Magnetic Particle Inspection (MPI) · Amsterdam, Netherlands

Crack Detection by MPI for Offshore Vessels, Dredgers and Cargo Ships on the Canal

Offshore support ships, dredgers and workboats work their steel hard, and between contracts they come to the quays at IJmuiden and the floating docks on the canal to be checked. Magnetic particle inspection is the method used to find fatigue cracks at crane pedestals, winch foundations, lifting points, rudder stocks and repair welds. It shows surface-breaking cracks on the spot, with their length, and needs little more than a yoke and a power supply. Our technicians are mobilised from India to the ship and inspect alongside or in the dock, and the results are the owner's own NDT records.

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Crane pedestals before a new contract

An offshore vessel's crane, A-frame and winch foundations see cyclic loads in every sea state. Between charters the pedestal welds and surrounding deck plating can be cleaned and examined, so a charterer's condition survey finds a documented clean result.

Dredger structure under heavy loading

Dredgers dig, lift and carry cargo that shock-loads their structure at the gantry, the pump foundations and the hopper edges. In the dock or at the quay these welds are cleaned and magnetised, and cracks are located before they run into the plating.

Rudder and steering gear while dry

When a ship sits on the blocks in the floating dock, the rudder stock, pintles and the steering gear fastenings are exposed. A cracked stock or pintle is far easier to deal with in the dock than after the ship has sailed.

Where can MPI be carried out on ships at Amsterdam and IJmuiden?

MPI is done wherever the weld or part can be cleaned to bright metal and reached safely. At Amsterdam that means the quays at IJmuiden and the basins, where offshore and project vessels lie for longer periods, and the floating docks on the canal, where the underwater parts of the ship are exposed. Tank terminals and cargo berths are possible for deck work, but flammable atmospheres restrict magnetising equipment, and a hot-work or electrical permit is normally needed, so the terminal's rules decide.

Dredgers and workboats using the docks are a common case: the ship is dry, the yard has staging and power, and a crack found in the hopper edge or the suction gantry can go on the repair list while steelwork gangs are on board. Offshore vessels more often lie alongside, with the crew and the superintendent free to remove paint from the weld and arrange the crane to be parked and made safe.

Which parts do we examine on these ships?

On offshore support vessels the list starts with the crane pedestal and its deck connection, the A-frame or tower foundations, winch bases, towing equipment fastenings and the welded connections of the deck cargo rails and fastening points. These parts carry fluctuating loads and are exposed to salt spray and wave impact, which is the combination that starts fatigue cracks.

On dredgers the list shifts to the gantry and its foundations, the pump and pipe supports, the hopper coaming and the connections of the bottom doors or valves where the type has them. On cargo ships the usual candidates are the hatch coaming corners, the toes of brackets in the cargo holds, mooring bitts and fairleads and the foundations of deck machinery.

For every ship, the shaft line and steering gear are ferromagnetic, forged or cast steel and well suited to MPI: rudder stock tapers and keyways, pintles, tiller or quadrant connections, and bolted flanges. Where a bolt or key is removed during the docking, the thread and the keyway are checked at the same time, because they are the points where a crack is most likely to have started.

  • Crane pedestal welds and the deck plating immediately around them.
  • A-frame, tower and winch foundation welds on offshore support ships.
  • Gantry, pump and pipe support welds on dredgers.
  • Hatch coaming corners, bracket toes and bitt foundations on cargo ships.
  • Rudder stock, pintles, keyways and bolted flange faces in the dock.

How the inspection is carried out on a ship's steel

The surface is first cleaned to bright metal, either by grinding or by needle gun and wire brush, because paint, rust and weld spatter hide cracks and weaken the magnetic field. The yoke is applied across the weld, a field is set up between its legs and magnetic particles, usually dry powder for rough ship surfaces or a wet suspension where finish allows, are dispersed over the area. A crack disturbs the field and the particles gather along it as a clear line.

The yoke is moved in two directions across each examined length, so cracks in any orientation are caught. Indications are marked with a paint pen, measured with a rule and photographed in place. Where a part is very close to the water, in cold weather or under a canal drizzle, we adapt the technique to the surface condition and protect the suspension from rain; the examination is not carried out on wet or contaminated steel where the result would be unreliable.

If an indication is found, grinding by the yard can follow under the surveyor's instruction, and the area is then re-examined to confirm that the crack has been removed completely. We record the before and after on the same plan, so the repair history of that weld is documented in one place.

What is reported and how it is used

Each examined weld or part is listed with its location, the technique used, the surface preparation and the result: no indication, or the length and position of each linear indication. A photograph accompanies every indication. The report is written for the superintendent and the yard's welding supervisor, who need to know what to grind out, what to re-weld and what can wait for the next survey.

A crack found at a crane pedestal or a rudder stock often changes the programme of the whole stay. The earlier we pass on the news, the more time the yard has to plan the repair, which is why we telephone the superintendent about any significant indication before the written report is finished. The report itself is the owner's or the yard's NDT record. It supports a discussion with the classification society, but it is not a class approval, and repairs to class items still need the surveyor's acceptance.

Planning MPI around a docking or a quay stay at Amsterdam

Time is spent mostly on preparation, not on the examination. Paint has to be removed from every weld to be examined, staging has to be erected for the higher parts of the structure and the area must be dry. We recommend that the ship's crew or the yard starts cleaning as soon as the list of locations is agreed, so the technician can examine each weld straight after it has been prepared.

Send us the ship's name and type, the list of areas to be examined, the class and any condition of class relating to cracking, and the planned dates alongside or in the dock. The team travels from India, so tell us the arrival and sailing dates early. The agent supplies the gate pass and the yard or ship provides power, access and a safe place to work.

How the job runs at Amsterdam

The sequence for a thickness measurement job at Amsterdam is short and written down, so the yard, the surveyor and the superintendent know who arranges what.

  • 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.

Who does the work

We send the team from India to the ship for each job rather than keeping staff at the port, and plan the mobilisation around visas and the vessel's itinerary. The work is planned and supervised by the founder, our Responsible NDT Level III (ASNT NDT Level III in UT, RT, MT, PT and VT, with more than eleven years of international field experience). Technicians hold certification under the company's written practice to ASNT SNT-TC-1A; Atlantis is ISO 9001 and ISO 14001 certified.

Governing codes and standards

  • ISO 17638 (magnetic particle testing of welds)
  • ISO 9934-1 on magnetic particle testing principles
  • ASTM E1444 on magnetic particle testing practice
  • IACS UR W7 and W8 on hull and machinery steel forgings and castings
  • Class society rules for welding, repairs and crack removal on ship structure

What you receive

  • Examination list by weld or part with technique and surface condition
  • Length and position of every linear indication, marked on a plan
  • Photographs of indications before and after grinding
  • Re-examination record after the yard removes a crack
  • Operator qualification statement under the SNT-TC-1A written practice

Industries served

  • Offshore support and anchor-handling vessels
  • Survey and project vessels
  • Trailing and cutter suction dredgers
  • Tugs and heavy workboats
  • Short-sea cargo ships with deck cranes
  • Handysize bulk carriers with hatch corner cracking history

Frequently asked questions

Can MPI be carried out on a ship afloat at the IJmuiden quays?

Yes, on any weld that can be cleaned to bright metal and reached safely. Crane pedestals, winch foundations, hatch corners and bitt welds are all examined alongside. The surface must be dry, and we protect the work from rain. Locations over the water or in the splash zone are handled with the crew's help on access.

Why do dredgers and offshore ships need crack detection more often?

Their structure carries repeated, heavy loads: crane lifts, towing, dredging and wave impact. These cyclic loads produce fatigue cracks at welded corners and foundations much sooner than on a cargo ship that follows a steadier cycle. Examination between contracts finds cracks while repairs are small.

Can rudder stocks and pintles be examined while the ship is in the floating dock?

Yes, and the dock is the best place, because the rudder area is dry and the yard often has the stock and pintles exposed for other reasons. We examine the tapers, keyways and flange faces for cracks, and report any indication to the superintendent so the yard can plan the repair before the ship leaves.

Is MPI allowed at a tank terminal berth?

Deck work is sometimes possible, but flammable atmospheres restrict electrical equipment, and the terminal's hot-work or electrical permit rules apply. A product tanker alongside in the western basins may therefore need to be examined at a lay-by berth or during a gas-free period. We follow the terminal's decision.

Does the report count as a class approval of the repair?

No. The report is the owner's or the yard's NDT record of what was found and where. It supports the discussion with the class surveyor, who still decides whether a repair is acceptable. We do not claim a class approval for the inspection or for the repair.

Planning a survey or a drydock?

Send the vessel name or IMO number, the class, the survey due and the port. We reply with the scope, the mobilisation plan and a quote for that vessel.

Request a Quote

Request a ship gauging quote

Send the vessel name or IMO number, the class society, the survey due and the port. We reply with the scope, the mobilisation plan and a quote for that vessel.








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