Answer MEP Question 39

Q. Describe the hull inspection that you would carry out as the Senior Engineer of a ship in dry dock stating what inspection you would make as the work started,

a. Large sea water inlet chest and valves.

b. Forward end of ship.

c. Propeller and stern bush.

Ans. Preliminary preparation prior to dry dock:-

i) Taking inventory of spares (for machinery to be overhauled), tool (spanners for propeller nut, poker gauge, rudder palm bolts, intermediate shaft bolts etc.) and stores (pipes, bends, flanges, valves etc.)

ii) Items for the continuous survey of the machinery or for the special survey are identified (e.g. Tail shaft, Propeller, Stern tube bearing, Rudder, underwater Valves, sea chests) and necessary spares and tools are kept ready.

iii) Existing defects identified and defect list prepared.

iv) Last dry dock reports checked — Tail shaft, stern tube bearing dimensions, poker gauge reading, clearances, propeller condition, sea chest gratings etc.

v) Stern gear and Rudder gear drawings to check, Engine Room double bottom tank plugs identified by frame numbers, which tanks to drain via plugs in dry dock and which plugs not to be touched, such as oil tanks, sea chest positions and overboard valve position identified.

vi) To inform Engineer Superintendent regarding any specialized services for automation equipment or any imported spare requirement at dry dock.

At dry dock:-

• Shore electrical connection has taken after checking voltage, frequency and phase sequences.
• Drinking water and sanitary water connection/disposal, fire hose Connection and dom Fridge condenser cooling water are taken if run.
• To keep the ship upright and slight trim by stern.
• Sounding of all tanks recorded before docking.
• Any abnormal noise to be noted while the vessel is grounded shove the Keel block.

Inspection:-

A. Large Seawater inlet chest and valves:

 Sea chest gratings, valve grids are examined from the dock bottom for any damage and the same is repaired or replaced with new gratings or plates. Any corrosion damage was examined and plate thickness checked. Sacrificial anodes are to be replaced, with new ones. Valves overhauled and checked with hose test for any leakage, Finally painted with primer and bituminous paint.

While flooding all the sea chests and underwater valves are to be inspected for any leakage constantly till the vessel is fully afloat.

B. Forward end of the ship :

The structure forward of the collision bulkhead is built to withstand the high dynamic stresses imposed (panting and pounding), bulbous bow to reduce wave-making resistance to provide increased buoyancy forward. Any damage to plate floors, deep floors, panting beams and panting stringers are to be inspected. Any damage to the flare surface due to falling anchor is to be inspected. Water tightness of forepeak store, forecastle store, forepeak tank to be ensured.

In addition to the above, all underwater parts of the hull are inspected for damage and corrosion. If any distortion or dent is observed, an inspection of the inside of the ship is to be made to determine internal damage and if serious, should be repaired. All sacrificial anodes are to be renewed or if fitted with impressed current cathodic protection, reference anodes and main anodes are to be inspected and covered during dry dock to protect against sandblasting and painting.

C. Propeller and Stern bush:

• Propeller surface and blade tips checked for roughness and damage due to cavitation pitting. Any major pitting on the surface is built up and the entire surface is smoothened by grinding. Blade tips rounded off. For keyed propeller, keyway, to be checked for any surface crack by magnetic particle detection for the keyless propeller, any ship between the tapered shaft and propeller boss to be examined, and forward one-third of the shaft cone is to be examined by a magnetic particle detection method.
• Stern bearing wear-down to be measured by poker gauge for oil-lubricated stern bearing, condition of oil glands and shaft liver to be examined. In case of previous records of oil leakage outside or seawater leakage inside, oil seal ring garter spring or worn seal ring to be replaced. Groove on the shaft liner, if noticed, due to which leakage occurred, the position of seal ring has to be shifted by a distance ring.

After complete assembly and during flooding close examination is required for any leakage. Crankshaft deflection, thrust bearing clearances are to be checked to ensure, alignment has not been disturbed.