Which precautions and procedures may reduce the negative effects of switching to Fuel Oil with Sulfur content less than 0.5%?
- MAN recommends installing Cermet-coated rings at next overhaul. Ceramic coating will scrape the liner thus keeping its surface open. Check Service Letters 685 and 659. Note, that the delivery time for such rings is 3 to 6 months so the order should be placed in advance.
- After installing Cermet-coated rings, use a coating measurement tool every time during inspection through scavenging ports to evaluate piston rings condition. Piston rings to be replaced when the coating thickness drops to 50 microns. The estimated lifetime of rings is 22000RH - 26000RH.
- Use onboard kit for scrape down analysis weekly/biweekly. MAN recommends a Dot Fast kit from Chevron as it is able to measure the full Fe content.
- Fe content in drains from underpiston spaces is limited depending on the bore size of the engine: Bore Max Fe 26-50 100ppm 60-70 150ppm 80-98 200ppm BN in the drain oil to be kept above 25% of the original oil BN.
- Cylinder Lubricating Oil feedrate to be set based on inspections, see Service Letter 671. The absolute minimum is 0.6 g/kW h. If signs of hard contact or micro-seizures are observed on piston rings or liner surfaces, the feed rate to be increased.
- It is recommended to use CLO with BN=40. Unfortunately, these oils have low detergency.
- Due to low detergency of BN40 CLOs, for piston parts cleansing purposes, it is recommended to change over to BN70 Cylinder Lubricating oil for 1-2 days weekly.
- Good purification is essential as VLSFO may contain up to 60 of catfines). Only 10 ppm of catfines are allowed at the engine inlet as per Service Letter 638.
- Arrange 2 storage tanks for CLO where possible: 1 for High BN oil and 1 for Low BN oil.
- Conduct frequent inspections through scavenging ports - not less than once a month.
- Refer to Service Letter 2014-587 page when incstalling new piston rings/liner.
