Clipper III: A Case Study In Monitoring Systems
The Clipper III, at 114 ft. (35 m) long and 88-gt, is the smallest of the three Clipper ships — high-speed passenger catamarans — owned by Clipper Navigation, Inc. of Seattle. The main route of the vessels is between Seattle and Victoria, British Columbia — a trip which, at a speed of 25 to 34 knots, they complete in about 2,5 hours.
Clipper III is powered by two 1,600-hp 16V 149 TI Detroit Diesels. The other two ships, the Clipper and Clipper IV, are considerably larger at 127 ft. and 427-gt and 132 ft. and 478-gt, respectively and each powered by dual MTU engines. Each of the three ships is propelled by a KaMeWa wateijet system. TheClipper andClipper IVare supplied with monitoring systems which adequately assess the ship's condition, providing alarms. The Clipper III reportedly had a much simpler system that provided less information, so the company invested in a monitoring system built by Ernasko of Lynnwood, Wash.
The System The system operates through an IBM or compatible 486 computer. Ernasko supplied all of the sensors (pressure, temperature, flow, etc.), cabling, fittings, and junction boxes, as well as the sensor/computer interface and software. There are a total of 63 sensors on port and starboard main engines and generators: 42 temperature sensors (one on each of 16 exhaust ports on each main engine, one each monitoring fresh water intake, engine and generator oil, and reduction gear oil); and 14 pressure sensors (for each engine, generator oil, cooling water jackets, raw water, reduction gear oil, bearing, and reverse/steering); fuel flow sensors (to measure the consumption and temperature of the diesel fuel); and rpm sensors.
The full color display shows each of the functions in digital and graphic form, displaying engine lube oil pres- sure and temperature, and the temperature of each cylinder exhaust.
The system can be operated using only a track ball, but also has an instruction line. Using the track ball, the user may change alarms, view a line graph (amplitude vs. time) of any function, save trip data to a disk, view any function since the beginning of the trip via line graph (amplitude vs. time), or quit. The system's logging function allows the user to study vessel operation and find potential problems.
The saved file can be imported into spreadsheet software and plotted to provide line graphs for all monitored functions. In the case of the Clipper III, the engineers knew that the ship's performance was not as good as it should have been, but hadn't yet concluded there was an engine problem. Viewing the graphs at the end of the trip showed one of the cylinders was operating erratically and at a much lower temperature than the others. Paul Brodeur, ship's superintendent, said that increased monitoring allows the establishment better preventive maintenance schedules and may prevent engine damage that could occur without this information. Some of the collected data has shown that there may be large savings in fuel with small changes in engine rpm. According to Ernasko, a three percent decrease in rpm can amount to a 13 percent savings in fuel. Because of the success of the system on the port engine of the Clipper III, one was reportedly fitted to the starboard engine as well. In this case, the software would allow the user to alternate between engine displays, indicating "S" or "P." And screens can be designed to suit customer needs. Peter Thordarson of Ernasko says a new screen can be designed in less than a half-hour if the company knows what the customer wants.
Another feature, according to Ernasko, is that a sensor's electrical output is a pulsed frequency which is proportional to the measured level. Since the system's computer board is designed to recognize this type of signal, it ignores all other electrical interference on the ship. Existing ship sensors can be made to operate with the system through the use of a converter. This allows updating of manually operated systems to fully automatic at reportedly reduced costs.
For more information on Ernasko