MEO Orals on Marine Electro Technology Function 5- Part 8

What documents to give to surveyor for switch board survey ?

1. Voltmeter, Wattmeter, Ammeter Calibration test result
2. ACB test result (Survey result)
3. Control Circuit Safeguard test results (Safety trips and Alarm test results)
4. Maintenance reports
5. IR test results of each terminal; all 440 V and 220  V main circuit

Data to be given Surveyor for electrical survey ?

1. Voltmeter, Wattmeter, Ammeter calibration test result
2. ACB test result (Survey result)
3. Control Circuit Safeguard test results (Safety trips and Alarm test results)
4. Maintenance reports
5. IR test results of each terminal : all 440 V and 220 V main circuits
6. IR test results of all motors & their safety factors, such as:

————–> Test date, time, place

————–> Voyage No.

————–> Ambient temperature

————–> Weather condition, hot or humid

————–> Machine is hot or cold

Difference between DC and AC generators ?

• DC generator has commutator and AC generator has slip ring or brush less.

What is drop test ? ( Volt drop test)

• It is a kind of test for exploring the open circuit fault, short-circuit fault of an armature winding or a set of field windings
• It is more reliable check than the growler test.

Testing in electric machines ?

1. Insulation test (Meggar test)
2. Continuity test
3. Voltage test 
4. Current test

How many types of motor starter ?

1. Direct on line starter
2. Star delta
3. Auto transformer

What is static electricity ?

• Electricity produced on dissimilar materials through physical contact & separation.
• Out going material negative, remaining material positive. After having high potential spark occur.
• This is occurs in thin oil. Explosion occurs when tank cleaning operation and gas freeing operation.

Protection against accumulation of static charges ?

• Bunker pipes are electrically bonded and from ship earthing arrangement to shore.
• Inert gas maintains above cargo in the tanks.
• C.O.W operation must be start after pumping out 1 m3 to make sure no water remain in the tank.

What is open loop in control system ?

• The loop is open, there is no feedback and the action of the controller has no reference to the result it produces.
• An open loop is a manual process where by information is not feed back to the control system. A man is required to sight visually or read display information and then make an adjustment.
• Manual control gives satisfactory results. Carelessness of the operator may lead to an end product of result that fails to meet the requirements.
• The arrangement may then decide to install automatic control. The controller must replace the human brain.

The close loop automatic control system

• In practical automatic control systems, the controlled variable must first be measured.
• This may require both a detecting (sensing) element and a measuring element, or two may be combined in a single unit; the measured value is then compared with the desired value in the comparison element. 
• The output from the comparator, commonly called the error, causes the amplifier to vary its output in such a way as to reduce the error.

What is closed loop in control system ?

• In an automatic process the closed loop is formed by the sensor, which feeds back information of the final process. This feedback or closed loop, return into a mixing point or comparison point where it compares itself against reference or set point signal. Any deviation between these two signals will alter or adjust the control mechanism.

What is data logger ?

• The data logger is capable of producing a printer record of off limit conditions.
• It can also produce a printed log of plant sensors at predetermined intervals or on demand.

What is meant by automation ?

• Any or all of the combined processes used aboard ship that have the ability to control work, notify the operator of its status and warn of malfunctions.
• This allows less people to control more machinery in a more accurate and efficient manner.

Reference:

Oral Guide by – MIN ZAR TAR

MEO Orals on Marine Electro Technology Function 5- Part 8