Dry-Dock

Question 1

How would you prepare for a Dry-dock Exam?

Answer 1

Verify inspection Intervals: ISE, Hull, Tail shaft, Sea Valves, Integral Fuel Oil Tanks, etc.; Review MISLE back to last Dry-dock and identify damage and temporary repairs that require permanent correction and identify areas for close inspection. Request records of outstanding Conditions of Class; Schedule/attend planning meeting with interested parties to communicate USCG inspection requirements and avoid omissions/interferences/duplication. Ensure the owner/operator understands the criteria for a credit dryocking i.e . hull cleaned, tanks gas free, etc.

Question 2

What are the various inspections normally completed during drydock and where would I find the
cites for each

Answer 2

Intervals for dry-dock, internal structural, and cargo tank internal exams are found in each subchapter as appropriate. These intervals range from 2.5 to l0 years depending on salt/fresh water service, construction or material. Also included in each subchapter is the interval for inspection of integral fuel oil tanks. The number and location of tanks to be opened is dependent on the age of the vessel.

Question 3

Are there any special reporting requirements in advance of the docking of a vessel greater than 20
years of age?

Answer 3

Yes. The traveling inspection staff at CGHQ must be notified as far in advance of such a dry-dock
ins inspection so the ma attend.

Question 4

Briefly describe SOP for confined space entry by marine inspection personnel.

Answer 4

“A certified Marine Chemist shall conduct the initial inspection and certify all confined spaces on merchant vessels “Safe for Workers” before entry by Coast Guard personnel.” rules require a Competent Person to reexamine the confined space at least every 24 hours or if conditions under which the certificate was issued under change.” “If the competent Person has not properly maintained the Marine Chemist Certificate, the Marine Chemist is required to reissue the certificate prior to entering into the confined space.”

Question 5

What are the in intervals for gauging hull structure res including shell plate? Where would you find these requirements ?

Answer 5

Under class rules required thickness measurements other than suspect areas called out by the surveyor generally begin at Special Periodical Survey No. 2. This represents vessels with roughly ten years of service unless grace periods were granted. There are different requirements based on vessel size and service. For instance vessels restricted to the great lakes need not conduct thickness measurements until Special l Periodical Survey No. 7. Considering the routine year of grace dispensation, required thickness measurements for these vessels do not occur until the 42nd year of service. There is also a requirement for periodic gauging of tank vessel mid-bodies more than 30 years old in subchapter D. However, classification with a recognized society is considered equivalent.

Question 6

What is a class 1 structural failure? What are the reporting requirements?

Answer 6

Class I: During normal operating conditions, either
(1) A visible, through thickness fracture of any length in the oil-tight envelope of the outer shell where threat of pollution is a factor; or (2) A fracture or buckle which bas weakened a main strength member to the extent that the safety of the vessel to operate within its design parameters is compromised. Immediate Corrective action must be initiated by the operator with the approval of the OCMI. Temporary repairs may be permitted to allow the vessel to transit safely to a repair facility.

Question 7

What is a class 2 structural failure? What are the reporting requirements?

Answer 7

A fracture or buckle within a main strength member which does not compromise the safety of the vessel to operate within its design parameters and does not create a threat of pollution either by location or containment. Necessity for corrective action
shall be evaluated and agreed
upon between the vessel operator OCMI when the failure is found. Temporary repairs until the next scheduled repair period may be authorized.

Question 8

What is a Class 3 structural failure?

Answer 8

Any fracture or buckle which does not otherwise meet the definition of a Class 1 or 2 structural failure or a fracture which might normally be considered a Class II but is determined not to be detrimental to the strength or serviceability of the effected main hull structural member. Corrective action or notification to the OCMI is not required.
Shall be noted for the record, monitored by the operator if deemed desirable and addressed at the next regularly scheduled repair period.

Question 9

What do you inspect on a bulkhead?

Answer 9

Inspect for watertight integrity and general condition as well as signs of overloading
( warped/deformed).

Question 10

What do you inspect on a deck?

Answer 10

Decks can be part of major longitudinal strength members. Inspect for watertight integrity and general condition as well as signs of overloading (warped/deformed).

Question 11

What do you inspect on a tank top?

Answer 11

Tank tops are the upper boundary of double bottom tanks. Like decks tank tops make up a major part of the hull girder and if wasted or deformed affect hull strength. Inspect for watertight integrity and general condition as well as signs of overloading (warped/deformed).

Question 12

What do you inspect on a Longitudinal?

Answer 12

Generally refers to. smaller structures run longitudinally to stiffen plating (e.g. bottom longs, side shell longs, under deck longs, etc). The term would not apply to larger
strength members such as side keelsons.
? If deflected or deformed, this may indicate impact damage to the side or bottom plating.
? Deflected or deformed members should be examined for cracks and to ensure they have not ‘‘tripped” (web no longer perpendicular with the stiffened/supported plate).

Question 13

What do you inspect on a floor?

Answer 13

A plate used vertically in the bottom of a ship running athwart ship from bilge to bilge usually on every frame to deepen it. in wood ships, the lowest frame timber or the
one crossing the keel is called the floor.
? Deflected or deformed members should be examined for cracks and to ensure they have not “tripped” (web no longer perpendicular with the stiffened/supported plate).

Question 14

How do you inspect frames?

Answer 14

A term generally used to designate one of the transverse ribs that make up the skeleton of a ship. The frames act as stiffeners, holding the outside plating in shape and maintaining the transverse form of the ship.
? Deflected or deformed members should be examined for cracks and to ensure they have not ‘‘tripped” (web no longer perpendicular with the stiffened/supported plate).

Question 15

How do you inspect Intercostals?

Answer 15

Situated or fitted between adjacent members of a ship’s frame. Occurring between ribs, frames, etc. The term is broadly applied, where two members of a ship intersect, to the one that is cut.
? Deflected or deformed members should be examined for cracks and to ensure they have not “tripped” (web no longer perpendicular with the stiffened/supported plate).

Question 16

How many double bottom fuel tanks must be internally inspected on a 5 year old subchapter I vessel? Where is the interval found?

Answer 16

None. see 46CFR9 l .43

Question 17

What arc reduced scantlings?

Answer 17

Reduced scantlings means simply that the various internal structures and/or shell plating were approved at sizes below standard rule thicknesses in order to save weight. This reduction in size directly affects corrosion allowances and special coating systems are a requirement of construction. MSM only discusses reduced scantlings in regards to VLCCs and ULCCs. However, NVIC 7-68 indicates that converted LSTs were lightly built and suggests max wastage at 15%. Note: Ballast tank coating systems may be required if reduced scantlings are employed).

Question 18

What factors are used in determining variations in the inspection interval for a cargo tank internal examination?

Answer 18

Variations in CTIE intervals are based on salt or freshwater service, construction (double/single hull, internal /external framed etc. and cargo grade. Intervals run from 2.5-15 years.

Question 19

When are ca cargo tank coatings important?

Answer 19

In certain situations cargo tanks on chemical tankers may require coatings or linings to prevent the rapid corrosion of tank structures. In these instances close inspection of the coating/lining materials is warranted.

Question 20

Why are cargo hatches an important inspection item and what are you looking for?

Answer 20

Answer: Hatch failure has been implicated in a great many total loss casualties and these openings interrupt the hull girder and introduce stress risers at the hatch corners. Inspection should include:
? Dogs or other securing appliances for condition;
? Hatch covers for structural integrity;
? Gaskets for condition;
? Coamings for structural and watertight integrity;
? The deck adjacent to coming comers for signs of cracking or stress corrosion .

Question 21

CG -840 DI mentions ash and rubbish chutes, what is an ash or rubbish chute and what would you inspect?

Answer 21

? Ash chutes are used on coal burning steamers and are essentially a large diameter pipe (4”) leading from the ash pit eductor to a skin valve above the waterline. This piping system is subject to abuse due to the abrasive nature of the effluent. The skin valve is susceptible to the same sort of damage as well as fouling. The piping should be examined for wastage and the skin valve for ware and function.
? Rubbish chutes are used to dispose of permissible trash and may represent watertight integrity issues.

Question 22

What are inner bottom drains (Docking Plugs) and what are you looking for?

Answer 22

Docking plugs are specifically mentioned as an inspection item in the MSM and in the CG-840 book. They are installed to allow for draining and cleaning out inner bottom tanks during dry-dock availability. They should be inspected for cracking. erosion or other modes of failure.

Question 23

Describe the following components found in and around rudder assemblies and what might you be looking for during an inspection? Pintles

Answer 23

Pintles: These are the pins in the rudder’s hinge. They do not support the weight of the rudder but do provide a stable fulcrum from which it can swing. The pintle is usually a tapered bar fitted into a casting called a gudgeon and secured by a nut.
? The pintle should be inspected for signs of looseness, ware, and cracking.
? Examine locking device (nut weld)

Question 24

Describe the following components found in and around rudder assemblies and what might you be looking for during an inspection?Gudgeons

Answer 24

Gudgeons: Are integrally cast into the stem frame, rudder horn, or shoe piece to receive the pintle. This area is subject to dynamic stress and should be examined for cracking.

Question 25

Describe the following components found in and around rudder assemblies and what might you be looking for during an inspection? Skeg

Answer 25

Skeg: ls a stern ward extension of the keel of boats and ships which have a rudder mounted on
the centre line.

Question 26

Describe the fo llowing components found in and around rudder assemblies and what might you be looking for during an inspection? Stock

Answer 26

Stock: The rudder stock is the piece that physically connects the rudder to the tiller or motor.

Question 27

Describe the fo llowing components found in and around rudder assemblies and what might you be looking for during an inspection?Steadiment Bearings

Answer 27

Steadiment bearings: Bushings or bearings maintaining the rudder stock in position.

Question 28

Describe the fo llowing components found in and around rudder assemblies and what might you be looking for during an inspection? Carrier

Answer 28

Carrier: Bearing mounted on the upper stock to carry the weight of the rudder assembly. ABS 3-
2-1 4117 .3

Question 29

Describe the fo llowing components found in and around rudder assemblies and what might you be looking for during an inspection? Rudder Trunk

Answer 29

Rudder Trunk: Space through which the rudder stock passes through the hull.

Question 30

Describe the fo llowing components found in and around rudder assemblies and what might you be looking for during an inspection? Palm and Palm Bolts

Answer 30

Palm and Palm bolts: Currently referred to as coupling and coupling bolts and are a means to attach the rudder to the rudder stock where such a des ign is used

Question 31

Describe the following components found in and around rudder assemblies and what might you be looking for during an inspection? Fairwater

Answer 31

Fairwater: Plating installed to cover fasteners or gaps in structural pieces that do not lend
themselves to watertight integrity but are principally installed for hydrodynamic purposes.

Question 32

Describe the following components found in and around rudder assemblies and what might you be looking for during an inspection? Bushing

Answer 32

Bushing: A bearing surface for pintles or rudderstock to move against.

Question 33

Describe the following components found in and around rudder assemblies and what might you be looking for during an inspection? Air or hydrostatic test

Answer 33

Air or hydrostatic test: ABS 3-2-1 4/1 9.7 requires rudders be watertight, Rudders are to be air tested lAW ABS 3-7-1/Table 1 at 2.2ps i.

Question 34

Describe the following components found in and around rudder assemblies and what might you be looking for during an inspection? Rudder Bearing clearance

Answer 34

Rudder Bearing Clearance: Minimum and maximum bearing clearances are based on pintle diameter but in no case should this gap be less than l .5mm (.06in) for rudder stock and pintle bearings ABS 3-2-14/ 17. I .2 and no more than 7 .5 mm (lACS). Tighter clearances may be accepted with manufacturer approval.

Question 35

Describe four types of rudders.

Answer 35

1) Semi balanced- Some surface area provided forward of the post to balance pressure. 2) Fully balanced Sufficient surface area forward of the post to balance pressure. 3) Unbalanced Simple hinge with no control surface forward of the fulcrum. 4) Spade rudder Fully supported by the rudder stock (no pintles).

Question 36

Other than traditional rudders, discuss other steering arrangements/systems currently in use.

Answer 36

1) Kort Nozzle Movable nozzle. 2) Pleuger Rudder (AKA Dutch Rudder) Extra propeller unit in rudder. 3) Voith Schneider Articulating paddle like blades (tractor tug.). Becker flap an articulating flap on the trailing edge of the ruder Azipod Directional propeller unit. Contra-Guide A rudder with two seoarate integral angles built into the unit.

Question 37

Where and what arc you looking for when inspecting a propeller?

Answer 37

The critical inspection zone of a low skew propeller is roughly the lower 1/3 of the blade on the pressure side. For a highly skewed blade the answer is more complicated. Severity Zone A still includes the lower third of the pressure side but extends up the trailing edge and across nearly half the blade width.
Note: Also, the candidate should indicate that tip damage is not of great concern unless it adversely affects balance.

Question 38

Describe propeller fit up and when fit up is requ ired.

Answer 38

For keyed or keyless shafts, minimum 70% contact, with no “non contact bands” either circumferential or length wise. Normally propeller fit tests are only conducted when a new propeller/shaft are being added or if there is reason to question propeller fit (e.g. damage consistent with improper fit).

Question 39

Describe the following components listed in the 840 book associated with tailshaft inspection and what might you be looking for during an inspection? Stern Tube and Gland

Answer 39

Stern tube and gland: Stern Tube (aka shaft log) is the tubular ship structure that allows the shaft to penetrate the hull. The stern tube is often encased in a cofferdam. Many
incorporate a stuffing box where packing can be inserted and pressure applied by a packing gland. ? The stern tube should be inspected for erosion, cracking, and general condition.

Question 40

Describe the following components listed in the 840 book associated with tailshaft inspection and what might you be looking for during an inspection? Key and Keyway

Answer 40

Many shaft interfaces incorporate a non sl ip device called a key. A groove is machined into the shaft and whatever is being connected (groove is called the keyway). A precisely fitted piece of metal stock (key) is placed into the space made of both keyways eliminating the possibility of rotary movement on the shaft. ? Keyways a re stress risers and should be examined for cracks

Question 41

Describe the following components listed in the 840 book associated with tailshaft inspection and what might you be looking for during an inspection? Shaft sleeve or liner

Answer 41

Sleeves or liners are often used as a wearing surface for water lubricated bearings or seals. Interference fit liners or sleeves introduce hoop stresses at their ends unless steps are taken to relieve said stress. ? Shafts should be closely examined at sleeve ends; also ? Sleeve surface condition is important to bearing life .

Question 42

Describe the following components listed in the 840 book associated with tailshaft inspection and what might you be looking for during an inspection? Strut and Strut Bearing

Answer 42

Struts are shaft support appendages extending out from the hull and terminating at the shaft in way of a shaft bearing. bearings ? Strut to hull connection should be checked for cracking ? Strut bearing: should be examined for excessive wear.

Question 43

Describe the following components listed in the 840 book associated with tailshaft inspection and what might you be looking for during an inspection? Tapered Shaft

Answer 43

Refers to the type of shaft to propeller interface whether keyed or key less. ? The forward third of the taper should be closely examined for signs of cracking (NDT).

Question 44

Describe the following components listed in the 840 book associated with tailshaft inspection and what might you be looking for during an inspection? Flanged shaft

Answer 44

Describes the propeller to shaft interface that incorporates a bolted flange in lieu of a tapered fit. ? The flange and flange bolts are susceptible to great stress and require NDT.

Question 45

Describe the following components listed in the 840 book associated with tailshaft inspection and what might you be looking for during an inspection? Evaluation of oil resevoir for oil lubricated bearing

Answer 45

Tail shaft bearing lubricant evaluation is a required component in exempting certain oil lubricated installations from being drawn for inspection. This lubricant evaluation is usuaJly conducted by a third party (e.g. lubricant or bearing manufacturer).

Question 46

What are the recognized sta ndards to reduce stress concentrations applied to the ta per end of a keyed shaft and how might this effect your inspection?

Answer 46

The recognized standard to reduce stress includes the following elements; ? Keyway comers with fillets and ground smooth. ? Keyway forward end properly spooned. (shaft and hub) ? Key tightly fitted and slotted (fishtailed) or tapered at the forward end ? Propeller hub and shaft liners grooved to relieve hoop stress. ? Radius top corners of the keyway The aforementioned elements as well as seals, liners, or corrosions resistant materials which prevent sea water related damage to the shaft and propeller components will extend the inspection interval to once every five ears.

Question 47

What is a shaft spark test?

Answer 47

Shafting materials which are not resistant to corrosion and would otherwise be exposed to sea water (such as the section of shaft between the stern tube and strut bearing) can be coated with glass reinforced plastic to prevent material degradation. The bond of these coatings must be complete and without porosity. Glass reinforcement must be applied in at least 4 plies. A shaft spark test is conducted to identify any defects in this coating system by creating an electric potential between the shaft and an electrode. The electrode is passed over the coating and where a defect is resent an electric arc will Jump the air and will give a visual indication of the defect.

Question 48

What method of NDT can be used when inspect ing tailshafts?

Answer 48

Magnetic Particle, Dye Penetrant, or other NDT. ABS specifically allows magnetic particle or dye penetrant but does not limit the surveyor to these types of NDT.

Question 49

Please explain the inspection of sea connections and associated fittings- Sea Chests, Spool Pieces, and Through-Hull Fittings.

Answer 49

These include sea chests and other through-hull fittings. Particular attention should be paid to the sea chest structure as well as any spool pieces or connecting piping up to the first valve. Damage in these areas could result in serious casualties. These components are for all intents and purposes part of the hull.

Question 50

Why do we inspect sea valves?

Answer 50

Sea valves are the fi rst closure inside the skin of the ship keeping the sea out. Should anything happen to the piping system downstream of this valve its performance would be critical in mitigating further damage.

Question 51

Name the most common types of valves you may encounter, the parts of each to be examined, and describe how you would inspect a sea valve?

Answer 51

A sea valve should be inspected as if it were part of the ship’s hull. Overall condition of the body and bonnet are important as well as the operational components. The valve should operate as intended and retain adequate strength to remain in service. Any number of valve types may be employed as sea valves the most common are gate valves however butterfly and globe valves may be found.

Question 52

Valve Part: Body

Answer 52

The bulk of the casting that includes bolting flanges and seats.

Question 53

Valve Part: Bonnet

Answer 53

A removable part providing access for assembly which houses the stuffing or seals for the stem and guides.

Question 54

Valve Part: Guides

Answer 54

Align the valve stem.

Question 55

Valve Part: Seats

Answer 55

A resilient machined surface for the gate or discs to seal against.

Question 56

Valve Part: Stems

Answer 56

Physically connects discs or gate to the operating handle.

Question 57

Valve Part: Disc

Answer 57

Component that blocks the flow.

Question 58

Valve Part: Plug Cock

Answer 58

Physically connects discs or gate to the operating handle.

Question 59

Valve Part: Hold Down Bolts

Answer 59

Attach the bonnet to the body.

Question 60

Valve Part: Closure tested

Answer 60

Test of local and remote control of the valve.

Question 61

What is a Bilge Injection Valve and why is it important during a dry dock exam?

Answer 61

The bilge injection valve is the emergency bilge suction taken by the main circulating pump (aka injection pump) on a steam vessel. This very large valve cannot be inspected with the vessel in service because injection pump must be running as long as steam is being admitted to the condenser. It is inspected during drv dock as if it were a sea valve and for function. This is a Stop-Check unit.

Question 62

Describe the inspection and replacement interval for non-metallic expansion joints and explain why they are of concern.

Answer 62

Nonmetallic expansion joints should be externally examined at each inspection. Any such expansion joint located below the deepest load waterline and that penetrates the side of the vessels (also below the deepest load waterline) must be renewed ten years after it was placed in service. 46 CFR 61.15-12. Nonmetallic expansion joints can deteriorate over time, failure in large diameter systems would likely result in catastrophic flooding.

Question 63

Can the renewal interval of nonmetallic expansion joints be extended?

Answer 63

The OCMI may extend this ten year renewal until the next scheduled dry docking. However if the nonmetallic expansion joints are at or beyond the 10 year replacement date and the vessel is on dock their renewal is required.

Question 64

During an inspection, the port engineer tells you she wants to install a nonmetallic expansion joint that has been in the company’s inventory since 1982 (never used). Is the installation of this nonmetallic expansion joint permitted?

Answer 64

Yes, the ten year replacement is based on when the component was actually installed, not its inventory or manufacture date.

Question 65

What is anchor cable and what are the inspection requirements?

Answer 65

Anchor chain is technical ly referred to as cable and is required to be laid out (ranged) for inspection at every Special Periodical Survey (every 5 years). Starting at Special Periodical Survey No. 2 the chain cables are to be gauged. Chain found wasted more than 12% must be renewed. Chain shots should be marked and connectin shackles and ins examined

Question 66

Can any vessel avoid mid-period drydock exams by having a diver video the hull?

Answer 66

No, there are many prerequisites for a vessel being considered for entry into a UWILD program. An owner or operator may make application to the OCMI to participate but must do so well in advance. The age of the vessel may be grounds for exclusion if the vessel is over 15 years of age. The vessel must be inspected on dock to verify compliance with required elements and the hull gauged. Some important components include: ? Hinged grates on sea chests ? Diving plan . ? Grid marking of the hull so inspected areas can be properly located ? A means for checking shaft and pintle clearance underwater Once accepted into the program the vessel may conduct an underwater survey in lieu of dry docking for every other scheduled hull exam.

Question 67

How can you tell the difference between ordinary strength steel and higher-strength steel?

Answer 67

How can you tell the difference between ordinary strength steel and higher-strength steel?

Question 68

What is meant by 10 pound plate, or 40 pound plate?

Answer 68

This indicates the weight of plating per square foot, 1/4 inch plate is roughly 10 pounds per square foot, 1 inch late is 40 pounds per square foot.

Question 69

As per ASME, what provides direction to a welder for making prod uction welds?

Answer 69

ASME Section IX, W-100.l

Question 70

In reviewing a Welder Qua lification Record it is noted that this welder q ua lified in the 6G
position. What does this mean’?

Answer 70

The welder has been qualified to weld in any poistion.

Question 71

Can the OCMI accept welders who have been qualified by other agencies/entities?

Answer 71

The OCMI may accept welders qualified by other agencies of the. Federal Government, by ABS, or by the fabricator provided the fabricator’s tests have been certified by an authorized Code (inspector National Board).

Question 72

How would an inspector know if a vessel was constructed with High Strength Steel?

Answer 72

lt will be indicated on the vessels COI in the remarks section with a print number specified.

Question 73

What should I know about repairs to vessels with high strength steel?

Answer 73

The print specified on the COi will show the locations where high strength steel was used in the
construction of the vessel. lf repairs or renewals are undertaken where high strength steels were used
during construction it is vital that the same material grade be used in the repair work.