United Kingdom

Brookes Bell 

All ferrous metals are prone to rust, even stainless steel, especially in a marine environment. It can be delayed but not denied completely. If identified promptly and precisely, however, the cost of repairing the damage caused by corrosion can be mitigated.&nbsp;Galvanic, stray current, oxidation, wind borne rust – there are various types of corrosion that afflict metal yachts. Some are easy to spot; others can remain hidden until the vessel undergoes a major refit or special survey. They all cost time and money to remedy. And it’s not just a question of getting rid of unsightly but superficial iron oxide: extensive corrosion, pitting or grooving of load-bearing components can lead to buckling, cracking and other structural defects.<img src="https://photo-assets.superyachttimes.com/photo/315543/image/large-937f72cb3647036d04e307df99cec7ff.jpg" data-gid="gid://syiq/Photo/315543">The traditional method for identifying corrosion is with the naked eye, which usually involves dismantling equipment and stripping off surface treatments to reveal the bare metal underneath. Finding out how deep the corrosion has penetrated then involves bashing away at the steel with a hammer. Ultrasonic corrosion monitoring with high-frequency sound waves is a non-destructive screening method, but metal thickness is measured only at the point where the sensor is placed and surface treatments still have to be removed.Pulsed Eddy Current Array is a non-destructive electromagnetic inspection technology used for measuring metal thickness and detecting corrosion in ferrous materials typically hidden under coatings like teak, fairing compound and fire insulation. The technology allows large areas of metal substrates to be rapidly scanned with multiple probes that can penetrate up to 300mm to provide high-resolution imaging. Using dedicated software, the results are compiled as a plotted corrosion map onto a plan-view of the vessel.<img src="https://photo-assets.superyachttimes.com/photo/315547/image/large-214ca0a9fe800318d7a3398f7171fbc9.jpg" data-gid="gid://syiq/Photo/315547"><a data-gid="gid://syiq/Company/7690" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Brookes Bell (Company)">Brookes Bell</a>With a history stretching back over a century, <a data-gid="gid://syiq/Company/7690" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Brookes Bell (Company)">Brookes Bell</a> is a go-to firm for incident investigation, forensic analysis, technical dispute resolution and expert witness work in the maritime and energy industries. Working closely with the naval and commercial shipping sectors, its PECA analysis process is the only one of its kind formally approved by <a data-gid="gid://syiq/Company/1452" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Lloyd's Register (Company)">Lloyd’s Register</a>. Assisting the company in bringing the same service to the superyacht world is consultant Patrick Yeoward, an MCA 3000t master mariner with over 20 years’ experience of building, refitting and operating large yachts. &nbsp;“A lot of our focus is on the dispute resolution and forensics side and probably 80 percent of the business is commercial shipping,” he says. “But there's a big tie-in with services for superyachts and something we've been looking at over the last few years is how to become more proactive and less reactive by helping to stop things happening, rather than putting a hand up after it happens and say ‘Oh, you shouldn’t have done it like that’.”<img src="https://photo-assets.superyachttimes.com/photo/315546/image/large-0e2ab23c4e9c90c427a8e413f4ec80bf.jpg" data-gid="gid://syiq/Photo/315546">Asset integrity inspection is a time-sensitive activity: owners and their captains need to balance private or commercial use of the yacht with downtime for appropriate repair and maintenance. Because PECA works through insulation and cladding, the scope and frequency of inspections can be ramped up without increasing downtime. Corroded areas can also be identified before a yard period, which allows shipyards to prepare work schedules and order materials in advance. Moreover, knowing the location of generalised corrosion beforehand improves the efficiency of complimentary methods such as radiography and ultrasonic testing that can specifically target these areas. It offers a further advantage when surveying yachts for sale:“Two of my colleagues were just in the south of France to scan a yacht that was being sold,” says Arron Jackaman, principal inspection engineer at <a data-gid="gid://syiq/Company/7690" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Brookes Bell (Company)">Brookes Bell</a>. “Potential buyers want to understand the state of materials and so we performed an inspection and found minor patches of corrosion. We’ve done other inspections where corrosion was suspected, but it transpired the steelwork was in good condition. Either way, it means buyers have a better understanding of the condition of the asset.”<img src="https://photo-assets.superyachttimes.com/photo/315544/image/large-e9a8d1c9d9229f4778e5e47dd7302de7.jpg" data-gid="gid://syiq/Photo/315544">Predictive maintenance&nbsp;<a data-gid="gid://syiq/Company/7690" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Brookes Bell (Company)">Brookes Bell</a> has a contract with the Royal Navy to inspect its Type 23 Frigates to create a baseline or snapshot of material state year on year in areas known to be prone to corrosion. Using its own powerful analytical reporting and modelling software tool called CMAP Marine, the resulting data can be overlaid one on top of the other to create models of how the corrosion progresses over time.“Predictive rather than reactive maintenance is key,” continues Jackaman. “But the complex electromagnetic data gathered from a PECA analysis is only useful or valuable if it can be correctly interpreted. It would certainly be difficult to relate the raw data to the actual vessel without the right visualisation tools. In fact, <a data-gid="gid://syiq/Company/1452" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Lloyd's Register (Company)">Lloyds</a> were very clear that our accreditation is not solely based on the PECA technology, but also on how our CMAP software makes the data easily legible for clients.”<img src="https://photo-assets.superyachttimes.com/photo/315548/image/large-57b1f6721bd0bbf6f95ea4ad5841c850.jpg" data-gid="gid://syiq/Photo/315548">Modelled on <a data-gid="gid://syiq/Company/7690" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Brookes Bell (Company)">Brookes Bell</a>’s 3D data visualisation software, CMAP basically highlights the condition of the remaining steel thickness and material loss in percentage terms. For ease of reference, a colour bar displays sound metal as dark blue and increasing material wastage is indicated as the colours progress through the spectrum to bright red. This provides an intuitive overview of the areas that may require renewal or ongoing monitoring. It doesn't take any special training to understand that red is an issue, but by providing understandable data in a legible format, CMAP allows yacht owners and operators to make better, quicker and more informed decisions.“We’ve spent a number of years honing our own analysis,” adds Jackaman, “because there are several things that can cause signals that look like corrosion but aren't necessarily. Seam welds, internal structures, cable trunking, aluminium scuppers, and many other features, can appear as corrosion. We routinely recognise false positives, which is just as important as identifying corrosion.” <img src="https://photo-assets.superyachttimes.com/photo/315542/image/large-a6d12f1695808a78cf716fc0e332b07a.png" data-gid="gid://syiq/Photo/315542">How PECA worksPulsed eddy current equipment has been successfully applied for the detection and sizing of corrosion under insulation (CUI) for several years. A pulsed eddy current technique uses a stepped or pulsed input signal for greater penetration depth and relative insensibility to variations in coating thickness, or what is termed ‘lift-off’. Unlike ultrasonic thickness testing, no direct surface contact between the probe and the object is necessary.PECA employs multiple elements in a sensory array for much faster scanning times. Intended for the rapid inspection of simple geometries in horizontal and vertical planes such as steel hull, deck and bulkhead plating, it is also suitable for steel pipework that may be encapsulated in fireproofing. Even complex shapes like bends in pipes can be inspected and it can be used in conjunction with other screening techniques if required. <img src="https://photo-assets.superyachttimes.com/photo/315545/image/large-1fda9912a3476b5a49f3c61789f40415.jpg" data-gid="gid://syiq/Photo/315545">The rules prescribing corrosion margins and deviations from the design values vary depending on the type of vessel and the Class Society, but the degree of “allowable material diminution” due to corrosion is generally between 10-30 percent (corrosion rates are expressed in terms of mm per year of surface wastage and are used to provide a corrosion allowance in the original thickness of the material).<ul><li>The areas to be analysed are mapped out into scan zones, either by individual plate sections or broken down into specific zones to tackle the various geometries aboard a vessel.</li><li>PECA probes scan the assigned sections or zone. The resulting data is integrated into a 3D file as a mesh layer to produce a model or digital twin called a CMAP and create a visual representation of the scan, highlighting areas of concern.</li><li>Each plate or zone is also given its own report sheet for further analysis. This provides a clear overview of the condition of each plate or zone, identifying areas that need to be repaired, replaced or carefully monitored. &nbsp;</li></ul>The final stage of the CMAP service involves the creation of a tabular report of each plate or zone. This sets out the physical characteristics of each location, illustrating the average remaining wall thickness, material loss and maximum wall loss values.<img src="https://photo-assets.superyachttimes.com/photo/311269/image/large-31c9223451adf520cb160ea88063b572.jpg" data-gid="gid://syiq/Photo/311269">Case studyIn the recent case of a 50-metre motor yacht scanned during a pre-sale inspection, <a data-gid="gid://syiq/Company/7690" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Brookes Bell (Company)">Brookes Bell</a> analysed the side decks and main deck fore and aft, equating to some 110 square metres, at a cost of around €15,000. Some patches of corrosion were found and 0.6 square metres of steel structure were earmarked for replacement. &nbsp;&nbsp;“When I first spoke with the Captain he was very worried because they’d already had to replace steel about a year-and-a-half ago and were starting to see signs of water ingress,” says Patrick Yeoward. “They were talking about ripping all the teak decking up and starting over again, which would have been massively more expensive in comparison.”<img src="https://photo-assets.superyachttimes.com/photo/311268/image/large-b9e138ad2e12e385e407d4e4a4687637.jpg" data-gid="gid://syiq/Photo/311268">The small area of steel and corresponding teak were eventually replaced by <a data-gid="gid://syiq/Company/5172" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Cantiere Rossini (Company)">Cantiere Rossini</a> in Pesaro, Italy, at a cost of less than €10,000 – a figure that doesn’t compare with the cost &nbsp;of replacing all 110 square metres of teak decking estimated at upwards of €220,000.“Critically, PECA allowed us to limit the scope of work to the deck areas that really needed attention without having to first remove the teak to assess the condition of the steel,” says Alfonso Postorino, shipyard director at <a data-gid="gid://syiq/Company/5172" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Cantiere Rossini (Company)">Cantiere Rossini</a>. “In these cases the precision of the measurement is of the utmost importance - just a few millimetres can make all the difference.”

Rust never sleeps: The tech that is changing the face of rust management

We take a look how Brookes Bell is using technology to help repair and mitigate the damage caused to yachts by rust corrosion. 