Saturday, September 13, 2008

Changing speeds with a low-speed Marine diesel

This ship is powered by a single 17,042 HP Kobe Mitsubishi, 8 cylinder, low-speed diesel engine, turning a fixed, right handed turning propeller. It is direct drive, meaning no gear box; the crankshaft of the engine is connected directly to the propeller shaft. The engine speed and rotation direction and shaft speed and direction are the same.

The engine is reversed by stopping the engine, shifting the cam and restarting the engine, turning in the opposite direction. This is a common merchant ship setup.At 58 RPM (12 kts) and below the engine speeds can be changed any time directly from the wheel house. Above 58 rpm the engine speeds are controlled by a computer load up or load down program.

The load-up program starts when the Engine Order Telegraph (EOT) is moved to any speed above full. The rpm is increased, by the program, about 1 rpm every minute. This is to allow time for the engine to warm up and avoid thermal stress. From full maneuvering (12 kts) to full sea speed (95 rpm, 18.5 kts) takes about 40 minutes.
Slow downs are also controlled by the computer, called the load-down program. Load down is quicker then load-up, from full sea speed down to full maneuvering takes about 25 minutes. The load-down program starts when the Engine Order Telegraph (EOT) is moved from any speed above 58 rpm to a lower speed. The program reduces the engine speed about 1.5 rpm per minute. When the load-down program starts a light on the engine consol lights to show engine speeds are controlled by the program. Twenty five minutes and about 7 miles later the engine will be at 58 rpm

In an emergency a program cancel button can be pushed and the engine will by-pass the program and answer the EOT directly. If the EOT is set on any speed below full (half, slow or dead slow) or any astern bell it will also by-pass the program.

No comments: