WORKING WITH RENEWABLES

Wind Turbine Bolt Failures

Bolt failures on wind turbines can be catastrophic, ranging from the separation of components such as rotors and blades from the structure to the total collapse of the tower. Although such accidents rarely result in human injury because of their relative isolation, the costs of replacement or repair can be extremely high - and every such failure requires investigation which may mean shutdowns and other interruptions to supply.

In most circumstances, turbine towers are constructed with a circular flange at the base which are secured by means of a series of threaded bolts that are embedded in heavy concrete foundations. Once the tower is lowered into place and levelled, nuts are screwed down on to the flange to prevent any movement.

In some cases, the entire flange, all the bolts and the nuts are then encased in a protective grout, in other cases the bolts and nuts are left exposed to allow for testing and visual inspection. Where grout is used, any problems with security of the bolts is completely hidden from view and failures in the bolts may not be identified until too late. In recent years in the UK there have been a number of tower collapses from incorrect installations and poor quality grout which have caused the bolts to fail.

Exposed nuts and bolts, as in the case study illustrated below, are vulnerable to the effects of weather and the environment but, as long as they are regularly inspected and some form of protection is applied, they can be safely maintained for many years without any risk of failure. Nevertheless, constant vigilance is required and, although a number of solutions exist for bolt protection on wind turbine foundations, none has met all the necessary criteria for long-term protection without constant remedial action. Recently both in the UK and the USA, we have been looking at ways that Enviropeel might provide an effective system for such bolt protection.

A close look at the base bolts shows how much corrosion can affect them

APPLICATION CASE STUDY

The photographs show an application in the US. Prior to application the bolts can be seen to have significant corrosion on the threads and there is a variation in bolt length which makes it difficult to apply a 'one size fits all' solution such as bolt caps. Because Enviropeel is spray applied, any variation in length or shape of substrate can easily be accommodated, so application to the bolts is very simply accomplished.

As most readers will be aware, application of Enviropeel not only provides a barrier to the effects of the environment - preventing moisture getting on to the substrate - but, through its continuous release of inhibitors, it also provides active protection against galvanic and other forms of corrosion which are endemic in bolted systems.

For this application the Enviropeel USA crew used the US-designed and built MA25, a larger capacity variant of the original MA10 workshop unit. Although heavier than the MA10, the MA25 is still easy to manoeuvre and can easily be moved around a work site. The image shows the operator recirculating the material from the application gun into the tank while adjusting for the perfect flow pattern.

The next image shows the Enviropeel being applied to the bolts. Using a standard two-coat system, the material is flowed on to the bolts forming a perfectly-fitting barrier against deterioration. Following application, excess material around the bases is trimmed and all waste material is returned to the application unit for re-use.

Following the application, all the bolts are fully protected from the effects of corrosion while, at the same time, they remain easily accessible for inspection or adjustment.

A short video of the application can be viewed by clicking this link

A CLOSER LOOK AT RISER CLAMP PROTECTION

So ... what are the problems?

Risers are the pipes that are used for the production, drilling and export of oil and gas from the seabed. They are a key component for the offshore industry and maintaining their functionality is central to the success of the production system.

On a platform, the risers have to be secured to the structure using clamps and, while there are many sizes, shapes and designs for the clamps, they share common principals and suffer from similar problems, no matter where they are found.

Steel clamps are especially vulnerable to corrosion because of the way they are constructed and deployed. Usually made up from two halves, one of which is connected to the platform by a stub piece, they are hinged and/or bolted together around the riser to hold it in position, as you can see in the picture on the right. Surrounded, as this clamp is, by significant signs of corrosion, it is easy to understand how the bolts and fixings holding the clamp together must be suffering from the effects of this extreme environment.

The second picture shows some disassembled clamp components. Nothing could be clearer from these pictures than the evidence of corrosion around the bolt holes and clamp faces. The main body of the clamp is able to withstand the marine environment but the cavities around the bolts and clamp faces create a perfect micro-climate for the creation of corrosion and, with the galvanic effects on the bolts and nuts, serious deterioration of the clamp is depressingly inevitable.

But ... we have a solution!

As you know, we have been working on a solution for corrosion problems in riser clamps for some time and we have spoken about the development of an integrated system in earlier blog entries. Now, with imminent mobilisation plans for riser-clamp applications on behalf of major international companies - and a patent pending on the overall system - it's time to talk more detail on a system that we believe has the potential to revolutionise riser clamp protection.

Strength and adaptability

Enviropeel's great strengths have always been in the corrosion-inhibiting quality of the material and its universal applicability. By moulding itself to any substrate, no matter how complex or bizarre in shape, it has been able to bring active protection to the most inaccessible structures in a way that has never previously been possible. Integrating these qualities into a system that can withstand the rigours of the most hostile marine environments, such as those faced by large offshore riser clamps, has been a long-term objective that has finally been achieved.

The system involves three potential stages with different levels of implementation tailored to match the specific needs of the structure to be protected. At the heart lies Enviropeel and its unequalled protection but, with the addition of a tough self-amalgamating outer wrap, it is now possible to withstand splash zone conditions and even submersion. With the potential for a final coat of marine-growth inhibiting, colour-matched epoxy, the system offers the most comprehensive protection ever provided by the A&E Group.

How the system works

Taking a fairly typical clamp as an example, the illustrations take us through the various procedures. The red arrows indicate the most vulnerable areas of the clamp: voids, exposed bolt threads and fixings. The green arrows indicate the application stages.

First, exposed bolt threads and voids are coated and filled, followed by application to the bolt ends using spray and casting techniques as necessary.

Once the voids are filled and the bolt ends given their initial protection, a first coat of Enviropeel is applied around the joint area and across the first half of one side of the clamp. Then, proceeding around the clamp, all four quarters of the clamp are fully coated.

Once the first full coat is completed a second coat is applied in the same manner around the entire clamp. The second coat is stepped in to allow application of the wrapping system.

Finished topside application

The first of the detail pictures on the left shows the step between the two coats.

Following the application of Enviropeel a sealing wrap is applied on the pipe up to the stepped edge of the Enviropeel. This is followed by a second wrap application that takes in both the first wrap on the pipe and the stepped edge of Enviropeel. For most topside applications, this is all that is required to provide long-term preservation of the entire clamp.


Splash-zone/sub-sea applications

For complete ingress and impact protection, a full wrap is recommended. Following the stages outlined above, the bolted areas are individually wrapped, followed by a total wrap of the entire clamp. The wrapping tape is self-amalgamating and moisture-cured. Once the curing process has completed, a coat of Alocit, colour-matched to the riser structure can be applied forming a final impenetrable barrier on a system designed to protect the clamp for many years. 
Large clamps in the splash zone

For large clamps with complex bolt and hinging systems, the most appropriate protection may not be to encapsulate the entire clamp. As previously noted, the areas most likely to be seriously affected by corrosion are the hinge and bolt areas. With clamps that may be one or two metres high, with numerous very large bolts/studs and nuts, the most appropriate and cost-effective approach may be to encapsulate the bolt section, as shown in the pictures on the right.

For large clamps it may be necessary only to protect
the  vulnerable bolted areas

Protecting the bolt area

Following a similar procedure to those previously outlined, the exposed studs are flooded with Enviropeel between the clamp faces and all the studs and nuts are coated. A coating of Enviropeel is then applied across the bolt area, followed by a wrap coat. As with the whole-system application, the wrap coat can be epoxy coated to provide the final finish.

Anti-fouling option

For areas suffering from marine growth, the final epoxy coat may include an anti-fouling (AF) option. Recently approved by the Royal Navy in the UK, Alocit AF has proved to be extremely effective in reducing marine fouling and, like other Alocit products, can be applied to wet and submerged surfaces.

Meet us in Kuala Lumpur next month ...

You know what exhibitionists we are, so you won't be surprised to learn that we are at it again ... this time in one of our favourite places ...KL!

Hall 10, Booth 10013 ... see you there!

The 15th Asian Oil, Gas & Petrochemical Engineering Exhibition will be held from 2 - 4 June, 2015 at the Kuala Lumpur Convention Centre. It is the biggest and most comprehensive event in the Asian region, with oil and gas industry exhibitors from around the world.

We hope that everyone in the area will come and see us ... you can find us on Booth 10013 in Hall 10. If you have any specific requests or questions about attending the event, please contact Sean Ong ... he would be glad to help in any way he can.

BREAKING NEW GROUND

Getting a new product into the market can be harder than it should be ...

Once upon a time in a land down under, as part of the Australian Corrosion Association's annual conference, our Perth manager gave a talk on introducing new technologies. 

Enviropeel was relatively new, and the paper focussed on the various different ways that a new genre of product, such as corrosion-inhibiting sprayable thermoplastics, could win the trust of notoriously sceptical corrosion and coating engineers. Ten years later, there are still people who do not understand how Enviropeel works ... they may have heard of it ... but some still don't get it.

At least, with an epoxy like Alocit, engineers can recognise a coating when they see one. Why anyone would need to apply underwater may be a mystery to the uninitiated ... but a coating that is applied in a traditional way using traditional methodologies is part of their known universe. And, of course, Alocit can be tested for hardness, abrasion resistance, adhesion and all the other tests engineers know and love ... not so with Enviropeel.

The only meaningful test that Alocit and Enviropeel have in common is the test of time ... but you won't find this in the ASTM catalogue, despite the fact that it is the only test that has any real importance.

Back in Australia, the talk came to the conclusion that the best way to convince the sceptics was to show them, through a combination of case studies, trials and appropriate testing ... a lot of which is summarised on our website. The case for effectiveness has been more than adequately demonstrated but, as part of the process, it has also been necessary to develop testing methodologies that reflect the unusual properties and strengths of Enviropeel. 

Last year, after years of gathering data, another A&E manager was in Beijing delivering a paper to NACE in China about Enviropeel on this very subject. More recently, I was discussing some of the data with a colleague and he suggested we make the paper available to our readers. Obviously, this was a good idea ... so here is a link to view it.

Sorry it has taken me so long to share it with you!

HANDS ON - AND LOVING IT

They say that a little knowledge is a dangerous thing ... and every so often a customer, new to Enviropeel or Alocit, will read something or hear something out of context and come to impossible conclusions about what we can or can't do. 

It would be great if we could ...

Sometimes it's our fault. Even though both products protect against corrosion, they have very different properties so, when we are at a show for example, a casual visitor will see a picture or video of Alocit being applied underwater, read about Enviropeel ... and then ask us how we spray Enviropeel underwater. Which, unfortunately, is against the laws of physics ... but it would be great if we could. Nevertheless, the most outlandish suggestions may contain a kernel of sense. OK, so we still can't apply Enviropeel underwater but, until recently, we also would tell people that Enviropeel was unsuitable for immersive service ... now we have a system that allows us to protect using Enviropeel underwater.

Testing the wrap system
on the back lot pipe rack

And the reason for this is that, when a suggestion is made, we don't dismiss it out of hand. If there is a good reason to do something, just because we can't do it today doesn't mean it will be impossible tomorrow. The potential to be able to do new things is part of what motivated the original development of Enviropeel and it continues to drive us every day.

Yes, you can ...

This can just be a day-to-day thing like the pipe rack which is set up on the back lot of our HQ. Here, simple suggestions are tried out ... 'can you paint Enviropeel?' Well, it turns out, yes you can but, at this point in time, we are not sure why you would want to.

'What happens when Enviropeel has water pouring over it for long periods of time?' You've seen the answer to that question (Blog 3-12-14) or, if you haven't, you should check it out. In a nutshell, the answer is nothing, it doesn't matter how much water pours over Enviropeel ... it just keeps on working.

Anyway, you get the point, some things are easy to test and having a permanent test bed is really useful ... but not every suggestion is quite so easy to assess.


Test facilities

There are certified labs all over the world with the ability to test products against almost anything. Usually this will be against a specific standard set by organisations such as ASTM or ISO in order to test a specific quality such as resistance to UV. In most cases this would involve a small test plate and a relatively short accelerated test for extrapolation into real-world predictions.

The hot salt fog cabinet at Group HQ is
capable of accepting large and complex test pieces

Different wrap techniques
were assessed to maximise
strength and flexibility

Nothing wrong with that but, if you are dealing with complex structures and complicated ideas, it can be very hard to set the correct parameters ... and paying for long-term testing just to see if something works can be an expensive business. So, as you may be aware, we have installed equipment at our HQ more suited to a test lab than a work shop but it allows us to just make things up and see what happens in real time. It's the best possible way to try things out.

Riser Clamp

I mentioned the Riser Clamp in our last post, but is an interesting insight into our approach to see how we arrived at a solution. When approached by Maersk, we had already completed testing of a range of wrapping materials as part of our development of a submersible Enviropeel system. Working together with our colleagues at Enviropeel USA, as a result of early trials for offshore wind generators in the UK, we arrived at a great solution that gave us just what we needed.

Large complete test pieces could
be tested in the salt cabinet

With this in mind, our Technical Director ... a real 'hands on' engineer who enjoys making things ... decided to have 1/3rd scale models of the clamps created to test different ways of protecting them. The fact that we had a very large salt-spray cabinet in which the models could be tested made a huge difference. Monitored in real time, it soon became apparent what was working ... and what was not.

Several methodologies were tested, different wraps, wrap patterns and top coats as well as adapting spray techniques to meet the requirements of the outer layer - all manufactured and tested without leaving the HQ building.

Any questions?

So, if you need to know whether or not we can make Enviropeel glow in the dark (actually, we can) or apply Alocit  with a toothbrush (probably not a good idea), then let us know ... we may not have a solution ... but we will enjoy trying to find one.

Click this link for more information on A&E testing facilities

MEETING OF THE MINDS

Kuala Lumpur is a great place for a visit, full of colour and vitality, it provides a vibrant backdrop for every possible activity - it even makes an AGM seem worthwhile!

KL puts on a spectacular welcome for A&E delegates

So, at A&E we are lucky that our group HQ is only an hour from the centre of KL and that those of us (i.e. me) who live in less tropical environs may sometimes get the chance for a warm up - even if it does mean quite a bit of talking shop. 

Earlier this month, managers from the UK, Australia and Malaysia were in KL to learn about two exciting new application developments and to discuss a range of future projects that are being planned, including product research and development.

We are a small team with a wide range of backgrounds and, as we work in very different environments, we get presented with an equally wide range of challenges. Meeting face-to-face really accelerates the problem-solving process, especially in KL where the facilities allow us to immediately test our ideas in practice or see first hand how suggestions are turned into practical solutions (see next blog).

THE A&E TOTEM POLE?

We were all surprised, on our arrival, to see that a totem pole had been erected outside the office entrance, apparently dressed in the yellow jersey and blue shorts of the Brazilian soccer team. It turned out that it was a test bed for a new riser-clamp protection system that had been temporarily moved outside for us to view more closely ... but it certainly added an artistic touch to the entrance while it was there.

NEW DEVELOPMENTS

Naturally, once we were all gathered together in the conference room, there was considerably more discussion about the riser clamp. The test bed demonstrates a completely integrated system, based around the anti-corrosion properties of Enviropeel but incorporating a partial or complete wrap sealing system, that has been extensively tested both for topside and splash-zone application. Developed specifically in response to a request from Maersk, the system can even be supplied with an anti-fouling coating, making it the most complete tailor-made system that A&E has ever offered. 

Testing and system details are available on request from tech@ae-sys.com.

Other new developments were discussed, one of which is set to revolutionise the Group's ability to offer underwater protection in areas where marine growth is a problem. Not quite ready for general release at the time of writing, information on this new system should be available in the next few weeks.

OTHER UNDERWATER NEWS

Talking, as we have been, of the tropics and underwater, I am glad to report that the Alocit and Enviropeel experimental fish team are thriving in the office gallery tank. You may remember the video from November 2013, you will be happy to know that all participants are still working on their escape plan.

ALOCIT TO THE RESCUE ... AGAIN

Repairing damaged SBM paintwork underwater for Hyundai

Hyundai is building an oil refinery in Musandam, Oman. An SBM* anchored offshore as part of the project had suffered significant damage to subsea paintwork and a repair was necessary to prevent further damage from corrosion. As there were no local facilities where the SBM could be dry-docked for repair, Alocit was recommended as a cost-effective solution to the problem.

In order to satisfy themselves that such a repair was viable, Hyundai undertook a series of tests. First, the principals were demonstrated to them on site by Sean Ong from our Malaysian HQ using plates prepared using the SBM coating system with areas masked off to allow corrosion with paint edges beside the exposed area chipped away to simulate the damage to the SBM. 

Using water that was specially collected from the harbour, the samples were submerged and prepared for coating using hand tools. A two-coat system of Alocit Tropical was applied to the plates while they were in the water and then left to cure.

Pleased with the onshore test results, Hyundai commissioned a trial application on the damaged area and arranged for it to be filmed. After curing, tests on the trial application showed that the repair had been successful and the Alocit system was adopted for the restoration of the entire damaged area.

A short edited version of the film of the trial application is available for viewing if you click this link.

* An SBM is a single-buoy mooring. These are specially-designed offshore storage tanks, usually connected by pipeline to the shore, that allow deep-draft tankers to offload their cargo without entering shallow waters. 

Alocit has a long history of application to structures of this type, a case history showing complete refurbishment of an SBM using Alocit is available for viewing by following this link.