Thermographical cameras can locate all excessively hot spots on engines and are also very efficient in the examination of electrical installations. Gard News takes a look at this useful safety tool.
Hot spots in the engine room
As much as two thirds of all fires on board ships start in the engine room, and the larger part of these are initiated by oil reaching a surface of a temperature above the auto-ignition point of the oil. For most oils such a critical temperature is just above 250×C. SOLAS regulations therefore require insulation of all hot surfaces with a temperature above 220×C, providing a "comfort zone" between the two figures.1 Even if the insulation of an exhaust channel is of a good appearance, there may be hidden inadequately insulated areas and smaller open hot spots which could start a fire if in contact with oil. To determine how hot a particular surface is, one may use the old-fashioned wax crayons or a surface contact thermometer. These are inexpensive means, but not likely to assist in finding concealed hot areas.
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See article "New fire safety regulations in the engine room" in this issue of Gard News.
A more modern tool is the so-called "Lasertracers", laser-based infrared heat tracers, which cost from USD 200 to 500. This tool is quite effective if used correctly, but as it measures the heat radiation from the object, the operator has to estimate the rate of reflection or emissivity. Also, as the instrument measures the average temperature of an area from a distance, it may be difficult to detect the exact temperature of the hottest spot without knowing the effect of average areas. Carefully examining all items of an engine room with such a tool will be very time-consuming.
The best method to examine a full engine room for hot spots and hot surfaces is to have a thermographical examination carried out; a thermophotographical examination to be exact. The hand-held camera, using infrared technology, has already been in use for some years in shore-based industries. Following many fires in Norwegian wooden farm buildings and the loss of livestock and equipment, insurance companies started to ask for thermographical examinations of the electric installations before accepting to provide cover. Another use, typical for Norwegian needs, is to have private houses examined for quality of built-in thermic insulation.
Thermographical technology applied to shipping
The shipping industry has been slow to pick up this new technology. Class societies are aware of the equipment and may have some guidance on its usage, but have not made such examinations an obligation. We believe, however, that, as the usefulness of this tool is discovered by the industry, and as public demands for safer ships continue to increase, it is just a question of time before flag states or class authorities start to ask for such examinations, as a part of Special Survey or Safety Construction Survey requirements, at least for vessels above a certain age. First in line would be vessels for which a fire in the engine room would have the most serious consequences, like older passenger vessels for instance. The price of advanced equipment is around USD 30,000-50,000, so not many owners are buying it. Less expensive cameras are also on the market, including a model costing USD 12,000, which is also said to be robust enough to be used by firemen searching for persons to be rescued. That is another use of the technology: to locate people in the smoke of a fire, by searching for 37×C. Advanced firemen helmets are even available with built-in infrared viewer.
On board a vessel the thermographical camera will locate all excessively hot spots on the engines, exhaust lines, boilers, incinerators, etc., but it is also very efficient in the examination of electrical installations. Weak couplings, risks of short circuit, etc., will be located by the electric component's emission of heat, and the exact temperature can be read from the photograph. Inexpensive adjustments to the electrical installations can be made before a short circuit and the consequences of a fire occur. For instance, Norwegian electric power stations are regularly having extensive thermographical examinations carried out to secure their installations.
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|Detail of fire pump electric terminal box and corresponding thermophotograph.|
Due to its ability to discover weaknesses in the electrical installations, shipowners may consider including thermographical examinations in newbuilding specifications and have such tests carried out during sea trials. Any defect then found is for the shipbuilder to correct, but if revealed by a fire outside the guarantee period, the then much higher price is the owner's own to pay. It follows from the above, that a thermographical examination of the engine room and the vessel's electrical installation should be carried out with engines and electrical equipment running. Some examination can be done at the quay, but the operator will need to follow the vessel on a short voyage for full benefit.
The thermophoto of the exhaust manifold of the main engine shows a maximum temperature of 250°C. The manifold should be checked for exhaust leakages and the insulation should be improved upon.
Some shipowners have hired operators at around USD 1,000 a day, which is really very reasonably priced. One Gard member took an operator on board a vessel in Gibraltar and he followed the vessel to Rotterdam where it was to dock for repairs. The findings, some of a quite critical nature, were included in the repair specifications for immediate attention. Another Gard member, Color Line, the largest passenger ferry operator in Norway, has hired thermographic camera operators to check the electrical installations on board their ships since the early 1990s. Since the fire on board the "PRINSESSE RAGNHILD" in 1999, caused by a burst fuel oil pipe and a hot spot, they have also introduced a regular thermographic examination of hot surfaces.
To ensure the quality of service, operators of thermographical equipment should be certified by the competent authorities. In Norway, certification is carried out by DNV and NEMKO. Above, a thermophographer in action.
Photo courtesy of Teknisk Assistance, Kristiansand.
There are probably some advantages in the hiring of camera operators rather than buying equipment to be used by the crew: the hired operator will be more strict and careful in his work, and at least in Norway he is approved by authorities on electrical installations. He will deliver good and clear reports and recommend actions to be taken. Such reports may be used by owners to demonstrate that they pay close attention to maintenance and to the safety of the vessel.
In addition to thermographic cameras, there is also infrared thermoscanning video equipment on the market, costing around USD 50,000. However, the still pictures of the reports by thermographic camera operators are so illustrating and easy to read, with both a normal photo of the item examined and an infrared picture showing the temperatures, that it is probably the most useful.