Can somebody provide a comprehensive guidance (photographs to be included if possible) for a thorough Main Engine scavenge space inspection?
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The inspection of the M/E condition through scavenge ports should be carried out frequently. The early detection of wear mechanisms (corrosive, abrasive and adhesive wear) and the determination of the root cause will prevent costly and catastrophic damages that may put the safety of the vessel at stake.
Equipment to be used during the inspection:
- Feeler Gauge
- Flashlight
- Vernier Gauge for CL grooves measurement
- Small Camera able to fit inside liner scavenge ports
-Pencil, marker/chalk
-Mallet with preferably wooden handle or bronze bar
-Screwdriver for non-return flaps of air intake
-Mirror with telescopic handle
-Clean Rags
A recommended procedure is the following:
- Carry out the inspection with the scavenge space “dirty” before cleaning and with the main lube oil pumps running.
- Measure the clearance of piston rings from grooves using a feeler gauge and compare with makers measurements
- Measure the CL grooves using a Vernier gauge (where accessible) and compare with maker values).
- Use a mallet or bronze bar to check the piston ring movements.
- Use a screwdriver to check the non-return valves.
- Evaluate the carbon deposits on the piston crown top and ring lands.
- Evaluate the condition of the piston ring running surfaces visually and check for signs of seizures, cracks, missing/broken parts, over or under lubrication. It is recommended to clean one scavenge port by a rag and leave the other ports in their current condition (lubricated). In this way you can evaluate the under or over lubrication. Take close-up photos.
- Measure the cermet coating thickness on the piston ring surface (where applicable) using an elcometer. The piston ring surface has to be cleaned before the elcometer measurements. Compare the cermet coating measurements with the maker values.
- Check for traces of water, fuel or lube oil leakages on the piston crown top.
-Check the condition of the piston skirt and for system oil leakages from the piston crown studs. - When the piston is at the bottom dead center check the condition of the cylinder liner surface (wave cut marks, seizures, polishing, corrosion).
Use the forms provided in the manual for reporting and always add in your report a representative set of clear photos for each unit. Upon completion, it is recommended to clean the M/E scavenge space and unclog the scavenge drain pipes.
I am attaching a photographic guidance for accurate reporting.
ME Scavenge space inpsection report.pdf (743.9 KB)
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Good morning Andrea
You may find the attached MAN document useful. It provides detailed procedures with photos and examples.
regards, Kostas
Procedure_Inspection_Cylinder_Condition.pdf (13.8 MB)
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Dear all good evening from my side.
Indeed the Cylinder Condition has become a hot topic during the recent years. The 2020 sulfur cap has contributed a great share to the wear rate increase of the Cylinder Liners installed on many 2 stroke diesel engines causing headaches to the ships’ operators and crews.
The previous responses (if followed) cover the 99% of good practice handbook when comes to the Cylinder Condition inspection. I would only add, that special care should be taken for eliminating the possibility of water carry over through scavenge air by inspecting the valve drainage arrangement and the condition as well as the installation of the WMC.
The water mist catcher/air cooler valve drainage arrangement should follow maker’s recommendations as described in the following plate found on all MAN ES engines (valves A & H fully open).
Despite the fact that 80% of the water separation is happening at the pre-catcher, the Water Mist Catcher is responsible for the 15% of the water amount. Hence the correct installation of the WMC is of great importance. Many times in the past during my attendances, related with Cylinder condition issues, the drain valves have been found half opened preventing the separation of air/water or the WMC has been wrongly installed (usually during the last Dry Dock) without leaving a gap for the water to exit the engine (SL2011-542).
Signs of rust on the Piston Rods surface (small yellow/brown spots) or presence of increased wear at the lower part of the Cylinder Liner are evidence that water is carried over inside your Cylinder through Scavenge Air.
Increased water amount inside the cylinder can easily break the lubricating
SL2011-542.pdf (1.2 MB)
film compromising the cylinder condition.
In addition to the above maintaining a Scavenge Air temperature as low as possible (for sure below 45 degrees Celsius), increases the efficiency of the Engine’s air/water separation arrangement (Service Letter SL2014-589/MTS).
SL2014-589.pdf (257.6 KB)
You may find hereunder an example, derived from MAN ES Operation manual, calculating the condensation amount on a 7K80MC-C Engine operating in an environment with 85% relative humidity.
Readings:
Engine type: 7K80MC-C
Engine load: 22,700 kW
Ambient air temperature: 30 oC
Relative humidity: 85 %
Scavenge air pressure: 3.25 Bar abs
Scavenge air temperature: 45 oC
Calculation procedure:
- Mambient = 0.21 kg/kWh found from figure 1 (as outlined)
- Mscavenge = 0.17 kg/kWh found from figure 2 (as outlined)
3a) k = 1.05 for K80 type engine
3b) Mcondens = 1.05 x 22700 x (0.21 - 0.17) = 953 kg/h
The condensate amount is estimated to be 950 kg/h (± 10%) or 22.8 t/day for the
7K80MC-C engine.
The estimation of condensate amount is based on nominal air amount for the engine
and even distribution of the air outlet temperature from the scavenge air cooler.
The expected condensate amount should, therefore, be taken as rough
guidance in case of small amounts of condensate (between -0.01 and 0.01 kg/
kWh).
Calculation procedure
- The amount of water vapour in the intake air (Mambient) is found in figure 1
based on measurements of ambient air temperature and relative humidity. - The maximum amount of water vapour in the scavenge air (Mscavenge ) is found
in figure 2 based on measurements of scavenge air pressure and temperature. - The expected amount of condensate is calculated by:
MCondens = k Ă— Engine load Ă— (Mambient - Mscavnege)* [kg/h]
where, k = 1.05 for K80-K98 type engines
k = 1.00 for S50-S90 and L50-L70 type engines
k = 0.90 for S26-S46 and L35-L42 type engines
*) The tolerance of the result is ± 10%
No water condensation occurs, if the result is negative.
The sea water temperature may alternatively be used in figure 1 instead of the ambient
air temperature and relative humidity. The 100% relative humidity curve applies,
if the sea water temperature is used.
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Excellent input @Dim ! Thank you very much!
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