POWER October 2015 - 16

High-Performance Synthetic
Rope Allows Craneless
Wind Turbine Blade
Replacement
Replacing blades on a wind turbine is not
a simple task. Blades range from 40 to 60
meters in length and can weigh 16 tons or
more. Combined with hub heights that can
exceed 100 meters and locations that are,
by definition, subject to prevailing winds,
replacing blades becomes challenging.
Add in the cost of a mobile crane capable
of hoisting the weight to the required
heights (as much as $150,000 to $200,000
per job) and the scheduling challenges of
getting equipment on-site, blade replacement
can become a major expense in both
time and capital.
Eliminating the Crane (and
Expense)
One turbine manufacturer, faced with
the need to replace several blades in
various locations, devised a craneless
blade replacement system using highperformance
synthetic ropes developed
by Samson Rope Technologies Inc. Using
a purpose-built, portable, skid-mounted
winch system capable of both hoisting
and controlling the blade as it is moved
into position on the hub, blades were
changed without the need for a mobile
crane (Figure 1).
Initially, steel-wire rope was considered
for the system, but when the components
for a three-part lifting/lowering system
(main lifting/lowering line, tag lines, and
control lines) were added to the weight of
the wire itself, an alternative was sought.
The snatch block and crane blocks required
to meet the D/d ratio-the relationship
between the drum diameter (D)
and the wire rope diameter (d)-for steelwire
rope weighed more than 400 pounds,
making it extremely difficult to maneuver
within the limited confines of the rotor's
hub. It was quickly determined that synthetic
lines would be preferable to steelwire
rope.
Synthetic ropes offer the same, or
higher, strength compared to steel-wire
ropes at greatly reduced weights and
manageable D/d ratios for the hardware.
In addition, the lighter weight allows
easier handling. Dangerous fish hooks
from broken wire strands are completely
eliminated. The result: safer, more efficient
operations.
16
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POWER | October 2015
Not All Synthetic Rope Is Created
Equal
The synthetic rope chosen for the initial
testing (a non-Samson product) proved
unsuitable-it was diving, that is, pushing
into the previously wrapped level
below it on the winch drum, causing
slack to form as the load was lowered.
The result was a series of short free-falls
as the slack sections on the drum came
under load. The jerky descent was hard
to control and had the potential to subject
the rope to shock loading.
With wind a factor at the turbine sites,
managing the orientation of the blade
with the tag line as it was being hoisted
was critical. The original synthetic tag
lines purchased for the job had far too
much elastic elongation to allow proper
control of the blade as it was hoisted
into position, allowing the blade to pendulum
back and forth, potentially damaging
the blade or the turbine tower in
the process.
1. Reaching new heights. Winch, control, and tag lines made of synthetic rope allow
the safe replacement of wind turbine blades without the use of a crane. Courtesy: Samson
Rope Technologies Inc.
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POWER October 2015

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