Marine Electrical Engineering: Ship's Control Systems

The field of automation and control system is vast; there are many different ways of achieving the required effects by the operator of marine systems. It is impossible to cover all the aspects of the controls used in ships; this article will give you an overview of automatic controls.

Introduction

Within the environment of a marine plant there are many parameters which need to be controlled or monitored including: temperatures, pressure, level, viscosity, flow control, speed, torque control, voltage, current, machinery status (on/ off), and equipment status (open/ closed).

In olden times it was the role of the watch keeping engineers to monitor and control the machinery plant. This was achieved by periodically taking rounds around the engine room and manually inspecting the condition of the running machinery. Often the engineer was totally dependent on his natural senses, frequently supported by only the minimum of widely distributed simple monitoring devices.

The demand to reduce manning level led to the development of automatic control arrangements for the engine room plant which enabled unattended operation of machinery spaces. With vessels capable of safe operation for any period of time in this mode, those ships were qualified as UMS (Unattended Machinery Space) ships.

In these types of ships, all the control systems and monitoring facilities are grouped together in an Engine Control Room and the ship machinery can also be controlled from this station.

Initially the control room was located in the engine room, with extended monitoring and alarm systems to the bridge and in the accommodation while the ship is running in UMS. But as of recent development, ships are built with the engine control room adjacent to the bridge.

In the latest trend, the control room uses the total integrated systems for all aspects of ship operation which includes engine room operation, cargo operation, navigation, and general administration.

Bridge Control of Main Engine

Bridge control of Main Engines:

Automatic control of the starting of the main engine can be done from the bridge as well as in Engine control room. The automatic controls employed in starting the engine is by the following sequence:

1. Automatic control used in correctly positioning of the cam shaft.
2. Admitting starting air
3. Admitting fuel
4. Starting air shut off
5. Speed adjustment to the value required

Thus the engine is started and the various parameters like temperature, pressure, flow and tank level have to measured at every watch to make sure that the engine is running safely.

Temperatures of lube oil, JCW, exhaust gas, etc. are measured.

Pressures of lube oil, JCW, fuel oil, and starting air etc. are measured.

Flow of fuel oil is measured while running.

Tank levels of Heavy fuel oil, diesel oil, and lube oil are measured.

For measuring the parameters we make use of the transducers, in turn sending the input signal to the automatic control system.

Boiler Control System

Boiler control systems:

Automatic control of boiler is also done from the engine control room. The automatic systems employed in controlling the following:

1. Boiler system (open / closed feed)
2. Steam pressure
3. Steam temperature
4. Water level
5. Feed water level
6. Feed pump
7. Feed water temperature
8. Fuel oil system
9. Air heater
10. Smoke density
11. Force draught fan

Thus if any of the above automatic system fails it give alarm and trips the boiler for a safe operation.

Turbine and Reduction Gear

In case of the steam propulsion ship the steam from the boiler enters in to the turbine and in turn it is coupled with reduction gear so some of the automatic controls used are.

1. Controlling the speed of the rotation of the turbine in turn it controls the speed of the ship.
2. Bleeder valve control
3. Lube oil temperature control.
4. Over speed trip control.
5. Condensate system.

Diesel Generator

This is employed in automatic starting and stopping of the auxiliary generator from the engine control room. So of the automatic control used are:

1. Starting and stopping of the engine according to the load demand.
2. Synchronization of incoming generator.
3. Closing the circuit breaker
4. Load sharing between the alternators
5. Maintaining the supply frequency and voltage.
6. Engine and alternator fault protection
7. Preferential tripping of non-essential loads.

Turbo Generator

In case if the steam propulsion ships they use turbo Generators for generating the power. In this type the small Steam turbines are coupled with the alternators and the automatic controls used are

1. Reset governor trip level.
2. Reset emergency stop valve.
3. Staring auxiliary lube oil pump
4. Staring the circulating pump
5. Apply gland steam
6. Starting extraction pump
7. Staring the air ejector
8. Opening the steam valve.