Hamburg, 27.09.2021: Naval platforms are by their very nature employed in dangerous and often hostile environments. To mitigate these dangers, ships have inbuilt protection systems to ensure they operate unhindered for all environmental conditions and threats.
Hostile environments can be both planned or naturally occurring, such as adverse weather or navigational threats. A deliberate or planned threat, such as an offensive action using Chemical, Biological Radiological and Nuclear (CBRN) warfare agents and threats, is the focus of this article.
The purpose is to highlight why a CBRN system should be fitted to Naval platforms and the benefits they offer by mitigating a CBRN threat and the risks they pose if these systems are omitted from the platform design.
The Ships Citadel
Naval platforms have a naturally inbuilt citadel. To prevent ingress of water, ships employ a welded construction, with all entry/exit points for personnel and systems having measures in place to prevent this water ingress. Further, ships are sub divided into watertight boundaries to ensure if one boundary (or sub citadel zone) is compromised/breached, the threat is contained to just that zone.
By enhancing this water-tightness, with a slight overpressure, any resulting leaks from door seals, hatch seals and penetrations are outward ensuring external contamination cannot breach the citadel.
An overpressure, unfortunately, is not enough to mitigate against a CBRN threat. The breathable air inside the ship needs to be clean, filtered and managed to reduce the build-up of CO2 and other non-breathable gases.
To achieve this, CBRN Protected ships are fitted with CBRN Air Filtration Units (AFUs) with dedicated inlets, typically fitted to each sub citadel zone. These AFUs process both gaseous and particulate external threats to ensure the air, which is delivered to the zone(s), is both fresh and safely breathable.
The AFUs are The Gas Mask of the Ship
The AFUs, are fitted with a high-performance fan, which boosts the pressure within the citadel to between 500-800Pa. A figure determined by the worst-case scenario of a ship travelling at Vmax into a prevailing wind, where any resultant small leaks in the structure could compromise the citadel and safety of ships staff.
A Citadel without AFUs
By ‘closing’ down the ship’s doors, hatches and penetrations may potentially prevent contamination entering the ship’s citadel. In reality however, noxious gases would very quickly build up, principle of which is CO2; a by-product of exhalation. In all likelihood contamination would still find its way into the ship through the lack of overpressure and leaks through door seals and penetrations; exacerbated by ships speed and prevailing winds.
An overpressure is the function of the AFU, no AFU equals no overpressure or filtration
Just wear Gas Masks
This is potentially possible but the restrictive nature of a Gas Mask/Respirator and the limited duration of their small filter elements, means this is for short durations only. However, the most important aspect is contamination has been allowed to potentially enter the vessel. Warfare agents are very resilient, retaining latency for long periods and with an ability to ‘off-gas’ many hours/days later. Naval platforms are an expensive investment and a contaminated vessels returning to Port would need to be dealt with in a very challenging, exhaustive and expensive way. Also, an important consideration in any resulting clean-up is How Clean is Clean? Any toxic material inadvertently left behind after clean-up has the ability to affect personnel post event.
The ENGIE Axima Air Filtration Units - a cost effective, managed solution to a simple problem
ENGIE Axima offers a range of high performance AFUs selected based on the flowrate required for the citadel/sub citadel zone and the space available. Designed to deliver the correct level of overpressure and providing clean, safe, breathable air for the ships staff.
The ENGIE Axima AFUs have been specified for many of the NATO and NATO partner Navies and fully supported throughout the platforms life to ensure performance and availability is maintained.
ENGIE Axima can advise on the correct selection of AFUs for the platform, the performance required and the design integration of the system into the final location. ENGIE Axima undertake all work on behalf of the shipyard and customer, delivered to a range of specifications based on the platform requirements.
All the systems can be integrated and commissioned into the platform using a dedicated team of experienced AFU commissioning engineers with the systems supported through the whole platform life as part of a contract option.
To hear more of the CBRN Protection systems available from ENGIE Axima please email hamburg-info.axima@engie.com or view the systems available here.
(Written by Russ Tidbury, Senior Commercial Director, ENGIE Axima Marine (UK))