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Wet cargo operations > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

Tanks are cleaned for
x4

A

quality control for next cargo
residue control
dry dock preparation
tank entry and inspection purposes

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2
Q

Tanks may be washed with
x3

A

clean sea water
crude oil
or water/chemical mixtures

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3
Q

Most tank cleaning can be successfully carried out with

A

clean sea water at ambient temperatures

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4
Q

Residues that solidify may require washing

A

with heated water.
Tank cleaning heaters are fitted on most tankers for this purpose.

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5
Q

Hot water washing should be carried out with a wash water temperature of
at least

A

60oC

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6
Q

Tank cleaning chemicals should only be used in

A

extreme cases for removing
persistent residues or in preparation for particularly sensitive ‘next’ cargoes

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7
Q

Tank cleaning is one of the most hazardous operations carried out on
tankers due to

A

vapour generation and the risk of electrostatic discharges

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8
Q

Tank atmospheres may be _____ or non-_____

A

inert
inert

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9
Q

ISGOTT gives operational restrictions on each of the

A

atmospheres defined

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10
Q

Washing in an ________ atmosphere is preferred

A

inerted

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11
Q

Tank cleaning machines may be portable or _____

A

fixed

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12
Q

Portable machines are lowered into the tank on

A

flexible tank washing hoses

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13
Q

The machines are driven by the pressure of the washing medium and rotate about both ____ to achieve ____ tank coverage by the ___

A

axis
full
jet

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14
Q

_____ machines are located on the end of steel pipes connected to the washing main

A

Fixed

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15
Q

Many _____ machines are programmable to allow the ____ to control which parts of the tank are washed

A

Fixed
user

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16
Q

Efficient tank draining is required. Stripping _____ or ________ are used for this purpose

A

pumps
eductors

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17
Q

Tankers over __,___ dwt that carry crude oil are required to ____ ____ ___
(COW)

A

20,000
crude oil wash

18
Q

Crude oil is drawn off from the main discharge of the cargo and directed

A

through the tank cleaning machines

19
Q

The pressure of the crude oil and its solvent effect achieve

A

a high level of tank cleanliness

20
Q

Some crude oils are not suitable for COW due to

A

their high wax content and/or viscosity or pour point

21
Q

MARPOL regulations dictate that all cargo tanks that will, or may, carry ballast plus 25% of the remaining tanks for sludge control purposes must be

A

cleaned prior to departure from the last discharge port

22
Q

COW can only be carried out with cargo tanks

A

inerted

23
Q

Fixed tank cleaning machines are required for ___

A

COW

24
Q

The ship will have a ___ Manual that details equipment and procedures to
be used

A

COW

25
Q

Advantages of COW
x5

A
  1. Reduced sea pollution
  2. Improved cargo outturn
  3. Reduced tank corrosion
  4. More cargo deadweight available due to reduced residues
  5. Less de-sludging time for dry dock preparation
26
Q

Disadvantages of COW
x4

A
  1. Higher workload during cargo discharge
  2. Extended discharge time
  3. Higher risk of pollution in port
  4. More equipment and personnel required
27
Q

Gas freeing is required to create

A

safe tank atmospheres for cleaning or
entry purposes

28
Q

Gas freeing can be carried out using portable fans, or

A

directing fresh air through the inert gas plant bowers

29
Q

Tanks can use the dilution or displacement method to change

A

tank atmospheres

30
Q

The dilution method relies on a high air input velocity to create

A

mixing

31
Q

The displacement method relies on a low air input velocity to maintain the

A

interface between the incoming air and the displaced tank atmosphere

32
Q

Full length purge pipes are some times used, especially when using

A

displacement method

33
Q

Tank atmospheres must be monitored for

A

oxygen content, hydrocarbon
levels and the presence of toxic gases

34
Q

Combustible gas indicators (‘Explosimeters’) are used to measure

A

the hydrocarbon content as a percentage of the lower flammable limit

35
Q

Hydrocarbon meters measure

A

hydrocarbon contents above the LFL

36
Q

Some combustible gas indicators cannot be used in

A

oxygen deficient atmospheres

37
Q

A common type of oxygen analyser uses electrochemical detection cells
which must be replaced at intervals
usually…

A

12 to 18 months

38
Q

Toxic gas detectors rely on

A

an aspiration unit into which is placed a glass
tube containing reactive crystals

39
Q

Toxic gas detectors rely on an aspiration unit into which is placed a glass
tube containing reactive crystals
* The crystals only react to

A

The specific substance being tested for

40
Q

A tank atmosphere should be tested in the following order:

A

oxygen content, ;hydrocarbon level and finally for toxic gases

Wet cargo operations (9 decks)

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