In an industry where meeting regulatory requirements that surround bunker fuel consumption is a challenge in itself, when secondary issues arise as a result of modifying fuel use or engine operating conditions, ship operators can face significant impact on the bottom line.
One such secondary issue that is exacerbated by modifying engine operating conditions and changing bunker fuel types is cold corrosion.
Ship operators today are unfortunately all too familiar with the problem of cold corrosion and its impact on the engine cylinder, which if unmanaged can cause catastrophic damage.
The impact of proactive management such as capital investment for mitigation purposes, and increased demands on crew time as a result of heightened maintenance requirements are minimal. Therefore, strategising to understand the process of cold corrosion, and more importantly, how to mitigate it is essential.
In this week’s spotlight, Fathom Maritime Intelligence examines one such mitigation technology that can be used to proactively monitor cold corrosion symptoms. Total Lubmarine’s iron test kit, the Tech’Care/TCC (Total Cylinder Care) solution is put under the microscope as we investigate how this bespoke technology works and how it can deliver benefits to ship operators by allowing them to reduce cold corrosion for optimum performance, capital, and time savings.
What Is Cold Corrosion?
Cold corrosion occurs when low engine temperatures and high operating pressures lead to water condensation on the cylinder liner walls, which then combines with the sulphur from the fuel engine combustion process, forming the corrosive material – liquid sulphuric acid. When sulphuric acid forms on the liner of an engine cylinder it corrodes the cylinder surface.
The Cold Corrosion Catalyst
In newer engines, emissions-related regulations can really impact the engine cylinder. For example, prior to regulations coming into force that govern fuel sulphur limits as they are today, engines that were prone to cold corrosion would often be operated with cylinder oils of high base numbers. However, in light of emission controls today, lower base number oils are often used, which actually further the risk of cold corrosion in the engine cylinder. Furthermore, engines that generate fewer emissions in order to comply with regulations, often operate at lower temperatures and higher pressures, causing condensation corrosive attack in the cylinder liner.
Additionally, the International Maritime Organization’s (IMO) limit on sulphur oxides (SOx) of 0.1% in ECAs since January 1, 2015, means that today the high frequency of changeover to low-sulphur fuels when entering an ECA, and the required change of cylinder lubricants, can lead to complications in the cylinder causing abrasion on the inside of the liner.
When it comes to compliance strategies for the IMO’s Tier II and Tier III (the latter enforced in the United States only since January 2016) nitrogen oxides (NOx) limits, the benefits gained by limiting NOx formation and increasing propeller stroke to lower fuel consumption, are sometimes compromised by the impact of cold corrosion on the engine due to intense engine pressures and lower temperatures that new long stroke engines operate under.
Furthermore, the increased number of ships that are ‘slow steaming’ has led to increased engine modification and has led to more intense operating pressures and cold corrosion potential.
The Necessity for Proactive Testing
A method that can alert ship owners and operators to the occurrence of cold corrosion in their engines is the use of on-board test kits that can identify the iron content in the cylinder drain oil, and hence the quantity and degree of cylinder liner corrosion.
Using the results from such test kits, the feed rate of the alkaline lubricant can be adjusted to exactly the correct level to counteract the increased acidity and eradicate the likelihood of cold corrosion. Without an accurate test kit, the quantity of alkaline solution required can often be overestimated, leading to resource waste as the alkaline feed rate is over injected.
Putting a Test Kit Under The Microscope
Total Lubmarine’s Tech’Care/TCC is a technology that can monitor and control engine cylinder liner wear and tear, cold corrosion and over-use of alkaline feed injection rate. It was initially developed for two-stroke engines, in collaboration with research scientists and two-stroke marine engine manufacturers.
Through sample analysis, the test kit provides the information required to counteract the effects of cold corrosion (by adjusting the alkaline feed rate) and reduce resource waste and time and money spent repairing or replacing the cylinder liner.
Total Lubmarine’stest kit works by establishing the quantity of iron in parts per million (ppm) in the cylinder drain oil. This, combined with the residual base number (BN) of the oil enables the correct quantity of cylinder lubricant needed to eradicate the beginning of corrosion on the cylinder liner to be identified. By providing the concentration of iron in the cylinder oil, the amount of cylinder lubricant needed to counteract the effects of cold corrosion can be monitored and optimised. By adjusting the lubricant to neutralise the effects of corrosion, the lifetime of the cylinder can be significantly extended to deliver vast cost savings in terms of the cylinder lifetime and the quantity of feed injector saved.
During the onboard testing procedure, samples are placed in a carousel allowing the concentration of iron to be measured. Non-hazardous reagents are added to the cylinder drain oil, thereby identifying the iron concentrations and corrosion using an optical device. The test kits ensures reliable measurements which when combined with laboratory results enables accurate readings of trends and engine conditions.
The Benefits of OnBoard Cold Corrosion Testing
Cold corrosion test kits, such as Tech Care/TCC, can significantly cut down the time it takes for samples to be analysed and results to be gained.
Instead of samples being sent to a laboratory for analysis, the Tech Care/TCC test kit can provide on-board results for immediate operational modification if required. Just 10 minutes are required to run a test on one sample. In addition, the simplicity of the testing kit means that any crew member can run the tests following the step-by-step instructions displayed on screen of the optical device, meaning that it does not fall upon the engineer to carry out all of the testing work.
According to the Jean-Philippe Roman, Total Lubmarine’s Technical Director, up to five hours can be saved when testing an average six cylinder engine compared to other equipment on the market. “There is a great demand on marine engineers’ time and we are pleased that we can offer a product that offers serious time-saving advantages” he said.
Significant cost savings are also delivered from the iron test kit by enabling the injector feed rate to be adjusted (preventing over injection, which leads to exacerbated costs). By tracking the cold corrosion based on the quantity of iron in the drain oil, the feed rate can be adjusted in line with the iron content reading and the residual BN. By doing this the acidity in the cylinder is neutralised whilst optimum lubrication of the engine is achieved, facilitating efficient running of the engine and potentially extending the liner’s lifetime for cost and maintenance savings.
What are the Long-Term Benefits?
Cold corrosion testing kits not only identify the problem at hand, but to also facilitate on-going monitoring and modification when required, without the need to send samples to an onshore laboratory. Regular use of such solutions provide ship owners with constant updates on corrosion potential, relative to the iron content and acidity, enabling them to take action before the problem builds. Test kits, such as Tech’Care/TCC provides the information ship owners need to determine the severity of the problem, while monitoring the parameters of iron wear in the cylinder oil for best practise regarding mitigation.
Cold Corrosion Is Here To Stay, So Act Now
Despite the advantages of engine modifications and alternative fuels for emissions reductions, slow steaming for fuel savings, and general ship adjustments to drive chartering possibilities, the problem of cold corrosion remains. Proactive measures that deal with the problem face on are vital to prolonging the lifetime of the cylinder liner. Testing kits that allow ship operators to proactively manage the impact of engine operating conditions and fuel type use have on the engine cylinder and enable a course of action to be taken before the problem arises, can be expected to propel into the industry’s future in light of the daily challenges that reactive measures just cannot meet.
