Case Study: SS River Embley controls re-engineering

WINNER PACE ZENITH AWARD – 2009 !
Transport and Infrastructure Category

pace-zenith-2009

Scope:

The Steam Ship (SS) River Embley is a purpose built bulk carrier of 76 305 DWT. She was built during the height of the 1983 Mideast oil crisis as a Bauxite carrier for the run between Gladstone and Weipa in Queensland. The vessel has coal fired boilers to eliminate the risk of fuel oil spills or leaks in the event of accidents in the environmentally sensitive areas of the Great Barrier Reef.

river embley

Due to the uniqueness and age of the vessel, the original control systems were proving unreliable and were no longer supported by the vessel manufacturer. Equipment reliability, while maneuvering through the tight channels of the Great Barrier Reef is essential. Therefore replacement of the control systems related to maneuvering, monitoring and Boiler control was necessary.

Controls re–engineering by I S Systems were carried out on 3 main systems.

  • Maneuvering and Main engine control
  • Alarm monitoring and engineer call system
  • Boiler control system

The proprietary maneuvering and main engine control systems were replaced by a standard off the shelf PLC system and HMI touch screen, adapted and programmed to fulfill the maneuvering control functions. Improvements were made in including the ability to log and track maneuvering commands and actual feedback signals into a NAS (network attached storage device, providing a virtual “Flight recorder” for the vessel). Fault annunciation and the ability to track calibration of the field transmitters were also added, increasing the ability to preempt potential issues that might arise with the system.

The proprietary alarm and annunciation system was replaced by dual redundant PLC’s with operator touch screens. Alarm sequence tracking and “out of service functions” were added, greatly enhancing the functionally to the system. Control and alarm flow diagrams now indicate clear parameters of ship operations and machinery functions with all scan actions historically logged into a NAS. Additional thin client displays were added at strategic locations to enable easier access to alarm data and thereby decreasing response times to alarms around the engine and boiler room. This is extremely beneficial as the vessel operates as an UMS (without engine room watch-keeping) and previously engineers would first have to go the control room to ascertain the nature of the alarm and only then address the cause of the alarm.

The vessel has two independent boilers. The original control for the boilers were achieved by a master slave arrangement with supervision and control from a single proprietary controller, this resulted in a single point of failure being able to render both boilers inoperative. A dual redundant PLC system was engineered to overcome this problem with each PLC able to control either boiler, giving the system far more robust and reliable control. Sophisticated programming techniques enabled the new system to enhance the fuel efficiency thus reduce coal consumption. Together with improved control over air/fuel mix this has resulted in significantly reduced emissions from the boilers.

The job presented a number of engineering and project management challenges. The vessel was generally at sea and needed to remain operational at all times. The control and alarm systems are central to the operation of the ship and its safety and that of the crew; therefore the new control system had to be fitted alongside the elements of the original and comply with classification society and marine regulations. Doing a changeover under these conditions would demand excessive time as it would have to be undertaken and programmed at sea. This would be aggravated by the fact that much of the original design and operational documentation was no longer available, implying that the system not only had to be designed from scratch but had to be seamlessly changed over from the original to ensure continued operation of the vessel. One or the other system would have to be operational at all times.

Engineers from I S Systems overcame these problems by setting up “virtual control systems” in the office that mimicked operation of the original control system. They used this as a basis for developing and programming the new control systems on shore. This planning and management resulted in the changeover and commissioning of all three systems in a period of two weeks while the vessel was underway, without causing any delays to the vessel's schedule.