desired reaction, such as deactivating the corresponding machine or activating the extinguishing system.

The clear and user-friendly fire detection visualisation system with WinGuard completes the Minimax fire detection and extinguishing systems.

Particularly suitable for production and industrial plants with expansive, complex building structures, WinGuard is said to offer ideal control and monitoring, which is also possible via the Internet. Signals from the fire detection and control system, such as alarms or faults, activate corresponding messages in WinGuard and launch pre-defined reaction sequences, and can even notify specific individuals via SMS, email or fax. Using the data recorder, an analysis of fire incidents can be made by numbers of events in specific areas over a configurable time period, or the fire development can be reconstructed to optimise production processes.

In a wood based panel factory, almost the whole spectrum of modern fire protection equipment comes into use. If such equipment comes from one source, less interfaces are required, thus ensuring perfect installation and operation, says Minimax.

It adds that the resulting uniform operation of the fire protection system also plays a significant role in increasing on-site safety, while customer service and replacement part supplies present considerable financial savings for the operator.

Minimax points out that it is a VdS-approved installer for all areas – whether for combined water, spark and gas extinguishing or fire detection systems – and is the only supplier of complete combined fire detection and extinguishing systems with VdS and FM approval.