Super Eco Speed


A question for engineers:
Large container vsls designed for speeds of up to 25-26 knots, and B&W engines of 75.000 HP to 90.000 HP (10 or 12 cylinders).
Max rpm 104 / 26 kts
Eco rpm: 80-84 rpm / 20 kts
The recent trend is to reduce speed to some 14 to 16 knots, which actually is manouvering speed.

The question:

  1. What is the long term effect on main engine?
  2. Once per day running on full navigation speed - can this help?
  3. Any other comment or advice.

1.) If the load reduction is made without attention to condition of injectors, cylinder lube quantity, fuel quality, exhaust temp, stack temp and jacket water temperatures, really bad stuff will quickly follow.

2.) That would be nice while the engine is at high load but it might also start a fire in the exhaust before the turbo and overspeed/wreck the turbo if the conditions in 1. were not addressed.

3.) The engine manufacturers are spending a lot of time working on solutions to the problems created by slow steaming. Read this, it might answere a lot of your questions and provide hints at other issues involved. [B][/B]

On 8 cylinder 17,000 hp B&W full sea speed is 96.5 rpm, about 19 kts, normal full sea speed is 95 rpm (about 18.5 kts). When ordered to use most economical speed we reduce to 85 (about 17kts) but increase to 95 twice a day to clean things out, I don’t know how effective that is.

I’ve never worked with B&W engines but thats standard proceedure for medium and high speed engines running at reduced load for extended periods. To reduce the chance of a stack or manifold fire, regular loading would be cycled. On the Storks, Wichmanns ect, we would water wash the turbos at the end of the cycle.

The newest generation engines (Cat ect)with smoke mapping programs, there can be be plural criticle ranges in RPMs and loads. Turbo inlet temp rise is the biggest problem. Pulsating and barking can be another.

Then there’s the high speed engines burning heavy blends…I took that as a sign to retire.