Gulf Wind Technology’s RootFusion Repair Method

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. Fill out our Uptime listener survey and enter to win an
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update on all things wind technology. This episode is sponsored
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YouTube channel here. Have a question we can answer on the
show? Email us! 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.