Underwater Repairs

Activities at SGS

An urgent request arose for US-based Subsea Global Services (SGS) to remove heavy debris from the starboard side anchor chain of a commercial vessel anchored in English Bay in the Port of Vancouver, Canada. The debris was reported to have surrounded the anchor and had several lines leading towards the ocean seabed.

The local Harbour Master required that all debris be removed and properly disposed of before the vessel could sail to her next destination. SGS hurriedly compiled a team of four expert commercial diver technicians from our Vancouver office to complete the task before the planned vessel departure. SGS mobilised out of the Macfish Dock in North Vancouver utilising a specialised workboat equipped with a hydraulic crane to assist with the debris removal.

The project was completed within the vessel’s planned departure time, eliminating the need of Pilot cancelation or rescheduling. The hawser line was disposed of through the proper channels and the client was pleased with the project completion time frame giving thanks to SGS for its quick response time.” SGS also performed a rudder inspection with Class in attendance for a vessel in Busan, South Korea where it was discovered that the rudder was suffering from heavy erosion and cavitation damage. The areas effected included critical locations such as the port and starboard rudder plates, pintle lower casting, in way of the lower pintle, the edges on rudder bottom plate, the area in way of bottom plug, the end of upper and lower fin plates, and more.

Considering there was not enough time to complete the underwater repairs before the vessel’s planned departure and a full underwater repair procedure needed to be written and approved by Class, a ‘Condition of Class’ (COC) to the client’s vessel was issued by the attending class surveyor. The COC required a permanent repair of the wasted areas and the de-watering of the rudder blade within 30 days. SGS carried out the repair in Long Beach, California, where the vessel had a oneweek time frame for cargo operations without requiring to go off-hire.

The repair was based on underwater welding only, eliminating the need for the installation of open top cofferdams or other barriers that would allow dry welding repairs to take place, which requires more time and resources. SGS Long Beach mobilised two five-man teams of commercial divers and welder divers to operate around the clock during cargo operations until the underwater repair was concluded. SGS began the repair process by removing the two existing rudder fins that were heavily corroded. Next, the team prepared each of the wasted areas of the rudder for build-up welding by cleaning them to bare metal using underwater grinding and brushing methods. This allowed SGS to start with an even and clean surface to restore the wasted areas to the original plate thickness.

A client contacted SGS requiring underwater support to replace a leaking rudder stock seal on the port side rudder during the vessel’s lay-up at a shipyard in Corpus Christi, Texas. The client had first contacted the shipyard for support on this project, but the shipyard was not prepared to take the responsibility for lowering the rudder while the vessel was still afloat. SGS, having years of experience with complex underwater repair projects such as this, was willing to take on the challenge with confidence for both segments of the work—internally and externally.

The SGS centralised Technical Repair Department worked closely with the rudder OEM, vessel owners, and Class to develop a

A SGS cofferdam in position

A SGS diving team with a damaged rudder

unique rudder repair procedure eliminating the need of cutting open the deck plate for the steering actuator removal and included both the underwater and internal works. Once the repair procedure was approved, SGS was ready to complete the works in five 14-hour shifts with six commercial diver technicians and one project manager from SGS Houston, SGS Long Beach, and SGS Port Angeles. The vessel superintendent was not able to be present on the jobsite due to COVID-19 travel restrictions, so SGS filled this void by handling the project logistics and responsibilities with the attending Class Surveyor.

A client contacted US-based SGS to perform an underwater repair for its vessel’s pre-existing hull fracture while at the Rustin Anchorage in Tacoma, Washington. This fracture had been temporarily repaired during the vessel’s port call in China and was 550 mm in length located in the starboard side shell plate at the turn of the bilge, and propagated through the bilge keel and grounding bar. The client required a solution that would serve as a class approved permanent repair and remove the Condition of Class (COC).

The SGS centralised Technical Repair Department provided the client with a class approved permanent repair solution. The proposed permanent repair solution comprised SGS providing all of the services to remove the fracture permanently with the installation of a hull insert. As required by class, SGS’s in house welding engineer drafted a repair procedure, which detailed the scope of work and included documents like class approved welding procedures and welder qualifications for underwater welding, dry welding, NDE procedures, material certificates, and more.

The internal welds where NDE tested to the satisfaction of the attending class surveyor employing UT shear wave inspection. After successful completion of the NDE and acceptance from the attending class surveyor, the dive team removed the cofferdam and successfully performed Magnetic Particle Inspection (MT) on the underwater welded fillet welds between the bilge keel grounding bar and the hull plating. Corrosion protection was applied over all areas of damaged coating.

A SGS partner agency in China had an urgent enquiry to perform an underwater inspection on a vessel that had experienced contact damage to its propeller while underway to an anchorage in Busan, Korea. The client indicated that they were experiencing severe engine loading and excessive vibration, so SGS prepared for various repair options to execute upon completion of the underwater inspection, including underwater propeller blade straightening and underwater propeller blade cropping and balancing.

The initial underwater inspection revealed large aft-ward deflections up to 100o on all four propeller blade trailing edge tips. Having a global presence SGS responded within an hour and provided the repair options to the client with cold static load propeller blade straightening as SGS’ recommended procedure. The client was reluctant to proceed at first, as they had received competing quotes from alternate commercial diving companies, which were more economical. It was understood that this was because the procedures proposed by the alternative commercial diving companies included methods such as underwater propeller blade cropping.

SGS’ Busan team mobilised three experienced commercial diver technicians, two in-house trained commercial diver propeller technicians, and the virtual support of a Senior Level 3 Propeller Technician from the SGS Vancouver office who could not travel to the job site due to COVID-19 travel restrictions.

SGS Vancouver is the home of SGS’ expert Propeller Technician instructors who work hard to educate and train 165+ full-time commercial diver technicians through the SGS Maritime Academy. SGS continues to adapt to the ongoing COVID-19 crisis by serving clients and

repairing immobilised vessels in whatever ways possible.

SGS began the underwater repair process with a close visual inspection for any linear surface defects in the deflected section tension sides (suction faces)—none were sighted. SGS then documented the current geometry of each blade to scale on the design drawings identifying the key locations to position an underwater propeller blade press while considering section thickness, fold lines, deflection angle radii, and the correct target geometry for propeller blade restoration.

Upon departure from Busan, the client reported a successful sea trial with all engine parameters and vessel performance restored to pre-damage values. The project was completed in a safe, professional, and efficient manner without removing any material from the propeller blades.

Another client contacted SGS needing support to remove and install two new spool pipes for its vessel’s SOx scrubber system during a port call in Singapore or Busan, both of which are home ports of SGS. The client was unsure which port these repairs would need to be executed in due to the charter’s timesensitive schedule, so SGS prefabricated the new scrubber spool pipes and flanges in both locations as per the client’s request.

It was indicated early on that both of the scrubber overboard pipes were repaired in the preceding six months and were now starting to fail again. The previous repair methods included build-up welding in way of the leaking area on the top spool pipe while the bottom spool pipe had a section cropped and replaced with schedule 80 piping compared to the original schedule 60 design piping. During the previous repairs, each spool pipe was recoated with epoxy, but in the end, the acidic outflow of the scrubber discharge was still compromising the spool pipes integrity. After several months, the client’s proactive NDE inspections were showing pipe thinning in several locations.

The location of the repair was finally decided for Singapore. The SGS centralised Technical Repair Department and SGS Singapore worked closely to manage each facet of the project for the client. The planned repair timeline included 60 hrs with two commercial diver teams and two internal technical teams working around the clock. The commercial diver team began the underwater operation by templating and fitting cofferdams over each of the damaged scrubber overboard locations maintaining the required distances from the heat-affected zone (HAZ) of the internal weld joints. A ship manager contacted SGS in need of underwater support to repair and overhaul a single leaking bow thruster blade seal during one of its managed vessel’s port calls to the M7 inner anchorage in Busan, South Korea. The client had made their first contact with the thruster OEM, but the OEM had connected them directly with SGS Busan, as SGS has been an approved OEM service provider over the last 15 years.

The client indicated that they were experiencing pressure loss from the blade seals, so SGS shared various repair options including wet and dry blade seal exchanges. This particular thruster type required repairs in a dry environment, so SGS provided thruster dry habitat options as well as trimming the bow thruster tunnel 2/3rd above the waterline to perform the overhaul on the surface. The client decided that since the vessel was in ballast that trimming was going to be the preferred option.

The SGS centralised Technical Repair Department and the SGS Busan team worked with the vessel manager to develop an efficient repair procedure that would minimise the off-hire time for the vessel. The repair procedure included SGS handling all spare part replacements and launching a commercial diver team to work in conjunction with vessel trimming process, which would take approximately 12-18 hours to achieve the specified forward draft.

The project was executed with two SGS teams working around the clock. While the vessel trimming process was in motion, the team onboard the vessel began to drain the oil from the thruster while the dive team began removing the bow thruster tunnel gratings to gain full access to the bow thruster. It was noted immediately that the other three thruster blade seals would also need replacing due to visual signs of leakage.

Thankfully, this did not burden the timeline greatly as all four blade seals were ordered from the OEM to have onsite in case a situation such as this occurred, as can often be the case with complex repair projects. The dive team began by removing the existing stainless steel keeper bars welded to the bow thruster blade palm fasteners. Next, they installed overhead rigging points to the tunnel by underwater welding pad eyes in the required locations for handling the thruster blade load while the seals were being exchanged.

Once the bow thruster hub and tunnel were at the targeted draft above the waterline, the SGS technicians were able to begin the blade seal exchanges without delay. As the thruster blades were removed, the team checked the condition of the contact surfaces for any mechanical damage and proceeded with each seal exchange. In conjunction with this, the team polished each of the bow thruster blades and performed a visual inspection for any unknown surface deficiencies before each blade was reinstalled.

After each of the new seals was in position, the SGS technicians proceeded to re-seat each thruster blade respectively and install the new thruster blade palm fasteners to the required OEM torque specifications. The thruster drain plug was replaced and then the thruster was filled up with lubricant to prepare for testing. The visual test, leakage test, and pitch test all successfully passed. The header tank oil level was stable after the testing, so the ship began de-ballasting to the normal operating level so the dive team could proceed with the final steps.

With the bow thruster beneath the waterline again, the dive team began underwater welding of the stainless-steel keeper bars between each of the neighbouring blade palm fasteners, while also removing the previously installed overhead rigging points to the thruster tunnel. Areas of the thruster tunnel with damaged coating were covered with protective barriers and the bow thruster gratings were re-installed and resecured with the fasteners being tack welded.

Busy times at Hydrex

A 130 m chemical tanker suffered erosion damage in the grey water tank. Hydrex was contacted by the owner to provide an underwater solution that would allow the vessel to keep its schedule. A team of their diver/ technicians therefore mobilised to Rotterdam to perform on-site repairs.

This type of smaller damage is created over time as the result of the recurring impact of for instance water on the exact same spot over again. On vessels this occurs regularly in the ballast tanks under bell mouths or sounding pipes as was the case with the chemical tanker.

If the damage is caught before the hull plates are perforated, clad welding can be used to fill up the area. This is also a permanent repair that will avoid a condition of class. During the operation in Rotterdam this was no longer an option as a hole had formed in the hull plating.

The divers started the operation by installing a cofferdam on the waterside of the affected plating. Next, they removed the sounding pipe covering the area on the inside. They could then safely remove a plug which had been installed as a temporary solution. The damaged plating was then cleaned and prepared for the

A Hydrex welder preparing a new scrubber pipe for installation

operation.

As agreed with the classification society, the team then cut away an area measuring 300 mm x 300 mm. Next, they prepared the edges of the hole for the insert and positioned the new plate. The insert was then welded following the Hydrex class-approved procedure for insert plates, using a full penetration weld.

An independent inspector carried out ultrasonic testing and the repair was approved by the classification surveyor who was present during the operation. The team then reinstalled the sounding pipe and removed the cofferdam. A small round doubler plate was installed under the pipe to prevent the new insert from eroding again.

Hydrex offers class approved permanent repairs for this type of damage. These combine underwater cofferdam installation and inside dry welding. The company has a wide range of cofferdams at their disposal as well as certified plating which they can mobilise immediately to any location.

Both parts of such an operation are performed by the same team of in-house trained diver/welders working at the highest quality standards. In most cases normal commercial activities can continue without disruption.

A 130 m chemical tanker suffered erosion damage in the grey water tank. Hydrex was contacted by the owner to provide an underwater solution that would allow the vessel to keep her schedule. A team of diver/ technicians mobilised to Rotterdam to perform on-site repairs.

This type of smaller damage is created over time as the result of the recurring impact of for instance water on the exact same spot over and over again. On vessels this occurs regularly in the ballast tanks under bell mouths or sounding pipes as was the case with the chemical tanker.

If the damage is caught before the hull plates are perforated, clad welding can be used to fill up the area. This is also a permanent repair that will avoid a condition of class. During the operation in Rotterdam this was no longer an option as a hole had formed in the hull plating.

The divers started the operation by installing a cofferdam on the waterside of the affected plating. Next, they removed the sounding pipe covering the area on the inside. They could then safely remove a plug which had been installed as a temporary solution. The damaged plating was then cleaned and prepared for the operation.

As agreed with the classification society, the team then cut away an area measuring 300 mm x 300 mm. Next, they prepared the edges of the hole for the insert and positioned the new plate. The insert was then welded following the Hydrex class-approved procedure for insert plates, using a full penetration weld.

An independent inspector carried out ultrasonic testing and the repair was approved by the classification surveyor who was present during the operation. The team then reinstalled the sounding pipe and removed the cofferdam. A small round doubler plate was installed under the pipe to prevent the new insert from eroding again.

Hydrex offers class approved permanent repairs for this type of damage. These combine underwater cofferdam installation and inside dry welding. Hydrex has a wide range of cofferdams at its disposal as well as certified plating which can be mobilised immediately to any location.

Both parts of such an operation are performed by the same team of in-house trained diver/welders working at the highest quality standards. In most cases normal commercial activities can continue without disruption.

Hydrex’s diver/technicians can perform a

A Hydrex welder preparing a new scrubber pipe for installation

wide range of repair or maintenance work on bow thrusters. An entire unit can be overhauled, propeller blades and seals can be replaced or repair work on another specific part of a thruster can be performed on-site. These repairs are performed in co-operation with all OEMs and can be carried out while the ship stays afloat with minimum impact on its schedule.

The goal is to offer the most efficient solution while maintaining the highest safety and quality standards. This article gives an overview of some of the more important recent bow thruster repairs carried out by Hydrex teams.

One of Hydrex’s teams removed a bow thruster from a 170 m containership during a stop in Rotterdam. The unit needed to be overhauled and the operation had to be carried out within a very short window that would fit the schedule available to the vessel’s owner.

The team mobilised to the ship’s location using one of Hydrex’s workboats loaded with all the needed equipment. These workboats are stationed in Antwerp and Rotterdam and can be used for a wide range of operations. This enables rapid deployment. It also increases flexibility, which was essential during an operation like this.

Hydrex carried out the removal following the specific procedures required by the involved OEM. This allowed Hydrex to remove the thruster unit with the blades still attached, speeding up the operation. Simultaneously the team sealed off the tunnel from the bow thruster room. Once the unit was lifted onto the quay it was prepared for transport to the workshop.

By performing the operation on-site and underwater the divers made it possible for the owner to keep the vessel out of drydock. The team worked in shifts around the clock. They finished the job well within the available time frame. This allowed the ship to sail on schedule, which was a key benefit for the owner.

A 200 m cruiseship experienced a problem with its bow thruster. Hydrex mobilised a team to Phuket, Thailand to perform the necessary underwater repairs with the use of flexible mobdocks.

A breakdown occurred in the feedback system that specifies the position of the vessel’s bow thruster blades. Taking into account the strict schedule of the cruise ship, keeping it sailing was essential. Hydex was contacted by the customer and asked to find a fast, on-site solution.

In co-operation with the manufacturer of the thruster, a plan was devised by Hydrex’s technical department. The diver/technician team would carry out an inspection and any necessary repairs afloat without removing the unit from the thruster tunnel. The customer gladly accepted this proposal as it meant he did not need to take his ship into drydock. This saved him substantial time and money.

The team had a very pleasant and smooth co-operation with the crew of the ship, the manufacturer of the thruster and all other parties involved. This helped Hydrex to perform the operation as fast as possible.

Hydrex removed a bow thruster from a 229m bulk carrier. Two weeks later the overhauled unit was reinstalled. Both operations were done during stops in Algeciras, Spain and had to be carried out within the tight schedule available to the charterer.

To keep the impact on the ship’s schedule to the absolute minimum, the divers performed an inspection of the bow thruster unit and tunnel, followed by some preliminary work while the vessel was berthed at a lay-by. The ship could then shift and start cargo operations while the team performed the rest of the operation without any hindrance to the loading schedule.

In just over a week Hydrex diver/technicians travelled to Finland, Germany, the Netherlands and France to assist shipowners with damaged propeller blades. On two bulkers the blades were cropped while on a third bulker and a general cargo vessel the bent blades could be straightened. In all cases the best solution was offered to the customer to restore the propeller’s efficiency as close to the original condition as possible.

One of the propeller blades of a 180 m bulk carrier was severely bent. A fast, on-site solution to restore the propeller’s balance and efficiency was needed. Hydrex therefore sent a team to the ship’s location in Rotterdam with one of the company’s workboats.

After the equipment arrived the team started the operation with a detailed survey of the ship’s propeller. This revealed that one of the other three propeller blades was also bent slightly. It was decided to straighten this blade as well.

With the survey completed and in close communication with the team leader in the monitoring station onshore, the divers returned the bent blade to its original state. When the straightening was complete, the technicians polished the blade to make sure that any remaining loss of efficiency would be minimal. The same procedure was then repeated on the other damaged blade.

The SMS ROV unit

The conditions for a similar repair in Tornio, Finland were a lot less warm. All four blades of a 144 m general cargo ship were bent. Hydrex mobilised a team to straighten the blades using the same procedure as on the vessel in Rotterdam. They travelled through the snowy landscapes with two vans and the needed equipment to the ship’s location.

During the operation the divers had to work in water filled with chunks of ice, but these conditions offered no problem for them. They are used to adapt to different circumstances and carried out the repair without any loss of quality. If straightening is not an option, the affected area on the blade will be cropped. By doing this the greatest possible efficiency is achieved for the vessel. This was the case for the operations described below.

With all four blades of a 235 m bulk carrier’s propeller severely damaged after impact with ice, the engine was overloading. Hydrex was asked to perform an on-site repair during the ship’s stop in Rostock, Germany. After the equipment arrived at the vessel’s location, the underwater operation started with a detailed survey of the affected propeller blades. The information acquired during the inspection was then used to calculate and determine the correct measurements needed to crop the blades. Next the divers cropped the blade tips. When the cropping was complete, the blades were smoothened.

The five-blade propeller of a 229 m bulk carrier had unfortunately suffered a similar fate. An identical repair was carried out by Hydrex diver/technicians in Dunkerque, France. The result of the operation was also the same - the propeller’s balance was restored, and the efficiency was brought back to optimum condition.

Underwater activities by SMS

Long-term partnerships, service agreements and an understanding of the ‘life-time value’ of customer relationships is at the heart of UK’s SMS Group’s growth and a recent investment in diving and sub-surface engineering. The SMS Group has an enviable reputation as specialists in shiprepair, marine engineering and major fabrication projects in the Commercial Marine, Defence, Cruise and Superyacht sectors.

The SMS Group, for many years, has supported its core customer base with diving and sub-surface engineering with equipment and Suitably Qualified and Experienced Personnel (SQEP) based in Dover, Kent. To improve response times and customer service the business has invested in new plant and equipment, and relocated legacy equipment, to create four new sub-surface ‘hubs’.

Led by John Webb and Danny Tolhurst the business has created four new Diving and Sub-Surface Engineering ‘Hubs’ at its existing marine engineering bases in Dover, Lowestoft, Portsmouth and Avonmouth, whilst simultaneously expanded its subcontract diving database of SQEP.

John Webb said, “The provision of support to core SMS customers around the Group is very, very important. To better look after our existing customers we’re proud and pleased to make this investment. It’s great news at the right time. Our service offering remains exactly the same.

“It includes pre-purchase surveys, hull inspections, underwater fitting and machinery, magnetic particle inspection (MPI) testing and Ultrasonic testing. “It also includes crack detection, planned and emergency diving support, Cathodic protection survey and renewal, in-water surveys, repairs and

installations, bespoke plant hire and heavy engineering equipment with barges, jack-ups, pontoons, safety and workboats.

“Propeller clearing, fouled running gear and underwater situation assessments, salvage and damage assessments, class extension inspections, utilities infrastructure, repair and maintenance, power stations, reservoirs and outflows, ROV deployment and ‘live’ data inspections as well as contaminated water diving.

“Services also include the provision of CSWIP accredited divers to 3.1 and 3.2 levels, and lock gate, dock gate and cofferdam manufacturing and installation. It’s a broad offering that is now supported by a larger geographical network. We’ve moved the diving offering from ‘local’ to ‘national’, and it’s been very well received by both new and existing customers.”

The SMS dive team has commercial, defence, in-shore and off-shore diving experience with specific quayside/ports and harbour marine civils capability.

ClassNK releases guidelines

ClassNK has released its ‘Guidelines for ROV/ AUV’ which summarise the performance and safety requirements for remotely operated underwater vehicles (ROVs) and autonomous underwater vehicles (AUVs) as part of its activities to meet industry needs related to the establishment of safety standards for innovative technologies and third-party certification.

Up until now, ROVs and AUVs have been mainly used for oceanographic surveys and offshore oil and gas field development, but in recent years their utilisation as a means for maintaining offshore wind power generation facilities and pipelines has been steadily increasing. Although the utilisation of ROVs and AUVs is increasing world-wide, no international standardisation of such technologies has yet been implemented, and the utilisation of ROVs and AUVs has, for the most part, been limited to certain fields.

With this in mind, in order to contribute to the safe and effective use of ROVs/AUVs, ClassNK developed the guidelines which establish requirements related to the equipment and basic items that are generally required for the operation of these vehicles, as well as precautions and safety measures, based on the knowledge obtained through demonstration experiments with experts and companies making advanced efforts.

The guidelines also explain related terms, classifications, and utilisation examples so that they can be used as introductory material on ROVs/AUVs. For implementing specific application cases of ROVs, they include the requirement for ROVs service suppliers as well as the procedures in using at ship surveys such as in-water surveys, internal hull surveys of flooded compartments, and damage verification. Appendices that contain excerpts of relevant rules and the results of demonstration experiments into the application of ROVs to ship surveys are also provided for supplementary purposes.

Recognising that the utilisation of ROVs/AUVs will be expanded in various fields, the society will gather the opinions and feedback of the industry and continue to update the guidelines in order to meet the needs for the safety standards development and third-party certification.

Change of personnel at Phoenix

US-based Phoenix International Holdings has announced the promotion of Troy Magness to Diving Operations Manager of the Louisiana location following the retirement of one of founding member Tom Bailey. In his new role, Troy will be responsible for overseeing offshore commercial diving activities and personnel including developing and managing project plans, scheduling, logistics, and tracking professional development, all the while ensuring that safety remains a top priority.

Prior to joining Phoenix, Troy’s 25+ year career began as a surface/saturation diver and he steadily progressed through the ranks from ROV Mechanical Technician/Shift Supervisor to Project Field Co-ordinator before moving into the office and Project Management in 2007. He has an Associate of Science in Marine Technology from the College of Oceaneering and served in the United States Navy as Radioman Third Class.

“For over two decades Tom Bailey has provided strong and principled leadership with a steadfast commitment to Phoenix’s core values of operational expertise for safe and practical underwater solutions,” stated Troy Tuner, Area Manager for Louisiana. “When Tom announced his plans to retire earlier this year, our successor planning process led us to Troy Magness who had joined Phoenix in 2019 as the HSE officer for our Bayou Vista, LA office. We were impressed by his deep understanding and wide breadth of experience in the commercial diving industry and felt confident that he would excel in this role and provide a seamless transition for our customers.”

Troy Magness