By their very nature, hazardous environments require a highly considered approach to fire detection. Apollo Fire Detector’s Senior Product Support Engineer, Warren Moyle, discusses meeting the challenges of protecting such environments.
A risky environment
There are a variety of different hazardous environments where providing effective fire detection solutions to protect people, facilities and the environment can be both complex and challenging. These include the marine, offshore and industrial sectors, where high risk environments – often coupled with vast site sizes and large numbers of personnel – mean that even a small fire incident could quickly develop into a major disaster.
An example of this can be seen in the 2010 Deepwater Horizon explosion in the Gulf of Mexico. The explosion had devastating consequences, resulting in the deaths of 11 offshore workers, and causing the largest offshore oil spill in American history.
This incident highlights the challenges of providing fire detection solutions in volatile and hazardous settings, and emphasises the need for the industry to ensure the correct protection is in place.
The intrinsically safe solution
For many hazardous industries, companies may be required to install intrinsically safe (I.S.) approved devices as part of their fire detection systems. In a nutshell, an I.S. system is an extra level of protection against fire and is defined as one that ‘comprises apparatus and interconnecting wiring in which any spark or thermal effect in any part of the system intended for use in hazardous areas is incapable of causing ignition’.
I.S. systems have a broad range of application uses, most often including 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 the BS EN 60079 series of standards, the codes of practice for installation and maintenance of electrical apparatus in potentially explosive atmospheres. These hazardous areas are most commonly found in petroleum and chemical engineering plants, offshore oil and gas platforms and in factories that process and store gases, solvents, paints and other volatile substances.
The design of electrical equipment for these areas needs to be carefully considered to avoid the ignition of an explosive mixture, not just in normal operation, but also in fault conditions. There are a number of approaches available to ensure that electrical equipment will not ignite under these conditions, including oil immersion, pressurised apparatus and powder filling.
The two most common methods in current use are flameproof enclosures and I.S. systems. As the name suggests, flameproof enclosures contain their equipment within a box so strong that an internal explosion will neither damage the box, or be transmitted outside the box. The surface must remain cool enough not to ignite the explosive mixture and when flameproof equipment is interconnected, flameproof wiring must be used. This method is most valuable when high power levels are unavoidable, but it is not permitted for areas where an explosive gas-air mixture may be present for long periods. Under these conditions, I.S. systems are the only approved protection method.
The basic principle of I.S. equipment is that it limits stored electrical energy and surface temperature by restricting both current and voltage, operating at such low power and with such small amounts of stored energy that it is incapable of causing ignition.
At Apollo we offer both addressable and non-addressable solutions for I.S. areas, with both methods requiring the use of a galvanic barrier before the hazardous area. This barrier limits the voltage and current – including any large power surges (which could result in devices sparking or over-heating) from entering the hazardous area. Generally, the recommended barrier type is galvanically isolated – this type of barrier enables safe wiring and installation without the added complications of earth screens being required.
A further required component in an addressable system is the protocol translator. This device is invisible to the control panel, but allows addressable devices within a hazardous area to communicate with the control panel even with much lower voltage and currents. Additionally, the wiring on an addressable system is manufactured in zonal circuits from the main loop. The scheme drawings for I.S. systems show spurs or radials of wiring into the hazardous area, but not looping back out again due to the system certification.
I.S. fire detection solutions are regularly specified for power generation plants, which carry a significant risk of explosion. Typical applications that Apollo has worked on include conventional and nuclear power stations, hydroelectric power, electric-switching and distribution stations. In the marine, oil and industrial sectors, Apollo has provided a range of analogue addressable and conventional I.S. solutions for cargo ships, passenger ships, ferries and military vessels, as well as offshore facilities.
Explaining I.S. legislation
With the potentially dangerous environments found in the marine, oil and industrial sectors posing such high risks, it is understandable that the emphasis placed on meeting strict health and safety standards is so high.
I.S. 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 I.S. equipment for certain hazardous environments became compulsory.
The ATEX Directive consists of two EU directives – one for the user of the equipment and one for the manufacturer. The first is the Directive 99/92/EC (also known as ‘ATEX 137’ or the ‘ATEX Workplace Directive’) on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres. The second is the Directive 2014/34/EU concerning equipment and protective systems intended for use in potentially explosive atmospheres.
The ATEX Directive is applicable to all equipment intended for use in explosive atmospheres (zoned areas), whether electrical or mechanical and including protective systems. It applies to a large range of equipment found in environments including fixed offshore platforms, petrochemical plants, mines, flour mills and other areas which carry the risk of a potentially explosive atmosphere.
Under the ATEX Directive, system owners are required to classify the areas where hazardous explosive atmospheres may occur into zones. 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.
Any electrical equipment located within these areas – such as sockets, lighting and computers – must be designed to be incapable of igniting any explosive mixtures, both in normal operation and also in a fault condition. Flameproof devices can be used in Zones 1 and 2 – areas where there is an intermittent danger or an accidental spillage – however, where there is a constant mixture of explosive gases or chemicals (Zone 0), I.S. equipment is the only permitted method.
The benefits of I.S. technology
In addition to providing reliable fire detection solutions, using I.S. technology in hazardous situations delivers a number of benefits, including:
- Least expensive – there is no requirement for lockable fused isolators, protected cable or special glands.
- Simple apparatus – it permits the use of normal industrial devices if they are non-energy storing.
- Fault tolerant – it is the only technique that stays safe after faults develop in cables and fallible components.
- Live maintenance – it is the only technique that permits live working without gas clearance certificates.
- Unarmoured cable – the system is electrically protected instead of being mechanically protected.
- Safe for personnel – it uses extra low voltages and currents.
- Safest technique – it is the only technique permitted for use in Zone 0.
Fully tested and certified
Given the volatile nature of the industries within which I.S. fire detection is installed, testing is a crucial part of the manufacturing process. At Apollo, we are dedicated to ensuring the safety of our I.S. technology, with all equipment rigorously tested in our Electro-Magnetic Capability (EMC) and fire test laboratories. Our production process protocol adds an extra level of confidence, requiring that all I.S. devices are tested at every stage and signed off by an approved operator.
As well as in-house testing, products used in I.S. settings also require approval by the industry authorities within the countries in which they will be used. Apollo’s I.S. products have, for example, received approval from BASEEFA – a British certification body for equipment intended for use in potentially explosive atmospheres.
I.S. systems and the future
The global demand for I.S. fire detection technology is predicted to continue to rise over the coming years in countries such as Russia and China with their ongoing investment in petrochemical plants, and in the UK where the offshore industry remains a significant user of I.S. equipment.
We’re well-placed to deal with this rise. Through innovative design and stringent testing procedures we’re confident that we can continue to meet evolving technologies and legislation within both the fire detection industry itself and the hazardous environments which we protect. The complex and challenging nature of fire detection is never more apparent than when we’re dealing with industries which carry potentially catastrophic risks, but we’re committed to working closely with specifiers and installers to ensure the best in protection.
For more information, go to www.apollo-fire.co.uk