I believe that most of you have noticed that most of the new and large engine models are equipped with temperature monitoring sensors on the cylinder liners. The systems are known under different names and layouts (e.g. Mapex) and are developed by different marine engineering companies (e.g. Wartsila, Kongsberg, etc.) but all serves the same purpose.

The cylinder liner temperature monitoring system is comprised of temperature sensors that are installed within the cylinder liners.

These temperature sensors monitor the temperature of the liner and are interfaced to the alarm system of the ship. In the event that the liner temperature goes over the predetermined thresholds, an alert will be triggered.

The system’s objective is to identify instances of thermal instability on the running surfaces of the cylinder liners, which can be caused by:

• • Oil film break down between liner and piston rings and subsequent seizure.
    Early action can stabilize the situation and prevent scuffing.
  • Loss of cooling. This will affect both fuel pumps and exhaust side sensors simultaneously on the affected units.
  • Broken or collapsed piston rings. The temperature level will increase over time. Piston ring failure can be detected during scavenge port inspection.

Two temperature sensors are installed in each cylinder liner, one on the fuel pump side and one on the exhaust side. These sensors are part of the cylinder liner temperature monitoring system.

The alarm set points need to be continuously optimized in the manner that will be detailed in the following paragraphs in order to ensure the quickest possible reaction time in the event of temperature instability and to avoid false alerts.:

If the parameters are set too low, false alarms will be triggered during any regular service load, such as 75% of MCR, hence it is imperative that Tmax and Tmaxdev are not allowed to do so. False alarms will occur if the values are not high enough. Whenever there is a variation in the level of engine load, Tmax needs to be recalibrated so that it corresponds to the new level.
It is imperative that Tmax and Tmaxdev be modified and set to values that are both as low and as close to the temperature band of each sensor as is technically possible in order to guarantee an adequate level of sensitivity. In the event that there is an abnormal temperature variation while the machine is operating at part load, this will ensure the quickest possible reaction time.

If many excessive temperature warnings are being raised by single cylinder units, it is of the utmost importance to inspect the condition of the cylinders on the units in question. Scavenge port inspection is performed at the next available opportunity in order to accomplish this objective. The purpose of this is to guarantee that the piston rings and cylinder liners remain in satisfactory working condition at all times.

Units that have just undergone maintenance will invariably exhibit temperature instability for the first few days of operation. In light of the fact that the overhauled unit is anticipated to stand out from the rest, the engineers should become accustomed with the typical temperature differences that occur after overhauls.

The same goes for when the load is increased after prolonged periods of steady (low) load operation; you should anticipate some light instability as a result of the abrupt change in ring geometry. This is quite natural, although the severity and pattern of it cannot be predicted. Therefore, one must have patience and provide enough time for the geometry to adapt.

In the event of scuffing, the temperatures of the liner will oscillate dramatically, and the peak temperatures will be higher than the average temperature measured by all sensors. However, when the load is lower, it may be essential to monitor more closely since the maximum temperature deviation from the average will be lower than when the load is higher; hence, the value of Tmaxdev must be adjusted downwards accordingly.

Above one unit is indicating scuffing, detected by AMS by a ΔTmaxdev set to 30°C or lower and a Tmax set to 170°C.

In the event of scuffing, increase cylinder lubrication and reduce the load and the Pmax on the cylinder unit in question.

Above two units are indicating scuffing, detected by AMS by a ΔTmaxdev set to 25°C or lower and a Tmax set to 150°C.

On the image above, one unit is indicating scuffing. This is difficult to detect but may be detected manually or by AMS by a ΔTmaxdev set to 15°C or lower and a Tmax set to 140°C.

If you have any questions regarding above, please feel free to use our existing forum Seafarer’s World and will try to answer to all your queries.

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Source and Bibliography:

• MAN B&W –  Circular letter 2245-0150-0001