B-Controllers:
1- Draw pneumatic / Electronic controller to perform Proportional action. Write the
equation relating the output/ input signal.
Rf
Vo=−Vi . =−Kp .Vi
R
2- Draw pneumatic / Electronic controller to perform Proportional Integral action.
Write the equation relating the output/ input signal.
( )
1
Rf +
CD −Rf
Vo=−Vi . = .¿
R1 R
3- Draw pneumatic / Electronic controller to perform Proportional Derivative
action. Write the equation relating the output/ input signal.
Vo=−Rf ( ViR +C . dVidt )= −RfR (Vi+ Td . dVidt )
4- Compare the effect of the P, PI, PD and PID controllers on the control system
Time response.
5- Draw the block diagram of closed loop and open loop control system, explain the
Difference with practical example.
Open loop
Process Output
Controller Actuator Process
Amplifier Valve Tank
Head h
Tank level control system where is the liquid level is to be regulated at a level within
reasonable acceptable limits even when the outlet flow rate varies.
It is clear from the system block diagram that there is no feedback signal from the
process output to the input and no comparison is hold between the actual tank liquid
and the desired level
Close loop
Process Output
Controller Actuator Process
Amplifier Valve Tank
Head h
Sensor / Transducer
The process can now regulated the liquid level at its desired value within
acceptable limits even in the case variations of the outlet flow rate from the valve
Comparison of Closed Loop And Open Loop Control
System
SR. OPEN LOOP CLOSED LOOP CONTROL
NO. CONTROL SYSTEM SYSTEM
The feedback The feedback element is
1 element is absent. always present.
An error detector is An error detector is always
2 not present. present.
3 It is stable one. It may become unstable.
4 Easy to construct. Complicated construction.
5 It is an economical. It is costly.
Having small
6 bandwidth. Having large bandwidth.
7 It is inaccurate. It is accurate.
8 Less maintenance. More maintenance.
9 It is unreliable. It is reliable.
Examples:
Examples: Hand drier, Servo voltage stabilizer,
10 tea maker perspiration
6- Draw the one parameter ( single loop ) control system used to control the
temperature of the fresh water cooling the M/E Jacket.
Control signal PI Error Set point
S.w. inlet
Fresh water Engine return
Thermal sensor
Fresh water Engine supply
3 wayes V/V
S.w. outlet
Automatic Viscosit Contro
Control Hot Cold
Signal water water
Temperature
Set point PI 3 wayes System
Controller V/V
7- Draw the cascade ( double loop ) control system used to control the temperature
of the fresh water cooling the M/E Jacket.
Two elements control loop (Cascade Control)
Controller
M/E
Sea Water
Controller Cooler
Control sea
Set Signal water
point
main Second. V/V Cooler M/E
Controll Controll
er er
Temperature
sensor
sensor
D-Corrosion and Fire:
1- What is meant by Corrosion? Explain the reasons of corrosions and the methods
of corrosions protection. .
Corrosion Means: the degradation of materials by chemical reaction with the environment in which the
material resides
Reasons:
1- Reactivity of metal
2- Presence of impurities
3- Presence of air, moisture, gases like SO2 and CO2
4- Presence of electrolytes
5-
Methods of Corrosions:
1- Impressed current cathodic protection (ICCP)
2- Sacrificial anode Cathodic protection (SACP)
2- Explain with a sketch the corrosions protection using SACP compare with ICCP.
The output of the ICCP system should be optimized to provide enough current to
provide protection to the target structure. Some cathodic protection transformer-
rectifier units are designed with taps on the transformer windings and jumper
terminals to select the voltage output of the ICCP system. Cathodic protection
transformer-rectifier units for water tanks and used in other applications are made
with solid state circuits to automatically adjust the operating voltage to maintain
the optimum current output or structure-to-electrolyte potential.
[15] Analog or digital meters are often installed to show the operating voltage (DC
and sometime AC) and current output. For shore structures and other large
complex target structures, ICCP system are often designed with multiple
independent zones of anodes with separate cathodic protection transformer-
rectifier circuits.
3- Explain with a sketch the corrosions protection using ICCP compare with SACP.
The materials used for impressed current cathodic protection can the pass a
current into the environment without being consumed at a high rate. Graphite
and high silicon cast iron are the most commonly used impressed current
cathodic protection anode materials, however, other materials (such as
magnetite, platinum, and newly developed ceramic materials) have been
successfully used.
Anodes in impressed current systems must be inspected and replaced if
consumed or otherwise damaged. As is the case for any electrical equipment,
rectifiers used for impressed current cathodic protection systems require
preventative maintenance to insure proper operation.
3- Explain with a sketch the use of Photo Cell in the following sensors.
a- Smoke detector. B- Flame detector.
b- Oil in water detector.
-Operation:
1- the tank is filled with water, hence the total capacitance Ct=Cw the bridge is balanced and
no output voltage (volt=0).
2- the tank filled with water and oil, hence the Ct is Greater Than Cw the bridge unbalanced
the output voltage ≠0
3- The voltage is amplified and causes the operation of solenoid valve opening path for the
discharge pump.
5- Explain with a sketch the operation principle of the Oil mist detector.
The oil mist detector uses a photoelectric cell to measure small increases in oil
density. A motor driven fan continuously draws samples of crankcase oil mist
through a measuring tube. An increased meter reading and an alarm will result if
any crack case sample contains excessive mist when compared to either clean air
or to the other crankcase compartments. The rotary valve which draces the
samples then stops to indicated the suspect crankcase compartment
THE ALARM WILL CAUSE AN ENGINE TO SLOW DOWN OR SHUTDOWN
6- Explain with a sketch the operation of the smoke detector in cargo holding space.
The sample extraction smoke detection system is used in the cargo holds onboard
the ship.
The sample extraction smoke detection system draws air samples from all cargo
space the fed to the smoke detection panel if the smoke density exceed the
bounds the system send out fire alarm. In most case, the pipes for CO2 fire
extinguishing system are used for draws air sample and the two systems are
connected to the same network by means of 3-way valves.
A- Measurements:
1- Explain with a sketch the operation of Bourdon tube for pressure measurement.
Use to convert the pressure into mechanical movement, the bourdon tube has a semi-eleptical section
and has the shape of C. one of the ends is opened and the second is fixed, closed and free to move.
The fluid which we want to measure its pressure is introduced inside the bourdon tube, because osf
inside pressure the free end will change shape as shown. This movement of the free end is employed
for display or control purposes
2- Explain with a sketch the operation of RTD for temperature measurement.
Write the equation relating the resistance / temperature in the RTD.
Operation: 1- Temperature = 0
R4=Ro…ΔV=0
2-Temperature ≠ 0
R4= Ro+ΔR….ΔV>0
3- Write the equation relating the resistance / temperature in the RTD, how the resistance
change is converted to voltage change in the Wheat-stone bridge
Operation: 1- Temperature = 0
R4=Ro…ΔV=0
2-Temperature ≠ 0
R4= Ro+ΔR….ΔV>0
4- Explain with a sketch the operation of LVDT as pressure sensor.
5- What are the standard signals in control systems? Explain with a sketch the
Operation of the current / pressure transducer
6- Explain with a sketch the construction and operation of the Bi - Metallic strip
thermometer as pressure sensor.
Bimetal strip thermometer consists of twp metals such as invar and brass welded together to form a
cantilever as shown. When heated both metals expand. Since brass expands more than invar, the result
is bending of strip as shown, this principle is used often in instruments to compensate for the effects of
change of ambient temperature
7- Explain with a sketch the operation of Pneumatic Relay.
C-Auxiliary Boiler & Steering Gear:
1- Describe the operation sequence of the Auxiliary Boiler, sketch the main parts.
2- Explain with a sketch the operation of Auxiliary Boiler Air / Fuel ratio control
system.
3- Explain with a sketch the operation of Auxiliary Boiler level control system.
4- Explain with a sketch the operation principle of the automatic viscosity control.
1- Fuel from service TK is heated by steam coil.
2- The visco meter measures the fuel viscosity.
3- The actual viscosity signal is compared with the desired viscosity signal (set point) and the error
signal is generated.
4- The controller generates the control signal.
5- The diaphragm V/V opening regulates the steam flow in the heater such that the actual viscosity
equals the set point viscosity.
6- The following is system block diagram.
Control Steam
signal
Viscosity
Set point Controller Diaphram Fuel
V/V
Viscosity
sensor
5- Explain with a sketch the operation of Hydraulic / electric Steering Gear.
4 power cylinders load θ
وحدة المنفــــ الحمــ
الراف
التحكم ذ ل
عة
مجموعة اسطوانة الدفــ
انتقال اشارة المنفذ
الخلفية الى انتقال حركة الحمل الى
من خالل Cالنقطة با لرافعة Bالنقطة
الفرقية من خالل عمود
اشارة أمر التحكم من غرفة القيادة تنتقل الى الرافعة الفرقية عند النقطة
Α
تنتقل النقطة Αزاوية معينة θوتتحرك أيضا النقطة Cفى نفس االتجاه بقدار
نصف ازاحة النقطة Α
يصحب ذلك قوى طرد وسحب لكل من مضختى األزاحة وينتج عن ذلك عزم دورانى
على عمود رأس الدفة وتتحرك الدفة الزاوية المطلوبة
تحدث ازاحة للنقطة Bللرافعة الفرقية فى عكس اتجاه ازاحة النقطة Αوهى
االشارة العكسية الناتجة من حركة الدفة عن طريق الوصلة الخلفية المبينة
نتيجة لذلك ترجع النقطة Cالى ما كانت عليه وتتوقف قوى الطرد والسحب
للمضخات عند ذلك يكون قد تم تنفيذ األمر وتكون الدفة قد وصلت الى الوضع
المطلوب هذا ويستمر التشغيل عكس األمر األول حتى تتحرك السفينة ناحية
االتجاه المطلوب لها وتصبح الرافعة الفرقية وكذا عمود رأس الدفة فى الوضع
الطبيعى لها األفقى
6- Explain with a sketch the operation of electric ( Ward Lenard ) Steering Gear.
Θinput Θout
ريوستا ت مولد المولد محرك الدفــــ
عجلة االثارة االساس الدفة ــة
القيادة ى
ريوستا ت
عجلة
القيادة
motor M1 is to be controlled which is powered by the generator G. The shunt field of the motor
M1 is connected across the dc supply lines. Now, generator G is driven by the motor M 2. The
speed of the motor M2 is constant. When the output voltage of the generator is fed to the
motor M1 then the motor starts to rotate. When the output voltage of the generator varies then
the speed of the motor also varies. Now controlling the output voltage of the generator the
speed of motor can also be controlled. For this purpose of controlling the output voltage, a
field regulator is connected across the generator with the dc supply lines to control the field
excitation. The direction of rotation of the motor M 1 can be reversed by excitation current of
the generator and it can be done with the help of the reversing switch R.S. But the motor-
generator set must run in the same direction.
Advantages of Ward Leonard System
1. It is a very smooth speed control system over a very wide range (from zero to normal
speed of the motor).
2. The speed can be controlled in both the direction of rotation of the motor easily.
3. The motor can run with a uniform acceleration.
4. Speed regulation of DC motor in this ward Leonard system is very good.
Disadvantages of Ward Leonard System
1. The system is very costly because two extra machines (motor-generator set) are
required.
2. Overall efficiency of the system is not sufficient especially it is lightly loaded.
7- Explain with a sketch the importance of the governor in the marine diesel
Engines.
8- Explain with a sketch the M / E speed control marine.
Operation:
1- The set point speed opens the pilot V/V partially, oil under pressure passes to the other
servo amplifier which is connected with fuel oil rack.
2- At the engine speed, the rotating weights create centrifugal force which balances the
spring force, hence the pilot V/V closes the opening of the servo amplifier and its piston is
fixed causing the fixing of the fuel oil rack and the M/E speed is fixed.
3- If a Load change causes speed increase, the F.B. signal represented by the centrifugal
force increases against the spring force, the difference between these two forces represents
the error signal to the pilot V/V, its spool raised up causing partial close, the signal goes to
2nd stage servo amplifier, oil under pressure leaks under the hydraulic amplifier piston.
4- The spring force overcomes the oil pressure force causing the piston to moves down with
the fuel rack decreasing the fuel quantity to the Engine.
9- Explain with a sketch the operation of the Fresh Water Generator.
10- Explain with a sketch the operation principle of the Salinity meter.
