NOAA Teacher at Sea
Aboard NOAA Ship Ronald H. Brown
February 15 – March 5, 2012
Mission: Western Boundary Time Series
Geographical Area: Sub-Tropical Atlantic, off the Coast of the Bahamas
Date: February 24, 2012
Weather Data from the Bridge
Position: Windspeed: 15 knots
Wind Direction: South/Southeast
Air Temperature: 23.9 deg C/75 deg F
Water Temperature: 24.5 deg C/76 deg F
Atm Pressure: 1016.23 mb
Water Depth: 4625 meters/15,174 feet
Cloud Cover: less than 20%
Cloud Type: Cumulus
Moving a ship through the water has come a long way since Ben-Hur was chained to a rowing bench as a Roman War Galley slave. I was interested in what systems powered the Ron Brown and Lt. James Brinkley was kind enough to take me on a tour of the ship’s engine rooms.
The Ron Brown has a total of six separate power units. Three of these are V16 (16 cylinders) diesel engines connected to electric generators.
These generators produce electricity to run the ship’s electric motors which turn the screws (propellers). In the past the diesel engines would have been connected directly to the propeller shaft, but in the last 20 – 30 years many ships have gone to using electric motors as an interface between the diesel engines and the propellers. On the Brown at any given time two of the V16 diesel engines are online running the generators while the third engine is held in reserve. These generators produce 600 volts of AC current. A transformer converts the 600 V AC to a DC current to run the ship’s large DC electric motors.
Image credit: nauticexpo.com
This image shows a diesel engine connected directly to the “Z” drive.
On the Ron Brown there is a generator and an electric motor between the
diesel engine and the “Z” drive.
Most ships have a propeller shaft that exits the rear of the ship parallel to the keel. The propeller is stationary – it can only rotate to propel the ship forward or backward. To turn the ship a rudder is employed which is usually controlled by a wheel on the bridge. The Ron Brown does not have a rudder; instead it is propelled by a “Z” drive. This type of propulsion system is specially suited for research vessels. In a “Z” drive the main drive shaft from the electric motors comes out parallel to the ship’s keel. It then is joined to a type of “spline gear” and makes a 90 degree turn down. At this point the shaft exits the ship where there is another “spline gear” which turns 90 degrees again parallel to the keel.
The region between the two “universal joints” is mounted on a kind of turn table which allows each of the screws (there are two – one on the starboard side of the ship another on the port side) to rotate 36o degrees. In addition to precise maneuvering, this system of two “Z” drives and a bow thruster, when interfaced with a computer control system and GPS, allows the ship maintain an exact position in the water to within a few feet or better.
The Ron Brown has three other smaller V8 diesel engines that power generators that are used to provide electricity for SS (ship services). This would represent things like radios, heating & air conditioning, lighting, computers, etc. The electricity produced by these three generators goes through two step-down transformers. The first reduction drops the potential from 600 V to 480 V. The next step down brings it from 480 V to 120 V. This is the form that is available to power the equipment throughout the ship. In addition, these three smaller engines and their generators can be used to power the Ron Brown’s propulsion in case of an emergency.
I would like to thank Lt. James Brinkley for the tour and Second Assistant Engineer Jake DeMello for explaining some of the technical aspects of the engines and answering my questions.