SECTOR FOCUS: TESTING & MONITORING Environmentally Acceptable
Lubricants (EAL) - Performance over the years
Anil Balan, Tribologist, SeaTec UK Limited
It has been 5 years since the US EPA introduced regulations that mandated a switch to environmentally acceptable lubricants in all oil-to-sea interfaces. In this technical update, we check on the sterntube lubricant samples tested by SeaTec over the years (2014-2018) where environmentally acceptable lubricants are being used.
The below figure shows the overall breakdown of the samples submitted over the years.
The common concern while using EAL is that most of these lubricants cannot tolerate a large amount of water. Presence of water will lead to the formation of acidic compounds and inturn they become corrosive lubricants. In these cases, the water would often be accompanied by a high acid number. When such lubricants (eg: synthetic ester based EAL) are used, it is suggested to maintain the water at minimal levels (<1000 ppm) to maximize the fluid life.
It can be seen from figure 1 that there is a decreasing trend in the percentage of satisfactory result (green) samples submitted from the ships over the years from 81.89% in 2014 to 66.67% in 2018.
The breakdown of the parameters highlighted can be seen in Figure 2. The most commonly highlighted parameters are: acid number, water content and wear.
Also, there have been cases with increased wear noted in some ships depending on the bearing composition. One common phenomenon is the sudden increase in lead content when the ship changes to an EAL. In most cases, this increase in the lead would be from lead-based paints/coatings as this lead content increase won’t be accompanied by an increase in other bearing metal elements. Since the classification societies provide strict wear limits (Refer IACS limits), it would be prudent to perform additional investigation analysis to identify the wear mode to decide upon a further course of action if elevated wear is detected.
SeaTec is able to provide additional investigation analysis such as Scanning Electron Microscopy (SEM) and ferrrography for such sterntubes with high wear and provide technical assistance if required.
These results indicate that there are potential areas of improvement with respect to maintaining water and other parameters within the stern-tube manufacturer’s and lube supplier’s guidelines, to avoid costly oil changes.
For more information, contact Anil Balan;
anil.balan@
seatec-services.com
LINK
www.seatec-services.com
LUBE MAGAZINE NO.151 JUNE 2019
29
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