REVERSING AIR CYLINDER HEALTH CHECK
HEALTH CHECK OF M/E REVERSING AIR CYLINDERS
After attending to overhauling or troubleshooting various reversing system problems for 2-stroke MAN B&W Diesel engines, we noticed that most of them could be prevented before they occur.
We have prepared the below experience share document for reversing system health check to get some idea about the system condition.
HEALTH CHECK OF THE REVERSING AIR CYLINDERS:
There are different ways to check reversing cylinder conditions without dismantling; here we will explain one of them, which is most convenient.
First, we would like to remind key point that, there is no continuous air supply to reversing air cylinders while the engine is on remote control.
Once the start order is triggered, air will be supplied to reversing cylinders for only about 6 seconds; hence, it is not possible to distinguish air leakages due to noise during the starting sequence.
On the contrary, if engine control changeover to emergency stand, there is continuous air supply to reversing cylinders. (Red button on Pos.102-stop valve- must be in pushed position). So, this phenomenon can be used to check the condition of the reversing air cylinders.
Please follow up below points to carry out the health check for the reversing cylinder system:
1. Engine to be in stop condition.
2. Confirm the control air is open.
3. Close the starting air from the main bottle and block the main starting valve. (Preferably drain the air line between the air bottle and the main starting valve.)
4. Engage the turning gear.
5. Changeover the control position from remote to EMERGENCY, make sure that red colour stop button of Pos.102 at the emergency stand is in the pushed position. If the red button is not pushed, air will not be supplied to reversing cylinders
6. If everything is okay, now there is pressure on the reversing cylinders, depending on the position of the ahead-astern arm of valve Pos.105 on the emergency stand.
7. To make sure, you may lose the air connection one of the reversing cylinder air inlets and confirm pressurized air is available.
8. Keep the astern-ahead changeover valve on the emergency stand at the ahead position. Now, if your reversing cylinder's internal parts are in good condition, there should not be any air leakage to the opposite side of the reversing cylinder. You can confirm this either by removing the opposite side connection or simply checking the drain of the pneumatic valve Pos.11. Please note internal leakage of the reversing cylinders will be reflected as an air leak on the Pos.11 drain port while selecting valve Pos.105 at ahead position. Also check if there is any local air leak on reversing cylinders or their safety valves (for large bore engines).
9. Turn engine 1 revolution with turning gear, confirm all rollers changed to the ahead direction, and all ahead lights lit. In order to change the position, engine should turn 1 revolution by turning gear.
10. Change the Pos.105 (Astern-Ahead valve) to astern, check if there is an air leak from the drain of Pos.10. Also check if there is any local air leak on reversing cylinders or their safety valves (for large bore engines).
11. Turn engine 1 revolution with turning gear, confirm all rollers changed to astern direction, and all astern lights lit. In order to change the position, the engine should turn 1 revolution by turning gear.
12. Even if slight air leakage is observed from drain of
Pos.10 or Pos.11, recommend find which cylinder(s) are defective and overhaul
them. In order to find out which cylinder(s) are defective, you can close the
ball valves on the cylinder inlet (applicable on most of the vessel) and see on
which cylinder air leak stops, or just remove the opposite side air connection
and see if any air is coming.
1. We recommend repeat above test at every 6 months.
2. Our experience shows that, in some cases, there is defect on the connection between reversing cylinder shaft and roller, hence, we strongly recommend that open the camshaft covers and confirm that rollers also changing position together with reversing cylinders.
If you have any question or require any service such as troubleshoot, routine maintenance or spare part supply; please contact to us.
