Emergency Lighting For Hazardous Areas
Published 24 Sep 2019
Hazardous areas are often located in high-risk environments with unstable power sources which make the need for an effective emergency hazardous area lighting solution absolutely critical to achieving the highest levels of safety on site.
In applications where there is a high risk of power failures emergency lighting plays a crucial part to safety of plant and personnel in hazardous areas. These hazardous areas mostly occur in high-risk environments with unstable power sources.
Differing to non-emergency lighting which usually uses mains/AC power Raytec emergency lighting enables a lighting solution even when the primary power source fails. The simplest way to ensure a back-up is supplied is to use self contained emergency lighting saving the need for a central battery system or standby generator. As previously mentioned emergency lighting has its own back up which is activated when the primary power source fails.
This paper will review a number of key topics surrounding emergency lighting:
- Why emergency lighting is required
- Key factors when specifying an emergency luminaire
- How LED technology has improved emergency lighting solutions
- The importance of maintenance on an emergency luminaire
- Technology developments and the future of emergency lighting
The Need for Emergency Lighting
in Hazardous Areas
Safety is the main reason for the development and the use of emergency lighting. Safety of personnel on site is paramount, a reliable lighting solution can greatly reduce the risk of injury especially in times where the mains/AC power is lost.
Emergency lighting is especially important if a site has an unstable power supply, such as offshore and mobile applications which rely on the use of generators as their primary source. These generators are prone to power failures which increase the reliance the site has on back-up illumination.
A good example of an application where emergency lighting is very important is offshore particularly in lifeboat systems where an effective emergency lighting solution is imperative.
Evacuating an offshore rig is a difficult change in itself – imagine trying to get all aboard safe without any lighting?! It just doesn’t bare thinking about.
Pro-Tip Emergency lighting is especially important for applications with unstable power supplies where light failures occur more frequently.
Industrial installations also require emergency lighting as clear escape routes need to be visible to allow personnel to exit emergency situations safety. Specific standards need to be adhered to ensure the site is compliant.
Specifying Emergency Lighting
With a better understanding of why emergency lighting is so important, now we take into consideration the criteria and performance that an emergency lighting needs to meet in order to be effective.
Performance is often measured by looking into the duration (length of time the light can provide back up illumination) and/or output (the light output it will provide during an emergency operation usually estimated as a percentage of total light output in normal operation.
Given that emergency light fittings 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 types 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?’ Some applications (such as the lifeboats which were mentioned earlier) will require maximum lumen output for around 30 minutes so those on site can be evacuated quickly. Other applications will require longer duration.
The majority of industrial applications in the UK will require a minimum of 3 hours, as per guidance from the Chartered Institute of Building Services Engineers (CIBSE). However each application has different requirements so it is very important that the correct emergency lighting is selected.
Overall lux levels that are reached when the mains/AC power is lost shows the amount of light output required during emergency operations. Each application will have a minimum lux level to which they must comply with during emergency scenarios.
It is not unusual for higher lux levels to be specified as the choice and quantity of luminaire affects how comfortably the lux requirements can be reached (all guided by emergency lighting standards).
Commonly, the lightout of luminaires can decrease dramatically when switching to an emergency mode, i.e. emergency fluorescent luminaires will typically drop to 20% of their light output (at best) under emergency conditions.For some applications this can be an issue as minimum lux requirements on emergency do tend to be lower than in normal operational mode therefore as previously mentioned it is best to have higher lux levels that are 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.
SPARTAN LED Emergency lighting offer up to 100% light output on emergency, ensuring there is no loss of output when switching to this mode. A high output must be maintained during an emergency so the lux requirments can be met with the smallest quantity of emergency luminaires, maximising efficiency.
Duration and level of output should be considered together as both affect the performance of the other. 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.
Instant restrike – emergency situations can be unpredictable so the solution must be capable of instant restrike. If a delay occurs the site will be in darkness possibly harming personnel and hindering evacuation plans
Maintenance – very important and will be discussed further later but for now it is important to be aware that emergency luminaires require more indepth inspection. Understanding the maintenance demands of a luminaire, and how it differs between LED and other technology types, is another important factor to consider.
Visual aids – clearly marked visual aids help with the management and maintenance of emergency luminaires. An indicator or status light, usually as part of a self-testing feature, quickly tells the user the health status of the emergency battery and whether the fitting is working correctly. Features can be used to clear identify which of the products on site are emergency eg SPARTAN emergency luminaires feature a red end cap or casting where the emergency battery is housed.
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. Specifically, we will look at LED technology and how it has helped to improve the performance and functionality of emergency lighting.
LED vs Conventional
Now it is time to detail the performance advantaged of LED lighting in emergency fittings considering other conventional discharge lamps in addition to the comparisons with fluorescent.
Discharge Emergency Lighting
Discharge lamps are almost extinct as they have many limitations and can only be used for specific applications due to the very large and very heavy battery back up systems (these are often more bulky than the light fitting itself).
These physical constraints meant the batteries could not be contained within the housing of the luminaire, causing difficulties with installation. Nowadays smaller lead acid batteries are an option as battery technology has developed, the high-consumption of discharge lamps means that any emergency variant would still require higher capacity batteries which are naturally larger and heavier.
Discharge lamps can’t instantly restrike meaning it could be minutes after mains/AC power is lost before the lamp is able to provide emergency illumination to the site. With time being crucial to safety, using more modern technology which allows an instant restrike is a much more effective solution.
The size, weight, cost and limitations in performance of emergency discharge lamps generally make them unsuitable for the majority of applications. For this reason, installations of these traditional solutions are rare with the vast majority of modern installations opting for fluorescent, or more recently, LED emergency luminaires.
Fluorescent and LED
Discharge solutions are now a thing of the past thanks to the development of fluorescent emergency lighting. One major benefit of fluorescent lighting is their low power consumption which in turn increases the emergency battery life.
Smaller batteries that can be housed in the luminaire are now available thanks to battery technology advancements. Nickel Cadmium batteries are most commonly used given that they boast a significantly better energy density, making them smaller and lighter to a comparable lead–acid battery.
Given the advantages of fluorescent luminaires over discharge lamps, you may wonder why a site should consider switching to LED?
Advantages of switching to LED and consider them in the specific context of emergency luminaires:
- Failures – fluorescent luminaires, especially with older units, have a tendency to fail when suddenly switching to run at a lower power. This is largely due to the deterioration of components, such as the ballast or starter, and being unable to provide the necessary punch to restart the tubes using the emergency battery. As LED fittings tend to use an electronic PSU (power supply unit) without the need for ballasts or starters, they are more reliable with less risk of failure.
- Performance drop – using UK standards as an example, over a 3 hour period when the luminaire is in emergency mode, even in optimum conditions, the lumen output of a fluorescent luminaire will decline significantly. LED luminaires do not suffer from this problem as they use a more advanced electronic PSU than the ballasts used in a fluorescent and the LEDs run at a constant power throughout the emergency duration and will not suffer from any drop in output. Maintaining a constant light output is important in order to achieve the minimum lux levels that are required to evacuate or restore power safely.
- Effect of environmental conditions – the performance of a fluorescent dips dramatically when exposed to extreme temperatures; this severely impacts output in emergency mode. A fluorescent luminaire will generally drop to at least 20% output in emergency conditions as a twin tube fluorescent will light one tube at a maximum 40% power. When taking into consideration the effect of a cold environment (and with the understanding that the lower the temperature, the greater the drop in output of a fluorescent tube) the performance in emergency mode of fluorescent luminaires can be significantly reduced and significantly underachieve the required specification in challenging environmental conditions. In contrast, LED luminaires provide a much more reliable emergency solution; the LEDs will run at the required power, across a much wider temperature range, ensuring the luminaire meets the demands of the application regardless of environmental conditions.
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. LED technology provides an effective and vitally important improvement on fluorescent lighting.
Maintaining Your Emergency Fitting
As emergency lighting is so important to site safety, understanding the importance of maintenance and following the correct procedures to ensure the luminaires are working effectively is essential to any site.
Inspection and Testing
All hazardous area lighting must be inspected periodically to ensure operations are safe and effective. LED’s decrease the time needed for maintenance by removing the need for relamping and by offering a longer lifetime.
While these benefits translate to emergency luminaires in the same way, more frequent inspection and testing should be carried out to preserve the life and performance of the emergency battery. Depending on how well maintained the batteries are they should only need changing every 5-7 years depending of frequency of use.
Pro-Tip Emergency luminaires should be inspected and tested regularly to preserve the life and performance of the emergency battery.
Faults in emergency lighting can be harder to spot (especially in non-maintained luminaires) as they don’t happen as often and unlike non-emergency can’t be identified by the loss of light input in normal operation. A detailed test procedure is required so faults can be established prior to an emergency situation arising.
Battery specification determines the type and how often the battery should be tested or inspected: 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.
As an example, every emergency SPARTAN luminaire will be shipped with the battery fully charged and disconnected to ensure there is no drain on the battery. On receipt of the product the customer should discharge and then recharge the battery prior to installation. This will ensure the battery is working to full capacity although future cycling will vary depending on the requirements of different sites
Upon receiving the luminaire, the user is advised to discharge and then recharge the battery before installation to ensure the battery is working at its optimum, while future cycling will vary depending on the requirements of different sites.
The testing procedure is simple: routinely cutting power and visually checking that all emergency luminaires are functioning correctly. More advanced testing measures
The developments in self-testing luminaires, which automatically cycle batteries and provide visual health indicators, are starting to make this process even easier with more intelligent testing methods.
Most of the time luminaires are not installed on site straight away and are just kept in storage as a back up in case the existing unit fails, needs replacing or requires a scheduled test and inspection break. The emergency lighting can be left a while before the luminaire is actually installed and switched on: this presents a risk. If the battery is left connected to the luminaire’s PSU, the there is a chance it will begin to slowly discharge.
This could affect the battery’s capacity, it is possible that cycling the battery could partly restore it however returning the battery to as good as new is rather unlikely. The effects of this degradation may render the luminaire useless if it no longer meets the minimum emergency duration and light levels required on-site.
Batteries should therefore always be disconnected if it is known that they are going to be switched off or left in storage before installation. This will ensure the battery cannot be drained and maintains its capacity for optimum performance. With this in mind, all SPARTAN LED emergency luminaires are shipped with the battery disconnected.
Pro-Tip Until the unit is installed, an emergency luminaire should have the battery disconnected to prevent any drain on the emergency battery.
Battery Maintenance Do’s & Don’ts
- Check for any specific conditioning procedures prior to installation
- Ensure there is a constant power source to the luminaire which keeps the battery charged
- Ensure a testing/cycling procedure is in place which meets the requirements of the battery/luminaire
- Leave the luminaire in storage with the battery connected
- Assume the luminaire and battery will perform as expected – batteries are consumable and ongoing inspection and testing is important
- Charge the batteries with anything other than the PSU provided by the unit
- Use replacement batteries from anyone other than the manufacturer of the luminaire. Using alternative batteries invalidates the hazardous area certification
The Future of Emergency Lighting
As discussed earlier the battery is a hugely important component of any emergency light fitting luckily as battery advancements occur this can only enhance emergency lighting solutions. Size and weight of batteries has been greatly reduced thanks to the change from lead acid to NiCd batteries.
While other battery 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 makes it unsuitable for use in hazardous areas.
Battery technology is improving from continued developments. Other industries such as the automotive welcome new developments also as they push towards electric vehicles.
Inevitably, battery technology will progress to combine greater energy density with improved functionality, which can be adopted to further optimise the design and performance of LED emergency luminaires.
Pro-Tip Energy density is the amount of energy stored in a given system or region of space per unit volume. In the context of batteries, those with a high energy density will be smaller and lighter than batteries with lower energy density, while offering equivalent capacity.
Advancement in LEDs
LEDs are constantly evolving, they are becoming more efficient using the same level of output and this can be achieved using less power. This will allow smaller batteries to be used to further improve the physical design of emergency luminaires, or alternatively could mean greater duration can be achieved thanks to reduced consumption and a smaller draw on the battery.
This whitepaper has already highlighted the importance of inspection and testing of emergency luminaires and touched upon the development of intelligent emergency products that help to make maintenance quicker and easier for users by automating the process.
Human error is greatly reduced when removing the need for an operator which could affect the performance in the event of an emergency.
Intelligent emergency solutions are starting to become more frequent, such as the one employed on SPARTAN Linear emergency luminaires. The cycle of batteries is automatically programmed every 2-3 months using a microprocessor. A tri-colour LED indicator highlight the self-testing results alerting the user if any issues need addressing.
SPARTAN luminaires have two important features built into the design of their intelligent emergency system:
Testing at 100% output – when a SPARTAN luminaire automatically enters a discharge cycle there is no drop in light output and the luminaire will continue to operate at full power. This is an important feature given that it is difficult to know when a luminaire will enter a discharge cycle. Without this function, there is a risk of a drop in light output under normal operation while an important task is being carried out.
Random testing – the microprocessor in SPARTAN’s emergency system is programmed with a random factor to prevent self-testing occurring at the same time. Without this, testing cycles between luminaires may occur at the same time; presenting a risk of the entire installation of emergency units being at low charge should an emergency scenario suddenly occur.
Reserve capacity – during a testing cycle SPARTAN will not discharge to below a third of its battery’s capacity, ensuring every luminaire will still be able to provide emergency output regardless of whether it’s in a testing phase.
It is imperative that disruption is kept to a miniumum when mains/AC power is lost during testing. Hopefully as further developments occur more design features will become available to make maintenance even easier.
Pro-Tip Intelligent emergency systems makes the process of maintaining emergency luminaires far easier and increases safety on-site by reducing the chances of human error and neglect.
Future Trends in Emergency Lighting
- Improved Battery Technology
- Increased LED Performance
- Intelligent Self-Testing
Technological advancements have had a positive impact on the design and performance of emergency lighting in particular LED’s when compared to traditional discharge and fluorescent solutions. Ultimately this improvement increases safety to those who work in areas where emergency lighting is required.
The nature of hazardous area equipment means maintenance and inspection of emergency luminaires still plays an important role in ensuring they are operating effectively, while the development of intelligent emergency systems have made this easier and safer for users. As LED and battery technology develops further the opportunity to make more improvements to the design and functionality of emergency luminaires increases.
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