CNC Onsite’s Innovative Yaw Ring Repair Method

Søren Kellenberger, sales director at CNC Onsite, joins the Uptime Spotlight to discuss their uptower yaw ring repair method. He describes the root causes of yaw ring failure, makes projections for the future, and introduces CNC Onsite’s patented yaw ring repair solution. Their portable precision machine can be lifted uptower to replace a damaged yaw ring, potentially saving operators significant downtime and repair costs.

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Allen Hall: When wind turbine yaw gears fail, operators face a costly choice. Hire a crane for a complete replacement or attempt a risky repair. This week we speak with Søren Kellenberger, sales director and partner at CNC Onsite. CNC Onsite brings precision machining up tower. Making yaw gear repairs faster and more reliable without using an expensive frame.

Welcome to Uptime Spotlight. Shining light on wind energy’s brightest innovators. This is the Progress Powering Tomorrow.

Allen Hall: Søren, welcome to the show. Thank you very much, Allen. And thank you for inviting me. Well, we want to understand first, what is causing yaw gear to break? teeth to be damaged in some of these turbines, because the photos I have seen are remarkable. The teeth are just gone. How does that happen?

Søren Kellenberger: I think there can be a number or there can be a number of reasons.

And it, it depends a little bit, I think, on the turbine, how the yaw ring was designed and stuff like that. But if you look at some of the older turbines the yaw ring. Wasn’t hardened. So there, in many cases, you’ll just see wear and tear from years of of use, operation. And typically in a, in a wind farm, you have a dominating wind direction, right?

So, Especially in Denmark, it’s mainly blowing from the west. So all our wind turbines are pointing that direction most of the time, which means that they are yawing within a limited area of of the yaw ring. So a limited area is taking the majority of, of the wear cycles. So, so therefore they, you, you see some, some local wear and tear and, and finally they will be worn down razor sharp basically and, and break off eventually.

So, so that can be, be just one cause of, of the, of the failure. We also see sometimes that even though they are hardened, they, of course, they don’t wear that much, but they will more break off and probably. Due to some extreme loading and I guess that can be caused by either some, some misaligned yaw gear it can be extreme loads.

You have some sites where you have Really wind directions changing very fast that is causing unforeseen loads on the turbine. So you have actual extreme loads that are, that are higher than the design loads. You could probably also sometimes see foreign objects that are, are falling into the, to the ying and being squeezed between the ying and your gear, causing some, some damages.

So. There are a number of, of different reasons for, for these damages, I guess.

Joel Saxum: Do you see anything environmental? Like in my mind, I think of these Arctic turbines, right? The ones that are operating in this, in the extreme cold. When, when metal gets cold, it gets brittle. Do you see more, more yaw teeth get damaged in those territories as others, or is it just kind of across the board the same?

Søren Kellenberger: No. We haven’t seen that, that these cold condition turbines are affected more than than others, but we do see that the weather conditions play a significant role. And. If you have maybe your ring damages on two to 5 percent of, of, of your turbine fleet, then they will not be evenly distributed across your different parks.

It tend to be that if you have an effective park due to some special weather conditions in that area, you seem to have a lot of problems in that one park, and you can have other parks that will run perfectly fine for, for your the entire lifetime without any issues on, on the yaw ring. Well, at least these inspections aren’t super difficult.

Yeah, it’s pretty obvious when they are missing.

Allen Hall: What’s the effect when they’re missing teeth like that? Is it, is, is the turbine just not able to yaw anymore or is it, it really, it risks some structural overloading when that happens?

Søren Kellenberger: Yeah. I mean, in in the beginning, I guess you, you won’t be able to, to yaw.

So at least you, you, it would be less accurate if you have. where it will start being less accurate. And that will of course cause some loss production. Potentially if, if you are misaligned on your, your system, you’re also introducing unwanted loads to your, to your turbine. So I guess it could have also other consequences when you are other than.

Just lost production when, when you have a yaw misalignment. But yeah, in, in the end you won’t be able to to yaw the turbine if you have too many damaged teeth.

Allen Hall: So is the turbine sent out an alarm when that happens? Is it just a, a complete shutdown? The turbine just says no more. I can’t move and I’m stopped or it doesn’t recognize that this is even a failure.

To be

Søren Kellenberger: honest, Alan, I’m not 100 percent sure. And I think it depends also on, on on the turbine how, how, how new or old they are and how advanced their control systems and condition monitoring systems are. Some of them, they just have on off on the, on the yaw gears. And, and they won’t recognize that, that one yaw gear is just spinning in free air but you can have others that have more advanced control systems where, where you can see that some of the yaw gears are suddenly using a lot more power to to yaw the turbine, which will indicate you have some kind of yaw issue.

If it’s a bad yaw. A broken yaw gear or if it’s some teeth missing in that area where that yaw gear is placed you, you can’t probably tell, but, but there are different warning systems possibilities, but again, depending on how old or how advanced your, your turbine is.

Allen Hall: Wow. So this is really serious.

It’s just beyond just the tooth missing. The consequences for the chairman can be quite dramatic. Now, CNC on site, obviously, is all about doing machining. How do you go about fixing this problem?

Søren Kellenberger: Basically, we have a a smaller CNC controlled, three axis CNC controlled machine that we bring up tower and these machines are adapted to the different different requirements.

Turbine types. As you can imagine, the turbines were not designed for these kinds of repairs. So the design engineers originally didn’t leave much space for for a machine in those areas. But so, so we, we customize the machines to fit the different turbine platforms and, and. Basically we use the internal crane of of the turbine to hoist the, the machine components to, to the turbine.

Use the internal crane to, to position it at the yar ring. And then we mount the machine on, on the Yar ring itself. Which also gives us the advantage that even if the turbine is moving a little bit due to, to wind we are moving along with it. So it doesn’t influence our our accuracy when, when machining.

Allen Hall: That’s quite impressive. Cause the alternative is, and what I’ve seen is you lift the whole, you take the blade set off and then you lift the whole in the cell off and then you go in, you try to replace the yaw gear, which is super expensive.

Søren Kellenberger: That is, that is very, very expensive.

Allen Hall: Yeah. So you’re really talking about taking up some precise machining equipment up tower.

Doesn’t really matter if the wind’s blowing or not. You’re, you’re fine. You’re all inside. And you’re going in and machining what remains of those teeth. I mean, I, I want to have a sort of a dentist equivalent of this. So it’s like you have a broken tooth and, and the dentist comes in and goes, okay, we’re going to grind that tooth off and we’re going to smooth out.

And we’re going to put a replacement. On top of it, like a crown, right? It’s basically a crown. So that process takes how long to do once you kind of uptower in your starting the machining process.

Søren Kellenberger: If we if we use like the, the Vestas V90, three megawatt platform as a sort of baseline then it takes we have, we have our, our teeth segments, our crowns.

If you, if you want in in segments of of six teeth and it takes roughly one day to once we are open and ready to, to replace six teeth. So for a replacement, you need to consider one day of hoisting and getting in place and then. One day for, for each segment you need to, to install and then one day to, to pack up and clean and get back down.

So so we, we get quite a fair bit done in a week.

Joel Saxum: Yeah, that’s, that’s impressive. So, so there’s a couple of activities here that have to be done, right? Of course, you’re getting up there, you mount the CNC equipment. That’s one big part of it. But then you’re, you’re, you’re milling up tower. So you have to deal with, you guys have a, you have a system to deal with all the filings and tailings and catching all that stuff.

And then, and then once you put the new teeth or the new teeth get in place, is, are they welded in place or how are you, how are you attaching that?

Søren Kellenberger: No we bolt them in place. So that because we have a CNC machine, we, we, we can do a very accurate milling process up there. So, so. So basically we, we, as you say, we, we remove the, the remains of, of the old teeth and, and we machine like a pocket in, in the yaw ring.

And that one is milled within a couple of hundreds of millimeters in tolerance. And then we have the benefit because we know the design of the yaw ring. So we. We bring prefabricated segments that have the exact same shape as, as the original yaw ring. And, and they are of course manufactured in a, in a machine workshop.

So, so they have very good tolerances as well. And then we basically create a press fit. So we either slightly pre bent the segment to, to install it or we, we freeze it. We have some small freezers we can bring up tower as well and cool the segment down to minus 80 degrees, which gives us just enough space to, to easily fit it.

And then as it heats up, it’s a, it’s a press fit. And then we keep it in place with bolts as well.

Allen Hall: Wow. I didn’t realize it was a press fit. That’s insane. That’s better than the manufacturer delivered on site when the turbine was new. Yeah, it could be. The other way I’ve seen this repaired, if you watch LinkedIn enough and Joel and I are constant viewers of crazy LinkedIn wind turbine repair videos and Instagram, there’s a lot of this in Facebook too, when they have broken teeth, you see guys up there with welders and they’re up in there and they’re adding filler, trying to rebuild it, trying to reshape it.

Then you see them grinding on this gear. What are the problems with doing that approach?

Søren Kellenberger: We do actually also work with some welding companies, but because you can have some situation where welding is your only opportunity, but, but we can, we can get back to that. But, but the, the challenges with welding is of course you have a big, massive, steel ring so it absorbs the heat quite fast.

So controlling the the heat and the temperature in, in your welding process is is difficult. The space is just as limited for, for welding and they need to fit a person in there. So so you also have the disadvantage of, of having like hot works and confined space, which is, is not so nice.

And then finally being able to grind those Teeth into the original shape is also relatively challenging. You don’t have much space when you are in there and you would want to try and get that contact surface quite straight to distribute your, the load from, from your York year when you start operating again, and, and I think that probably the most challenging part where we have the benefit of, of machining, bringing a pre machined segment that has that exact shape.

I think that is probably one of the, the biggest benefits to, to, to our process. And, and because it’s such a manual process of, of grinding, it can be difficult to get that shape. And, and that can be, Can give you some extra loads on a, on a welded tooth which can lead to damages again faster than, than what we see on,

Joel Saxum: on segments.

There’s, I mean, there’s one thing for rebuilding teeth on like an excavator by welding, welding up a bunch of metal and, but, but, but teeth that need to be used in a, you know, basically a ring and pinion set or a ge you know, a a tooth gear thing. It’s gotta be exact. It has to be, because if not, you’re just gonna be back up there in a year or two.

Doing the same process because it’s just not going to last. It’s temporary. Does the, there’s

Allen Hall: a yaw motor gear and all the machinery that’s there and the mechanism there, does that need to be updated too? Because it’s been working against these, these gears that have been not the right shape for a long time, that in order to get this really fixed, you need to put the proper.

teeth in the R gear, but also on the motor, you need to take a look at it and make sure it’s up to snuff. Yeah,

Søren Kellenberger: I think that is a typically also a part of the inspection. They, they do that. They, they check that all the motors and, and gear wheels there are okay. It’s normally not a part of, of our process to do that, that, that would be the turbine owners or the, their own technicians who would check that.

Up front or, or right after we, we complete our work. So, but yes I mean, when you are up there fixing it, I, I, I would definitely recommend that you check the remaining system and potentially also try to look for the, for the root cause if you do have. Misaligned your gears or something like that.

It could for sure be an advantage to to get them aligned to avoid having the same damage again soon after the repair. So how many of

Allen Hall: these teeth replacement are you doing in a year? Because my guess is it’s a good Quite a number from what I’ve seen out in the field,

Søren Kellenberger: you can say it’s still a relatively new technology, even though we’ve been doing it for five years.

It’s still a conservative industry. You know, they, they want to see new technology introduced and, and see how it operates and works. So it’s not that we do a oaring every. But we we have installed more than a hundred segments since we started and, and we see that it is taking off now the first segments have now been running for more than five years and, and proven them themselves very well.

So, so we, we certainly do and also you see that. The turbines, the number of turbines that are reaching that age where you can could expect some, some wear or damages to your, your ring is also increasing significant significantly. So we, we will be seeing more repairs over the coming years for, for sure.

Joel Saxum: I think that’s a big part of the conversation here is you know, looking, looking in the European market, like if you look at Spain right now, their fleet is starting to get to that Close to end of life or life extension. What does it look like? Is it repower? Is it refurbished? How do we keep these things running?

And Alan and I just had a conversation with a company here in the States that’s doing a lot of repowers just the other day. And I was thinking about that there too, because in the States we have this, you know, PTC driven repower thing where you could put certain amount of value back into the turbine, still qualify for some subsidies.

And I was thinking, man, with all these older turbines. What else can be done here? And some of that would be refurbish, refuel, fix these raw yaw gears, fix these kinds of things to make sure that you’re, you’re maintaining that level of performance that you want. Or, I mean, if you’ve been operating like this for a long time, you may be getting back to back to baseline as well.

I mean, at a minimum would be nice to get that out of it. So I think that the market for what you guys are doing is going to grow massively. Globally right now, right? We’re seeing, we could see a lot of applications from here for it in the States with our 75, 000 and change turbines we have plus that European market that’s changing.

So are you guys starting to get some calls from, you know, how, is it, is it more like damage during regular operation and this is what’s happening or, Hey, we’re at getting close to end of life. Can you help us do an assessment on what this looks like? Are you getting those calls? Both. Yes.

Søren Kellenberger: So, so. Most most operators I guess they, they start really looking for this when they see an issue but if they have had turbines or in other wind farms, for instance, or, or even some of them that, that have been damaged earlier in the lifetime, they are more aware of these issues and, and they would also contact us for, for inspections and, and evaluations if, if what can be done and, and to get some, some budgetary quotes and, and stuff like that to see if there’s a return on, on investment within their potential lifetime extension.

So, so yes, we, we do get both And, and I mean, we’ve been in, in Japan to, to fix teeth on a, on a turbine. We’ve, we’ve been across multiple countries and in Europe we’ve just sold a machine to New Zealand together with the first 25 segments. They will, they will get together with this machine.

So it is picking up around the world. And, and we also have several inquiries from from the U S so, so I would be very surprised if we weren’t doing some turbines in, in the U S next year also on, on the Jolring site.

Allen Hall: So can an operator buy the machinery and do this process themselves with your direction, of course?

Or is it always required that CMC on site people be there to do the process?

Søren Kellenberger: No, it’s a, it’s not a requirement that, that we operate a machine. It, it is a very much a case by case discussion with with our customers, if, if they have The technicians with the right skills and, and they have the volume of turbines to keep them up to, up to speed on, on using these machines.

It can make sense that they buy a machine and we train them. Others prefer that, that we come and do an all inclusive service. So it is, it is basically up to, to the customer. And, and we discussed that case by case how, how we make the best project.

Allen Hall: What process is used if you’re offshore on these massive 8, 10, 12, now 15 megawatt turbines?

Is the process basically the same on those turbines?

Søren Kellenberger: It is. Completely the same process only, only difference is is, is the transport there that we have to go by CTV and not not a, not by car. So that, that is basically the only difference if the turbine is onshore, offshore, doesn’t make any difference for, for us.

It is still the, the exact same milling process and yeah. installation process. We don’t need any other external equipment.

Joel Saxum: How big is one of these kits? Like, if you’re going offshore, if you’re transferring, I know like, on offshore, on the transition piece, there’ll be a little crane sometimes and stuff, but like, how, like, weight and dimensions, what, what does it look like?

Søren Kellenberger: That depends on on the turbine. As I mentioned before, though, most of these turbines weren’t designed for this kind of, of repair. So, so we don’t have a one fit fits all machine. And, and the segments are also different because the yaw ring in a 8, 10, 15 megawatt turbine is, is way bigger.

Bigger than in a two or three megawatt, of course. But if we take the, the two, three megawatt size turbines, our machine is around 80 kilos. And the segment is weighing eight to 10 kilos. So it’s, it’s, it’s easily transferable. And we always make sure that we can, if the machine is too big or heavy when it’s assembled, we always make sure that each component can be handled by the internal crane and go through the hatch in, in in the nacelle.

Because that is very important also. And, and in terms of keeping the cost down that you don’t need any external cranes for, for this operation. But I think our, our heaviest machines for these large offshore turbines is around two, 300 kilograms. So when they are fully assembled.

Joel Saxum: So for me, if I’m, if I’m, if I’m an ISP in the States and I’m listening to this podcast, I’m thinking, Ooh, new service line.

I need to get ahold of Søren. And so I can, so I can be the, I can be the person that gets called in the States to do this. And

Allen Hall: Søren, how do people get ahold of you? How do they reach out to CNC onsite?

Søren Kellenberger: Either through our, our website cnconsite.dk where we have all our, our contact details listed or directly to me at my email ssk@cnconsite.dk or call me.

Yeah, the, my phone number is also also on, on the website. So, there they are most welcome to to reach out to us.

Allen Hall: It’s amazing technology and it needs to be utilized across the world because I’ve run into a number of operators with yaw gear problems and they’re stuck and they didn’t realize you existed.

So hopefully this podcast gets to them and we can connect you up and get you busy because there’s a lot of yaw gear repairs that need to happen over the coming repair seasons. So. Søren, thank you so much for being on the program. Joel and I have learned a ton. Thank you very much for having me.