Substantial fines can be avoided by having in place a well-trained crew following well-established procedures with well-maintained, up-to-date equipment
With the 2020 low-sulphur fuel requirement looming, it is imperative that readers are aware of issues surrounding cat fines, as Marine Propulsion urged in October last year.
At the time we cited reports from ExxonMobil and Fuel Oil Bunkering Analysis and Advisory Services detailing the issues, and since then Wilhelmsen has added its voice to the chorus with a white paper.
Cat fines are tiny particles created during the process of catalytic cracking used to make low-sulphur fuels. These tiny, very hard particles can easily embed themselves into engine components, especially in two-stroke engines, increasing wear and tear and leading to costly breakdowns.
Filters and purifiers catch a great deal of cat fines before they can enter an engine, but this assumes filters are correctly operated and maintained.
Wilhelmsen says engine manufacturers have deemed 10-15 parts per million (ppm) as an acceptable level of cat fines in fuel entering the engine. It noted that the majority of engine damage from cat fines, some 86%, “will always be there, more or less”, depending on how efficient filtration is, but it notes that bad conditions can lead to more serious damage.
Cat fines tend to settle at the bottom of tanks, but in rough seas the sediment is stirred up, increasing the likelihood of them finding their way into the engine. It is possible to monitor cat fine levels on board ships with a range of commercially available test kits. Wilhelmsen produces the Unitor Catalytic Fines Test Kit, which allows for fuel to be tested on board vessels at sea to identify cat fine content as low as 20 ppm.
As well as testing bunker fuel, this kit enables the monitoring of filter system efficiency. It can be used before and after filtration and purification and can be used in rough conditions to determine the effect this is having on the cat fine content of fuel entering the engine. Should high levels of cat fines be detected, Wilhelmsen recommends different courses of action depending on the kind of purifier fitted.
Older filters used gravity discs, which could result in poor separation due to interphase levels being too close to the centre of the disk. The advice therefore was to run such purifiers in sequence.
However, modern filters that do not use gravity discs always operate at an optimum level. Due to this, the working life of filters should be maximised by running them in parallel operation, thereby reducing the throughput of each filter, Wilhelmsen said.
Using redundant filters
Alfa Laval’s Moatti 290 Hydraulic Control Oil (HCO) filter has been approved by Man Diesel & Turbo for its two-stroke engines, following testing on four Stena bulk carriers. The filter is built to MAN’s most recent recommendations, which require an automatic filter and a redundant filter that can retain particles of 6 micrometres and below.
Hydraulic control systems, which have replaced camshafts in MAN’s new generation of two-stroke engines, have their valves actuated by a continuous flow of lube oil. To ensure reliable, safe operation, this oil requires fine filtering without creating additional pressure drop. In the Moatti 290 HCO system this is done via continuous backflushing, driven by the pressure of the oil itself and therefore requiring no electricity or air supply.
Alfa Laval filters business manager Herve Gourdon explained how the Moatti 290 system differs from those reliant on disposable filters: “Disposable filter elements add up to a significant cost over time, whereas components in the Alfa Laval Moatti 290 filter can be removed for cleaning and simply put back into operation. Combined with the reliability achieved by continuous backflushing, that means a lower operating cost for the filter overall.”
The redundant filter can be used during maintenance, for initial oil cleaning and when new oil is added to the system. It is not used to clean the small flow of backflushing oil, which is cleaned in a diversion chamber.
Mr Gourdon said: “The redundant filter is fully separated to ensure it will be fully operational in the case of emergency.”
MAN and Alfa Laval started working together on the filter in 2008, with a prototype first presented in 2014.
This protoype underwent more than 24,000 hours of testing over almost two years on Stena Suède, a Suezmax crude tanker.
Following this, the final design was tested for 3,000 hours on board three Stena Bulk IMOIIMAX vessels.
“We are extremely proud to have the Alfa Laval Moatti 290 filter validated for use with HCO systems,” said Mr Gourdon.
“This is the culmination of 10 years of intense cooperation, development and testing.”
Counting the costs of oily-water discharge
As well as the detrimental environmental costs, noncompliant oily water discharge can weigh heavily on the balance books, as Nitta Kisen Kaisha discovered in May.
The Japanese company was fined US$1M, placed on probation for three years and ordered to implement a court-approved environmental compliance plan, after it admitted its engineers had failed to document the illegal discharge of oily waste from the fuel and lubrication purifier systems and bilges of the 33,457 dwt bulk carrier Atlantic Oasis.
According to a US Department of Justice press release, during a May 2017 US Coast Guard inspection a junior crew member told officials of the existence of so-called ‘magic pipe’ hoses that the vessel’s chief engineer, Jihnyun Youn, had ordered crew to use to bypass filtering systems. The same chief engineer also misled inspectors regarding the existence of a Sounding Log, used to record engine room fluid levels.
The company was convicted of obstruction of justice and falsification of an oil record book. Along with the sentence imposed on the company, Mr Youn was put on a year’s probation and fined US$5,500.
Alfa Laval are attempting to solve the issue of how to ensure oily water is discharged in a compliant manner with their Bluebox SA system
“Filters are expensive and quickly become saturated in rough seas, where they merely compensate for the separator’s lack of performance,” said Alfa Laval’s oily water treatment sales manager Shinya Tanehashi.
“When the vessel’s costs become high or large volumes of oily water accumulate because they can’t be processed continuously, it becomes tempting to dump oily water overboard,” he added.
Alfa Laval believe it has tamper-proofed the Bluebox , an oil content monitor (OCM) and data recorder that can be used with existing filters and separators regardless of manufacturer.
“For overboard discharge to take place, a whole range of conditions must be verified, such as the direction of the sample flow through the OCM,” said Mr. Tanehashi.
“All key operational data, including GPS position, alarms and any unlocking of the BlueBox SA cover, is logged and stored for 18 months.”
The system also aims to make it easier for discharge compliance to be reported, as all data it stores can be exported in PDF format.