Safety is key

Danny Constantinis, EM&I Group, Malta, outlines how remote based inspections can contribute to efficient tank inspection, maintenance, and cleaning.

Safety in confined spaces has been a problem in the industry for many years and a number of fatalities and injuries have occurred.

Robotic alternatives are now available, so it is not necessary to put personnel at risk working in hazardous areas, at height, or in confined spaces. The legal, financial, and reputational risks of fatalities in confined spaces can cause serious problems for companies if they have not considered alternative methods that are safer, such as robots or remote methods of inspection, maintenance, and cleaning, etc.

Professor Andrew Woods of the BP Institute at Cambridge University recently carried out a study of fatalities in confined spaces, which revealed that many senior managers are unaware of the safety levels required by regulators – usually one in a million or ALARP (as low as reasonably practicable).1

His research has revealed that most companies are operating below the broadly accepted levels of safety with consequent concerns on reputation, costs, and legal challenges if senior managers knowingly allow work to be carried out when safer methods are available at reasonable cost.

In 2020, HM Treasury in the UK assessed that the cost of an incident resulting in a fatality might be in the order of £2 million (~US$2.75 million).2 The ALARP principle, and regulatory guidance, suggests that expenditure to mitigate the risk should be in ‘gross disproportion’ to the cost of an incident, may be up to 10 times the cost.

Table 1. Risk-based inspection methodology

What and where to inspect? When to inspect? How to inspect?

Determine inspection scope: risk-based prioritisation of components and damage mechanisms of concern Determine inspection interval Determine appropriate inspection methods

Figure 1. Typical FPSO tank.

Figure 2. Typical manned entry.

As far as floating production assets are concerned, nearshore or jetty moored assets are much easier to inspect than offshore, where different rules apply. With the current rush to install floating storage regasification units (FSRUs) around European coasts, many will probably end up in offshore or deepwater moorings.

The Classification Societies will almost certainly apply similar rules to those applying to FPSOs, drillships, and semi-submersibles.

Also, as far as LNG and hydrogen is concerned, cryogenic storage presents additional challenges in the ‘warming up’ and ‘cooling down’ of assets to minimise out-of-service periods. Robotic methods of inspection can be carried out at temperatures much lower than manned entry methods so tanks can be back in service sooner.

FSRUs usually have very large tanks so manned methods of inspection are difficult when it comes to coping with high level inspections, which would normally require scaffolding on very delicate tank linings. Most of the ‘sloshing’ damage of the liquid LNG or hydrogen occurs at mid-high level in the tanks so this is important.

Remote methods use tripods and telescopic masts with cameras lowered through tank openings to achieve the same objective and are much safer and faster. Out of service periods can be very costly, so the sooner that tanks can be back in service, the better.

EM&I has led a number of joint industry projects (JIPs) including hull inspection techniques and strategy (HITS) on behalf of the Global FPSO Research Forum, together with ‘FloGas’ and ‘FloWind’ for floating gas and wind assets. This keeps the company in touch with all the main stakeholders in each market sector so that all of the innovations are ‘industry driven’ and what owners and operators want. This has worked well in the FPSO industry where the HITS JIP has been operating successfully for eight years.

The ODIN® diverless UWILD (Under Water Inspection in Lieu of Drydocking) was one of the first innovations to come out of the HITS JIP, quickly followed by the NoMan® remote camera and synchronous laser scanning technologies. These have already been successfully used on many offshore projects.

The ODIN technology allows examination of the hull, propellor, rudder, bilge keels, sea chest inlets, and mooring chains, etc., using integrity Class ROVs. It is also possible to examine critical valves in operation from within the hull while the asset is on hire, on station, and in use, thus eliminating any out of service periods.

The valves can be inspected using patented ODIN access ports installed adjacent to the valves, so that specialised cameras on manipulators can be inserted through the access ports to examine the valves in operation. If any anomalies are detected, remote methods of isolation can be used to allow repair or replacement of faulty valves.

A number of associated technologies have also been developed to check pressure systems and electrical items safely, quickly, and economically. The ANALYSETM pressure system technology significantly reduces the

number of ultrasonic thickness measurements (UTMs) that need to be taken on piping and pressure vessels to ensure safe operation.

Electrical items can be checked easily and simply using the patented ExPertTM technology, which can ‘see through’ the junction boxes using specialised scanners to detect any anomalies, instead of having to isolate the circuit so that the electrical items concerned can be dismantled for inspection and then reassembled. This can often result in damage to the electrical components during dismantling and reassembly, so a less intrusive method is desirable.

Other technologies for extending the life of offshore assets include the diverless HullGuard® anode technology, which allows for cylindrical anodes to be inserted through Class approved access ports in the hull and then connected to an impressed current cathodic protection (ICCP) system.

Remote tank cleaning

It has become increasingly clear that, whilst remote tank inspection techniques are now developing apace, present and future techniques employ line-of-sight, that is to say that they need a clear line of sight to the structure under survey. Therefore, the success of such remote inspection techniques (RITs) is heavily dependent upon the extent to which such lines-of-sight are achievable. Risk-based inspection (RBI) is now a Class-accepted methodology for carrying out Class surveys on floating units. The methodology is described succinctly in Table 1. It is apparent that the scope, ergo the extent, of inspection is related to the method of inspection proposed.

To date, the predominant inspection strategy has been the continuous hull survey cycle permitted by the Class Societies’ rules, whereby the prescriptive Class inspection requirements are applied i.e., general visual inspection (GVI) of an entire tank, close visual inspection (CVI) of a defined portion of the tank, and UTM of the defined structure within the tank. Up until very recently, RITs were unable to demonstrably carry out UTM to an acceptable Class standard. They have also been limited in performing GVI and CVI by the level of cleanliness in the tank. Of note, however, is that this is not from a failing in their functionality (unless their line-of-sight requirement is considered to be their failing and not one attributable to lack of cleaning). Instead, this is due to a lack of appreciation during the evaluation phase of the RBI strategy development. Because of these issues, RITs have not demonstrated effectively their ability to satisfy the inspection requirements of the continuous hull survey strategy under which they are being deployed. As a result, the benefits of remote inspection, which include significant safety benefits, have yet to be fully appreciated by operators and Class alike; in effect, we have been trying to fit the square peg of modern RIT methods into the round hole of traditional prescriptive inspections.

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Figure 3. A NoMan camera on a carbon fibre pole for high level inspections

Figure 4. Typical FSRU tank.

Figure 5. A NoMan camera can pan, tilt, and zoom. With the increased uptake of RBI for hull structure, there is an opportunity for remote inspection to be shown to be commercially beneficial and much safer.

Whilst the stages to develop a RBI strategy are now well understood by floating unit operators, there can often be a misunderstanding by operators at the outset regarding the objective of adopting a RBI strategy. Since Class compliance can be achieved using the aforementioned continuous hull survey cycle, where 20% of tanks are inspected annually so that all tanks are inspected over a five-year survey cycle, one must ask what the benefits are believed to be for operators who wish to adopt a RBI strategy when the sought-after result must surely be the same i.e., Class compliance.

Operators generally perceive the benefits of adopting a RBI strategy to be some, or all, of the following: n Reduced operational interference. n Reduced production interference. n Greater intervals between inspections. n Lower number of inspections based on comparable tanks. n Reduced extent of inspections. n Quicker inspections.

Remote inspection can play a significant role in achieving these benefits, particularly. What operators sometimes fail to appreciate is that the inspection findings will incur the same responses from their Class Society as if the findings were to be obtained from a traditional inspection by man-entry.

These responses may entail immediate repair, further inspection e.g., non-destructive testing (NDT), or increased inspection e.g., annual inspection. Such responses are not failings of the RBI or RIT, these are simply the consequences of inspection.

It is easy to denounce a remote inspection technique, for example because the tank subsequently requires manned entry. However, assuming the correct RIT and scope has been used, manned entry might be required to carry out remedial work (nothing to do with the RIT), or to carry out additional or confirmatory inspections (which are likely to incur less time in the confined space than carrying out the full traditional scope). It may also be simply the case that it was not understood that manned entry might be an outcome.

Of course, the response may also be one of acceptance by Class, resulting in no further intervention and time, safety, and cost savings that are attributable to the RIT. The advantage of developing an RBI strategy is that some of these potential outcomes are identified during the evaluation phase, their risk can be quantified and, if necessary, mitigated during the asset’s design or conversion, or during the RBI implementation phase.

So, what is the objective of adopting a RBI strategy? The answer is not Class compliance but survey compliance, where the potential outcomes from the survey have been risk assessed as part of the process and either mitigated or deemed acceptable. Therefore, it is clear that the adoption of any RIT actually needs to be driven by the inspection strategy.