Case Study on cold corrosion prevention

Case

Case Study: Cold Corrosion Prevention

During slow steaming, cold corrosion attacks cylinder liners
and piston rings in the form of sulphuric acid. The effect
becomes steadily more damaging as the surface of the
piston rings loses integri and, as a result, particles are
emitted that cause severe abrasion of the rings and liners.

As a consequence, the probabili of adhesive wear (scuffing)
is considerably increased.

Vessel: M/V H/A
Ring pack: 8,429 hours
Engine: 8,429 hours
Cylinder oil feed rate 1.05g/kWh
70 BN standard cylinder oil
Fuel S = 2.9%
Average engine load = 35%

For maximum effectiveness, the surface of the piston ring
should be hard and “chemically inert”. However, during slow
steaming operation it is likely to become both weakened and
activated. Figure 1 below shows an example of a corroded top
piston ring damaged by sulphuric acid (the whitened areas).

With the lowest feed rate, the Blending-on-Board Variable
BN cylinder oil enables you to preserve the integri
of your piston ring’s surface against acid attacks and
eliminate the effects of cold corrosion (figure 2).

Vessel: M/V Maersk Tanjong
Ring pack: 15,329 hours
Engine: 40,455 hours
Cylinder oil feed rate 0.85g/kWh
95 BN Blending on Board cylinder oil
Fuel S = 3.26%
Average engine load = 26%

Liner Corrosion Prevention

- comparison of two 12RT-Flex96C-B Engines

Cold corrosion is distinguished by the appearance of black
patches on the cylinder liner, as seen in figure 3. e black
patches are a combination of cold corrosion creating an active
and spongy surface on the liner wall and a lack of additives in
the cylinder lubricant. Without these additives,
the lubricant is unable to neutralize the acid and remove the
carbonaceous deposits.

Vessel: M/V B. E
Ring pack: 2,257 hours
Cylinder liner: 6,000 hours
Engine: 6,000 hours
Cylinder oil feed rate 1.05 g/kWh
70 BN standard cylinder oil
Fuel S = 3.1%
Average engine load = 35%

The SEA-Mate®

Blending-on-Board lubrication system
adjusts the additive dosage in the cylinder oil according
to the engine’s needs. In this way, the variable BN
cylinder oil Blended-on-Board is able to prevent the
total depletion of the cylinder lubricant and thereby
eliminate risk of damage from severe cold corrosion,
as shown in figure 4.

Vessel: M/V Maersk Tanjong
Ring pack: 2,994 hours
Cylinder liner: 40,455 hours
Engine: 40,455 hours
Cylinder oil feed rate 0.85g/kWh
95 BN Blending on Board cylinder oil
Fuel S = 3.26%
Average engine load = 26%

Piston Ring Cold Corrosion Wear Prevention

– using SEA-Mate® Variable BN Blending

After the onset of cold corrosion, using a standard fixed BN
cylinder oil will only lead to faster and more aggressive degeneration. For piston rings, such excessive wear dramati-
cally reduces the time-between-overhaul (TBO) of the ring pack. Graph 1 illustrates this development, highlighted by
the purple and orange lines.

The fit-for-purpose BOB Variable BN cylinder oil
effectively neutralizes the sulphuric acid and thereby
increases the TBO of the ring pack, even in extremely
corrosive conditions. is was demonstrated on vessels
with RT-Flex engines, outlined by the red and green line in
the graph. e same results of the BOB lubricant system
also apply for similar conditions in MAN ME and MC
engines.

Piston Ring Cold Corrosion

– BOB Lubricant Impact on Reliabili

When using 70 BN standard cylinder oil during slow steaming, the wear rate of the ring pack and the liner is typically reduced
and the TBO of the cylinder unit (ring pack overhaul) can be as low as 2,000 hours (see graph 2). However, the BOB Variable BN cylinder oil allows the TBO to reach at least the recom-mended OEM levels – and in most cases can be as high as 30,000 hours.

Similarly, in cold corrosion conditions, the TBO of the cylinder
liners are reduced from 70,000 hours to approximately
40,000 hours.

Cylinder Oil Feed Rate Optimization

– using the SEA-Mate® BOB lubrication System

e use of BOB Variable BN “fit-for-Purpose” cylinder oil
enables the operator to use the recommended OEM
minimum feed rate with no need to compensate for sulphur
(which is necessary when using standard cylinder oils).
Consequently, cylinder oil consumption is pically decreased
by as much as 25-40%.

Cylinder Wear-pe Proportions

The effectiveness of BOB Variable BN “fit-for-Purpose” cylinder
oil is highlighted in the graph below. In particular it demonstrates
how cold corrosion wear can be prevented using the SEA-Mate®
BOB lubrication system and contributes to minimizing the
overall wear process.

The BOB cylinder oil also contains anti-wear additives that
directly reduce abrasive and adhesive wear.

Conclusion

As the figures and graphs show, the adjustable BN
cylinder oil Blended-on-Board gives a drastic overall
reduction in cold corrosion wear.
This information was validated and confirmed
over 1 million operating hours on board vessels,
numerous OEM inspections and laboratory tests.
The findings are crucial for vessel owners seeking
to optimize engine performance and reduce
operating costs.
The improved TBO results are achieved by improving
the balance of BN and sulphuric acid, and by
optimizing lubrication feed rates.

By improving the integri and performance of piston
rings, cylinder liner conditions and lubrication
management, users can reduce the lubrication-related
Total Cost of Ownership by 25-40%.
The conclusions made on board vessels fitted with
RT-Flex engines are similar to those with MAN ME
and MC engines. Consequently, the SEA-Mate®
Blending-on-Board lubrication system provides
similar results and benefits when used with both
engine pes.