Equipment for safe and reliable operation
Changes in legislation and technology related to portable lighting for confined spaces and ‘EX’ hazardous areas.
Confined spaces and ‘EX’ hazardous areas are locations where explosion hazards, caused by potentially explosive gas, vapour, mist or dust atmospheres, can be commonly found. Such atmospheres are present in many industries and sectors, including the petrochemical, marine, offshore and aviation industries, in the utilities and in fire-fighting activities; and are most likely to occur in areas where flammable materials are stored or used in manufacturing, and in enclosed or partially enclosed spaces, such as process vessels, storage tanks, culverts, sewers, tunnels and shafts.
Why ATEX lighting?
Tasks carried out in hazardous areas and confined spaces can often be in conditions of reduced visibility or darkness; lighting can become critical to any activity in such areas. Due to the nature of confined spaces and hazardous areas, the presence of permanently installed lighting is unlikely. When such areas must be accessed, for inspection, cleaning or maintenance activities, portable or temporary lighting must be used. Risk of explosion or fire from ignition of the atmosphere means that any electrical equipment used must be safe in such dangerous environments. The UK Health and Safety Executive advise that, with regard to the Confined Spaces Regulations 1997, ‘specially protected lighting [is] essential where flammable or potentially explosive atmospheres are likely.’
All new lighting for use in these conditions must be ‘ATEX’ approved, confirming the equipment is designed and tested to relevant EN standards for safe use in potentially explosive atmospheres, even in fault conditions.
The major ignition risks considered when portable ‘ATEX’ lighting equipment is designed and approved are:
- High temperatures (from lamps/light sources, and from battery packs and electronic components in short circuit fault conditions)
- High-energy incendive sparks (caused by battery pack short circuits and circuit faults)
- Electrostatic hazards (from the enclosure)
- Damage to a torch resulting in exposure of the lamp hot filament to the surrounding hazardous atmosphere, enhanced mechanical protection of the torch enclosure is required to minimise this risk
ATEX lighting selection
A wide variety of ‘ATEX’ explosion-protected lighting is available. To ensure safe use, the correct selection criteria are critical:
- Characteristics of the explosive atmosphere (temperature class, gas group, zone)
- Amount and type of light required for task
- Task duration
- Conditions (e.g. wet, harsh)
Legislation and regulations – ATEX equipment
The ATEX Directives now place a legal obligation on the employer to ensure appropriate electrical equipment is used by workers where a potentially explosive gas, vapour, mist or dust atmosphere may be present.
The 94/9/EC (ATEX Equipment) EU Directive deals with ‘equipment and protective systems intended for use in potentially explosive atmospheres’. Only ‘ATEX’ equipment CE marked compliant with this Directive may now be sold within the EU for use in shore based applications or on fixed offshore platforms where potentially explosive atmospheres may be found.
The 99/92/EC (ATEX Workplace) Directive covers the ‘minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres’. The Directive lists a set of obligations for employers, requiring a risk assessment based strategy for the prevention of explosions and fire. All workplaces within the EU where explosive atmospheres may be found must comply with this Directive by 1 July 2006 .
The UK Government has implemented the 99/92/EC Directive as the Dangerous Substances and Explosive Atmosphere Regulations 2002 (DSEAR). These regulations also include the fire safety aspects of the 98/24/EC Chemical Agents (CAD) Directive.
ATEX and DSEAR require that all equipment for use in explosive atmospheres must be risk assessed for safe use, risk assessment should include:
- Confirmation the ‘ATEX’ or ‘Ex’ equipment has an approval for use in explosive atmospheres (existing ‘Ex’ equipment may continue to be used)
- Verification that all equipment is appropriate for use in the explosive atmospheres expected to be encountered. The equipment approval code (incorporating temperature class, gas group, and indication of compatable hazardous area zones) should be compared with the properties of the hazardous materials anticipated to be met (temperature class and gas group) and the likelihood that the material will be present (hazardous area zone). Consideration must be given to the way in which mobile or portable work equipment is used, identifying whether this may lead to the use of equipment in areas with different hazard potentials (zones, temperature classes or gas groups)
- Environmental conditions the equipment will encounter should also be considered (resistance to water, dust, chemical attack, impact and harsh conditions, etc.)
- Confirmation that equipment is operated and maintained with due regard to safety
ATEX portable lighting technology – light sources
An incandescent filament must burn in an oxygen-free atmosphere to prevent oxidisation and premature filament failure. The glass envelope surrounding a filament must contain a vacuum, or an inert gas that can support the burning of the filament. The original vacuum lamp technology works effectively, but has a lower efficiency and gives a beam with a less desirable ‘warm’ colour temperature. Safety torches using lower power vacuum bulbs can have the benefit of a cooler burning light source, giving a universally usable T6 temperature class.
With the drive to have higher power, whiter beamed, more efficient light sources, lamps filled with inert gases such as krypton, xenon and halogen, have been developed, allowing the filament to burn hotter. Halogen offers the advantage of the highest lumens per watt efficiency for a filament lamp, with an impressive white beam. Halogen lamps are a high specification technology, with a higher cost per unit compared to other filament lamp types. Many users readily accept this premium to benefit from a superior light output, particularly in safety applications where visibility is critical.
LED or Light Emitting Diode technology is the next generation light source for lighting in general, and for portable safety lighting in particular. The white LED was developed in 1996; from very limited initial application, LEDs have seen greater and greater use in portable lighting over the last 10 years. White LEDs were originally restricted to low power devices such as the widely used 5mm package, effective as an indicator, but poor as an illuminator and unable to offer a real alternative to the incandescent torch bulb, even when used in a cluster. It was not until the development of the high-power 1-watt LED, six years ago, that a serious contender to the filament lamp emerged.
For a simple low cost torch the incandescent lamp is still the favourite, high power LEDs are still too expensive. However LEDs come in to their own when a technical product with a higher specification, higher performance and higher reliability is required.
Incandescent lamps use a comparatively fragile tungsten filament light source, susceptible to fracture if subjected to impact from knocks or drops. LED technology offers a far higher reliability because of an inherently more robust construction with a greater resistance to the rough use expected from harsh environments. Furthermore, the 20-30 hour typical filament life of an incandescent torch bulb is insignificant when compared to the 25,000 plus hour life of an LED. LED light sources are ‘fitted for life’ and will more than last the life of a torch, requiring zero maintenance.
LEDs have always been marketed as offering a far greater efficiency than incandescent filament sources, more lumens per watt. Until recently this has been a difficult comparison to make because of the significant differences in achievable light output levels. With the advent of the high power LED, the true comparison can be made. Currently the difference in efficacy between halogen incandescent torch bulbs and LEDs can be double (typically 12 lm/watt on low voltage halogen lamps compared with 24lm/watt on high power LEDs), with the promise from LED manufacturers that their efficiencies can and will increase significantly in the near future.
Specific benefits for ATEX equipment
In addition to the benefits already outlined, LEDs offer real advantages for portable hazardous area equipment. They are a ‘cool’ solid-state technology; they do not present the hazards of hot filaments in incandescent lamps, but lend themselves to higher levels of protection with the opportunity of use in category 1 equipment for Zone 0.
LEDS give an excellent, controlled light, which is considerably whiter with a higher colour temperature than halogen lamps. However with high power LEDs still in their infancy, there has been a lack of experience and knowledge in applying optics. ‘Off the shelf’ solutions are available, generally developed for commercial lighting installations, but are often not suited to torches. Portable lighting manufacturers are starting to develop products with bespoke LED optics, some offering very impressive solutions.
Good LED optical solutions can offer excellent beams without the shadows, rings and black holes often found using filament bulbs. Poor LED optical solutions can result in low light levels, uneven beams or high intensity ‘tight’ beams with no fringe light outside the beam. These can all give problems, but the latter can create real hazards in a confined space where surrounding obstructions or obstacles are not visible; users have reported with such products that when pointing the beam straight ahead, nothing can be seen on the ground, above, or to the sides, ‘which is like walking with blinkers on’.
Traditionally the light output from torches has been measured in ‘candlepower’. This can give an indication of light intensity, but does not give the full picture, with no suggestion of how effective the beam is. A fuller picture is given when looking at the power of the light source in watts (generally the more watts the brighter, although different types of source can be more or less efficient), the lumens output from the light source will convey the amount of light generated by the bulb or LED, and finally the lux value for the torch or lamp to identify light intensity at a particular distance, typically 5 metres. Ultimately the recommendation is to take a number of different torches into a dark area and compare the light. This is the only way to get a true feel for how effective the beam spread and intensity is, in the actual conditions.
ATEX portable lighting technology – batteries
Primary cell safety torches have traditionally used low power zinc cells. Zinc cells are still specified for use with some T6 torches, but now with newer methods of assessment and changes in safety standards, ATEX torches using high power alkaline cells are becoming the norm. Alkaline cells typically have 3-4 times the capacity of zinc cells, giving the benefit of a torch able to run higher power light sources for longer durations. Users must be beware though, safety torches now have tighter restrictions on the approval of cells, only specified brands and types of cells may be used.
Consideration should be given to the number and size of primary cells required by a particular torch, and how long the cells will power the torch light source, as this will affect product ‘life-time cost’. Small sized primary cells can be less expensive than larger cells, but will have considerably less capacity; generally D sized cells offer the best value with the lowest price per ‘watt hour’.
Additional features are now becoming available with primary cell safety torches, such as spare bulbs and low battery warning indicators. Such features can attract a price premium, however users should not forget the benefits. In addition to the added user safety from the low battery indicator, particularly in confined spaces where the risk of being ‘left in the dark’ is reduced, users are reporting environmental and financial benefits over previous practice, now cells are replaced only when they need to be.
In the past, rechargeable ‘Ex’ equipment has been regarded as unreliable, users reporting bad experiences with devices such as rechargeable torches, radios and gas detectors. Reliability problems appear to have centred around the nickel cadmium (NiCd) and nickel metal hydride (NiMH) battery chemistries, and have related to ‘battery memory’ and loss of capacity. Battery suppliers claim the problems experienced relate more to the control and use of the rechargeable batteries, rather than the batteries themselves. Rechargeable battery technology has made many advances in recent years.
As a result of consumer demands for an ever-increasing array of electronic devices to be made available with greater reliability, and without the inconvenience and expense of primary cells, rechargeable batteries and the associated charge and discharge control technology has improved immeasurably. Lithium Ion (Li-Ion) rechargeable battery chemistry has emerged over the last few years as the battery technology of choice for high-end electronic equipment from cell phones to laptop computers. The key advantages of Li-Ion cells are a very high power density with a low weight, high cell voltage, environmentally friendly, low self-discharge, no memory effect and a fast charge rate. The advances in rechargeable battery control technology and the use of Li-Ion cells are starting to be applied to rechargeable ATEX torches.
- Intrinsic safety protection. Small, fully portable ATEX compliant equipment will most likely be approved partly or fully to the ‘Intrinsic Safety’ protection concept, providing current limiting of battery power to a safe, non-incendive level
- Battery charge control. For long-term reliability of rechargeable systems, equipment should have full electronic charging control, cutting off charge but monitoring capacity once the battery is fully charged. This is essential for both cyclic (continuous regular use) and standby (emergency) applications
- Low battery cut-off. Shuts the battery off when capacity gets too low; prevents battery damage and premature battery capacity loss and failure
- Low battery warning. Alerts the user to immanent battery cut off; warning can include switching output to low power and repeatedly flashing the beam off momentarily
- Battery power indication. Shows battery state of charge for both charging and discharging
- Dual power light output. Cuts down the light output for extended battery duration
- Quick charging. Particularly important for critical and emergency applications
- Multi voltage charge input. Facility to power from a variety of voltages including 12V for smaller vehicles, 24V for trucks and fire-vehicles, 120V for site voltages, 230V for general mains charging and 254V for offshore ‘rig’ voltage
- Low and easy maintenance, including battery replacement
- Emergency lighting mode, illuminates the torch when power to the charger fails
The selection of one battery system over another comes down to a number of factors:
- Level of usage, high usage may justify higher cost rechargeable equipment
- Size of equipment/light output required, generally larger lamps will be rechargeable, smaller torches will be primary cell
- Level of acceptable maintenance – primary cell equipment is higher maintenance
- Level of equipment issue – generally primary cell torches are personal issue, rechargeable products are often for general usage, supplied for a task
ATEX portable lighting technology – other factors to consider
- Is the product construction resilient enough to withstand anticipated usage?
- Are the enclosure materials resistant to any chemicals that may be encountered?
- Is the equipment suitable for the environmental conditions (dust/water tight)?
- How easy is the equipment to hold and use, does it offer single-handed switching?
- Is the equipment sufficiently lightweight?
- Is there a ‘hands free’ requirement? Can the equipment be head mounted or is it a right-angle style torch with clip for use on a belt or jacket?
- Consider product ‘life-time cost’ of primary cells versus the purchase cost of a rechargeable unit
- Consider product ‘life-time cost’ of a filament bulb torch, with replacement lamps and maintenance cost, versus the cost and performance of an LED unit
- Consider the comparative levels of maintenance and ease of maintenance required for individual products
- Some emergency service organisations now look at a ‘spend to save’ policy, believing that spending more on better specification, better performance and lower maintenance equipment will give long term cost savings
Different tasks in confined spaces or ‘EX’ hazardous areas will require different types of lighting; following is a list of portable and temporary ATEX lighting product types and examples of where how they are used.
Safety torches – the most commonly found and generally lowest cost form of portable ‘Ex’ lighting. Frequently found as a personal issue light source for simple maintenance and inspection. Straight torches are more commonly found in continental Europe, but the right-angle torch with integral clip is more prevalent in the UK for ‘hands free’ applications. Torches are most generally primary cell, but rechargeable safety torches are becoming more popular.
Handlamps – generally ‘Ex’ handlamps are more powerful than a safety torch. They are commonly found as a rechargeable product, but are also available in primary cell form. Again, usage is centred around inspection and light maintenance work.
Mini torches – now more commonly used because of their greater availability and convenient small size, they are ideal for use in very localised inspection work. Many use a filament bulb as a light source, more are now starting to use LED light sources. Mini torches are almost exclusively primary cell powered.
Head torches – ideal for true hands free use, useful for maintenance, but can have limitations. The original ‘Ex’ head torches were developed from miner’s cap lamps, newer products benefit from being smaller and lighter weight without the belt mounted battery pack, but often lack the light output and long duration of their predecessors.
Worklights – offer a greater level of light output than portable equipment but are bulkier and much heavier. Worklights are generally used in temporary lighting installations, and are ideal for involved maintenance activities, such as cleaning, shotblasting and re-coating of tanks, or for general illumination to and from the site of maintenance work. ATEX worklights can be battery powered, mains powered lead lamps, or compressed air powered lamps.
A wide selection of specialist ‘ATEX’ lighting equipment is available for use in confined spaces and ‘EX’ explosive atmospheres. Legislation has changed dramatically in the last few years, as has torch technology, making it important that users keep up with developments. It is critical that equipment is selected, used and maintained correctly to give safe and reliable operation.
Alex Jackson B.Sc. (Hons), MA, Technical Director, Wolf Safety Lamp Company
Saxon Road Works, Sheffield, S8 0YA, EnglandTel: +44 (0) 114 255 1051
For a free copy of the ‘ATEX Explained’ Poster Guide, e-mail with contact details including address to [email protected] , or go to www.wolf-safety.co.uk and visit the ‘ATEX’ section to view in electronic form.
Published: 01st Apr 2006 in Health and Safety International