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Solving Wind Turbine Pitch Bearing Problems with Malloy Wind

We interview with Cory Mittleider of Malloy Wind, a company specializing in providing bearing solutions for wind turbine applications. Cory shares insights into common pitch bearing failure modes, how Malloy Wind analyzes failed bearings to develop improved designs, and the importance of factors like grease and manufacturing processes in bearing longevity. Visit for more info!

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Allen Hall: Welcome to the special edition of the Uptime Wind Energy Podcast. I’m your host, Allen Hall, and I’m here with my co host, Joel Saxum. If you were an owner, operator, or technician in wind, you have come across pitch bearing problems. And those pitch bearing problems can get really hard to detect early. But once you see them, they’re expensive to repair.

So Joel and I thought it was time to bring on an expert. In bearings to the podcast. So our guest today is Cory Mittleider of Malloy Wind. And Cory has an extensive background in wind bearings. Now, Malloy, if you’re not familiar, is based in Sioux Falls, South Dakota, which is in the middle of the United States.

And Malloy Wind specializes in providing solutions for wind turbine. applications. So they’re a total wind focus organization. They offer a variety of services, including upgrading gearbox bearings, blade bearings, main shaft bearings, pitch motor renewals, and generator bearings. Cory, welcome to the program.

Cory Mittleider: Hey guys, thanks for having me.

Allen Hall: So there’s so many questions about pitch bearings and just having been down in San Diego at the ACP OMNS one of the complaints is, Oh, I got a huge bearing replacement program going on this summer. And my first thought was of you were thinking, wow, you guys must be really busy because Bearings are probably after lightning, it’s lightning and then bearings were one and two of the problems for wind turbines at the moment.

Cory Mittleider: Yeah, it’s been it’s been a busy couple of years. There’s certainly standout platforms that are having their own platform specific failure modes that we’re discovering as we work with operators.

Joel Saxum: Yeah we talked a little bit off air about some of that thing. Okay, so we’re in lightning space.

We know if someone calls and says, I have this turbine with these blades, you go, Ooh, you got problems. So I know that it’s the same thing in the Bering world, generators, like you know the ones that are going to happen. So when you guys initially talk with someone, What are some of the points that you asked them right away?

Okay. They’ve called, what are we looking at?

Cory Mittleider: Sure. Sure. So to your point, it’s a lot of platform specific. We know platform X has this history of problems. Platform Y has a different set of history and platform Z is a pretty stable, pretty robust platform, for example. So we start to, to investigate, is it one of those platforms that we already know has some issues that we either maybe have something developed for, or are currently working on.

We talk about how soon are they experiencing their first failures or how are they detecting them? And most importantly, I think is how long do they plan to run the site? Are they two thirds of the way through the life of the site? Then, we probably propose a different solution to them than we do to some of the worst case scenarios where they’re having failures in the three year ballpark and they’re trying to get to 25.

Joel Saxum: Yeah, no. One of the things that we talked about was, hey, you’re on platform A. With bearings, but you have bearings B and C, same design. But different manufacturers, and sometimes you run into issues there as well.

Cory Mittleider: Yeah. It’s really interesting when it comes down to it. There’s only four parts in a blade bearing.

There’s the rings, the rollers, the seals, and the cage or the spacers, depending on the configuration. It sounds easy, right? But there are a lot of process controls quality checks, things like that. That can be done to ensure. The best long life operation. We actually got a call about three years ago from an operator in our neighborhood that said we have platform a and we have two bearing manufacturers installed across our fleet, all from original build.

The site was about 10 years old. They said, why are all of brand X failing and none of Brand Y. So we worked with them. We investigated that a little bit and we found exactly that, that the bearings are the same dimensions, from a raceway load capacity point of view they should have been the same, but what we found is it was some subtle manufacturing differences from the way the the races were hardened. control point of view. And corrosion protection of the bolt holes, for example, that were leading to that. So very small details, right? That lead to larger implications a decade later.

Allen Hall: And just seeing some of the pictures. That Malloy Wind has on its website and there’s some great technical information about bearings. So if you want to know anything about bearings, go to the Malloy Wind’s website and start looking at the technical explanation, because it’s written in English for in simple terms that even I can understand for me.

Yeah. For people like me that don’t know a lot about bearings, that was really helpful because I’m a picture person, right? I want to see how, what the, how these things break down. The pictures of these pitch bearings coming apart was fascinating because essentially, from what I could tell, it starts to degrade internally and it starts to blow out the seal.

So it starts spitting out metal parts that. Once that begins, it’s bad stuff. You really can’t fix it from there. That’s my understanding of it.

Cory Mittleider: Yeah, then maybe I’ll dive into that, right? Yeah, to your point and you mentioned right at the top that blade bearings are almost impossible to get a health assessment on.

It’s not like a high speed gearbox bearing where you’ve got vibration and temperature because it’s running fast and at full revolutions. But Blade bearings are they don’t ever go full revolution and they go so incredibly slow. So you really can’t apply any of the traditional bearing monitoring tools.

That we’re used to, right? So health assessment is incredibly difficult. Even when you look at the construction of the traditional two row four point bearing type that’s used as a blade bearing it actually stops you for the most part, for most part from even trying to bore scope them.

Joel Saxum: But you can’t access them by design.

Cory Mittleider: Yeah. Yeah, you really can’t access it. To your point Allen a lot of the times what what leaves people to look at them or operators to look at them is pitch faults. For example, especially electric pitch turbines, you’ll start to see an increase in pitch faults, asymmetry type stuff or overload over current on electric pitch.

Or I think you mentioned the seals come out, and grease leaks all over, you’ll get dirty blade ruts, and that’s a signal you can see from further away. But you may have some blade bearing health issues. What we do we and we support in the field. We don’t climb. We don’t do the installation removal, but as the bearing distributors, the bearing experts supporting these operators we’ll get pictures from the field.

We’ll get a call. What am I looking at? If they’re not used to navigating that kind of external inspection, we help that way. But when we get I say a new platform with a new failure mode. We haven’t heard of, we’ll have them replace it. We bring it back to our shop in Sioux Falls, South Dakota, and we’ll dismantle it.

And I think there’s a couple of those pictures, those dismantling pictures on the website that you talked about. It’s it’s a terrible job. It’s dirty. That grease is really sticky, especially electric pitch turbines. That tooth the open gear grease is really sticky stuff. But you work through it, you dismantle it.

Sometimes they’ve been locked up such that we had to cut the bearing in half. To get inside to see it. Other times we’re able to remove the filling plugs, pull the balls out and rotate the inner ring around. And that still takes half a day to do. So it’s a really dirty process. Then you got to clean everything after you get it dismantled.

But then we put all that diligent diligence and effort into we’re inspecting the rolling elements that came out, inspecting the raceway, looking for signs of wear. Or electrification or, what they’re called micro pitting or spalling of the raceways, things like that, that help inform the updated designs that we are offering to operators that have had these premature failure problems.

Joel Saxum: One thing you talked about offshore, and this is just a funny note when you were talking about an extreme cases. We’re like, how do they know when it fails? When does the seal go bad? When does it get enough holes in it? And you’re like, yeah, sometimes you have water that runs into the hub from the outside, or you got to put, you got to make sure you got your hard hat on when you get out of the truck, because you might have pieces of bearing falling down from the top.

Cory Mittleider: So to that point, one of the common problems in the last five or eight years has been cage failures. And I’ll emphasize this by saying none of the failures I’m talking about are, I’ll say design failures in terms of, usually when you talk about bearings, the design life is based on rolling contact fatigue, right?

The raceway fatigue. All these premature failures are other failure modes. It’s the real world. It’s the environment. It’s things like that. So in the last several years, it’s been cage failures has been a big topic, which is internal that cage will start to rub and tear up. It’ll get overrolled by the rolling elements.

It’ll get sharpened. And start to tear up that seal and evacuate and cut up that seal and that’s where the grease comes out. Eventually that cage can degrade so much that the balls begin to bunch together because there’s so much gap opened by the cage that’s missing, that was, that’s no longer there.

So I I’ve seen some where All the cage was gone from the blade side row, for example, and only about half left in the hub side row because there are two rows. And I, if I remember right, it was about 40 to 50 degrees because the balls were all bunched together. 40 to 50 degrees didn’t have any balls.

Joel, to your point then you can see straight through it. And on my shop floor, that’s easy, right? You can see the blue rag underneath. But I have heard techs tell me that they’ll be out in a hub and they’ll see all kinds of water is ingressed, or they’ll one just last week at OMS told me that he was in a hub and it was dark.

I don’t know if it was night or what was going on, but he looked and he saw starlight through the gap where balls, cage, and seal all should be blocking your view of that. Just gone.

Joel Saxum: Yeah. So As we’re recording this, I have on my other screen here, some of their technical resources go malloywind. com. And it has a bunch of tabs on there, but one of them is resources. And I’m looking at technical things. I’m looking at the ones that says blade carry blade bearing cage failures. And there’s pictures here that literally, it looks like a pineapple grenade. Like it’s just fragments Sharp fragments, right?

They look like they would if you touch them like they would just cut your hand up and there’s tons of them.

Allen Hall: I want to talk about grease for a minute because from my experience working on car engines and all kinds of rolling products, airplanes what you grease these bearings with is really critical to lifetime.

Is that part of the magic here? Not only just the way that the bearings are built and some of the hardening and the coatings, but is the grease and proper maintenance there part of keeping the bearing to have a longer life?

Cory Mittleider: Absolutely. So grease, I like to view it as grease already is.

A compromise. It’s just a carrier for oil. Oil is what you need, the lubricant that separates from the soap and gets between the balls and raceways. So definitely lubricant health is important. In all bearing applications in blade bearing specifically, because the whole bearing is turning end over end during operation, that ball can move up and down the raceway or move micro movements right around the raceway.

So the additives in the blade bearing grease does support avoiding things like false Brinelli. So that, that can be important there. But yes, the frequent relubrication cycle, some turbines it’s put a bunch in at a six month interval, walk away and come back. Other turbine models have auto lubricators, which maintain a more consistent level of grease in that bearing.

So both options do exist. And to your point Allen On the electric pitch turbines that use a, an electric motor and a pitch driver, a gear box with a spur gear on it they have teeth cut into the bearing. Most of them it’s on the inner ring, but there are a couple turbines electric pitch that use a geared outer ring.

That needs grease too, right? That needs a lubricant in place to to support that so you don’t end up with metal to metal contact and rubbing and wear on gear teeth. We actually have seen that in some turbines that Didn’t have as diligent grease applied to the gear teeth during operation as well.

Joel Saxum: Is there a certain kind of grease that you recommend or is it seasonality, right? Do you put a different grease in when it’s going to be cold if you’re in those kind of climates versus when it’s hot? Or is it Specific to a manufacturer.

Cory Mittleider: Yeah,

no, cause you can’t really purge the grease, right? It’s just, so you couldn’t say you couldn’t switch it in that scenario.

But largely we typically as the bearing supplier, we don’t really change the grease. We use what the OEM specified. But to your point we do know that some turbines have an Arctic package, which may have a different grease than the either tropical or standard. package that’s applied to the turbine so that can influence what grease is put in the blade bearings.

Allen Hall: So then the failure mode for, if it’s not grease and lubrication, the other failure mode, which I picked up from your website, was the sort of the stresses on the bearing where you take this big strong metal bearing and you shape it like a potato chip. So you’re putting this incredible stresses on those rings and on the rollers.

Is that I assume that’s built into the design though, right? Are they made to handle those stresses or is that something about the way it’s installed or the blade or how it’s operated that creates those stresses?

Cory Mittleider: With wind we often talk about say design modes is a topic of conversation.

I view it as air is invisible. They probably had a pretty good idea, but there’s, who knows what we don’t know. Whether it’s, whether she or turbulence there’s probably some unknowns going on in these applications is how I like to view it. What we do know is we do know there’s deformation to your point, right?

We do know from the failures we’ve done from the X ray analytics that our manufacturing partners have done with their FEA tools. We do know that there’s deformation going on. Everybody we’ve talked to pretty well acknowledges that yes it’s deforming. And what you’ll see when you look at that tech article sitting on our website is that one of the other failure modes to your point, Allen, is is ring cracking.

That one’s a little, it’s not a new problem. We’ve seen ring cracking and wind probably a decade ago already, but the prevalence is increasing. So it’s been a much more active topic. It’s happening on younger turbines. So it’s been a lot more active conversation for us.

Joel Saxum: Would you tie that younger turbines to larger turbines, right?

We’re talking, if you’re talking older turbines, you’re, You’re six, eight ton blades, and now you’re getting 10, 12, 15 ton blades. Is that why you’re seeing more?

Cory Mittleider: Sure. That’s how I view it too. When we look at the blade bearings support a moment, right? So that’s forced at a distance.

And when you look at the center of pressure for, from an aerodynamic load the center of pressure is further out on a longer blade. And when you look at just strictly the weight of the blade, the center of mass is further out. So at the same time as the aerodynamic load is getting higher, the weight and the bending moment from the gravity load is getting higher.

One of the diagrams that I know I have in those tech articles is we simplify it into two different load sets, the aerodynamic load and and the gravity bending moment load, just from the way we presented on the website. Obviously the FEA tools can consider everything in a very much the more complex application that it is.

But Both of those have gone up at the same time. So really and then at the same time, the blade bearing diameter has gone from maybe 1. 9 meters to 2. 5 meters. So it’s only grown by two feet, 600 meters. Approximately because that’s how you support a moment load, right? A larger diameter would reduce that applied load to the raceway.

Definitely attributed to that. We’ve seen when we talk about ring cracking in the younger turbines, it really seems like once we broke about a hundred meter rotor diameter is where that conversation has picked up for us. In in the last.

Joel Saxum: For five years, like I say, the immediate thought that came to my mind was we talk with quite a few people in Brazil and their average megawatt size down.

There’s three

Cory Mittleider: for new installations.

Joel Saxum: Yeah, for new for just the average fleets because their fleet is so young. So they’ve only installed a lot of brand new, bigger turbines. They had, they don’t have a lot of 20 year old, 15 year old turbines on. So I’m thinking to myself Man, they must, the bearing issues they must have down there.

It’s going to be fleet wide.

Cory Mittleider: To, to the point from earlier manufacturer A or B does have a reputation for certain failure modes, right? We know, we know those. And to that point we’ve, we, because of our tech articles both on our website and what we shared on LinkedIn, we have talked with operators in.

South America, South Africa, actually a couple different places in Europe. We’ve been able to set up some teams meetings and share, some of the investigation that we’ve done to help inform them where to look, how to start addressing it, both on turbine models that we know that are global turbine models, but also on some that we don’t know that aren’t installed in the U. S., but they just happen to be, similar failure modes.

Joel Saxum: So this is the important thing I wanted to get to here with Malloy wind and the awesome place you guys fill in the market. So we know that when you buy a turbine, you get whatever the OEM built for blade bearings, pitch bearings, yaw bearings, whatever that may be you.

That’s what you get. Malloy fills the space where if that fails, or if you need new ones, if you’re doing a repower, if you have some kind of issue, you guys are the experts and you have feedback mechanisms built in. So like earlier in the call or earlier in the chat here, we were talking about you guys going and Diving into the problem, getting that problem bearing or representative problem bearing of a fleet or whatever it may be back at your shop, tearing it down.

But then you guys go the next step further to provide value to the industry. Can you walk us through that?

Cory Mittleider: Yes, so that process so we work really closely with one particular manufacturing partner IMO based out of Germany. They know a lot from the analytics side, from the manufacturing side, and then also some feedback they’ve had from education globally.

But our role in the U S here is to work with those operators and collect that empirical data, right? The tear downs the, even the real world stuff. And the nice thing about working with them has been that we can use the baseline knowledge that they had from 30 years of history, little 30 years of history and wind.

In blade bearings for them and inform that and we take their, this basic part number we’ve known from from a serial production point of view and add on to that, right? We’ve added, for example, two years ago, we took a blade bearing that was designed about 20 years ago for an older turbine model, and we’ve taken all the best practices of a 2021, 2022 wind turbine blade bearing.

And applied it to that. It’s improved sealing, it’s corrosion protection, it’s different raceway hardening practices, orders of operations in in manufacturing processes that, that weren’t known back then, but we’re applying all this field education to the new product. So that’s what that looks like.

Allen Hall: I love that. That’s how the rest of the industry should work. That’s why Malloy exists, right? Because it’s hard to find somebody who knows enough about bearings to then incorporate design changes into the next generation so you don’t have those problems. There’s not a lot of Corys around. That’s why we want to have you on the podcast.

And from a Malloy Wind standpoint, you’re then Really changing the industry, right? And in a sense that you have an OEM product, it’s pretty good, starts to fail, and operators want to upgrade or put something on them that’s going to last. That’s why they’re coming to you. That’s a big change for the industry, right?

It just makes the wind industry more resilient in the long run. And that’s where we need to go. And as Joel’s pointed out many times, there’s a lot of companies that are in the wind industry that don’t do that service. Don’t provide that actionable information. And when you weren’t across one, it’s so remarkable because you just want to hold them up and say look here, this is the way it should happen.

Look at Malloy Wind. Here we go.

Cory Mittleider: That’s interesting. I so I started at Malloy almost 15 years ago now, and I started supporting other industries. And that’s that’s how we support all of the industries across our company is we look at and we’re not just say, hey, there’s a part number we can offer you that part number.

We like to ask why. I guess is what I like to say. Why are you replacing it? So that’s I guess I cut my teeth doing that learning with from our shop and to our other our other industries. And I’ve just applied the same approach as we discover problems with our wind customers too.

Joel Saxum: Yeah. At the end of the day A bearing is a wear part. Now it’s a long, a very long life wear part, right? It’s not like the brakes on your car where you’re like, yeah, it’s going to go now. They should last a long time, but they do wear down, right? Especially in industrial applications.

But you guys so let’s talk about this then when customers come to you, are they usually Hey, we’re repowering or is it like, man, we’ve got a fleet wide issue. We need to solve it. What do you think that split is?

Cory Mittleider: Yes. So repower projects aren’t as active in the aftermarket, I think. So a lot of the repowers are done with OEMs, right?

So you’re using those turnkey OEM designs that we talked about already. There are some repowers, I like to call them overhauls. Where you’re starting, I like to describe you start on the low speed side because that’s the big stuff. That’s the heavy stuff. It’s stuff takes a big crane, right?

You start at the blades, the hub and work backwards. So on those overhaul projects we are able to help offer something that I’ll say we learn of the history on that platform and apply this 2024 current generation wind. Blade bearing technology to make sure that they meet their goals. On the other hand, there are some turbines that are to your point, Jill, younger three, four, five years.

They maybe had their first failure in blade bearings two and a half, three years. They’re really striving to hit the 20. And some of these newer sites that we’re talking 25, maybe 30 year. Is the desirable time horizon to operate those sites. And if, if an application doesn’t matter what the application is if a blade bearing failed in three years that’s a big problem and you need an impactful solution.

To try and get another 22 years out of that, for example.

Joel Saxum: Otherwise it’d be replacing them every three years.

Cory Mittleider: Yeah. Yeah. We have some bigger solutions for that big of a problem and then other ones like the one I mentioned a minute ago they made it to 10 years maybe they’ll try and hit 20 and maybe they’ll try and coast a little past 20, get a little gravy on the end.

But let’s do. So we have a little bit of different tools we can apply. We have we can do a little bit better. We can update the design by that 10, 15 years, the corrosion protection, the bolt holes, larger balls, maybe things like this, we can still use the same basic bearing type. We don’t need to bake this big overhaul change like we do.

So that’s why we ask the questions we ask early on. What’s your failure rate? How old is the site? And what is your time horizon? So we can try and apply the right tool to help them meet their goals.

Allen Hall: Malloy Wind is a big resource. People should get on to your website and check out all the information you have there.

How do people get a hold of Malloy Wind and how do they get a hold of you if they have bearing issues?

Cory Mittleider: I’ve always got my email on just about any of us, right? So I definitely have my email address which is cmitleider at Cause we are, our wind division is a part of our bigger company Malloy electric wind at Malloy electric, much easier to spell his is a good one.

We have a shared inbox shared amongst the inside team here. Or message me on LinkedIn, like Allen, you did recently. So yeah, LinkedIn website, email phone is my direct line is 605-357-1076.

Allen Hall: There you go. So if you have bearing issues, better give Cory a call. All right, Cory, thank you so much for being on the program.

Joel and I have learned a tremendous amount.

Cory Mittleider: Thanks, guys.

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