As of January 2015, ships working in emission control areas (ECAs) have been obliged to comply with the 0.1% sulphur content for fuels. With the ECA limits on sulphur now in much wider use, more ships and crews will need to observe the operational changes brought about by new methods and technology, and understand the long-term impact that compliance will have on the vessels.
When the issue of low-sulphur fuels for ships first arose some years ago, attention was paid mainly to the need to match main engine lubes to fuels of different compositions. Later in 2010, when the EU (European Union) prohibited ships in port from burning fuels with sulphur content above the current ECA limits, there was a flurry of guidance issued on switch over procedures.
The sulphur limit imposed in ECA waters has caused substantial change in the composition of marine fuels. As a result of the limit on sulphur emissions, many have expressed concerns over an increase in issues with fuel quality, compatibility and stability. Fuel testing agencies continue to correlate declining sulphur levels with increasing levels of catalytic (cat) fines and subsequent engine damage. The current ECAs cover both the Atlantic and Pacific coasts of the USA, along with the North and Baltic Seas and the English Channel, which means that many vessels will operate within ECAs for at least a portion of their journey. With a global cap of 0.5% likely to come into force within the next decade, the number of vessels affected will only increase.
In order to achieve compliance, operators are adopting new technologies and procedures such as switching between heavy fuel oil (HFO) and compliant low sulphur fuel oil (LSFO) when entering ECA areas. Constant, real-time monitoring is the ultimate tool for safely and cost effectively managing the impact of new operational processes. As operators are now required to employ fuel of different specifications than previously used, it becomes critical to manage the process of fuel switching safely, not only to ensure legal compliance, but also to protect the safety and welfare of the crew and the vessel. Even when fuel is obtained from reputable and trusted sources, damage and wear to critical equipment is not uncommon.
With appropriate monitoring equipment, operators can have quick and easy access to the information they need to identify where adjustments must be made to alter the operating conditions within the system. Many engines and systems are designed to burn primarily HFO, therefore when switching to alternative fuels there are various factors that must be considered. For example, it is very important that the correct oil be used in the system. When operating primarily on low sulphur fuels, cylinder lube oils with a lower Base Number (BN) are required. The lower viscosity and inherent reduced lubricity of low sulphur fuels adversely impacts the lubrication of the fuel pumps, resulting in scoring of the fuel pump plungers and barrels. This leads to significant levels of wear, potentially causing leaks which can result in a loss of power. Low-viscosity fuel can also leak into the oil via the fuel pump, compromising the lubricating properties of the lube oil. Furthermore, issues of compatibility between fuel and lube oil can result in deposits forming in the fuel pump, causing the pump to stick or even seize, resulting in a significant compromise in operational safety and efficiency.
Modern four-stroke engines are designed to operate using a range of fuels, including distillates. However, when using mainly LSFO, combustion deposits are lessened. This affects the lubrication of the valve seats, meaning that an injection of lube oil is required to prevent wear, therefore increasing operating costs. If the engine is fitted with water cooled injection nozzles, the lower temperature and viscosity of LSFO means that the injectors are ‘over-cooled’, resulting in deposits on the nozzles, which leads to corrosion when temperatures fall below the dew point of the acids in the combustion gases. As engine designs evolve to drive improvements in efficiency, consideration must be given to the effects this has on the operation of the rest of the vessel. Operators must be aware of the risks associated with these new operational processes. These can include
These are all problems that can lead to costly damage in the system, negatively affecting vessel efficiency and operational effectiveness. To repair damage caused by these issues, some operators have had to replace expensive engine components such as pistons, liners and injectors — with costs often running into many thousands.
Following the introduction of ECAs, the requirement for testing density, viscosity, water contamination and pour point is no longer simply to ensure that the correct fuel has been delivered, it is now a critical part of ensuring safe and compliant operations. The stability of the fuel and its compatibility for blending needs to be assured. In an ideal world the mixing and blending of fuels from different sources would be avoided. However, bunkering in different ports necessitates the use of varying fuel suppliers. For those vessels transitioning through an ECA, and therefore potentially switching from HFO to LSFO, blending cannot be avoided. Issues with incompatibility are therefore, inevitable.
Whilst fuel is manufactured to be stable — in that it doesn’t have the tendency to produce asphaltenic sludge — two stable fuels are not necessarily compatible when blended. A blend is regarded as stable only if it is homogeneous immediately after preparation, remains so in normal storage, and at no time produces sludge on a significant scale. If the fuel blend performs this way, the fuels forming the blend are considered to be compatible with each other. Incompatibility results from the tendency of a residual fuel to produce a deposit on dilution or on blending, typically resulting in blockages of bunker and service tanks, pipe runs, filters and centrifuge bowls. In extreme cases, the only remedy is to manually remove sludge build-up, which is both time-consuming and extremely costly.
It is therefore important that operators have the tools they need to monitor every aspect of the fuel switching process to ensure that it is carried out safely. Experts at Parker have designed a range of solutions and tools to aid operators with this process, which, when coupled with advice and guidance from knowledgeable industry specialists, can ensure that compliance is navigated safely and without impacting operational efficiency.
Testing the viscosity of both residual fuel and lube oil will help inform engineers of the measurements they need to prevent system damage when switching to compliant fuel. The Parker Heated Viscometer monitors changes in lubricating oil viscosity, preventing costly engine and machinery failures. The test verifies that the correct grade of fuel is delivered, and by using the results, operators can calculate combustion performance as well as inform any adjustments of fuel handling and injection systems, mitigating against the risk of blockages and damage. Viscosity of lube oil is of critical importance, with the correct viscosity providing optimum film strength in system clearances, with minimum friction losses and leakage.
On board testing for fuel compatibility when fuel switching is very simple and takes just minutes. The Parker Compatibility Tester provides engineers with the information they need to confirm that the fuel delivery will remain stable in the bunker tanks, or identify potential stability issues before the fuel is blended, therefore negating the risk of sludge forming. Compatibility testing can prevent damage to fuel handling systems and reduce combustion related engine problems.
Constant, real-time monitoring is the ultimate tool for safely and cost effectively managing the impact of new operational processes. With the presence of cat fines on the increase, monitoring the impact of this is crucial and tools such as Parker's LinerSCAN system can be used to minimise liner wear, improve maintenance scheduling, and decrease sampling and testing costs. Using magnetometry to quantify the iron in used cylinder oil, LinerSCAN sensors report changes caused by abrasive wear, highlighting periods of increased physical or thermal stress.
By monitoring wear levels in real time, engineers are alerted to escalating cylinder liner damage and are able to react quickly to changes, enabling preventative maintenance during the ship’s passage to the next port and insuring against expensive downtime. When used in conjunction with on board tests such as the Parker Cold Corrosion Test to identify iron compounds in used oil, operators have quick and easy access to the information they need to identify where adjustments need to be made to alter the operating conditions within the system, effectively minimising corrosive wear and reducing costs.
With so many variables influencing fuel quality and the resulting impact on combustion and engine damage, effective and reliable testing and monitoring becomes critical to ensure the safety and operational efficiency of the vessel. Monitoring wear is essential in identifying problems at the earliest possible stage. Online diagnostic equipment can continuously and automatically provide complete sets of trend data showing levels of wear in critical equipment and machinery, enabling immediate action to be taken to prevent costly damage, before wider and much more expensive issues are created. Onboard testing gives operators quick and simple access to the information they need to effectively manage maintenance requirements and prevent damage, which, when supplemented with laboratory testing, gives operators the best chance of protecting the bottom line.
Originally published in The ShipInsight Journal - Summer Edition 2015
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