Show notes
David King from Gulf Wind Technology discusses RootFusion, their up-tower blade root bushing repair method. By eliminating the need for cranes, the solution reduces costs and operational complexity. And their NDT diagnostic process allows for non-invasive inspection and repair.
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Allen Hall: David, welcome to the podcast again.
David King: Yeah, thank you very much. Thanks for having me. It's an exciting event that we're here at. So we're really looking forward to this.
Allen Hall: There is so much happening at Gulf Wind at the minutes. Uh, just been watching some of your intellectual property pop out and some of the new things that are at this show.
Uh, all kinds of areas that you're investing in, in terms of blade repairs that have been needed for probably two or three years and. At this point you, you have good solutions. The one I think we're most interested to hear about is the blade route, bushing, or insert. Repair that happens of tower because
Joel Saxum: everybody's asking about it.
I think that's the important thing there is, first off, we need to get some common language around what this problem is. Yeah. So everybody's calling it root, bushings root and this infusion like, ah, what are we actually calling? What are the terms, how you brand this? Exactly.
David King: Yeah. I mean, just you say it's really been a long time coming.
It's something we've been involved with now for well [00:01:00] over. Three years, and we got introduced originally as an RCA. And so, you know, when you get into something like a root cause analysis, you know, one of the first things you gotta do is actually establish the terms you're gonna use, establish the definitions, create a common framework that you can communicate around.
And so when it comes to this particular issue, a lot of it really starts with how do customers get sensitized to this? We've seen everything from some customers getting sensitized through, uh, unfortunately a blade failure. A blade that ends up on the ground.
Joel Saxum: Yeah,
David King: that's probably the worst scenario. We've seen others where they'll see things like.
Dust, uh, on the outside of the gel coat that's starting to build up, uh, gapping, where you have fundamentally a, a visible gap forming between the blade root and the pitch bearing, uh, where you see visible daylight in some cases. Yeah. Um, you really want to try and catch things, obviously much earlier than that, but kind of the, the, the common themes here all around a loss of connection between the metal root bushing and the composite laminate, which caused the blade to become loose from the pitch bearing.
So just kind of walk through that system maybe a little bit. Um, you've got the composite blade which has to transfer [00:02:00] load into a metal pitch bearing,
Joel Saxum: right?
David King: Metal pitch bearing's gotta be able to spin so the blade can pitch, produce, power, and do all the things we need to do. And it's one of the most complicated parts of the blade really.
'cause you're trying to transfer load from composite to metal and you have this massive stiffness difference between metal. And composites. And so it takes some very clever engineering to bring those things together and, um, get an even load distribution. And so the way that's done today is through a metal root bushing.
So it's essentially a, uh, precast metal piece, um, that has geometry to it that allows both mechanical and a chemical connection between the composite, the metal bushing. The metal stud, which is threaded to the metal bushing, and then that stud goes back to the pitch bearing. You joint all that together with some, some wedge lock washers and some nuts, and, and you've got your, your root connection really, and that's what's fundamentally breaking down here.
Allen Hall: Okay, so the, the breakdown is occurring. Where in that assembly? Is it where that bushing meets the composite? Is it the composite itself? The way the composite is sort of wound [00:03:00] around that area and how it's strengthened? Or is it that we're pulling on the studs too hard and basically pulling that bushing out of the composite?
What are the, what creates a scenario why I need to be paying attention to this?
David King: No, absolutely. One thing that's I think quite fundamental to this is actually separating damage and defect. And so I'll talk a little bit to the damage, 'cause that's what you're observing when you see this is the damage that's resulting in this loosening effect.
And so fundamentally what's breaking down is that metal bushing with that geometry that's making the physical connection to the composite is, uh, funnily lost. Its, its pretension on it. So it relies on both mechanical connection. So you've got this. Basically sine wave looking, uh, um, you know, geometry that you've got composite laminate going into those grooves of that sine wave and you're getting a, a physical compression joint connection there.
And then there's a little bit of chemical connection as well. And so as that. Breaks down over time. You get the composite that's inside those grooves actually forming into [00:04:00] a dust and eventually loosening and slowly sliding out.
Allen Hall: So is there fiber
David King: inside of those grooves or is it just resin? That's the goal.
So the goal is to have fibers inside of that groove, basically, if you're going to. Have a metal bushing and you're gonna have composites around it that you want to perform well, you've gotta have the right, right fiber, weight fraction, the right combination of fiber and resin in that area to really get the best strength out of it.
One key piece there though is, is that we talked earlier about compression strength, and that means that you're relying on the resin strength, which is the weakest part of any composite. Uh, and that's really where the challenge is.
Joel Saxum: So, so is the issue that we're seeing in the field now. Is it from manufacturing incorrectly or is it just from wear and tear?
Or like why? Why is this thing rearing its head or is it materials?
David King: Yeah, I mean, these are all great questions and really there's a variety of answers to those questions that are very dependent on which blade type it is. What the fundamental problem is, it really comes down to having a proper root cause [00:05:00] analysis or RCA on that particular blade type.
And, and you know, in our experience it's usually a combination of many things. Um, you know, these, these, uh, uh, blades are incredibly difficult to manufacture. They're complicated, they're incredibly difficult to design, they're incredibly difficult to maintain. And it's really a combination of all three of those things that fundamentally leads to really any problem in this industry.
And so to solve it, you know, you've gotta have a creative solution, but you also have to be addressing those three or four different things. And so you really need that proper root cause analysis. I dunno if you're familiar with the eight D kind of process, but. You know, having something where you're really trying to look at this holistically and address each of those things you just mentioned and asked about,
Allen Hall: what are the first signs that an operator has this issue?
Is it just seeing the dust on the outside or is it something you can hear as the tire as it spins or what? What's usually that first like uhoh with the technician? Yeah. It's kinda
David King: like, you know, put your yourself in the shoes of the technicians, the operators who are trying to face this challenge, right?
And trying to manage risk ultimately, right. Is, um, you really don't obviously want your first knowledge of this [00:06:00] to be a blade on the ground. You want to catch this earlier. And so just as you said, dust that's forming on the outside is, is one big, big telltale sign. The other one is, is if you've got, uh, visible gapping where you put that blade in the six o'clock position, technician can go up there, feeler gauge.
And measure that, that gap that's starting to form do something about it. The, the other thing is, you mentioned audible. You can, in some cases hear this, you can hear that blade moving, but that's a very, um, let's call it mature damage. You really wanna be catching it before that, uh, just because you're, you're getting into a risk profile where there's a lot of uncertainty, whether or not you're gonna catch it in time.
And that's really important. 'cause we, we don't want blades on the ground. I think especially in today's environment, we've gotta do right and wind.
Joel Saxum: So an operator comes to you and says, Hey, we believe we have one blade doing this. Is the next step to do NDT work on the whole fleet or on that whole wind farm to understand what the risk actually is to that wind farm or what, how does that process move?
David King: Yeah, so you know, really it comes down to understanding that operator's business case, because everybody's gonna have a different risk profile. [00:07:00] Everybody's gonna have a different approach to whether, are we trying to repower in a couple years? Are we trying to get 20 years and we're only 10 years in? Is this something that's only two or three years old and we got another 17 years to go and there's a variety of different solutions.