UWILD hull inspection ROV

UWILD Best Practices

Marine Survey / Shipping, Oil and Energy

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Large vessels are required to be inspected thoroughly every year, as well as have a secondary inspection every three years and half decade by a classification society in order to remain certified to be in operation.  Why do these classifications exist?  Classifications began as technical assessments for marine insurers in the second half of the 18th century (IACS 2011).  What started as a program for insurers to protect their interests developed into a fair assessment by a third party organization with all stakeholders’ interests in mind.

The goal of having certified vessels versus suspended or non-certified vessels is to protect owners, employees, insurers and the companies who depend on the ships getting to their destinations. These classification societies know that credibility is the main source of business for them and they have no commercial interest in any side of the shipping industry.

The classification societies that implement these certifications for vessels are ABS, DNV-GL, Bureau Veritas, and Lloyd’s Register, among others.  ABS has a very comprehensive program that we have summarized below, other classification societies use similar criteria making it relevant to all owners and stakeholders of the shipping and offshore drilling industries.  Mobile Offshore Drilling Units (MODUs) have very similar guidelines to vessels as well.

A full, thorough inspection similar to the 5 year inspection is required to become ABS certified.  Once classed, ABS uses a Hull Inspection and Maintenance Program to make it easier for vessels to stay certified or become reclassified if a suspension takes place.  The program is the most important part of a classification because it ensures long term sustainability of the vessel.

The Process

The Hull Inspection and Maintenance Program (HIMP) has been developed for ABS classed vessels to remain certified and safe.  In order to enroll in this program, the vessel must be ABS certified, there must be a ABS certified inspector of the hull and the HIMP software must be installed on the vessel’s computer (s) (ABS 2015).  All previous documentation for the vessel is to submitted and reviewed by the ABS surveyor.

All inspections, above board and below the surface, are to be completed by the ABS certified inspector from the vessel’s company with a ABS employed surveyor in attendance.  The surveyor’s responsibility is to ensure that all visuals of the vessel’s hull, motors, ballast tanks and maintenance equipment are in operating condition.  If an area is suspected of needing repair, the vessel can be placed on temporary suspension without losing certification, while a repair is made and reassessed by the inspector and surveyor once again.

The inspections occur annually, with additional focuses in three and five year time periods.  These are referred to as Annual, Intermediate and 5 Year Inspection Intervals.

Annual Inspections

The areas of a vessel that must be examined and reported for the surveyor annually are:

  • Any suspect or critical structural locations identified
  • Deck area
  • Structural/Coating Condition of all Ballast Tanks (Including Cargo Tanks, Peak Tanks, etc.)
  • Hatch Covers and Access Hatches with Closing Appliances
  • Deck Equipment, Fittings, Helicopter Landing Pads
  • Piping and Supports
  • Superstructures and deckhouses
  • Shell plating above the waterline
  • Cargo holds, tanks and spaces
  • Voids and cofferdams
  • Pipe ducts and tunnels
  • Longitudinal box girders and cross deck box beams
  • Sea connections and overboard discharges
Intermediate Inspections

The areas of a vessel that must be examined and inspected for the surveyor every 3 years are:

  • All Areas included in the Annual Survey List
  • External Shell Plating below the waterline
  • Internal condition of boundary plating, internal bulkheads, framing, girders
  • Internal condition of all tanks containing bilge or oily water
5 Year Inspections

The areas of a vessel that must be examined and inspected for the surveyor every 5 years are:

  • All Areas included in the Annual and Intermediate Survey List
  • All Tanks including Fresh Water Tanks, Fuel Tanks, Diesel Tanks, Lube Oil Tanks, etc.
Submerged Inspections

Though the inspections are of the entire vessel, the tricky part for owners is the inspection of the hull and the interior of the liquid filled tanks because they are submerged.  The hull of the ship is crucial to maintain to get the longest life cycle out of the ship.  However, inspecting said hull is difficult.  In the past, dry-docking has been performed to ensure thorough inspection of the hull.  This process is extremely time consuming and expensive to perform.

Classification societies then began allowing Underwater Inspections in lieu of Dry Docking (UWILD).  These UWILDs are the most scrutinized by the surveyor because the inspector is the only one with direct access to the hull in these situations.  These have been performed by ABS certified divers traditionally.  This method is still costly and places humans under the hull of a ship with no direct access out of the water.  This is a dangerous scenario and is avoidable with the use of a ROV.

ROVs have been scrutinized in the past for UWILD inspections because of poor picture quality of the cameras, inability to access the areas beneath the hull because of their size and inability to get a proper visual because of inflexible camera operation.  Generally inspections performed by a ROV had to be redone by a diver, increasing the cost of the UWILD even more.

That is until Deep Trekker introduced their mini ROVs, with 270 degree rotating high definition cameras and small size allowing for a thorough hull inspection to be performed top side by a single inspector.  Here is an example of a hull inspection video shot by a DTG2:

UWILDs

What are you looking for in particular in a UWILD?  First, the owner of the vessel must ensure that they qualify for a UWILD instead of having to dry-dock.  This is becoming more infrequent as technological advances are made, however if there are outstanding recommendations for repairs to propellers, rudders, stern frames, sea valves or other underwater structures, dry-docking may be the only suitable option (ABS 2015).

Now that your vessel is qualified to save money, the areas that must be visualized underwater are the stern bearings, rudder bearings, sea suctions, sea valves and shell plating.  These are the areas that will show signs of wear and when compromised can cause major problems for a vessel.

Stern Bearings

It is important to check that the seal assembly remains intact on any oil-lubricated bearings, as well as verify that the clearance or wear down is within limits on the bearing.  Oil-lubricated bearings should include accurate oil-loss records and a check for contamination from sea water.  Wood and rubber bearings can be inspected through an opening in the top of the rope guard and a suitable gauge or wedge should be sufficient for clearance inspection.

Rudder Bearings

Condition and clearance of the rudder bearings are important to inspect. More specifically, ensuring that all parts of the pintle and gudgeon assemblies are intact and secure.  When access to these structures is deemed impractical, clearance verification can be foregone if the Surveyor is satisfied with the physical condition and securing arrangements of the pintle.  The operating history and onboard testing will also be considered before foregoing any structural inspection such as the rudders.

Sea Suctions and Valves

Sea suction openings must be clear and are in good condition.  Sea valves and their attachment to sea chests to be examined externally, including expansion pieces in sea water cooling and circulating systems.

Shell Plating

This is the majority of the surface area that is to be inspected, though most problems arise underwater wherever a seal is made or where two surfaces join together.  The general procedure of inspecting the plating begins with an examination of the plating above the waterline, as well as other exposed portions of appendages (propeller, rudder and rudder bearings).  The next step is to follow these portions under the water line.

This is the point where the surveyor does not have direct visualization of the plating and submerged structures.  The only way that this inspection is approved is if there is two way communication from the inspector to the surveyor and all parts of the inspection are recorded.  The time at which the diver or ROV inspection commences to the end of the inspection must be documented.

The video provided must clearly show the condition of the hull markings, all sea chests, inlets and discharges, rudders, pintles and propeller.  Any points of corrosion or damage must be examined further internally and thickness testing may be required by the Surveyor.

Though thickness testing is not required for all UWILDs, the surveyor is very likely to request this data when an area of suspicion is located.  The video above shows Deep Trekker’s DTG2 equipped with a thickness gauge to perform these measurements.

The other “forgotten” advantage of having a ROV on staff instead of hiring a diver to perform the inspection is that you are able to have a inspection rehearsal or a quick inspection before the official, supervised one.  The advantage of this is that if a problem is found or a possible area of contention with the surveyor, a solution could be implemented before hand without having to pay for a diver twice.  If a problem is not found until the surveyor is in attendance, this could result in a classification suspension or removal, which costs the vessels’ owner tremendous amounts of money and time to get their unit back up and running.

Overall, inspections are a nuisance.  The bureaucracy of classification societies is a nuisance.  However, these same checkpoints are what save lives, protect assets and make the shipping industry as a whole fair.  Deep Trekker provides the most cost effective and easiest to implement UWILD solution available, contact us for more information on how to protect the hulls of your ships today.

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4 Comments

  • Misarma says:

    Share your article is very useful for me. Thanks a lot 🙂

  • N PARAMASIVAN says:

    Understanding and very knowledgeable information. Thanks.

  • Chris O - Offshore Construction Manager says:

    You forgot to mention that the ROV cannot remedy any issues when they are found. A diver can clean the sea chest while they are there inspecting. An ROV will have to document it and get a dive team in to clear the sea chest after the fact which the ABS inspector may want a follow up UWLD to show the proper cleared sea chest. Let’s give the whole picture. ROV’s are very useful but do not have the same capabilities as a diver. I organize the UWLD program for numerous clients every year and would never use an ROV alone unless the vessel is in pristine condition which is not very often.

    • Cody Warner says:

      Hello Chris, We certainly understand that we will not be replacing divers! This article just looks at one alternative for the visual inspection of hulls and the regulations that follow. Reducing dive time in the long run and saving divers for intricate tasks such as clearing sea chests and repairs will save both the customer and the contractor money and reduce risks.

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