CPP – LINK FAILURE :


Given below is an incidence of interest that happened in one of the OSV vessel of my company. I was serving as chief engineer in one of the OSV vessel of our company. Configuration of our vessel is like this. There are 2 main engines (DAIHATSU 6 cylinders, 1350 BHP at 735 RPM), Twin screw, two reduction gears, 2 CPP, 2 Nos, rotary vane steering gears, 2 No. shaft generators, one no Electric Motor driven B/T. Two M/ES are coupled to one induction generator and to one shaft generator.

The incident took place in one of the sister ships having similar configuration.

When M/E is started it runs at idle RPM (400), and we have to engage M/E clutch for increasing M/E RPM to full (735) at zero pitch. On the particular day when engine started and clutches were engaged port engines were getting highly over loaded and same could not be clutched in. Cargo work was carried out with only one shaft generator working. As the pitch indication was zero they suspected that the port shaft may have got fouled with rope or net. To clear the suspected fouling, the above vessel came to port for repairs. My vessel was loading at same port. So I just went to the above vessel for a friendly visit.

I went to engine room started port engine and tried to engage clutch, but port engines were getting overloaded badly. Engines were stopped and I took a round in E/R and CPP room. In CPP room I observed that the distance between CPP follow up rod collar and reference flange was not normal and indicating pitch was high in astern direction though pitch indicator was showing zero pitch.

Same was confirmed with a trammel gauge available on board. On further investigation it was found that one metallic link connecting CPP potentiometer to its pitch transmitter locking had failed and fallen down below floor plate. Same was recovered from place and connected in place. Now when CPP pump was started port CPP automatically came to zero pitch. Port engines were started and clutched in and found to be normal costly repairs originally planned were avoided.

Lesson learnt :

While tracing the fault, start from very basic. When a break down happens we presume it to be complicated and start working from higher levels. Also we should not solely depend on instruments we have to cross check then in break down condition. Never become panic and never be hasty. Look into all possibilities.