HAZARDOUS AREAS FEATURE EMERGENCY LIGHTING SOLUTIONS


Raytec examines the important role that emergency luminaires play in improving safety in hazardous areas


W


hile emergency lighting is required for a wide range of different


applications, hazardous areas are often located in high-risk environments with unstable power sources which make the need for an effective emergency lighting solution even more important. While non-emergency lighting tends to use mains/AC power (or through a generator if the site is off-grid), emergency lighting is designed to provide light when the primary power source fails. Although there are different methods in how this back-up is supplied, such as through a central battery system or standby generator, the simplest and most common way is to use self-contained emergency luminaires. These emergency luminaires have their own back-up power source designed to initiate when the primary power source fails. As they are used in times of emergency (when the likelihood of power failures are high), having a system with an effective emergency lighting solution is essential. It assists in making evacuation quicker and safer and is a critical part of protecting the workers on-site. Imagine trying to evacuate an offshore rig. There would be a multitude of challenging elements facing you; now imagine the near impossibility of doing this in a blackout. This is why emergency lighting is so important. Aside from offshore applications, safe evacuation is important for industrial installations. Escape routes must be clearly identified and illuminated to allow safe movement towards exits in emergency scenarios. Standards exist to provide guidance on the specification of emergency lighting and every installation should comply with these standards as a minimum in order to protect workers.


SPECIFYING EMERGENCY LUMINAIRES With a better understanding of why emergency lighting is so important, we must consider the criteria and performance that an emergency luminaire needs to meet in order to be effective. Most commonly, the performance of a luminaire tends to be judged on its duration and/or output (the light output it will provide in emergency operation - generally measured as a percentage of its total light output in normal operation).


DURATION Given that emergency luminaires are powered by a battery, they are designed to provide output for a set time until the mains/AC power can be restored or the


site can be evacuated. As standards between sites differ, and the emergency duration requirement varies, it is important to consider the capability between different luminaires when specifying emergency lighting. Essentially, the question is: ‘Will the


luminaire provide adequate light output for a long enough period in order to evacuate or to restore power?’ The majority of industrial applications in the UK will require a minimum of three hours, as per guidance from the Chartered Institute of Building Services Engineers (CIBSE).


OUTPUT The amount of light output a luminaire can provide during emergency operation significantly affects the overall lux levels achieved on-site when mains/AC power is lost. Each application will have a minimum lux level to which they must comply with during emergency scenarios. This will be guided by emergency lighting standards. However, in practice, higher lux levels are often specified to account for any site specific tasks. The choice and quantity of luminaire affects how easily these lux requirements can be achieved. Traditionally, the light output of


luminaires can drop significantly when switching to emergency mode. Emergency fluorescent luminaires will typically drop to 20 per cent of their light output under emergency conditions. This may cause an issue if higher lux levels need to be maintained. More luminaires would need to be installed to raise lux levels on emergency. However a simpler, more cost effective solution would be to find a luminaire which can offer a greater output on emergency. Duration and level of output should be


considered together. The higher the light output on emergency, the shorter the duration - and vice versa. It is important to analyse the requirements of sites to get this balance right.


OTHER FACTORS Instant restrike – Emergency situations tend to arise without any warning, so having an emergency lighting solution capable of instant restrike is important. Maintenance – An emergency luminaire


will generally require greater levels of maintenance than a non-emergency luminaire. Batteries are consumable items that need to be replaced, but also depend on how well they are maintained. The extent of ongoing inspection and testing


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will depend on the specification of the battery - it will dictate the level of conditioning which may be required prior to the luminaire being installed and also how often the luminaire and battery should be cycled in normal operation. Understanding the maintenance demands of a luminaire is another important factor to consider. Visual aids – Visual aids can make


emergency luminaires easier to identify quickly, manage and maintain. For example an indicator or status light, usually as part of a self-testing feature, can quickly tell the user the health status of the emergency battery. Understanding why emergency lighting


is required leads us to look at the technology that enables this.


Emergency flood luminaire - UAE jack-up rig


LED VS CONVENTIONAL LIGHTING Earlier versions of emergency luminaires used traditional discharge lamps. However, these were very rare due to their size, weight and cost limitations and generally only used for specialist applications. Currently they are not considered a viable emergency lighting solution. When fluorescent emergency lighting emerged, it represented a significant development from discharge solutions. However, LED emergency lighting offers even greater performance advantages. While it is relatively easy to find a


luminaire which meets the required output and duration on paper, it is important to consider the other factors which affect the luminaire’s performance in real terms. With reliability being imperative to the effectiveness of an emergency luminaire, LED represents a big improvement on fluorescent technology.


THE FUTURE - BATTERY TECHNOLOGY The battery is an essential component of any emergency luminaire, so as battery technology advances it aids the development of new and improved emergency lighting solutions. The progression from lead acid to Ni-Cd batteries has helped to reduce the size and weight of emergency systems thanks to their higher energy density. While other battery technologies with greater energy density than Ni-Cd exist, such as Ni/MH (Nickel Metal Hydride) or Li-ion (Lithium Ion), other limitations prohibit them from being commonly adopted. Ni-MH suffers from a shorter life cycle and the volatility of Li-ion leads to concerns over its suitability for use in hazardous areas.


INDUSTRIAL COMPLIANCE | AUTUMN 2017


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