Drydocking (Before)

Question 1

How often does a cargo ship have to go into drydock / have a bottom survey?

Answer 1

SOLAS requires the hull to be inspected before going into service and then at least twice every five years - no more than 36 months between inspections

SI276 of 1985 requires the surveys to be carried out in drydock but may allow the periodical to be carried out in water

Question 2

How often does a passenger ship have to go into drydock / have a bottom survey?

Answer 2

SOLAS requires the hull to be inspected before going into service and then yearly

SI276 of 1985 requires the surveys to be carried out in drydock but may allow the periodical to be carried out in water

Question 3

What does UWILD stand for and what is it?

Answer 3

UnderWater Inspection In Lieu of Drydocking

A program offered by some class societies and flag states which allows a ship to drydock only once every five years, all other inspections are carried out in water

Question 4

What are the requirements for being in a UWILD program?

Answer 4

Must be allowed by flag state
Must have the UWILD class notation
Must not have any obvious issues with hull
Must have effective coating and cathodic protection
Vessel must be less than 15 years old
Must carry out a thorough underwater inspection (with class attendance)

Question 5

How would you deal with the ballast tanks before dry dock?

Answer 5

Drain / Press them up if possible

Otherwise filled to achieve required drafts

Question 6

Can a Laden ship go into drydock?

Answer 6

Yes, but it should only be a last resort

Lighter the ship

Question 7

What are the concerns when bringing a laden ship into drydock?

Answer 7

Higher stresses on the ship

Question 8

If a laden ship must go into drydock, what may be done to reduce the stresses on the ship?

Answer 8

Make it a wetdock
Use more blocks

Question 9

If a laden ship must go into drydock, where will the extra blocks be placed?

Answer 9

Likely near the cargo carrying areas, but the exact positions will need input from the dock master

Question 10

What needs to be done before entering drydock?

Answer 10

Drydock scope (joblist) made
Documents sent between Dock + Ship
Stability calculations completed

Question 11

What do you do if you cant make the requested drafts from the drydock?

Answer 11

Get in contact with the dockmaster

Question 12

What needs to be discussed in the pre-docking meeting (i.e. for the dock entry operation)

Answer 12

Location of tugs
Mooring line arrangement
Securing arrangements
Sequence of events
Pilotage arrangements
Timings
Duties and Responsbilities
Contingencies

Question 13

What needs to be done before an emergency drydocking?

Answer 13

Essentially the same as a normal drydocking, but there may need to be some changes due to the exact extent/nature of the damage (for example if a ballast tank is pierced you might need extra ballast elsewhere to have the correct trim)

Question 14

Why is stability important in the drydock?

Answer 14

As the ship takes the blocks she may capsize if not in the correct condition of stability

Question 15

What will you do as the water is pumped out of the dock?

Answer 15

Monitor the Drafts and List

Question 16

What is the concern when the vessel is taking the blocks?

Answer 16

P-Force

Question 17

Why do you enter the dry dock with a stern trim?

Answer 17

The P- force will be acting on a single point at the stern frame during the critical period, which is specifically strengthened for this

Question 18

Can you go into drydock trimmed by the head?

Answer 18

Only if necessary due to damage

Question 19

Once the vessel has started taking the blocks what is the concern?

Answer 19

You’re in the critical period, GM is being decreased

Question 20

What is the negatvie consequence if the p-force is too large / the GM becomes negative?

Answer 20

The vessel hits an angle of loll and slips off the blocks and into the side of the dock, damaging the ship and/or the dock

Question 21

Once the water is all pumped out of the drydock, what do you need to do now?

Answer 21

Connect ISC
Land Gangways
Connect shore power
Do the drydock meeting with the dock master

Question 22

You have a condition of class going into drydock, what do you need to do?

Answer 22

Ensure the repair is included on drydock scope
Ensure a class surveyor inspects the repair once completed

Question 23

What plans will you send to the drydock?

Answer 23

Drydock Plan
Shell expansion Plan
Tank arrangement
Fire and Safety Plan
General Arrangement
Stability Condition

Question 24

What is the shell expansion plan?

Answer 24

A 2d diagram of the 3d structure of the ship

A detailed drawing of the thickness of plates, hull openings etc, can be used to indicate areas requiring repair + Painting during drydock

Question 25

How is the shell expansion plan numbered?

Answer 25

K indicates the keel Alphabetically from A to S (Sheer Strake) and numerically from aft to forward. Longitudinals - Port to Stbd

Question 26

How would you know where plate C3 is?

Answer 26

Check the shell expansion plan

Question 27

How would you indicate to the dockmaster the location of a shell plate which has a hole and needs repair?

Answer 27

Mark it on the shell expansion plan

Question 28

Why does the dockmaster need to know the location of damage before you get to the drydock?

Answer 28

So the blocks can be placed in a way which allows for repairs to be carried out

Question 29

What are the contents of a drydock docking plan?

Answer 29

Indicates the position/pitch of the blocks Projections from the hull Plugs Sea chests Transducers Rudders Propellors Shape and form of the hull

Question 30

Does a docking plan stand completely on its own?

Answer 30

No there will often be text based manuals or drawings assosciated

Question 31

What information would you expect from the drydock?

Answer 31

Required Drafts Required Trim Declivity of the Dock

Question 32

What is the declivity of a dry dock?

Answer 32

The slope of the dock bottom

Question 33

What is the purpose of the dock declivity?

Answer 33

It ensures the water can be pumped out of the drydock

Question 34

What is the relationship between the vessels entrance trim and the dock declivity?

Answer 34

The vessel's trim needs to be larger than the declivity

Question 35

Why does the ship need to know the declivity of the dock?

Answer 35

To ensure the vessels trim is larger than the declivity

Question 36

Why does the ships trim need to be larger than the dock declivity?

Answer 36

To ensure the vessel touches the blocks stern-first because the stern is strenghtened for that purpose

Question 37

Is more trim always better when entering a drydock?

Answer 37

No, more trim = more P-force

Question 38

What is the P-Force when drydocking?

Answer 38

The upthrust on the ships stern from the blocks as the water is drained from the drydock

Question 39

When does the P-force stop?

Answer 39

Once the ship has fully taken the blocks

Question 40

When is the P-force at its strongest? What is this called?

Answer 40

Just before the ship fully takes the blocks The critical instant

Question 41

What does the P-force do to your stability?

Answer 41

Decreases the GM

Question 42

Is it okay to just calculate that you have a positive GM when you enter the dock?

Answer 42

No you need to calculate to ensure you have a positive GM for the entire time you are taking the blocks taking into account the P-force

Question 43

What is the critical instant in a drydock?

Answer 43

The point just before the ship fully takes the blocks The point of maximum P-force

Question 44

What is the critical period in a drydock?

Answer 44

The period between the vessel taking to the blocks at the stern and fully taking the blocks When the vessel is experiencing the P-force

Question 45

How do you know when the vessel is on the blocks in a drydock?

Answer 45

The draft starts to decrease Salty Answer: hang a heaving line off the bow and stern with a monkeys fist on, lowered to the waterline. Once the fist leaves the water and the line hangs, the vessel has taken the blocks at that point

Question 46

Why do you need adequate GM when going in to drydock?

Answer 46

The P-force will decrease your GM

Question 47

What are the stability requirements for entering a Drydock?

Answer 47

Drafts as per dock requirements Slight stern Trim Calculated positive GM throughout draining

Question 48

What special requirements does a tanker have to meet prior entering drydck?

Answer 48

Tanks must be gas freed and a gas free cert issued

Question 49

How would you know when the vessel has taken the first block astern?

Answer 49

Divers may let you know (if any) Aft Draft Decreases

Question 50

You’ve not taken to the blocks fully and the dock is empty, what next?

Answer 50

Raise it with the Ships Master and Dock Master

Question 51

What factors effect where the dock master positions the blocks?

Answer 51

Location of sensors Locations of planned repairs Minimising Stresses on the ship

Question 52

Once all boarding and connections are completed in drydock what needs to happen?

Answer 52

Meeting with dock master to discuss jobs and responsibilities

Question 53

Once the water has been pumped out of the drydock can you just start pumping your remaining ballast into the dock?

Answer 53

No, consult with the docking master first

Question 54

You are captain and the chief officer doesn’t know how to prepare for drydock, what are your concerns?

Answer 54

Just list the things that need to be prepared for a drydock and say you will need to check they are correct

Question 55

If the ship falls to one side when draining the drydock is it an angle of loll or list? Why?

Answer 55

Loll Its caused by a slight negative GM, not a shifting weight