Gray / Bennett Centralized and Automatic Controls in Ships

1. Auflage 2014
ISBN: 978-1-4832-2698-9
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 254 Seiten

Centralized and Automatic Controls in Ships provide a non-mathematical basic introduction to the subject of control engineering applied in the marine field. This book is composed of 20 chapters that cover the basic principles of the equipment in ships. The opening chapters deal with ship components, construction, and commissioning routine for certain automated plant. The next chapters consider the basic principles of automatic control and controllers. These topics are followed by discussions on logic units and data processing equipment, other control elements, steam turbines, and diesel engines. Other chapters illustrate the application of control techniques to the major areas of the ship's machinery. The final chapters examine ship and ship's control system commissioning and maintenance. This book is an invaluable source for marine engineers and marine engineering students.

Autoren/Hrsg.

Gray, D.

Bennett, A. J. S.

Inhaltsverzeichnis

1;Front Cover;1
2;Centralized and Automatic Controls in Ships;4
3;Copyright Page;5
4;Table of Contents;6
5;Foreword;8
6;Editor's Preface;10
7;CHAPTER 1.
Introduction;12
7.1;1.1. AUTOMATION;12
7.2;1.2. AUTOMATIC CONTROL;13
7.3;1.3. EARLY FORMS OF AUTOMATIC CONTROL;15
7.4;1.4. CYBERNETICS;16
7.5;1.5. APPLICATION OF CONTROL;16
8;CHAPTER 2.
Ship Construction;19
9;CHAPTER 3.
Main Machinery;20
10;CHAPTER 4.
Central Control Room;25
11;CHAPTER 5.
The Monitoring System;29
11.1;5.1. SENSING DEVICES;29
11.2;5.2. TRANSDUCERS;35
12;CHAPTER 6.
The Display System;44
12.1;6.1. INDICATORS;44
12.2;6.2. INDICATION AND DISPLAY;48
13;CHAPTER 7. Actuators;59
13.1;7.1. HYDRAULIC ACTUATORS;60
13.2;7.2. PNEUMATIC ACTUATORS;63
13.3;7.3. ELECTRIC ACTUATORS;66
13.4;7.4. SELECTION OF ACTUATORS;68
14;CHAPTER 8.
Non-automatic Control Elements;70
14.1;8.1. PNEUMATIC CONTROL ELEMENTS;70
14.2;8.2. ELECTRIC CONTROL ELEMENTS;82
14.3;8.3. HYDRAULIC CONTROL ELEMENTS;96
15;CHAPTER 9. The Principles of Automatic Control;111
15.1;9.1. In this chapter the principles and terminology used in the application of automatic controllers will be explained;111
15.2;9.2. CONTROL ACTIONS;120
15.3;9.3. PLANT CHARACTERISTICS;127
16;CHAPTER 10. The Basic Principles of Automatic Controllers;137
16.1;10.1. PNEUMATIC CONTROLLERS;137
16.2;10.2. ELECTRONIC CONTROLLERS;156
16.3;10.3. HYDRAULIC CONTROLLERS;158
17;CHAPTER 11. Logic Circuits;162
17.1;11.1.;162
17.2;11.2. TRANSISTOR THEORY;171
17.3;11.3. CONTACTLESS PROXIMITY LIMIT SWITCH;184
18;CHAPTER 12.
Final Control Elements;185
18.1;12.1.;185
18.2;12.2. RANGEABILITY AND TURN DOWN;188
18.3;12.3. VALVE POSITIONER;190
19;CHAPTER 13.
Applications of Control Engineering;192
20;CHAPTER 14.
Steam-raising Plant;196
20.1;14.1. AUTOMATIC COMBUSTION CONTROL;196
20.2;14.2. AUTOMATIC CONTROL OF BOILER DRUM LEVEL;200
20.3;14.3. STEAM TEMPERATURE CONTROL;201
20.4;14.4. SAFETY CIRCUITS;203
20.5;14.5. SUBSIDIARY CONTROL LOOPS;203
20.6;14.6. INSTRUMENTATION;206
21;CHAPTER 15.
Steam Turbines;207
21.1;15.2. SUBSIDIARY CONTROL LOOPS;209
21.2;15.3. A TYPICAL TURBINE CONTROL SYSTEM;209
21.3;15.4. INSTRUMENTATION;212
22;CHAPTER 16. Diesel Engines;214
22.1;16.1. DIRECT REVERSING DIESEL ENGINES;214
22.2;16.2. UNIDIRECTIONAL DIESEL ENGINES WITH REVERSE GEAR;216
22.3;16.3. A TYPICAL CONTROL SYSTEM;216
22.4;16.4. INSTRUMENTATION;220
23;CHAPTER 17.
Generation and Distribution of Electric Power;221
24;CHAPTER 18.
Pumping of Liquid Cargoes;225
25;CHAPTER 19. Refrigeration;230
25.1;19.1. BRINE SYSTEMS;230
26;CHAPTER 20.
Commissioning and Maintenance;236
26.1;20.1. COMMISSIONING;236
26.2;20.2. MAINTENANCE;247
27;Glossary of Terms used in Automatic Control;252
28;Bibliography;256
29;Index;258

Leseproben

CHAPTER 1

Introduction

Publisher Summary

The primary aims of automatic control are to reduce the inefficiencies inevitably associated with human machine minding. An automatic control system thus includes: (1) the plant, (2) the detecting or sensing element, (3) the measuring or indicating element, and (4) the controller. Closed-loop control represents an automatic process. Automatic control is at present recognized by all progressive industrial organizations as being an essential aid to efficient plant operation. In most organizations, the design of new plant provides for full instrumentation and automatic control as a matter of standard practice and specialist engineers are employed to improve the application techniques and to investigate the possibilities of new equipment. In the case of automatic control, the instrument settings and further settings that are required to achieve correct computation are not easily established as they depend on the measurement of the actual dynamic characteristics of the function being controlled.

1.1 AUTOMATION

To the layman, largely guided by the popular press, “automation” appears as a startling modern invention which will lead to the wholesale establishment of automatic factories and the building of automatic ships. To the engineer automation is merely a contemporary phase in the process of technical evolution that has gone on continuously since the first crude machines. The engineer’s aim has always been to make the best use of machines, materials and money. The answer, of course, does not lie in the mass installation of “black boxes”, electronic or otherwise. It lies in the ingenuity and breadth of vision of the people involved in designing the control system.

Automation has been, and is still, a greatly misused word but its proper meaning and, therefore, its implications, is gradually becoming better understood. It is a concept through which a machine system is caused to operate with maximum efficiency by means of adequate measurement, observation and control. It involves a detailed and continuous knowledge of the functioning of the system so that the best corrective actions can be applied as soon as they become necessary. Thus automation should produce the optimum result. Unfortunately the word has gathered many wrong and half-wrong associations all of which imply mechanization, which in turn implies unthinking repetitive motion and this is the exact opposite of automation.

Instead of using the word automation it is better to talk of automatic control or to use the word cybernation, the theory of communications and control.

The primary aims of automatic control are to reduce the inefficiencies inevitably associated with human machine minding. A complete elimination of human judgement is quite impracticable. However highly developed an automatic system may become the skill and experience of the trained operator will still be essential.

Countless mechanical devices can be named which, to some extent, work themselves. For instance, a hoist can be made to stop at the end of its travel; an electric furnace or the domestic oven can be made to switch on when the interior temperature drops below a certain pre-set value. In certain conditions such devices possess varying degrees of “intelligence” in so far as they automatically do what is required. They do not, however, embody fully automatic control in that they cannot control the whole process from information derived from the end product. Very few control systems at present approach the ideal of being fully automatic.

1.2 AUTOMATIC CONTROL

An automatic control system is defined in the glossary of British Standard 1523 as one “in which the value of a controlled condition … is compared with a desired value and corrective action is taken dependent on the deviation, without the inclusion of a human element in the closed loop formed by the comparing and correcting chains of elements”.

An automatic control system thus includes:

(a) the plant,

(b) the detecting or sensing element,

(c) the measuring or indicating element,

(d) the controller.

The difference between manual control (whether local or remote) and automatic control is shown in Fig. 1.1.

FIG. 1.1 Schematic diagram of open-loop and closed-loop controls.

With hand control, or open-loop control, an instrument connected to the plant gives what is known as feedback of information, but this feedback initiates nothing on its own. Corrective action is left to the human operator.

Closed-loop control represents an automatic process. The information fed back from the sensing device via the indicator is made to energize the controller so bringing about the necessary corrective action. Such a closed loop is often referred to as a servo mechanism, i.e. an automatic closed-loop system controlled by feedback of information. In the same context it is as well to note that the term “servo motor” (derived from the French language and literally meaning “slave motor”) is often used very loosely but it is really the final control element in a servo mechanism. It is the motor which receives the output from the amplifier and which drives the load. It must be emphasized that the term servo motor can describe a motor which produces linear motion as well as a motor which produces rotary motion. An example of a linear motor could be an ordinary hydraulic ram.

1.3 EARLY FORMS OF AUTOMATIC CONTROL

Devices which enabled a machine or process to be left unattended so that the operator could devote his energies to other tasks are of considerable antiquity.

Papin’s “digester”, the forerunner of safety valves, was developed in 1680. By the end of the eighteenth century many windmills and waterwheels in Britain had automatic speed control so that a mill could be tended by one man. In 1788 James Watt designed an engine governor; without this the speed of a steam engine would fluctuate violently with every change of load. The thermostat was patented by Andrew Ure in 1830 and led to immense improvement in heat control. The Bourdon tube, probably the most widely used of all detecting and measuring elements, is well over 100 years old. Clerk Maxwell, the originator of modern control theory, discussed the stability of governors in 1868. He proposed what is the equivalent of anticipation in control action and so led to the measurement not only of “deviation” (or error) but also of its “rate of change”.

In ships the action of the steering system of a large ship gives an idea of the direction in which control mechanisms have developed. The characteristic features of such a steering system are:

(a) the considerable distance between helmsman and rudder;

(b) the amplification of a light touch at the wheel into the great torque (up to 1000 tons feet) required to move the rudder, which may weigh up to 30 tons, against the forces of the ship and sea;

(c) the position feedback which indicates on the bridge the exact position of the rudder;

(d) the final closing of the loop in the shape of the automatic pilot. This is a classic example of automatic control.

1.4 CYBERNETICS

The study of the theory of communications and control, or “cybernetics” (from a Greek word meaning steersman), has been greatly extended in recent years. It has illuminated many points of similarity between the human nervous system and the complicated control circuits in use today. The German philosopher Leibnitz seems to have been the first to suggest, about 1680, that “feedback” could provide a unifying base for work in economics, sociology and other sciences. At a later date Ampère coined the word . The theory of control, therefore, has a longer history than is often assumed.

1.5 APPLICATION OF CONTROL

Automatic control is now recognized by all progressive industrial organizations as being an essential aid to efficient plant operation. In most organizations the design of new plant provides for full instrumentation and automatic control as a matter of standard practice and specialist engineers are employed to improve application techniques and to investigate the possibilities of new equipment. The widespread use of automatic control in these industries provides the most convincing proof that it is a profitable investment.

The advantages which accrue from the application of automatic controls in ships are:

(a) Improved conditions for the seagoing staff by transferring much of the “donkey work” from manual operation to automatic operation, particularly the more unpleasant tasks such as soot blowing, cleaning of oil purifiers, etc.

(b) Savings due to more efficient use of seagoing staff by transfer from watchkeeping to day work; routine maintenance can be carried out more efficiently by a day...