Operating Cats 3196 on low RPM

[Cpt.JackOcean]

Never post this question, as I have never been exposed to this type of challenge.
Recently, due to an issue with a shaft vibration, I have been forced to operate at very low RPM. I have a pair of 1999 Cat 3196s with almost 1000 hours on them, and I am forced to push no more than 700-1000 RPM.
I was told that running the engine under load at idle RPM may shorten its lifespan. I would normally operate at 1850 to 2000 RPM under normal circumstances.
Any professional opinion would be greatly appreciated.

 

[Fire99]

This isn't professional but from experience, the only real no-no I've come across is running the engines for long periods of time NOT under load. Under load, particularly if you're able to run the engines near 1000rpm is unlikely to cause major engine wear issues. However, my only caveat would be that the Turbo may not enjoy minimal activity and for me I'd make sure the operational temps (oil and water) are reaching normal level. Other than that I can't see anything catastrophic occurring.

Out of interest, how long are you planning on operating in this condition? Will you be getting the vibration resolved?

PS - Personally, I'd be ensuring regular oil changes.

 

[Alicatt]

We tend to run one engine at a time to give it a bit of load, still we are at 700 to 900rpm on the driven engine to keep to the speed limits on the canal. That also helps getting the engine up to temperature, turbo does not really produce any boost below 1500rpm, it is fairly singing at 2000rpm, and tops out at 2400rpm.
We have a pair of old mechanical injected 5.8litre turbo diesels of 145hp each, after running for about an hour there is a load of unburnt stuff in the exhausts, giving a blast on the throttles leaves a huge smoke screen for a few meters and then clears and the next hour or so the exhaust is clear.

 

[NBs]

Old-school engines require a load over the long term, otherwise they will have a number of problems, at some point.

Common rail engines can generally run at low loads because the fuel is precisely controlled and burning is better.

I have asked this at the Cummins factory and they said it is ok to run 830rmp 24/7 with no problems. Idle is 600rmp and the recommendation is max 5 min.

NBs

 

[Cpt.JackOcean]

This isn't professional but from experience, the only real no-no I've come across is running the engines for long periods of time NOT under load. Under load, particularly if you're able to run the engines near 1000rpm is unlikely to cause major engine wear issues. However, my only caveat would be that the Turbo may not enjoy minimal activity and for me I'd make sure the operational temps (oil and water) are reaching normal level. Other than that I can't see anything catastrophic occurring.

Out of interest, how long are you planning on operating in this condition? Will you be getting the vibration resolved?

PS - Personally, I'd be ensuring regular oil changes.

Thank you for your reply. The water temperature is always at its normal ~90 °C. I occasionally hit 1800 rpm just to spin the turbo and clean up some residue. I will try to address the vibration as soon as i am on the dry dock, ~ 90 days.

 

[Cpt.JackOcean]

We tend to run one engine at a time to give it a bit of load, still we are at 700 to 900rpm on the driven engine to keep to the speed limits on the canal. That also helps getting the engine up to temperature, turbo does not really produce any boost below 1500rpm, it is fairly singing at 2000rpm, and tops out at 2400rpm.
We have a pair of old mechanical injected 5.8litre turbo diesels of 145hp each, after running for about an hour there is a load of unburnt stuff in the exhausts, giving a blast on the throttles leaves a huge smoke screen for a few meters and then clears and the next hour or so the exhaust is clear.

Thank you for your input,

 

[Cpt.JackOcean]

Old-school engines require a load over the long term, otherwise they will have a number of problems, at some point.

Common rail engines can generally run at low loads because the fuel is precisely controlled and burning is better.

I have asked this at the Cummins factory and they said it is ok to run 830rmp 24/7 with no problems. Idle is 600rmp and the recommendation is max 5 min.

NBs

Thank you for your input,

The gauge that reads the load shows "0%" with idle in gear (at 700rpm) and going about 7 knots. I can accelerate to 850 rpm, and it will show about 5-8% load, with a speed of 8knots, but now I am pushing more water aside, so there is more resistance. I am curious to know if anyone has experienced a similar scenario.
Other though, I am planning a long trip next year (obviously, I will address the vibration prior) and I enjoy the speed below 10 knots, but I want to find out if I am not shooting myself in the foot with this approach.

 

[Tranona]

That suggests overpropping or overpowering the boat, or both. What boat is it?

 

[Cpt.JackOcean]

That suggests overpropping or overpowering the boat, or both. What boat is it?

Hi, thank you for your reply. It is a 1999 Viking Princess 52 ft.