Making the Case for Quality
Wind Power Company Gets to the
Root of an Icy Issue
• A root cause analysis
project saved Clipper
Windpower $1 million
in lost revenue.
• By identifying the root
causes of turbine failure
during inclement weather,
• This project also supported
a key supplier’s quality
process, as Clipper’s team
helped redesign and test
an improved anemometer.
• Team members mastered
quality tools and strategies,
preparing them for future
At a Glance . . .
With a steady breeze, a wind turbine—stretching
262 feet high—majestically turns its three power-
ful blades, generating enough clean, renewable
electricity to power 750 homes for a 24-hour
period. When the breeze turns into a driving wind
combined with ice, freezing rain, snow, and even
freezing fog, the turbine’s anemometer, which
measures wind speed and force, can freeze up and
result in costly downtime for wind power compa-
nies such as Clipper Windpower.
About Clipper Windpower
Headquartered in Carpinteria, CA, Clipper
Windpower is a rapidly growing company engaged
in wind energy technology, wind turbine manu-
facturing, and wind project development. Clipper
employs more than 850 people in the United States,
Denmark, and the United Kingdom. At the heart
of its manufacturing operations is an ISO
9001-certified manufacturing and assembly facil-
ity that began operations in Cedar Rapids, IA, in
Turning to Quality to Improve Turbine Availability
As Clipper’s first wind turbines came online in northwest Iowa, western Illinois, and western New
York near Buffalo, the winter of 2007-08 hit hard and fast with freezing rain and fog causing
anemometer units to fail. While the towers continued to run, without the anemometers there was no
guidance on which direction to move the 153-foot blades to harness the wind most effectively. Clipper
initially tried to address the problem throu gh software upgrades, but soon additional anemometers
began to freeze, compounding the problem and impacting turbine availability.
Without a quick solution available and with growing numbers of anemometers impacted each day,
Clipper initiated a root cause analysis (RCA), an integral part of the Six Sigma define, measure,
analyze, improve, and control (DMAIC) problem-solving process (as shown in Figure 1). The rigorous
DMAIC approach defines the steps a team follows, starting with identifying the problem and ending
by Janet Jacobsen
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with implementing a long-lasting solution. To evaluate potential
RCA projects, Mike Trueg, manager of field quality assurance/
continuous improvement at Clipper’s Cedar Rapids plant, uses
a matrix that measures the impact of safety, quality, and turbine
availability. “For this project the scoring met the criteria because
of the big impact on turbine availability,” explained Trueg, an
ASQ Senior member.
An RCA project was chartered to address the weather-related
anemometer issues. The project objective was to identify the root
cause of the anemometer failures that was leading to downtime
and decreasing turbine availability. A project team was tasked with
creating an action plan and implementing corrective actions by
the start of the next winter season.
Following the DMAIC Approach
Selecting team members for this RCA project was somewhat
challenging, recalls Ellen Sennett, who served as the project’s
co-leader. “We started with people who had experience with
electrical issues since that seemed to be the problem,” said
Sennett, an employee of Clipper for two years. In all, seven
stakeholder areas were represented on the improvement team, as
shown in the table in Figure 2. Not all team members partici-
pated during every stage of the project; for example, the vendor
representatives came onboard once the root cause was identified.
The team worked through the steps as outlined in Figure 3.
Defining the Problem
Soon after the initial weather-related failures, the company began
collecting data each time inclement weather took a turbine offline.
This early data collection led to the charter of the RCA project.
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Figure 2— RCA project team members
Stakeholder Area Represented Number of Team Members
Quality assurance 2
Fleet services 3
Electrical engineering 2
Anemometer supplier 2
Vendor recovery 1
Figure 1— Clipper Windpower’s Six Sigma DMAIC problem-solving approach
Find the root causes of
the problem and
their effect on process
the critical Xs).
baseline the current
performance of the
process through a set
of relevant and robust
Develop clear project
based on a real problem
that is relevant to the
customer and that will
benefits to the business.
Develop, select, and
implement the best
Ensure the solutions are
embedded, the process
has robust controls,
and the project has
a clear closure.
Closeout Tollgate Review:
Successful projects need clear and
visible closure, the key elements of
which should include documenting
lessons learned, transfer of the process
back to business as usual, and effective
controls. A project review is required
to gain a consensus that the project is
ready to close.
Remediation Tollgate Review:
Projects that require potential
fleet remediation require a
project review to gain a
consensus that a fleet
remediation is required and
a budget has been approved.
</= 5 weeks
>/= 7 weeks
RCA kickoff to root cause(s) identified and approved.
Goal is five weeks or less.
Root Cause Tollgate Approval:
The end of the analyze phase
is a review point. A project
review is required to assess
the root cause identification,
to gain a consensus that the
root cause has been identified,
and to commit any additional
resources required for its success.
Figure 3— Clipper’s DMAIC-based RCA project steps
Define the problem
• Define and document problem or gap.
• Collect data to understand magnitude of failure.
the problem and
of the root cause.
• Gather data on current situation.
• Develop SIPOC and fishbone diagram.
• Filter fishbone items through cause and effects matrix.
• Analyze top items through FMEA.
Analyze data to
determine the root
cause of the defect.
• Develop data collection plan for top priorities from FMEA.
• Develop test plan.
• Confirm root cause with test data.
and implement the
• Evaluate design improvements through validation testing.
• Identify corrective action.
• Develop implementation plan.
• Ensure 100% inspection at vendor.
• Mistake proof (poka yoke) wiring.
• Update installation instructions and training.http://www.asq.org
Measuring to Quantify the Problem
The data collected indicated that, although the winter weather
conditions were severe, both precipitation and temperatures fell
within the supplier’s specifications for the anemometer. The
RCA team developed a supplier-inputs-process-outputs-customer
(SIPOC) matrix to quantify the problem and any perceived
aspects of the root cause. To pinpoint possible root causes of
equipment failures, they also completed a fishbone diagram,
which generated 45 items for further study. Next, RCA team
members entered the potential causes into a cause and effects
matrix to focus on the most likely culprits. The matrix tool
enabled the team to pare down the potential causes to nine items
for a failure mode and effects analysis (FMEA).
Analyzing Data to Determine the Root Cause
The next step for Sennett and her team was to develop a data col-
lection plan covering the potential causes with the highest risk
priority numbers from the FMEA. In all, data were collected from
tests performed on 13 FMEA potential causes—ranging from
improper training on work instructions for wiring the heating cir-
cuits to issues with heating the transducer cap on the anemometer.
After data collection and testing of the anemometer, the RCA
team concluded that the supplier’s design of the heating circuit
did not meet the advertised specification. This failure led to an
insufficient heating circuit for Clipper’s application and thus
caused weather-related failures of the company’s wind turbines.
Sennett remembers that getting the supplier of the anemometers
to acknowledge that its product did not work in the field as
promised was a real challenge. Eventually, data from the field
and the RCA project convinced the supplier. In hindsight,
Sennett feels that perhaps her team could have involved the sup-
plier in the project a little sooner. “It would have been beneficial
to have the supplier go through the DMAIC steps with us and
discover the root cause, instead of us finding it and telling them
they had a problem,” she said.
Identifying and Implementing a Solution
With the root cause in hand, the team began to evaluate improve-
ments to the anemometer’s heating circuits through a series of
winter weather-simulated validation tests. Trueg reports that,
having 405 units to replace, data analysis was vital: “That’s why
we created our own winter weather environment with a wind
machine and a misting device to verify our solution. We didn’t
want to remediate all these sites and then have to do it again.”
Following military standard 810F section 521.2 for icing/freez-
ing rain, the Clipper team directed three rounds of laboratory
testing to analyze the performance of three prototypes for an
improved anemometer. The first new prototype was immediately
rejected because the simulated winter conditions created an ice
build up, which quickly caused the anemometer to fail. A second
prototype also failed before a third version finally withstood the
extreme weather conditions of the lab.
Once the testing was completed, the team created an action plan.
The plan goal was to have all anemometers on each of the 405
turbines throughout the country replaced with the newly designed
version by March 30, 2010.
Controlling to Confirm Improvement
In addition to the heating circuit improvements based on the lab
testing, several other controls were introduced:
• The vendor conducts 100-percent inspection of the product
through a three-day burn test of the unit’s heating system.
This eliminates the shipment of any defective products.
• All anemometers are tested with a turbine control unit in the
manufacturing facility to validate functionality.
• The new anemometer design also incorporates a connector
that can only attach one way to the junction box, thus
eliminating improper wiring in the field.
• The wiring is color-coded for the operators who install the
New Design Stands Up to Mother Nature
While field testing began late in the winter of 2008-09, Clipper
realized the importance of carrying over the testing into the
winter of 2009-10 to confirm the effectiveness of its improve-
ment plan. Once again, Mother Nature cooperated by throwing
her full bag of winter tricks as 40-50 mph winds, one half inch
of ice, four to eight inches of snow, and temperatures of minus
15 degrees and below were reported at various wind farms.
Despite these conditions, Clipper recorded only two weather-
related anemometer issues for a 1.6-percent failure rate. Clipper
soon discovered that the two failures were caused by a sup-
plier assembly team issue and were not directly related to the
improvements generated by the RCA project. With the improve-
ments and control verified, the RCA project was officially closed.
The RCA team kept turbine customers informed throughout
the DMAIC process with presentations about remediation steps
to reduce the weather-related failures. Team members walked
through the entire DMAIC process with key customers and
explained how the root cause was determined, as well as plans to
implement corrective action. Sennett added that many of Clipper’s
customers are familiar with Six Sigma tools, so the RCA process
is the type of problem solving they like to see. “This process helps
with customer satisfaction as [customers] know we are taking
the time to find the root cause and using trained people to do
the right way the first time,” Sennett said.
External customers weren’t the only ones who benefited from
this RCA project. Employees at Clipper’s remote monitoring dis-
patch center, which controls the turbines from the Cedar Rapids
facility, saw a decreased workload as fewer turbines required
attention during inclement weather.
Sennett believes that this RCA project and others that followed
help Clipper’s employees think more proactively and address
issues before they become fleet-wide issues. “Our goal is to
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become more preventive and look at things before they start to
fail, and with the Six Sigma processes you can do a better job of
designing out the defects in the beginning before implementation,”
Building a Culture of Quality
Both Trueg and Sennett credit this RCA project for opening
their eyes to key issues such as internal testing and expanding
the company’s supplier base. As a result of this improvement
project, Clipper created a plan for introducing new suppliers to
avoid potential problems caused by single sourcing. “We’ve also
developed testing here at the manufacturing site so if we have
quality issues, we can test before sending something out into
the field that potentially causes failures or creates the need for a
replacement part,” explained Trueg.
Sennett said that while some team members were initially
skeptical about the DMAIC process, they quickly learned the
importance of taking the time for each step, recognizing that
without the structured process, people tend to collect unnecessary
data unrelated to the issue. For several team members, working
on this project sparked an interest in learning more about process
improvement and prompted them to request further training and
the opportunity to earn Six Sigma Green Belt certification. Trueg
is amazed at the change in Clipper’s staff once they serve on an
RCA team: “The attitudes and focus on problem solving with
data are a strong part of the Clipper culture.”
For more information:
• Sennett and Trueg recommend the following books to guide
your process improvement activities: The Lean Six Sigma
Pocket Toolbook by Michael L. George, David Rowlands,
Mark Price, and John Maxey, and Statistics for the Utterly
Confused by Lloyd Jaisingh.
• Visit the Knowledge Center at www.asq.org/knowledge-
center to find additional resources on root cause analysis and
About the Author
Janet Jacobsen is a freelance writer specializing in quality and
compliance topics. A graduate of Drake University, she resides
in Cedar Rapids, IA.http://www.asq.org/knowledge-centerhttp://www.asq.org/knowledge-centerhttp://www.asq.org
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