CSWIP 3.1U Underwater (NDT) Inspection Diver (TWI, UK)

What is the primary objective of performing a preliminary subsea visual inspection (General Visual Inspection / GVI) on an offshore jacket structure?

• ATo assess overall structural integrity, detect major mechanical damage, and locate gross…
• BTo detect subsurface micro-cracking inside structural tubular members.
• CTo measure exact sound velocity variations across welded nodal joints.
• DTo measure internal wall loss without cleaning surface deposits.

How does Close Visual Inspection (CVI) differ from General Visual Inspection (GVI) during a CSWIP 3.1U subsea survey?

• ACVI is conducted entirely using ROVs without diver intervention.
• BCVI requires localized surface cleaning down to bare metal or tight marine growth removal…
• CCVI is restricted to top-side splash zone structural members only.
• DCVI replaces all non-destructive magnetic and ultrasonic testing requirements.

Which surface cleaning tool is most appropriate for removing heavy hard marine growth (such as thick barnacles and tubeworms) prior to CVI and MPI without gouging the underlying steel weld?

• AHeavy oxy-arc cutting torches
• BCoarse angle grinding discs removing 3 mm of parent plate
• CHydraulic wire brushes or needle scalers used with controlled pressure
• DHigh-explosive micro-detonation cords

When inspecting a subsea structural tubular weld, what visual appearance distinguishes a fatigue crack from a superficial surface scratch?

• AA fatigue crack is always perfectly straight and perfectly perpendicular to the water sur…
• BA scratch always exhibits rust staining while a fatigue crack remains shiny steel underwa…
• CA fatigue crack only forms inside internal structural air pockets.
• DA fatigue crack typically follows stress concentrations at the weld toe, showing depth an…

What surface preparation cleanliness standard (equivalent to ISO 8501-1) is required before conducting underwater magnetic particle inspection (MPI) on structural steel welds?

• ASa 2.5 / Very thorough blast cleaning to bright metal
• BSa 1 / Light brush cleaning leaving loose scale
• CSt 2 / Hand tool scraping leaving firmly adhering paint
• DNo cleaning is required prior to subsea MPI

In subsea structural inspection, what is 'weld undercut'?

• AExcess reinforcement metal deposited on the top cap of a butt joint.
• BA groove melted into the parent metal adjacent to the weld toe or root that has not been…
• CInternal gas trapped in the center of the weld metal pool.
• DAn intentional drainage slot cut through structural tubular joints.

Why must an inspection diver visually examine the splash zone of a fixed offshore platform with special care?

• AThe splash zone is completely shielded from marine growth and cathodic protection current…
• BCathodic protection systems operate with double efficiency in the splash zone.
• CThe splash zone experiences high oxygenation, wave action, cyclic wetting/drying, and sev…
• DSteel in the splash zone is immune to pitting and stress corrosion cracking.

Which instrument is used by an underwater visual inspector to measure the depth of pitting corrosion on a steel plate?

• AAn ultrasonic flaw detector set to shear wave mode
• BA high-frequency eddy current phase angle meter
• CA optical refractometer
• DA dial-gauge or needle-point pit depth gauge

What is the primary visual indicator of galvanic corrosion on a subsea steel structure near a bronze valve?

• AAccelerated metal loss and heavy rust scale on the steel adjacent to the bronze joint.
• BSevere pitting on the bronze valve body while the steel remains unattacked.
• CFormation of thick white calcium carbonate scales on the copper alloy only.
• DDiscoloration of seawater into a deep purple hue.

Which visual defect term describes a localized depression on a tubular member caused by an external mechanical blow or collision?

• ALamination
• BDent
• CPorosity
• DInclusion

Why must high-pressure water jetting equipment used for subsea cleaning incorporate a retro-jet nozzle configuration?

• ATo heat the sea water to boiling point before it touches the steel surface.
• BTo mix magnetic ink directly into the high-pressure water stream.
• CTo balance thrust forces so the diver is not pushed backward by reactive jet pressure.
• DTo prevent water from contacting the diver's drysuit.

What visual feature indicates that a concrete subsea structure or grout sleeve is suffering from alkali-aggregate reaction or freeze-thaw degradation?

• AUniform dark green discoloration without surface fractures.
• BSmooth glassy surface finish across structural joints.
• CComplete conversion of concrete into metallic iron.
• DMap-cracking (spider-web pattern cracking) accompanied by gel exudation and spalling.

Which visual inspection technique involves placing a flexible profile gauge against a deformed structural pipe wall?

• AProfile gauge tracing to record exact cross-sectional shape and depth of damage
• BUltrasonic compression wave flaw gating
• CImpressed current cathodic potential logging
• DEddy current phase rotation calibration

When inspecting subsea riser clamp bolts, what visual defect requires immediate non-conformance reporting?

• APresence of thin green algal film on the bolt head.
• BMissing nuts, loose tensioning, broken studs, or severe crevice corrosion.
• CA layer of soft silt deposited on horizontal flange surfaces.
• DUniform gray paint matching original specification.

What is the main operational limitation of subsea Close Visual Inspection (CVI)?

• AIt cannot be performed in saltwater environments.
• BIt requires heating the subsea structure to 100°C.
• CIt can only detect surface-breaking defects visible to the human eye or camera lens, not…
• DIt damages the atomic lattice of structural carbon steel.

What physical phenomenon forms the basis of Magnetic Particle Inspection (MPI) for detecting surface cracks on ferromagnetic steel welds underwater?

• AAcoustic impedance matching between water and iron ore.
• BElectrochemical oxidation of zinc sacrificial anodes.
• CThermal expansion of magnetic ink under infrared light.
• DMagnetic flux leakage at surface-breaking discontinuities attracting fine magnetic partic…

Why are Alternating Current (AC) electromagnetic yokes preferred over Direct Current (DC) yokes for underwater surface crack detection?

• AAC produces a strong skin effect that concentrates magnetic flux at the extreme outer sur…
• BAC magnetizes the entire internal volume of 50 mm steel plate equally.
• CAC yokes do not require electrical umbilical cables to the surface.
• DAC yokes permanently magnetize the steel structure so repeat inspections are unnecessary.

Under CSWIP 3.1U rules, what lift force must an AC electromagnetic yoke achieve during a pre-inspection surface check?

• A1.0 kg (2.2 lbs) at minimum pole spacing
• B4.5 kg (10 lbs) at maximum pole spacing
• C18.0 kg (40 lbs) using DC battery packs
• D50.0 kg (110 lbs) in seawater

What type of magnetic ink is used for underwater MPI under ultraviolet (UV-A) / black light illumination?

• ADry iron filings blown through a subsea air hose.
• BRed oil-based paint mixed with aluminum powder.
• CFluorescent magnetic particle ink suspended in a water-based carrier with anti-foam and w…
• DRadioactive cobalt isotope fluid.

What is the minimum UV-A light intensity required at the inspection surface during subsea fluorescent MPI?

• A0.1 W/m² (10 µW/cm²)
• B500 W/m² (50,000 µW/cm²)
• C10,000 Lux of visible daylight
• D10 W/m² (1,000 µW/cm²)

Why must an inspection diver apply magnetizing current while simultaneously applying magnetic ink (continuous method) during subsea MPI?

• ASubsea water currents rapidly wash away magnetic particles if the magnetic field is turne…
• BResidual magnetism in low-carbon structural steel is zero under water.
• CApplying ink without current causes electrical short circuits in the diver's helmet.
• DThe continuous method turns the ink into permanent solid epoxy.

To ensure 100% defect detection coverage across a welded seam during MPI, how must the yoke be positioned relative to the weld toe?

• AParallel to the weld axis only, without changing orientation.
• BIn two perpendicular orientations (90° offset) covering overlapping test segments.
• CAt a 45° angle held 300 mm away from the steel surface.
• DPositioned exclusively on the root side of the internal pipe wall.

What device is used underwater to verify sufficient magnetic field strength and field direction across a weld seam?

• AA-scan digital thickness probe
• BAg/AgCl half-cell potential probe
• CPie gauge or Berthold flux indicator
• DBourdon tube depth gauge

When using black magnetic ink underwater on dark oxidized steel plate, what contrast enhancement method is applied?

• AIlluminating the steel with infrared laser beams.
• BEtching the steel with concentrated nitric acid underwater.
• CHeating the black ink to 80°C before diving.
• DApplying a thin, quick-drying white contrast background paint to the steel before magneti…

How is particle concentration checked in a subsea magnetic ink reservoir before starting an MPI dive?

• AUsing a ASTM pear-shaped centrifuge settling tube to verify 1.5% to 2.4% settled volume f…
• BBy measuring the electrical resistance of the ink with a digital multimeter.
• CBy smelling the ink vapor above the reservoir tank.
• DBy timing how fast 1 liter of ink flows through a funnel.

What constitutes a false indication during underwater MPI?

• AA true surface fatigue crack verified by eddy current testing.
• BParticle accumulation caused by geometry changes, toe undercut profiles, high magnetic pe…
• CA through-wall crack leaking oil.
• DA linear defect confirmed by grinding.

Why must permanent magnet yokes be handled with extreme care by an inspection diver near subsea structures?

• AThey dissolve rapidly when exposed to seawater.
• BThey emit lethal levels of gamma radiation.
• CThey cannot be switched off; if trapped against flat steel plate, releasing them underwat…
• DThey generate 10,000 Volts of static electricity.

What photographic record is required when a relevant MPI crack indication is discovered on a subsea structural node weld?

• AA blurry photo taken from 5 meters away without scale markers.
• BNo photo is needed if the diver verbally describes it on comms.
• COnly an X-ray film exposure.
• DA clear photograph showing the indication with a flexible scale rule, weld identification…

How is residual magnetism demagnetized after completing MPI with an AC yoke?

• ABy energizing the AC yoke, placing it on the component, and slowly withdrawing it away fr…
• BBy hitting the steel weld repeatedly with a heavy lead hammer.
• CBy pouring warm freshwater over the weld.
• DBy short-circuiting the surface dive generator.

What is the primary advantage of underwater fluorescent MPI over black ink MPI in dark subsea conditions?

• AFluorescent ink does not require surface preparation or marine growth removal.
• BSuperior visual contrast under UV light, making fine, tight fatigue cracks easily recogni…
• CFluorescent ink repairs cracks automatically upon contact.
• DFluorescent ink works on non-metallic plastic structures.

What principle underlies Eddy Current Testing (ECT) for subsea weld inspection?

• AHigh-frequency acoustic resonance bouncing off backwall steel boundaries.
• BIonizing gamma ray attenuation through carbon steel plates.
• CElectromagnetic induction creating circulating eddy currents in conductive metal whose fl…
• DCapillary action drawing dye into open surface pores.

What major operational advantage does subsea Eddy Current Testing (ECT) offer over underwater Magnetic Particle Inspection (MPI)?

• AECT requires no surface calibration or probe selection.
• BECT can detect internal hydrogen blisters 100 mm below the surface.
• CECT works on non-conductive fiberglass composite pipes.
• DECT can inspect through non-conductive paint and protective coatings up to ~2 mm thick wi…

What is 'lift-off' in Eddy Current Testing, and how is it compensated for on subsea instruments?

• AThe signal change caused by varying distance between probe and metal surface; compensated…
• BThe physical floating of the diver off the seabed due to buoyancy; compensated by heavy l…
• CThe detachment of magnetic particles from the weld toe; compensated by increasing water p…
• DThe erosion of paint coatings due to high water velocity; compensated by applying epoxy.

What calibration reference block feature is used to set sensitivity for subsea ECT weld inspection probes?

• ADeep drilled 50 mm diameter holes through the center of the block.
• BElectro-discharge machined (EDM) precision notches of known depths (e.g. 0.5 mm, 1.0 mm,…
• CA mirror-polished chrome plated surface with zero flaws.
• DA layer of heavy barnacle fouling.

How does test frequency affect flaw detection depth in subsea Eddy Current Testing of structural steel?

• AHigher test frequencies penetrate deeper into the steel core.
• BTest frequency has no effect on electromagnetic penetration depth.
• CHigher test frequencies decrease skin depth (penetration depth), concentrating sensitivit…
• DLower test frequencies eliminate all lift-off signals completely.

When inspecting subsea carbon steel welds with ECT, why is a differential probe configuration commonly selected over an absolute probe?

• ADifferential probes do not require electrical cable connections to the surface display.
• BDifferential probes work on non-conductive wood pilings.
• CDifferential probes emit acoustic pulses that replace ultrasonic testing.
• DDifferential probes cancel out gradual background variations (liftoff, permeability, temp…

What visual indication on an impedance plane display signifies a surface crack during subsea ECT inspection?

• AA distinct vertical or angled signal trace moving away from the horizontal lift-off basel…
• BA complete disappearance of all screen graphics.
• CA steady circular ring centered on the origin.
• DA continuous horizontal drift across the screen.

Why must an inspection diver maintain probe orientation perpendicular to the weld seam during subsea ECT scanning?

• ATo prevent sea water from entering the probe tip.
• BTo ensure probe coils cross transverse and longitudinal weld toe fatigue cracks at optima…
• CTo increase diver descent speed.
• DTo discharge electrical ground currents.

Which subsea component is commonly inspected using Eddy Current Testing due to complex geometry and difficulty of post-inspection cleaning?

• AFlat sacrificial zinc anode bars.
• BUnpainted gravel seabed mats.
• CNode welds and K-T-Y tubular joints on jacket structures.
• DConcrete gravity base ballast compartments.

What effect does localized magnetic permeability variation in carbon steel welds have on subsea ECT signals?

• AIt increases sound velocity through the steel plate.
• BIt converts AC current into pure high-voltage DC.
• CIt causes the ECT display screen to shatter.
• DIt generates noise signals that can mask or mimic crack indications unless specialized we…

What is the function of a flexible encoder wheel attached to a subsea ECT weld probe scanner?

• ATo measure distance along the weld seam and correlate crack indications with precise posi…
• BTo scrub hard barnacles off the weld toe ahead of the probe.
• CTo generate electrical power for the subsea probe.
• DTo measure sea water temperature during scanning.

When conducting subsea ECT through a paint coating, how is coating thickness variations accounted for during inspection?

• ABy multiplying the signal voltage by the diver's depth in meters.
• BBy calibrating the lift-off signal using non-conductive plastic shims of known thickness…
• CBy increasing the frequency to 100 MHz.
• DBy filling the probe face with magnetic ink.

Under CSWIP NDT guidelines, what action must be taken if an ECT indication exceeds the threshold flaw criteria on a primary structural node?

• AIgnore the signal if the top-side paint appears undamaged.
• BGrind away 20 mm of parent steel without logging the location.
• CReport the anomaly immediately, record signal data/position, and perform supplementary ve…
• DFill the crack with subsea quick-setting epoxy.

What sound wave mode is primarily utilized by subsea digital ultrasonic thickness gauges to measure steel wall thickness?

• ATransverse (shear) wave
• BSurface (Rayleigh) wave
• CPlate (Lamb) wave
• DLongitudinal (compression) wave

What is the approximate speed of longitudinal sound waves in structural carbon steel used for calibrating subsea UT thickness meters?

• A5,920 m/s (approx. 5,900 - 5,960 m/s)
• B1,480 m/s
• C3,230 m/s
• D12,000 m/s

Why are dual-element (twin-crystal) compression wave probes commonly preferred over single-element probes for subsea corrosion thickness measurement?

• ADual-element probes eliminate the need for surface cleaning.
• BDual-element probes separate transmitter and receiver crystals, improving near-surface re…
• CDual-element probes measure cathodic protection electrical voltage simultaneously.
• DDual-element probes operate without surface couplant.

When calibrating a subsea digital UT thickness gauge, what two-point calibration procedure is conducted on a stepped calibration block?

• AFrequency calibration on a plastic block and gain calibration on a zinc anode.
• BBattery voltage check and depth sensor zeroing.
• CZero adjustment on a thin step and velocity calibration on a thick step.
• DWater salinity adjustment and temperature offset.