When working in confined spaces offshore, safety is of the utmost importance. Lighting plays a crucial role, not only in ensuring visibility but also in maintaining a safe working environment. In this blog, we explore the key differences between low-voltage (typically 110V) and extra low-voltage (typically below 25V) ATEX lighting, focusing on their applications, benefits, and limitations.
ATEX Lighting and Safety Guidance
The Health and Safety Executive (HSE) provides guidance/recommendations on safe practices in confined spaces. One such recommendation includes the use of extra low voltage equipment (typically less than 25V) to reduce the risk of electric shock, in certain confined spaces such as “inside metal tanks”. Our interpretation of this recommendation is that it’s aimed towards lighting used in smaller confined spaces, such as pressure vessels/silos, where extra low voltage lighting is a more suitable and pragmatic control measure. The reference to “metal tanks” can and has caused a lot of confusion/ambiguity when considering the lighting requirements for very large confined spaces such as the hull tanks of offshore floating structures.
It’s important to note that this is guidance, not legislation. The Confined Space Regulations 1997 do not mandate the use of extra low voltage lighting, but it’s use should be considered as part of a broader safe system of work, based on the nature of the space, the risks present, and the activities being carried out within.
Key Safety Considerations
There are three main safety considerations which dictate the choice of lighting we use for our offshore work scopes involving entry in very large, confined spaces:
- Ability to illuminate large/complex spaces.
- Risk of electric shock.
- Risk of explosion from electrical sparks.
Definition of a Large Confined Space
Under UK regulations, a confined space is defined as one that is fully or mostly enclosed, where there is a foreseeable risk to workers from hazardous substances or unsafe conditions. These risks might include low oxygen levels, exposure to toxic gases, or the danger of fire or explosion.
Importantly, confined spaces aren’t always small. The Health and Safety Executive (HSE) notes that confined spaces can range from narrow chambers to very large areas like grain silos, which can hold hundreds of cubic metres.
On Floating Production Storage and Offloading units (FPSOs), the hull tanks clearly meet this definition. Cargo tanks typically have a volume capacity of more than 5,000m³, while ballast tanks range from around 2,000m³ to 8,000m³. These are large, enclosed environments that still carry significant risks, particularly during inspection and maintenance activities.
Keeping the FPSO’s hull in good condition while on-station requires maintenance teams — usually 4 to 10 people working inside these tanks for days or even weeks at a time. Access can be challenging: the furthest parts of a tank might be 80 metres from the main entry point.
Because of this, any thorough risk assessment should consider what would happen in an emergency. If power fails, workers could be left in complete darkness, creating a serious safety issue. As such, proper emergency lighting must be installed to allow safe evacuation.
Practicality and Deployment
One of the primary advantages of 110V systems is their scalability. With the ability to link up to 20 lights in series, these systems can illuminate large tanks or spaces without significant voltage drop. This makes them ideal for extensive offshore projects in very-large/complex confined spaces, where workers need sufficient illumination in very-large/complex spaces and over long distances.
Extra low-voltage systems, on the other hand, are more suited for smaller, enclosed areas where only a few lights are needed. Their limited range and linking capacity mean they are less practical for larger applications. At 24V, voltage drop becomes a significant issue, limiting the distance between the power source and the light to around 5 metres. Furthermore, only about five lights can be linked in series before performance deteriorates.
Electric Shock Mitigation
Low-voltage lighting, such as 110V systems, can still be used safely when proper precautions are in place. Offshore, we ensure all tank lighting is powered from our Safe System of Work (SSOW) power distribution skids fitted with residual current breakers (RCBs). These devices quickly cut off power if a leakage to ground is detected, typically caused by any cable damage. Additionally, all cables are protected by earthed steel wire braiding and are routinely inspected before and during use.
In contrast, extra low-voltage lighting reduces the potential for electric shock due to its inherently safer voltage levels. This makes it particularly suitable for smaller, metallic confined spaces like pressure vessels or silos, where workers are in close proximity to conductive surfaces.
Explosion Risk and ATEX Certification
All lighting used in potentially explosive atmospheres must be ATEX certified for the appropriate zone they’re being used within. Zone 1 lighting is standard for many offshore operations, including ballast and cargo tank entries. Regular certification ensures that both the light fittings and cables are safe for use in hazardous environments.
Both low-voltage and extra low-voltage lighting components are readily available with ATEX Zone 1 certification, but powering extra low-voltage lighting components will typically need an on-deck voltage transformer to drop the readily available 110V power to the required extra-low voltages required by these components.
Compatibility with Other Equipment
Another factor to consider is the presence of other electrical equipment. During hot work operations such as welding or plasma cutting, much higher voltage systems (e.g. 440V at 32A) are used. These cables often run into the same confined spaces. If these high-voltage cables are considered safe when installed with proper systems of work, it follows that 110V lighting systems, which are significantly lower in voltage, can also be safely used under the same conditions.
Conclusion
Choosing between low-voltage and extra low-voltage ATEX lighting depends on the specific conditions of the confined space, the nature of the work being done, and the need for scalability. While extra low-voltage lighting offers enhanced protection against electric shock, it is less practical for larger areas due to cable length and power distribution limitations.
Low-voltage 110V systems, when used with RCBs, earthed cables, and thorough inspections, provide a safe and efficient solution for larger confined spaces. Their ability to support more lights over longer distances makes them the preferred choice for many offshore operations.
In the end, the goal is to implement a safe system of work that considers all hazards and uses the most appropriate tools and technologies available.