Control systems

Control systems on ships are complex. Some are automatic and some are manual controls.

Many control systems use pneumatic dry compressed air because of its non-explosive nature, and availability. In modern ships, more and more electrical and electronic controls are installed, especially in the control rooms. Hydraulic remote controls are usually used in tanker cargo control rooms for valve operation.

A marine engineer has to be familiar with control systems in order to maintain the operation condition of his machinery well. He has to handle controllers, positioners, measuring elements, set points, transducers, and transmitters. He has to know how to tune for optimum performance in proportional, integral and derivative modes in order to achieve steady state pressures, temperatures, or level conditions.

In a modern Unmanned Ship, the control system is designed so that no personnel are necessary to be in the engine room during the night. All the machinery is designed to be automatic in operation, while the main engine can be controlled on the Bridge.

In actual practice, control systems do fail, and marine engineers have to troubleshoot and rectify on the control systems also. For that reason, all the automatic control systems can usually be switched to manual control when necessary.

Text C

Engine control room

The engine room of modern ships can be regarded as power generating plants with many different auxiliary systems. This plant shall be operated with a high degree of reliability according to the “on demand principal”. This means that the engine room shall deliver propulsion power and rudder angles as required from the bridge.

The critical failures of a ship can be related to propulsion, steering and electrical power generation. If any of these functions fail, the ship is more or less unseaworthy and can not be operated. These facts are already taken care of at the design stage. Type of machinery as well as back up equipment are thoroughly regulated in the classification requirements. These requirements do not only regulate how critical parts shall be designed, constructed and tested, but also which parameters that shall be monitored, equipped with alarm functions and presented in the engine control room.

The primary task in the engine control room, from the loss prevention point of view, is to detect when something is wrong. Observation of parameters like fuel and lube oil pressure, cooling water temperature, hydraulic oil pressure in the steering gear, etc. over time can indicate faults.

Observation of the machinery in operation during engine room rounds can also reveal if something is wrong. Changes like leakages, vibrations, noises and smells, each tell a story that can indicate faults. When the engine room crew has done their job and adjusted/repaired deviations from normal operation, the alarm system is expected to alert when any of the monitored parameters are outside the prescribed values. This way of working has proved to be reliable to a level where unmanned engine rooms are permitted. The classification societies have special requirements for such operations. The ship is given an automation class notation if followed correctly. Most modern ships sail with some level of unmanned engine room.

Once the crew has detected that something is wrong they need to control the situation. Critical functions and connected auxiliary systems are built with redundant functions. This means that electric motors, pumps, engines etc, are equipped with a stand by unit with either automatic or manual start depending on the degree of automation.

If a stand by unit does not function as planned, the crew is expected to control the situation. This is the situation where many minor faults develop into larger breakdowns due to lack of competence and experience. Many detected faults are neglected. Another common scenario is to leave the problem be and taken care of at a later point in time. Provisional repairs is another common scenario.

The ECR is to provide the means whereby staff can control plant parameters and execute control of important functions. It is to be possible for a single engineer to monitor and control all equipment within the machinery spaces from CCR.

The ECR shall contain all major controllers, including the main turbine controls, boiler combustion control and burner management systems. Pump start/stops and electrical generating plant controls, together with sufficient instrumentation and control equipment, is to be provided to enable a single engineer/supervisor to monitor and adjust all major items of machinery and systems within the machinery spaces.

In the Engine Control Room a Main Operation Panel (MOP) screen is located, which is a Personal Computer with a touch screen as well as a trackball from where the engineer can carry out engine commands, adjust the engine parameters, select the running modes, and observe the status of the control system.

A conventional marine approved PC is also located in the ECR serving as a redundant unit for the MOP and also as backup unit for same.

The Engine Control System primarily consists of the electronic controllers, the mechanical-hydraulic system and the pneumatic system.

Following equipment shall be arranged in the ECR.

- Engine control console

- ACC & BMS control panel

- IAS I/O cabinets

- Main turbine main panel

- Ship side valve control panel,

- Machinery condition monitoring panel,

- Desk and chair

- Printers for IAS