Materials Selection Flashcards
7 cards from real DPO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Materials Selection flashcards as text
On a DP drilling vessel, which material is selected for the riser tensioner cylinders to provide corrosion resistance in a splash zone environment with high dynamic loading?
Answer: Precipitation-hardened stainless steel (17-4 PH)
17-4 PH stainless steel provides high strength, good corrosion resistance in the splash zone, and resists stress-corrosion cracking better than lower-grade stainless steels under dynamic cylinder loads.
Which non-destructive testing (NDT) method is most appropriate for detecting subsurface fatigue cracks in DP thruster shaft keyways?
Answer: Ultrasonic testing (UT) with phased array
Phased array ultrasonic testing can detect and characterize subsurface cracks in shafts at depth, unlike PT or MT which are limited to surface or near-surface indications.
For DP vessel accommodation modules, which material is preferred for bulkhead panels to satisfy both fire rating (A-60) and weight reduction requirements?
Answer: Mineral wool-insulated steel sandwich panels
Steel-faced mineral wool sandwich panels achieve A-60 fire rating (no temperature rise on unexposed side for 60 min) while keeping weight lower than solid steel plate, meeting SOLAS regulations.
When specifying cathodic protection for a DP vessel's underwater hull, which sacrificial anode material provides the best protection efficiency in tropical high-salinity seawater?
Answer: Aluminum-indium-zinc alloy anodes
Aluminum-indium-zinc alloy anodes have higher current capacity per kilogram than zinc, remain active in warm high-salinity seawater without passivating, and are preferred for tropical DP vessel hulls.
Which property of UHMWPE (ultra-high molecular weight polyethylene) makes it suitable for DP vessel fairlead liners and chafe protection on mooring lines?
Answer: Extremely low coefficient of friction and high abrasion resistance
UHMWPE has one of the lowest friction coefficients of any solid material and outstanding abrasion resistance, reducing wear on mooring lines and fairlead contact surfaces on DP vessels.
For DP vessel thruster motor stator windings, which insulation class is required to handle continuous operation at elevated ambient machine room temperatures?
Answer: Class F (155°C maximum) or Class H (180°C maximum)
DP thruster motors in hot engine rooms require Class F or H insulation to maintain dielectric integrity at elevated winding temperatures without premature insulation degradation.
When selecting paint coatings for DP vessel underwater running gear (thrusters, propellers), which coating type is prohibited in many jurisdictions due to environmental toxicity?
Answer: Tributyltin (TBT) self-polishing copolymer antifouling
The IMO AFS Convention (2008) banned TBT-based antifouling systems globally due to severe ecotoxicity to marine organisms, particularly causing imposex in gastropod mollusks.