Technology sails ahead
Published: 01 January, 2007
So what if a fire actually breaks out in a bulkhead or compartment and the fire team leaders decides on a ‘burnout’? How do you know that it is safe to enter?
One conventional way of determining the circumstances after a fire on naval vessels is to use a magnetic thermocouple to track the bulkhead temperatures and plotting its decline to an acceptable level.
“It can take many hours to plot a decrease in temperature,” Andrew French, Capability Leader of Fire Research for Defence and Security company QinetiQ told IFJ at the Lloyds List International Fire Onboard Ships Conference in London, last November.
QinetiQ’s fire research laboratory has existed for about 20 years. It started off in Portsmouth's Naval Dockyard. Events such as the Falklands War highlighted the need for more research in materials that are onboard ship. "In our laboratory we look at parameters such as smoke, toxicity, flame spread and suppression. Predominantly, we have been working for the MOD, researching naval materials and fire fighting procedures for Marine Equipment Survivability and Habitability (MESH) and Sea Systems Group (SSG) Integrated Project Teams. We have also been involved with the Halon Alternatives Working Group (HAWG) and the Alternative Agents Working Group (AAWG)," comments Andrew.
The MOD tasked the QinetiQ fire laboratory so see if they could come up with a device to help them make a more informed decision about when it was safe to go back into a compartment affected by a fire. Accordingly, the company developed the Re-Entry Evaluation Detector (RED), a piece of equipment that would allow firefighters faster entry into a fire-affected compartment.
"The Re-Entry Evaluation Detector has commercial off the shelf (COTS) sensors and a sample probe on it. This means we can suck the gases from the compartment through a small hole or an inspection port. The probe is connected to the main unit where the data is logged and processed by a computer algorithm indicating the temperature and the amount and type of gases in the room," he reports.
"It can, for instance, indicate the levels of hydrocarbons. When they are really high and you open the door the influx of oxygen can cause these gases to ignite. We recently added a pressure sensor to it as well to look at things such as the pulsing of the flames. Basically, if there is a large pulsation of the flames this means that there is an oxygen depletion, which can cause a back draft," he explains.
The Re-Entry Evaluation Detector began with a 'traffic light' system which indicated the state of affairs in the confined space; Red means 'do not enter'. Amber indicates that 'the situation is improving but it is not safe yet', and green implies it is 'safe to enter'.
"We have been tweaking the system over the past year to get it more applicable to the fire service. Now the detector can even do things such as monitoring the other gases in real-time. This mean that even when the firefighters have gone in the room it will keep monitoring the levels of carbon-monoxide, dioxide etc.
"The final unit will be designed to clip on your side and when things start to go wrong, such as when the CO and CO2 levels start climbing indicating a re-ignition may occur, the device produces a warning for the firefighters to leave the space."
QinetiQ is currently looking at methods of puncturing through doors and other thick surfaces to get the probe in the space and to start sampling.
Currently the company is considering several options, such as a small spring gun and a fire axe with a probe built in.
Andrew points out that there are many personal detectors on the market that monitor gases in the atmosphere or the occupational exposure limits. "What we are doing is taking gas detection a step further by monitoring rates of change, heat and we log it on the data card. This means that people can look back in retrospect and see what happened exactly," he explains.
"We did some tests at the Fire Service College, Moreton-in-Marsh, where they did some back drafts for us, so we could demonstrate the detector. We are currently talking to a company about manufacturing the unit and we are hoping to launch the Re-Entry Evaluation Detector in a small handheld format in the first half of 2007."
Cutter and extinguisher in one
Once again, the Lloyds Maritime Conference proved a fruitful source for new developments in firefighting. IFJ talked to Ian McWilliam of Cobra Cold Cut Systems who explains that the invention of a high pressure, portable cold cut extinguisher was a definite case of serendipity.
When trying to make a entry hole to get to a fire on a Norwegian ship undertaking repairs in Gothenburg, the rescue workers used a torch-burner (the ship was declared gas-free, which it was not). There was an explosion and ten people were killed. Lars G., who is a former sea-captain wanted to find a safe way of making holes using a cold cutting technique. When experimenting with a cutting frame to make holes on burning buildings, it turned out that before the hole was finished, the fine mist of water which is a result of the high pressure (300 bar), had actually extinguished the fire. Thus the idea of the Cold Cutting Extinguisher lance as a firefighting tool was conceived.
CCS-Cobra is a Swedish-based company, founded in 1988. In those days the company specialised in industrial cutting using high-powered water jets. The owner of the company, Lars G. Larsson, realised that the water jet might have other applications too. Any hot cut systems tend to set things alight on the inside of the material being cut. It was discovered that Cobra’s high-pressure cold jet offered excellent extinguishing capabilities. The company went out to research the possibilities with the Swedish Rescue Services Agency (Räddningsverket).
The result was the Cobra Cold Cut extinguisher, a versatile tool that can be used for structural firefighting as well as industrial and maritime applications. Basically, it can cut through any surface as well as extinguishing the fire behind it.
Today, it has been sold in over 15 different countries worldwide and can be delivered in both a hand lance and a fixed cage mounted lance version.
The Cobra system has been sold to more than 18 countries worldwide
“What we have done is reversed the main function. Instead of being a cutting tool, it is now an extinguisher with a cutting function. The CCS is extremely effective on steel – hence fires in compartments or bulkheads are its forte. This system enables the firefighter to put very fine water mist in a compartment without any added oxygen, which is the big difference compared to any firefighting technique. The natural development from this is to install a fixed system On the ship,” says Ian.
The extinguishing capacity of the cutting extinguisher was tested in a container at the Navy rescue school in Karlskrona in Sweden. Four tests were performed and for each test a mock wall was made, containing three sandwich panels, and mounted in front of a container opening. The mock wall was exposed to the radiation from a fire of 3.6 MW in which the temperature was approximately 500 °C.
In two tests the fire was burning for five minutes –in two others, for ten minutes – before the cutting through one of the sandwich panels was initiated. The cutting turned to fire extinguishing once the sandwich panel was penetrated and water was sprayed for 30 seconds in two tests (5 and 10 minutes pre-burning) and for 60 seconds in the remaining two tests.
Once the sandwich panel was penetrated, the fire was put out in approximately 10 seconds. The equipment that was tested delivered a water flow of 28 litres per minute, which equals a theoretical extinguishing yield of 6.5 MW.
Smit Salvage
The company received an order from Smit Salvage bv. in Rotterdam in the Netherlands, some time ago.
Ian continues: “They took delivery of one unit at first because they were intrigued by its simplicity and its portability. The unit was destined for the main yard in Rotterdam earlier this year. At the same time a fire occurred on one of the container ships they were contracted to deal with, lying off Singapore.
“This fire proved extremely difficult to put out because it was located above deck in several heavyweight metal containers. Smit could not deal with it successfully in a conventional way so the company flew the CCS from Rotterdam to Singapore and then took it to the firefighters’ vessel by helicopter.
“Literally within hours the fire was dealt with and the ship was allowed back into the harbour and the containers could be unloaded on the quay.”
Smit Salvage, the world’s biggest salvage company took delivery of two more Cobra systems early 2006. Both systems were built onto Smit Salvage’s own standard skids for effective and quick transport by air and/or sea to the salvage location. At the location the Cobra systems are connected to Smit Salvage’s own power packs which deliver the necessary power to the Cobra Cold Cutting Extinguisher or possible additional cold cutting tools.
Rather than fly the CCS around the world to each incident as it occurs, Smit is currently in negotiations to put at least one Cobra system on every seaboard where it operates.
Other major salvage operators are also currently evaluating the system too.
Compliant with IMO regulations
Stefan Gordin, Vice President of Marioff’s Marine Division, was one of the speakers at the Conference. In his presentation he told the international shipping community how the HI-FOG water mist system is one of the best working fire suppression systems available for ships.
In an exclusive interview with IFJ he explains that, although the HI-FOG system has been around for 15 years, the commercial shipping sector, which is growing increasingly more safety-conscious, hasn’t fully grasped the advantages of a high pressure water mist system. However, in certain sectors, such as the passenger sector, for instance, on board cruise liners, this safety awareness is at a very high level and HI-FOG is used extensively.
“According to IMO regulations, all vessels must have a total flooding system On. Halon used to be the future, but has been forbidden, CO2 is lethal and foam is costly and the clean-up is terrifying. Water mist is an excellent way to extinguish fires and the fire is usually completely extinguished within about one minute.”
The HI-FOG system uses high-pressure water mist that comprises the most minuscule droplets. Where a conventional sprinkler produces one drop, high-pressure water mist produces 8000. The drop size compares with one conventional drop of water of >1000µm to a high-pressure water mist dropsize of 50µm. This means that the vaporisation process takes a fraction of the time it takes with conventional droplets. The vaporisation cools down the heat and replaces the oxygen; it takes away two essential parameters of the fire triangle.
Recently, Marioff launched a new total flooding system for engine rooms, the HI-FOG MT 4, says Stefan. Total flooding water mist systems in machinery spaces have to comply with IMO MSC/Circ 1165, which comprises 13 different fire tests. The performance of the system is assessed by the following criteria: extinguishment within 15 minutes and with no re-ignition. HI-FOG MT4 has successfully passed these tests, is fully compliant and has been approved by the major classification societies and administrations such as the US Coast Guard.
“The main difference between HI-FOG MT 4 and conventional systems is that there is no need to evacuate personnel, seal the space, or shut off the ventilation. The fire will be contained and extinguished in its infancy and the damage can minimised, because the key feature of this system is that it can be activated the second a fire is detected. There are no added chemicals or foam in the water, so there are no dangers for humans involved at all. Nor does the HI-FOG cause corrosion,” Stefan comments.
The system can be tested on a full scale to ensure that it is always working properly. Furthermore there is no need to divert to a port to recharge the system, because it works on a pump unit rather than compressed gas.
The HI-FOG MT4 total flooding system can be integrated with HI-FOG ML9, a local application system, using the same pump unit, tubing, valves and spray heads.
Insulation for bulkheads and deck
Unifrax is a manufacturer of fire insulation materials and products. For the marine and offshore fire protection market the company has developed the FireWrap Marine blanket, a completely inorganic, flexible, high-temperature insulation blanket.
Unifrax delivers to the largest shipping yards in the world, such as Meyer Werft in Germany and Chantiers de L’Atlantique in France.
“The largest part of our maritime business is focussed on cruise liners,” explains Jean Marie Garnier, Marine and Offshore Senior Marketing Engineer. Firewrap is made from a product called Insulfrax which is made from biosoluble fibre. The product comprises calcium, magnesium and silicate. These are the same composites found in clay.
Unifrax uses a special spinning technology combined with mechanical needling to produce the fibres, eliminating the need for binders in the product. This results in a product with high tensile strength and very high quality thermal and acoustic properties. The Firewrap is chemically stable and remains unaffected after exposure to water immersion or high humidity.
Jean Marie explains that the Insulfrax differs from a conventional ceramic fibre, which comprises 50% aluminium and 50% silicate chemistry.
“For cruise ship we have to comply with very specific regulations set out by SOLAS, the Fire Test Procedure code. The latest regulation in this code is the A754 for passive fire protection. There are three parameters in this code that need to be taken into account; insulation, stability and integrity.”
Built in steel or aluminium, a ship needs to be as light as possible, says Jean Marie.
“These cruise ship are normally less than 32 metres wide, because that is width of the Panama Canal. This means that you can increase the length and height of the ship, but not the width. When you do increase the length and height, the stability of the ship decreases.
“This is why they build the top decks in aluminium, this means it can’t surpass an ambient temperature over 200°C otherwise the aluminium will lose its strength and expand in volume.”
The third parameter in the FTP code is the integrity, this means that for example when you have an A-60 bulkhead to insulate, if there are any windows or ventilation ducts you have to be careful that these are fire and smoke tight, he continues. There should not be any penetrations in the structure.
In the past many shipyards used mineral wool as an insulation material. The problem with this is however that it melts at approximately 1,000°C. Furthermore, this type of insulation requires thick layers, which adds a large amount of weight.
“People spend a lot of money to replace steel by aluminium, which is more expensive than steel. They do this because they have a weight problem this means the insulation material needs to be as light as possible.”
The Jewel of the sea
The Jewel of the Sea was delivered in April 2004 to the Royal Caribbean International, the fourth ship built in the Radiance Class.
“This 90,000 GT creation is one of the most technologically advanced ships afloat. Powered by 60,000 kW and capable of 25 knots cruising speed, she can carry 2,500 passengers on 15 decks – of which four are aluminium,” says Jean Marie.
The build started in 2003 and was completed in January 2004. The 50,000 m2 square of steel and aluminium structures were insulated with Firewrap (Insulfrax) in order to provide A-60 fire rating. To get compliance, a thickness of 50mm and 96 kg/m3 density was applied on the aluminium structure, whilst a 38mm and 96 kg/m3 material was used on the steel part of the ship. The ventilation ducting was also fire protected with the FireWrap blanket up to A-60 rating.
“Thanks to the application of our product the Meyer Company was able to realise several benefits,” Jean Marie continues. “They were able to save around 160 tonnes in weight versus mineral wool. And they increased installation speed by using overlapped joints. One layer of blanket was installed directly from standard sized rolls available from stock. We did not need to pre-cut the material and only two standard products were utilised. This compares with more than 100 different sized pre-cut pieces that would have been needed when using mineral wool slab.”
