Crack Detection by Magnetic Particle Testing on Ships Alongside in Ghent

Where can MPI be carried out on ships at Ghent?

MPI is flexible about location, because the equipment is portable and the method needs only a clean steel surface and electrical power. At the car terminal and ro-ro berths, the ramps are accessible when the vessel has finished working cargo, and the hinges and stoppers can be reached from the ramp or the quay. On multipurpose ships at forest-product and general cargo berths, crane pedestals and their welds are accessible from the deck.

At the steelworks and agribulk quays, hatch corners and coaming welds are tested from the weather deck after the covers have been opened or secured, and holds can be examined for cracked frame welds and repaired areas once discharge is complete. Where grab impact has torn a flange or buckled a bracket, the weld repairs that follow are tested as they are completed.

The weather deck is open to the weather, so the team plans around rain and wind. Where the surface cannot be kept dry, a tent or a different time slot is used. Inside holds, lighting and ventilation are arranged with the crew before work begins.

• Ro-ro and car terminal berths: ramp hinges, stoppers, lashing points and ramp structure.
• General cargo and forest-product berths: crane pedestals, slewing ring supports and hatch coaming corners.
• Steelworks and agribulk quays: hatch corners, hold frame welds and grab-damage repairs.
• Any berth where a repair has just been welded: insert plates, doublers and renewed brackets.

How is MPI scoped on a Ghent call?

The scope lists the welds and components to be tested, with their location, material and surface condition. For a ro-ro ramp this means the hinge brackets, hinge pins where accessible, the stopper and securing arrangements and the welds of the ramp's primary stiffeners. For a crane pedestal it means the welds that join the pedestal to the deck and the supporting brackets underneath.

Before testing, paint and rust are removed from the weld and a band of parent metal on either side, so that the magnetic field reaches the metal. The yoke is applied in two directions at each position, since a crack lies across the field to be detected. Contrast paint and black or fluorescent particles are chosen to suit the surface and the light, and a lifting-power check of the yoke is made with a test weight.

Cold weather has a practical effect, because particle suspensions and contrast paint behave differently near freezing. The team adapts the method and, where necessary, warms the surface. All indications are measured, marked and photographed, and the position is tied to the structure on a sketch.

How should an MPI job be planned at Ghent?

Tell us what is to be examined and what the surface condition is. If paint removal is required, the crew or yard should prepare the areas before the team arrives, or tell us beforehand so that we allow time for cleaning. A ship whose ramp must be lowered for access should confirm with the terminal when this is possible between rotations.

Electrical supply and lighting on the ramp, on deck and in the holds are arranged with the crew. Where hot work is going on in the same area, the testing sequence is agreed with the person controlling the work, because a freshly welded repair has to cool before it is tested.

The team travelling from India needs Schengen visas, which we begin as soon as the call is confirmed. The ship's agent arranges the gate pass. The report is an NDT record for the owner or yard, and it is the attending surveyor who decides what the class requires.

How the job runs at Ghent

A gauging job at Ghent runs the same way whatever the ship type. The sequence below is what the superintendent, the attending surveyor and the yard can expect from us.

• Send the vessel name or IMO number, ship type, class society, the survey due (annual, intermediate, renewal survey number, CAP or owner's condition survey), the port and dates, and the scope you expect.
• We confirm the scope against the class rules for that survey, prepare the thickness measurement plan with frame and section references, and say whether the measurement will be credited to a class survey.
• Mobilisation is planned around visa lead times and the vessel's schedule; the ship's agent arranges port access, and the yard or ship arranges staging, lighting, ventilation and gas-free certificates.
• Gauging with calibrated ultrasonic thickness gauges: through sound coatings only where the gauge's through-coating mode has been verified on a coated reference, otherwise on cleaned bare steel, with every reading tied to its frame, strake and location on the sketch.
• Readings are compared with original thicknesses as work proceeds; substantial and excessive corrosion and any cracks are reported to the attending surveyor and the superintendent the same day.
• The final report is issued on the class thickness-measurement formats with sketches, a summary of locations exceeding the allowable margins, piping tables where piping was in scope, and the gauge calibration and technician certificates.

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