Main Engine Starting Problem.

 MAN B&W 6S 50 MC ENGINE 

 

               Once Main Engine was not starting on fuel but was able to turn on air kick, we tried starting it from Local control, ECR control , Bridge control but could not start. 

            Later to investigate we opened up the control air connection on top of the fuel pump puncture valve for one of the unit .An air kick was given , we noticed the control air supply was continuously supplying air on top of the fuel pump puncture valve .This control air is suppose to stop once engine turns 30 rpm as after 30 rpm fuel takes over , which was not the case. 

            After further more troubleshooting we decided to open and check the stop engine button spool valve located at emergency maneuvering platform , although we had earlier checked and reseted the button , but still now we decided to open the spool arrangement located below the stop button. 

        After dismantling the stop spool arrangement  , we found the spool was stuck inside , so when we were resetting the button from outside the spool was not coming up. 

                    As the  engine stop button spool at emergency maneuvering platform was stuck , so the switch over from air to fuel mode was not happening , because the engine stop signal i.e the puncture valve air was continuously supplying air to puncture valve.

            Once the spool was made free, the engine picked up on fuel immediately as soon as  the air kick was given !!!!!.so please remember always to check puncture valve air supply.

Main Engine Starting problem.

 MAN B&W 6S 50 MC  ( 1997 BUILT ENGINE )

           In this new era of ME electronic engines ,this post might not be relevant to engineers not sailed on this type of engines , but one  can read through it to get some ideas..

         Once we were not able to start the engine on Astern , but could start it on Ahead mode . In ECR on NOR control panel found the Astern LED is  not coming "ON" when astern movement is given on Telegraph. 

           At first instance we suspected problem might be in manoeuvring system , so we opened up air  blocks for Ahead and Astern in manoeuvring air system , checked all the valve block spool arrangement all found to be normal.

             Later after extensive troubleshooting we noticed one of the units fuel pump reversing cylinder piston locking nut had come off and the disc was found fallen inside the reversing  cylinder.

                If we had noticed externally on the fuel pump inward side that one of the units reversing cylinder rod is not sticking out . ( when the lever is put in astern telegraph mode) .we could had immediately identified the problem at first instance and could had saved from vessel getting off hire .

              Later in port as per makers advice we changed the reversing cylinders for all units fuel pump with new robust design type cylinders.

I

Main engine piston rod stuffing box assembly

   MAIN ENGINE SULZER RTA 48 

During dismantling the air sealing rings from the Main engine spare piston rod stuffing box for cleaning , nobody noticed how are these air sealing rings arranged .so after cleaning all the parts ,while assembling the air sealing rings were wrongly assembled. 

             Later when this piston was put in the unit with wrongly assembled stuffing box air sealing rings, as the scavenge pressure increased, crankcase was found pressurized and crankcase oil was found splashing out from the flywheel shaft seal. 

                 Immediately Unit piston was changed with correctly overhauled stuffing box , found crankcase pressure normal.

                  Later on investigation we found out that the air sealing rings are to be overlapped with each other. It is written top on each part of air sealing ring ,the bottom part is to be  overlapped with the other top part. Please see these photos for clear understanding.

 The top part in photo shown is wrong  assembly wereas the lower part shows the correct assembly , maintenance manual does not have any  clear instructions So be careful and while dismantling the stuffing box for cleaning of sealing rings , senior engineers must be present and photos to be taken of every part dismantled, to enable correct reassemble.