IMT – Safety Alert
International Marine Transportation Ltd (IMT) has recently issued a Safety Alert Bulletin in the aftermath of “a significant increase in the number of incidents which were caused by fuel with high catalytic fines” as follows:
Over the last year there has been a significant increase in the number of incidents which were caused by fuel with high catalytic fines. In view of the operational disruption combined with the high costs associated with severe engine failures and ISO accepted levels of catalytic fines being much higher than engine manufacturers’ recommended guidelines, it is clear that the on-board fuel purification and filtration issue warrants increased management attention.
It is not our intent to provide tanker operators with direct guidance on how to operate, inspect or maintain onboard machinery. However, investigation analyses from various incidents indicate some common measures which could reduce the likelihood of sudden severe failures occurring. The objective of this bulletin is to highlight the importance of good onboard fuel treatment and to encourage an internal review of ships’ planned maintenance systems for continued reliability of machinery.
Because cat-fines are generally very hard, and very abrasive to pumps, atomizers, piston rings and liners, major diesel engine manufacturers recommend the maximum amount of catalytic fines in the fuel injected into the engines to be 10-15 mg/kg. Since ISO 8217:2005 regulates the maximum amount of catalytic fines permitted in bunkered IFO, expressed as Al+Si, to 80 mg/kg (ppm), it is possible to receive bunkers that exceed an engine manufacturer’s recommended maximum limit and without adequate treatment the main engine may suffer catastrophic wear rates and related failures.
Catalytic fines being hydrophilic, an increased level of contamination is also possible during transport in the barges and in insufficiently drained and insufficiently cleaned ship’s tanks by loading / pumping on top of bottom sediments. The larger sized catalyst particles (the average particle size is generally seen as proportionate to the overall concentration) typically cause very accelerated wear rates in the cylinder assembly area. Accelerated damage can also be expected on injection pump inlet valves, exhaust valve seating areas, and turbocharger turbine blading.
These larger sized particles have been associated with catastrophic wear rates. For safe and reliable operation and to take the benefit of longer recommended intervals between unit overhauls, it is required that best practices regarding on board fuel handling provided by major engine manufacturers, classification societies, P&I clubs and by fuel testing companies are rigorously followed. Also, frequent piston, rings, liner inspection are carried out to identify the problem at the earliest. The following may be considered as best practices for the handling and processing of fuel oil:
1. Regular draining of water and settled bottom sediments from fuel storage, settling and service tanks.
2. Cleaning fuel storage, settling and service tanks frequently. Large particles will settle in the storage, settling and service tanks, and over time the concentration of abrasive particles in the bottom of the tanks can be significant. During rough weather these particulates can be thrown up and enter the separators, sometimes in concentrations above the 80 mg/kg limit. For the same reason, it is therefore best practice to utilize all separators, even when the bunker supplied has an apparently low level of catalytic fines.
3. Drained oil from engine fuel oil backwash filter (50 micron candle type) should not be reintroduced in fuel treatment system when using high cat fine or high ash content fuel oil. Optimize the use of purifiers and clarifiers by keeping the HFO inlet temperature at correct temperature (around 98oC). Clean preheaters, clean purifiers and sensors, minimize turbulence before purifiers, minimum flow rate are required for optimization. Also for separators without gravity discs it is generally recommended to use all available HFO separators and to operate them in parallel, with appropriate feed rates. If the separators are of the manual type with gravity discs, they should be operated in series with a purifier followed by a clarifier, utilizing the lowest possible flow rate. Regular checks of the separators by the manufacturer’s service engineers will also enhance the efficiency of the system.
4. In order to check the efficiency of the fuel system, it is recommended that samples are taken of the fuel oil before and after each separator at intervals of 4 or 6 months. The samples should be sent for analysis by an accredited service provider. Results of the analysis are more accurately representative of clarification efficiency if bunkered fuel is with high cat fine content. Bunkers with catalytic fines above 30 mg/kg are considered suitable for this test.
5. If bunkered oil contains more than 50mg/kg of catalytic fines, then due to the limitations of onboard fuel treatment system it is still possible to have higher than the recommended levels of catalytic fines in the oil injected. Therefore, some operators opt for catalytic fine filtration system. Typically these are mounted on the fuel line (in a loop) after the purifiers and before the service tank. These replaceable filters can remove catalytic fines of 5 microns and over.
6. Ensure that personnel responsible for the operation and maintenance of the separators are properly trained and are familiar with the equipment and how to perform the regular maintenance. This increases reliability, and reduces the consumption of non-wear parts.
Operators may wish to focus their attention on the subject discussed within this bulletin and to carry out an internal review of their bunker handling and treatment procedures and requirements. They may also wish to enhance their planned maintenance by increasing inspections of engine cylinder assembly parts in order to provide early identification of fuel related severe wear problems.
Source: International Marine Transportation