Fire detection in high hazard environments
30 September 2013
Providing fire detection solutions is a complex task at any time, but in high hazard applications, there are additional risks and challenges to address. Here Simon Flavell, Global Business Development Manager at Apollo Fire Detectors, examines the challenges in high-risk environments such as the marine, oil & gas and nuclear sectors, and provides an implementation case study at a hydro power facility in Wales.
The engine control room of a container ship
Legislation plays a vital role in defining requirements for fire protection in high hazard industries, helping to ensure that the very highest levels of safety are met. However, the marine and oil and gas sectors have gone one step further with their approach to protecting lives and property, introducing a raft of industry approvals that suppliers to these industries have to meet.
Let’s look first at an issue which all three industries have in common – the need to provide reliable fire detection solutions in hazardous areas.
The ATEX Directive
Where a risk of explosion is present, it is necessary to install equipment that is specifically intended for use in explosive atmospheres. This includes any locations where an explosive mixture of air and gas or vapour is – or may be – present continuously, intermittently or as a result of an accident. These are defined as hazardous areas by BS EN 60079, the code of practice for installation and maintenance of electrical apparatus in potentially explosive atmospheres.
Any electrical or mechanical equipment located within these areas – such as sockets, lighting and computing devices – must be designed so that it cannot ignite these explosive mixtures both in normal operation and also in a fault condition. This equipment is referred to as being ‘intrinsically safe’ (IS). The marine, oil & gas and nuclear industries are all major users of IS fire detection products.
IS technology was first introduced into fire detection equipment in the early 1980s but it was not until July 2003, and the introduction of the ATEX (Atmosphere Explosive) Directive, that the use of IS equipment for certain hazardous environments became mandatory.
Under the directive, facility owners are required to classify areas where hazardous explosive atmospheres may occur into zones. The classification given to a particular zone, and its size and location, depends on the likelihood of an explosive atmosphere occurring and its persistence if it does. Within these hazardous areas, three zones are identified:
* Zone 0 – Category 1 – where an explosive gas-air mixture is continuously present or present for long periods
* Zone 1 – Category 2 – where an explosive gas-air mixture is likely to occur in normal operation
* Zone 2 – Category 3 – where an explosive gas-air mixture is not likely to occur in normal operation, and if it occurs it will exist only for a short time
In Zone 0 areas, IS systems are the only approved method. An IS system operates at such low power and with such small amounts of stored energy that it is incapable of causing ignition in normal conditions, with a single fault or with any combination of two faults. In any of these conditions, every component must remain cool enough not to ignite the gases for which it is approved. It is critical that both sources of ignition – sparks and overheating – are considered. IS ensures that even with as many at two faults on the circuit board, the equipment will not spark or overheat.
IS fire detection solutions are often specified for power generation plants where the risk of explosion is present. Typical applications include conventional and nuclear power stations, hydroelectric power, electric-switching and distribution stations.
Global demand for IS fire detection equipment is predicted to rise, with countries such as Russia and China identified as major growth areas due to their ongoing investment in petrochemical plants. Closer to home, the UK offshore industry remains a significant user of IS equipment, and demand from power stations in mainland Europe looks set to rise in the future.
The Marine Equipment Directive
While the need to adhere to the ATEX Directive applies to all three industries we are considering here, those responsible for specifying fire detection solutions for use in marine and offshore settings may also be required to install products that comply with the Marine Equipment Directive (MED). The EU Directive on Marine Equipment (96/98 EC) applies to ships or vessels that are registered under the flags of European Union member states.
The Directive sets standards that both manufacturers and their products have to meet, ensuring the safety and quality of marine equipment carried on board ships or offshore facilities.
Given the volatile environments found in the marine and oil and gas industries, it is understandable that so much emphasis is placed on meeting strict health and safety standards. In fact, both industries have gone one step further than the legislation by introducing a raft of industry approvals.
Those responsible for specifying fire detection equipment for use in marine and offshore settings may have to adhere to the requirements set by one or more approval bodies, depending on where the facility is located. Marine products, for example, can be approved by the American Bureau of Shipping, Bureau Veritas, the China Classification Society, Det Norske Veritas, Germanischer Lloyd, Lloyd’s Register of Shipping, the Maritime and Coastguard Agency and Marine Marchande Française, amongst others.
A further example of industry seeking to improve its safety standards is the introduction of the Safety Integrity Level (SIL) approval. SIL ratings were established to define a metric for evaluating a system’s – or function’s – level of operational reliability with regards to maintaining safety.
Although not a legal requirement, a SIL evaluation establishes the functional safety of products by illustrating how reliably and correctly they respond to inputs. While onsite testing and maintenance are vital in ensuring the ongoing functionality of any fire detection system, they do not provide evidence that equipment will function as planned in a live situation. A SIL rating, however, gives confidence that it will. Through a series of extensive evaluations, this certificating process demonstrates a product’s integrity to perform its primary function in a real life situation.
This additional level of assurance is particularly important in high risk environments where a high level of functional safety is critical. Recent years have seen a rise in the number of marine and offshore companies specifying products that are SIL approved.
Demand for SIL approved products from marine and offshore companies is likely to rise over the coming years.
Advances in technology
Clearly adhering to industry legislation and specifying approved products are vital considerations when specifying fire detection solutions. But, on a more simplistic level, it is also essential that the right technology is chosen for each environment, ensuring accurate and reliable fire detection.
Some of the most common types of detection products include:
* Optical (photo-electric) smoke detectors. These are good for a wide range of smoke types symptomatic of early stages of fire. They respond particularly well to slow-burning, smouldering fires. These detectors use a proven technology, are insect-immune and offer improved designs for airflow and drift compensation.
* Heat detectors. These use a reliable and inexpensive technology and are ideally suited for areas such as kitchens, laundry rooms and boiler rooms.
* Multisensor detectors. These offer a combination of smoke and heat sensors and, for their sheer flexibility, are the best general-purpose detectors currently available. They combine optical readings with temperature change to give a rapid response to the widest range of fires of any detector type, dramatically improving rejection of unwanted alarms.
* Ionisation smoke detectors. These are good specialist detectors that respond well to fast-burning (flaming) fires and are now used to overcome specialist problems.
* Carbon monoxide (CO) detectors. These provide good early warning of deep-seated, smouldering fires and are unaffected by common sources of unwanted alarms such as steam, cooking or dust. However, CO detection should only be used as an adjunct to general purpose smoke detectors, never as a substitute.
Conventional and analogue versions of all of these products are available. In both the marine and oil and gas industries, there has been a shift away from conventional products towards the use of addressable products. Analogue addressable devices are individually identified with an address (number) on a loop of wiring. The control panel communicates with each device in turn and each device reports back an analogue value, based upon how much smoke or heat is present. The control panel, not the detectors, then makes all the decisions with regard to sounding the alarms. With an intelligent system, if a fire is detected, its position can be pinpointed because each device has its own unique address, meaning its precise location can be identified.
Fire detection is a complex business and never more so than in some of the high risk environments found in the marine, offshore and nuclear sectors. Evolving technology and changes in legislation mean that even those specifiers and installers with considerable experience have to identify and work in partnership with fire detection experts to ensure that the chosen technology is appropriate, meets industry legislation and is, where required, approved.
Underground at Dinorwig
Case study: Fire detection on Electric Mountain
Built in 1984, Dinorwig hydroelectric power station near Snowdonia National Park in North Wales offers one of the fastest response times of any power facility in the world, generating 1,728MW from standstill in just 90 seconds. Virtually all the critical plant at Dinorwig is situated underground.
The operator of the facility, International Power, specified a networked fire detection system to cover overground and underground areas of the power station sited several kilometres apart. The solution also had to be based on an open protocol and include aspirating fire detection. Apollo Fire Detectors and Kentec Electronics put forward a fire detection system based on Apollo’s open digital protocol that would fulfil these unique requirements.
The solution is based around 12 Kentec Syncro analogue addressable control panels – eight of which are installed underground. Three graphic panels based on Kentec’s GUIDE system provide a single point of co-ordination for all alarms. These are positioned in the pressurised main control room underground, the administrative offices, and at the main gatehouse.
More than 1,500 Apollo XP95 fire detectors and ancillary devices are incorporated in the fire system. Optical smoke detectors are used in the main areas and approach tunnels, with heat detectors protecting rest rooms and kitchens. In excess of 450 addressable sounders and sounder beacons alert staff to an emergency and around 250 manual call points enable employees to raise an alarm.
An aspirating system is fitted in the main cavern so that air turbulence will not affect the system’s ability to detect fire. Water spray and gas extinguishing systems are also installed in the transformer rooms at the power plant. Approximately 100 Apollo interfaces enable this equipment to link in to the main fire detection system.
A spokesperson for International Power said: “We were able to use standard fire detectors from Apollo’s range to achieve the reliability levels we required in our subterranean environment. This helped to control costs and timescales on the project. The inclusion of aspirating fire detection could have been an issue, but the choice of an open digital protocol, plus the existence of an Apollo interface to link this in, avoided any compatibility problems.”
Although the power station is highly complex in its fire detection requirements, the evacuation principle is simple: one alarm, all out – except a few essential staff in the control room.
The site plays host to regular tours for the general public so evacuation procedures needed to accommodate people who were unfamiliar with the site layout. The new fire system meets modern standards by providing reliable noise dispersal, with loop powered sounders and sounder beacons in the machine hall where noise levels may prevent audible alarms being heard.
The fire detection system at Dinorwig now offers comprehensive coverage across the entire site. Thanks to Apollo’s open digital protocol, the fire detection, aspirating detection and extinguishing systems are fully integrated. Kentec’s sophisticated graphics controls provide a user-friendly interface that enables routine maintenance issues and sources of alarms to be pinpointed and responded to effectively.
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