Water In Oil Monitoring System
All MAN B&W engines are as standard specified
with Water In Oil monitoring system in order to de-
tect and avoid free water in the lubricating oil.
In case the lubricating oil becomes contaminated
with an amount of water exceeding our limit of
50% of the saturation point (corresponding to ap-
prox. 0.2% water content), acute corrosive wear of
the crosshead bearing overlayer may occur. The
higher the water content, the faster the wear rate.
To prevent water from accumulating in the lube
oil and, thereby, causing damage to the bearings,
the oil should be monitored manually or automati-
cally by means of a Water In Oil (WIO) monitor-
ing system connected to the engine alarm and
monitoring system. In case of water contamination
the source should be found and the equipment
inspected and repaired accordingly.
The saturation point of the water content in the
lubricating oil varies depending on the age of the
lubricating oil, the degree of contamination and
the temperature. For this reason, we have chosen
to specify the water activity measuring principle
and the aw-type sensor. Among the available
methods of measuring the water content in the
lubricating oil, only the aw-type sensor measures
the relationship between the water content and
the saturation point regardless of the properties of
the lubricating oil.
WIO systems with aw-type sensor measure water
activity expressed in ‘aw’ on a scale from 0 to 1.
Here, ‘0’ indicates oil totally free of water and ‘1’
oil fully saturated by water.
Alarm levels are specified as follows:
Engine condition Water activity, aw
High alarm level 0.5
High High alarm level 0.9
The aw = 0.5 alarm level gives sufficient margin
to the satuartion point in order to avoid free water
in the lubricating oil. If the aw = 0.9 alarm level
is reached within a short time after the aw = 0.5
alarm, this may be an indication of a water leak
into the lubricating oil system.
Please note: Corrosion of the overlayer is a poten-
tial problem only for crosshead bearings, because
only crosshead bearings are designed with an
overlayer. Main, thrust and crankpin bearings may
also suffer irreparable damage from water con-
tamination, but the damage mechanism would be
different and not as acute.
Liner Wall Monitoring System
The Liner Wall Monitoring (LWM) system monitors
the temperature of each cylinder liner. It is to be
regarded as a tool providing the engine room crew
the possibility to react with appropriate counter-
measures in case the cylinder oil film is indicating
early signs of breakdown.
In doing so, the LWM system can assist the crew
in the recognition phase and help avoid conse-
quential scuffing of the cylinder liner and piston
rings.
Signs of oil film breakdown in a cylinder liner
will appear by way of increased and fluctuating
temperatures. Therefore, recording a preset max
allowable absolute temperature for the individual
cylinder or a max allowed deviation from a calcu-
lated average of all sensors will trigger a cylinder
liner temperature alarm.
The LWM system includes two sensors placed in
the manoeuvring and exhaust side of the liners,
near the piston skirt TDC position. The sensors
are interfaced to the ship alarm system which
monitors the liner temperatures.
For each individual engine, the max and deviation
alarm levels are optimised by monitoring the tem-
perature level of each sensor during normal serv-
ice operation and setting the levels accordingly.
The temperature data is logged on a PC for one
week at least and preferably for the duration of a
round trip for reference of temperature develop-
ment.
In the Extent of Delivery, the Liner Wall Monitoring
system is available as option: 4 75 136.
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