FEATURE EMERGENCY LIGHTING
AN ILLUMINATING INSIGHT INTO EMERGENCY LIGHTING TRENDS
Raytec looks at how developments in LED and battery technology is improving the design and functionality of emergency luminaires
E
mergency lighting is critical to safety in hazardous areas, especially where there
is a risk of power failures. While 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. In times of emergency, safe evacuation is
important for industrial installations. Escape routes must be clearly identified and illuminated to allow safe movements towards and through the exits. Specific 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 site personnel. Specifying Emergency Luminaires: Most
commonly, the performance of a luminaire tends to be judged on its duration (the length of time the luminaire can provide backup illumination) 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 (a limited power source), 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
26 SEPTEMBER 2017 | PROCESS & CONTROL
require a minimum of 3 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. 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, so more luminaires would need to be installed to raise lux levels on emergency, or a simpler solution is 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 for an end user to analyse the requirements of their site to get this balance right. Other factors affecting specification
Emergency Flood Luminaire - UAE Jack-Up Rig. Lifeboat systems found on any offshore vessel or jack-up rig, are a good example of an offshore application where emergency lighting is required. Having a lifeboat system with an effective emergency lighting solution is essential. It assists in making evacuation quicker, easier and ultimately safer and is a critical part of protecting the workers on-site
include the capability for instant restrike, maintenance requirements, and visual aids that can make emergency luminaires easier to identify quickly, manage and maintain. Understanding why emergency lighting is
required, and the features and performance criteria that go into an effective emergency luminaire, leads us to look at the technology that enables this. LED technology has helped improve the performance and functionality of emergency lighting, and offers advantages over conventional emergency lighting. While it is relatively easy to find a
luminaire which meets the required output and duration on paper, it’s important to consider the other factors which affect the luminaire’s performance in real terms. With reliability being imperative, LED represents a big improvement on fluorescent technology. When it comes to the future of
emergency lighting several factors will have an influence. Battery Technology –The battery is an essential component of any emergency luminaire, and 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 batteries technologies with greater energy density than Ni-Cd already 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. Continued advances in battery technology will further optimise the design and performance of LED emergency luminaires. LED technology –As LEDs become more
efficient, the same level of output can be achieved using less power. This will allow smaller batteries to be used to improve design or to offer greater duration. Intelligent Emergency – Developments
in self-testing luminaires, which automatically cycle batteries and provide health indicators, are starting to make inspection and maintenance quicker and easier for users by automating the process. Removing the reliance on operators reduces the chances of human error or neglect, which may affect luminaire performance. Intelligent emergency solutions use a microprocessor which is programmed to automatically cycle the batteries - typically every 2-3 months. The results are then highlighted using a tri-colour LED indicator, visually notifying the user if everything is working as it should be or of any faults which require further investigation.
Diagram shows the energy density of various battery technologies
Raytec
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