Allen Hall and Joel Saxum discuss the critical issue of failed blade bolt inserts with Edo Kuipers of We4Ce. Edo explains the problem, its widespread impact on the wind energy sector, and introduces We4Ce’s innovative solution – an upgraded blade bolt insert that can be retrofitted in the field, potentially saving operators significant downtime and repair costs.

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Allen Hall: Welcome to the Uptime Wind Energy Podcast. I’m your host, Allen Hall, along with my co host, Joel Saxum. On this episode, we’re addressing a critical issue that is plaguing the wind energy sector, the problem of failed blade bolt inserts in wind turbine blades. And these failures have a significant concern for wind energy operators, leading to downtime, costly repairs, and the potential for liberated blades.

Our guest is Edo Kuipers, owner and engineering manager of We4Ce. And We4Ce is based in the Netherlands. We foresee offers a range of services related to the design and engineering of wind turbine rotor blades. And they have designed an upgraded blade bolt insert that can be retrofitted in the field. And this new insert product could dramatically lower a wind turbine operator’s downtime and blade repair costs.

Edo, welcome to the show.

Edo Kuipers: Thanks for having me here, Allen and Joel.

Allen Hall: So this is a really interesting product, but I first, I want to get to how big of a problem do we have in the industry? And Joel and I have been traveling around the United States quite a bit. And pretty much every farm we stopped at had blade bolt insert issues.

They didn’t know why they were having them, but they had them and they were deeply concerned about it because of what could happen to the turban. And Edo, are you seeing the same thing? Are you getting a lot of reach out that way?

Edo Kuipers: Yeah, more and more we see this. I think in 2021, we were contacted by the Indian market for the first time.

Those were 40 meter long blades, 1. 5 megawatt platform. And those blades were like 13 years on the turbine. And then all suddenly started flying off basically. And more and more recently, this is popping up basically not after 13 years, but after six years, for example, already on a 2. x platform. So yeah, we have been contacted first on the Indian side.

We have seen it in Brazil. We have seen it in Thailand, for example, also. So it’s more and more addressing the problem. Also from the Northern America, we have the first context.

Joel Saxum: So I think that if we describe basically the breadth of the problem so there’s the, when you bolt the blades on, and if you’re in a, if you’re a wind technician, this stuff, right?

You’ve seen it, you’ve done it. You’ve been around these things. For some people that are, yeah, some people that aren’t as technician minded, you may not know exactly what the problem is, but what it is basically when you bolt the blades onto the hub, there’s all these studs, right? And the studs come through, or the studs stick out, you stick it into the receptor on the basically on the hub, and then you bolt ’em on.

But if the, where the stud connects into the blade. It doesn’t stay true to its design and becomes loose, it starts to move, then however it’s bolted doesn’t matter at all.

Edo Kuipers: Correct. Also, it’s not a bolt problem, it’s the connection between the steel bushing itself. This is like a plug in the wall when you hang up a painting, for example.

This plug in the wall is getting loose from the laminate.

Allen Hall: All right. So if the inserts are becoming loose. What’s the scale of the, what we think the scale of the problem is. Do we, is it like a 50 percent of blades have this issue? 20 percent of blades have this issue? Cause it sounds like it’s more than 10 percent at the moment.

Edo Kuipers: It can be what we have seen, what we’ve noticed that in the past, blade designs had quite a lot of margin, safety margin in them. And what we’ve seen is that, yeah, in time we are as wind energy, we are reducing our margins. And because we are losing. these margins are getting closer to 1. 0. Let’s say like then where we had in the past like 6.

These margins are getting lower and then the chance of loose bushings is also getting earlier with the, let’s say, the 2. x or the 3 megawatt turbines. If you Build it in exactly the same way, of course, and I’m not sure, we don’t know if the manufacturer has built it always throughout all these years in a consistent way.

We don’t know that, of course. The only what we can do is observe what we see now. And what we see now is basically, first of all, the reserves or the mass moment, basically. The mass is getting higher with the given pit circle diameters and longer blades. remain on the same pitch circle diameter with the same number of balls for longer distances of rotor blades.

So lower reserve margin, that’s one of them already. What we then also noticed, because we did three root cause analysis projects on different locations in the market. And what we noticed is that in all these cases, it was concerning polyester blades. It was concerning a special mat, which was basically wrapped around the bushing as an interface material.

And this mat had what we have seen an irregular distribution of the polyester resin in it. And it had these dog bone shaped, yeah, it was prefabricated parts in there. And what happens there is basically, due to this, unregular distribution of the polyester resin, we get differences in curing cracks, basically, our curing features.

Polyester resin is more sensitive to curing cracks, shrinkage cracks, basically, shrinkage cracks at the curing than an epoxy is. And if you then have this irregular distribution of your resin around these bushings, then you can also imagine that on different location, you get these micro cracks already from the start.

And then it depends a little bit on the reserve factors, which you had from the start, how long this will last. So what happens is due to these micro cracks, we are losing a certain amount of the bonding area of the area that has to transfer the loads from the tip to the pitch bearing, for example.

If we are losing this load carrying area, that means that the stress levels, they are going up, they are rising. And when we realize that there is a non linear relation between stress level on the, let’s say on the vertical axis of your diagram and your lifetime on the horizontal axis of your diagram, this is not linear, but it’s, let’s say a logarithmic.

And. Realizing that if you are losing, let’s say 10 percent of your area of your load carrying area and, or with other words, if your stress levels are raising with 10%, you can already lose like 50%. You can halfen your lifetime already.

Allen Hall: If I have a polyester blade, how would I know I have this defect in the blade?

Is there any way to detect it before the insert becomes loose?

Edo Kuipers: When you’re a park owner, you have always these six months inspection intervals or one year inspection intervals. Then you go inside the hub and there’s, let’s say like a sealing done between your blade root and your pitch bearing.

This is this little line with sealing component filler. Check for cracks in that area, especially on the trailing edge, for example, and on the leading edge. If you see there are some kind of cracks inside, then cut it away with a knife and go with a filler cage inside.

Check how the distance is and do it on different pitch settings. So turn the blade, different pitch orientation, and see again this distance. Then you can measure if there is a variable cap going on, yes or no. And if you see a variable cap, for sure you have some way a loose bushing there.

Especially check for the trailing edge and the leading edge.

Allen Hall: Is there an audio component to this? Can you hear it when the turbine is running? Can you hear the blade shift around a little bit? Cause it’s such a massive load. Is it making noise?

Edo Kuipers: No, I would, I don’t expect that. I don’t expect.

Maybe a little bit on your torque drives. You could see it in the pitching because you have a little bit more sweeping forward and backwards of your blades, if you are, but then you’re already really far and then you really have huge, loosened boostings, but you can imagine that the pitch inertia changes in that respect.

So you will feel it on your pitch drives, but I guess Okay. Apart from that, the blade has then not flew off yet, but you’re already too far.

Joel Saxum: It’s already too far off. That’s the question I want to ask. I want to get into here a little bit is okay. I’m now I’m asking from an operator standpoint.

So if I’m an operator, if we’re doing a yearly inspection or end of warranty or whatever that may be, and we discover some of these gaps or we have, we go, Oh, here we’re suspecting that there’s something going on here. Okay. What is that, basically the delta in time between, I know you can’t say it’s 16 hours or, 22 days, but what does it look like?

Do you have, if it starts to loosen up, does an operator have a year or do they have a day? Like, how long before his up blade decides to come off?

Edo Kuipers: You have to ask a blade, but it depends in the mood when it’s maybe when it’s autumn earlier than it’s spring. Not sure about that, but no we have had these monitoring systems also are not us, but our customer have some kind of monitoring system.

Try to expect exactly what you say here, Joe, try to monitor. How long do we have? It’s not years. It’s not days, but it’s two, three months, I would guess.

Joel Saxum: That’s what I would think, too. Once it starts loosening. Because at the end of the day, what you’re trying to avoid is catastrophic blade failure.

Blade breaks, blade takes down the tower, the whole thing can come down, or you liberate a blade. Safety for everybody, aside from the financial loss in the wind farm. So there’s a lot of, this isn’t oh, we have some leading edge erosion and we need to get it fixed at some point in time. This is a big problem that if you’re seeing the early signs of it, you need to address immediately.

Absolutely. Absolutely.

Edo Kuipers: Totally right. And the sooner you address this, the better it is for the repair as well. Because what we also noticed, what we are doing is with one customer, this is basically the launching customer here. It’s in Asia. What we’re doing is we’re checking at different locations of your blade route.

What is the capping? So what is the variable capping? Let’s say, is it like 0. 2 millimeters variable capping? That’s the values where we are starting to talk about. Or is it also 50? millimeters variable capping. That’s also what we’ve seen. So we are trying to destillate the remaining strength of when the bushing is already, let’s say, loose from the from the laminate with 15 millimeters.

What is the remaining strength? And what is the remaining strength if it’s only 0. 2 or 0. 5 millimeter loose? We are trying to quantify that to get a repair qualification scheme. Let’s say it like that. Hey guys, if it’s 0. 5 millimeters. Yes, lower down the blade. It makes sense to repair.

But if it’s already like 5 or 10 millimeters, of course, also lower it down. But there’s not such a good chance that there is a suitable repair, because there is already so much damage going on in the surrounding area. With all the materials.

Joel Saxum: Yeah, with all the movement. Yeah, I get it. And I think something important to touch on there, for just one bullet point is, you guys may you, we’re talking about a solution that you have, but in the grand scheme of things, what we foresee is, and you guys have been working in the sector for a long time, you are root bushing specialists, so this isn’t just like something that you’ve dreamed up a one off product, you’re good at you’re a consulting firm, you’ve designed blades for, or helped put things in manufacturing facilities and all kinds of stuff.

Edo Kuipers: Correct. Since 2008, early 2008, with the first blade design, because we are not only the root expert here, if I may say so, but we are originally, we are a blade design company for aerodynamic design, structural design, et cetera, et cetera. So in our first design, we, from the start, we decided, okay, when we want to do this, we are going to do it with our own bushing.

development included. And that started with the M30, so the metric 30 millimeters size of bushings, suitable for M30 threaded ends for the 1. 5 megawatts. And then we developed that through the years to a M36, which is quite popular in most of the turbines now, and also M42 we have fully certified. So indeed, based on this idea of the bushing, when we encountered the problem, we thought, okay, come on guys, we are, we know quite well what we are doing with our own bushing for new blades, although they are in epoxy blades, I must say.

So let’s find here a solution. Let’s Alternate or let’s alter, let’s change our bushing for which we have already so much testing, testing coupons and test data available. Let’s alter our solution for having a solution for, yeah, let’s say the retrofit.

Allen Hall: So the problem Edo is that the repair side, and you have these inserts, you’ve been putting inserts in Blaze for a long time.

But if you have an existing polyester blade and you need to do a repair today, six months ago, what does that process look like? Is it even possible to make a repair without basically tearing the blade hub apart, the root of the blade apart?

Edo Kuipers: That’s where we started with. In 2021, the first customer we started with grinding open the root.

We said, we don’t have a solution. Just grind it open, use your grinder. It’s really labor sensitive. There’s a lot of dust going on. Of course, it’s not nice for the people underneath the sun, sunshine of the Indian sun, let’s say it like that. It’s also the quality where you’re ending up is really depending on how the person is doing the scarfing, for example.

We also even have seen problems after these repairs that somebody did not do a proper scarfing job, for example. So you really need to. Take care who and what is going on there and who is doing the job. At that start, at that time, we said, okay, we need to optimize this. And we also need to concentrate on where the problem is.

So when there is now a new customer popping up there, we always say we start with the root cause analysis. So we go up there, we take a piece. We do some, preferably a hydraulic puller test if needed preferably we cut down some roots and bring them to our office. We see if it is actually an interface problem, but We see many times, is it really an interface problem of the bushing with the surrounding laminate or not?

If it is an interface problem, then we can offer a solution here by taking this interface layer out of it. We are using a drilling machine. We are having a cooperation there with the company called CNC on site in Denmark. They are really the experts in drilling. They are doing a good job there. And then once this hole in the laminate is created and the old bushing is thrown away, let’s say like that, then we have a clean situation.

No interface layer is there anymore, is present anymore. And then we can come up with our own bushing, which we modified for a special infusion process on site. So then we implement our bushing. In there and we do an infusion strategy by infusing it from the front. We call it it’s a repair by means of front infusion technology.

It’s let’s say like a big bushing and we have a steel part and which is wrapped around with all kinds of roving and it has a hollow threaded end. So what we are doing is we are implementing. This steel bushing with materials around it, we are implementing that in the hole that has been created.

And we are vacuumizing it here. We are vacuumizing it, the bushing at the front. There is a special flange. There’s a special flange and we have a hollow threaded end and we are infusing, not injecting, through a hollow threaded end all the way to a dispenser at the back on the tip side of the bushing.

And then gradually the resin will be pulled around this bushing, bushing with a roving around it to the front. So it is a really, yeah, a controlled process what we are doing there from the tip. infusing to the root site. And once the resting is coming out of the front where you have the vacumization connection, then you know that it’s almost full.

You also have to go into the depth of the roving. And so you leave it for a while. And this process takes, let’s say 30, 40 minutes, and then it’s basically, then it’s basically full.

Allen Hall: Okay. So CNC Onsite cleans out the existing bushing insert, creates a standardized clean hole, your new product, the We4Ce insert is then slid into this clean polyester hole.

And you’re injecting, are you injecting polyester resin or infusing? I don’t want to say injecting. You’re actually pulling a vacuum, you’re pulling it through. Are you putting polyester resin back in or are you using a stronger structural epoxy to attach this insert?

Edo Kuipers: We tried it with polyesters and it did not work.

We do it with with epoxies, and it works great. It’s much stronger.

Allen Hall: So the roving the fiberglass you have wound around your steel insert, when that becomes infused with epoxy, is then a new structural member of that blade. And how strong is that once it’s installed versus the OEM insert?

Edo Kuipers: The good thing is that we are taking the certification body along with it. And so far they are saying it is equal or higher in strength than the original one was. Wow. Okay. I must say, Allen, the more you test, the more you learn. And sometimes you do, let’s say these tasks, like three steps forward and two steps back again.

So we, yeah, that’s good. That’s good. And then you scratch behind your ears and you think, oh my God, what did we but is there still a solution? But as long as you know what was going on with this testing, then you can then make the next step again. Yeah, for sure. For sure. I’m still saying it’s good.

It’s as equal as the original one is. And even if it would be, let’s say 10 or 20 percent lower in strength. It still is good enough to to have the remaining years on the turbine. We are going for, let’s say like 15 to 20 years. The original one is always going for 20, 25 years. So even in that case, it would be, for me, it would be satisfying.

It would be good enough because our target is quite high. Quite high. We are testing with a bushing, which is our strength results on the testing are with the bushing, which is smaller in length. It’s around, I should wear my gloves here. It is with, let’s say a 60%.

Bushing lengths from the one, which we are going to implement. In the real life later on. So we are basically already 40 percent more conservative with our results.

Allen Hall: So the new insert and the approach you’re taking, which makes tremendous amount of sense, by the way that can be installed on site, right?

So you would take the blade down so you can CNC machine, clean out these holes. Do the infusion, put the insert in, do the infusion, vacuum, pull through the epoxy, let it all cure up, that’s essentially it, right? You’re not replacing all of the inserts typically, how many on a blade are you replacing, percentage wise?

Edo Kuipers: I would say we are now having, let’s say, a blade which has eight inserts. 92 bolts bushings. And we are going to, the idea is now that we are going to replace like 15 to 20 on the trailing edge and 15 to 20 bushings on the leading edge, because It’s not fully trading as, it’s not fully edgewise look loaded, but it’s a little bit between the flavis and edgewise in so that this is where we start.

Allen Hall: So that’s good to know because I think a lot of operators right now who have this problem think I have to replace every single one of these inserts. Oh my gosh, that seems like a tremendous amount of time to do this. But the engineering says no, right? The loading and these inserts are failing on the leading edge and the trailing edge, essentially.

So we’re going to fix those, provide more strength in those, which is going to stabilize the blade. Isn’t that the approach?

Edo Kuipers: That’s the approach. Exactly. This is an interactive decision, basically. So what we are going to do is some testing with hydraulic puller system together with our customer. At the moment, the most suspicious one are at the trailing edge and leading edge side due to the high mass moment loading.

And but for example, if the highest loaded would be exactly the training as we, oh and the first four would be the most suspicious one, then we always do one or two or three extra, of course, on the side. But if flap wise loading for this turbine is non issue, then don’t repair that.

If you go to the dentist, if you have a toothache, he’s not replacing all your teeth, right? You’re concentrating on the problem area.

Joel Saxum: Yeah. Yeah, that’s true. Yeah. One of the things again, from the operator standpoint is it’s going to be replacing costs. So I know I’ve looked at some of your materials and it looks like if you were to do a blade, you’re depending on the level of repair, 30 to 50, 000 euros per rotor blade for fixing.

Which is a lot less than a new blade, right? Because that’s what you, that’s the alternative. If this thing’s loose, these are loosing up, the alternative is, hey, we have to replace this blade because there’s no other way to fix it. But you guys can do it. 30 to 50, 000 euros a blade is the conservative estimate.

But how long does it take in the field? 10 days. Oh, wow. Because what we’re looking at for a market here, of course, there is the, there’s certain models out there that are having issues with this at early life, right? So there’s some possible serial defect thing here in a couple of these models that we’ve been hearing about.

But. One of the other large looming things is. All right. The wind industry has been around since, it has been in a lot, big swings since the nineties early into the 2000. So there’s a lot of fleet at a global basis that right now is looking for lifetime extensions. That’s looking for I know like the country of Spain, they just put something out.

That’s Hey, we’re in a hurt because we have a lot of our fleet 15, 20 year old mark where we’ve got to decide what to do with all this stuff. So you guys are looking at a big market. What do you see that for?

Edo Kuipers: We see the same once this is heading off, then I see a huge demand for this repair technology.

Absolutely.

Allen Hall: And for safe Harbor blades, and a lot of operators in the United States have a number of blades and safe Harbor for the time that they got to go swap blades, right? They have them just sitting on the ground. If you have this polyester problem. Why are you not doing this insert while those blades are sitting on the ground so that when you do deploy them, you do not have this failure out in the field because that’s the point of safe harbor at the moment.

And that seems like the almost the perfect situation for the We4Ce solution is blades are already on the ground that we’re going to be deployed pretty soon. Does that then. It helped fix this problem before it gets out in the field that we can fix these blades on the ground.

Edo Kuipers: And you have to, you need to have the blades on the ground.

It’s not an up tower solution. Unfortunately not. That’s not possible. I don’t see that working. So we, we have to hoist them down. And the nice thing is also, if you, once you have them down, you can also do an aerodynamic upgrade. If you want, you can also fix the leading edge erosion issues. For example, we have now one, one, one customer.

This is he’s having the problems already. He’s ordering some new blades, of course, he’s combining sets. So he’s making from three turbines now, two turbines. So we are because of each of the three turbines has one blade with loose bushings. So he’s combining. Combining that to two new turbines.

He’s keeping them in storage until he basically receives the machine from us. So this morning I had a conference call, call with him. Okay. So when do we get the order, then we can start building them, building the machine. But he’s nicely keeping them in place for us so we can start with those already.

And then at the same time he can do the leaning edge erosion maintenance and repairs on that one even if needed an upgrade with vortex generators or whatever he wants, strike take? A lightning protection

Joel Saxum: upgrade? Lightning protection upgrade. It makes absolute sense, right? So I’m thinking about this in the large scheme, right?

Okay, because we’re, of course, we work globally, but we’re very focused on the U. S. market. So when I look at some of these larger wind farms here, I know some of them have a set of blades or sometimes two sets of blades at the O& M yard, right? So if they have one that has an issue, The, and the crane is there.

They’ll take that down. If that’s going to be out for 10 days, they might even just throw the other blades up. So you, if you have, if you’re looking at a turbine, you’re like, okay, this has got some issues. We could work on these things. Drop that one, put your good ones on, and then you’re getting no downtime out of that turbine while you’re on the ground fixing it.

And it’s just recycle as you go. Yeah. That’s what

Edo Kuipers: we’re doing. And one of the biggest problems we will encounter, is crane availabilities. Absolutely. Absolutely.

Joel Saxum: Because that’s, right now in the States, with how many are being built and how many, I tell, say this too, Allen, we’ve been talking to a lot of people doing main bearings and pitch bearings.

So there’s a lot, there’s a lot of cranes running around, just dropping rotors and swapping bearings and going back up. So the crane availability I know is, it’s tough right now in the States.

Edo Kuipers: Yeah. In Europe, we are developing systems working with cables that we throw basically a cable on the, around the hub.

And then let’s, from the inside, lower the blades. It’s not our idea as we foresee that we are doing the service job ourselves. What we want is we want to hand over the technology to the market. So we want to have cooperation with service companies will want to learn the trick.

And then we license the technology out to them so that on different areas in the world North America, South America India Thailand, for example, and we have different groups where we work together with, so we educate them. So CNC on site is educating them on the machine. We are educating on the refit implementation process.

So we transfer the know how. We give, let’s say two weeks, three weeks, maybe one month. We guide them until the first turbine has been repaired, for example. And then we move on to a next customer and then, of course, the customers always can come back to us, but then this speeds up the process of the repair.

If we want to do all in the house with a small group as we foresee, we are not able to do this is not, that’s not, it’s also not the fun part of the work, the fun part of the work to provide new technology to the market.

Allen Hall: This is a really interesting product and it’s going to make an impact and already has made an impact.

And we’re going to see a lot more of these new upgraded inserts applied in the United States and Europe and all around the world. And I’m just fascinated by this because this is the kind of technology that we need today to keep wind energy moving forward. And I really appreciate you coming on the podcast and describing this to us because.

Joel and I have run into so many operators that need this service. So congratulations, Edo. And thank you so much for being on the podcast.

Edo Kuipers: Thank you very much for having me here. It’s a really an honor to be in the show, Allen and Joel.

We4Ce’s Solution for Stronger Blade Root Bushings

The Uptime Wind Energy Podcast