- Mark 9 engines by MAN were introduced in 2006 with an ultra-long stroke.
- These engines were offered for efficiency optimization.
- It recommends the use of Category II Cylinder Lubricating oils (CLO) for the Mark 9 engines.
- Category II CLO has been tested to specifically ensure their cleaning ability.
- For Mark 8 and lower engines either Category I or Category II CLO can be used.
The Mark 9 engines by MAN were introduced in 2006 with an ultra-long stroke for efficient operation at lower speeds, says a technical update released by The Viswa Group.
Efficient optimization
These engines were offered for efficiency optimization. Recently MAN has published a
new Cylinder lubrication oil strategy for these engines or higher grade engines, which function at higher temperatures and higher pressures.
The new strategy recommends the use of Category II Cylinder Lubricating oils (CLO) for the Mark 9 engines or higher as the Category II CLO show higher performance. The Category II CLO has been tested to specifically ensure their cleaning ability. At the current time, only CLOs with TBN of 100 and 140 have passed the process to become Category II CLO.
Category I or Category II CLO
For Mark 8 and lower engines either Category I or Category II CLO can be used.
With the sulfur IMO regulations of 2020, increasingly Category I and II CLOs will be used with VLSFOs (0.5% S). With these VLSFOs and CLO, abnormal liner wear was seen (as raised in our Technical Update published in April 2020). The abnormal liner wear was thought to be related to a combination of a high TBN CLO, high feed rate, and lower detergency properties of the Category I CLO which resulted in liner wear.
Category II CLOs are recommended for Mark 9 and above engines. These CLOs have high TBN (100, 140). While high TBN assists in removing deposits (detergency properties), high TBN can also increase the topland deposits, which at increased levels can cause rubbing with the liner.
CLO strategy effective with the described checks
It is suggested that this CLO strategy can only be effective with the described checks.
Monthly visual inspection of the cylinder and piston. The goal is to minimize the feed rate of the CLO while keeping the piston as clean as possible and with acceptable wear.
- Consistent evaluation of the drain oil samples is recommended between 14 days to a month. The BN in the drain oil should be kept above 25% of the original BN value. However, if deposits start to build up inside the engine, the BN level may need to be increased to remove these deposits.
- Monitoring iron content from drain analysis is crucial. The iron has to be maintained below
certain values based on the bore of the engine. - Cylinder liner wear measurements should be obtained at least once a year.
- Piston ring related wear should be measured during every scavenge port inspection
Guiding drain oil levels
| Engine bore size | Max. Fe content (ppm) |
| 26-50 | 100 |
| 60-70 | 150 |
| 80-98 | 200 |
References
1. Excessive liner wear caused by VLSFO, Viswa Lab.
2. Cylinder and system oil MAN B&W low-speed two-stroke engines, Service Letter SL2020-
694/JUSV, MAN Energy Solution.
3. Cylinder lubrication update for 0 to 0.50% sulfur fuels, Service letter SL2019-671/JAP, MAN Energy Solution.
Dated: July 27th, 2020
Engine bore size Max. Fe content
(ppm)
26-50 100
60-70 150
80-98 200
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Source: The Viswa Group
