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NRG_34m_TallTower_Installation_Manual_and_Specifications_Rev_1.05.docx
19 April 2011
Lift the Tower
When all crew members are ready, the winch operator will begin to lift the tower. Remember that most electric
winches are designed for intermittent use, and frequent rests must be taken to prevent the winch motor from
overheating. Help the cable to wind evenly by using the winch control handle to move the winch motor from side to
side.
Warning:
Allowing the cable to wind unevenly will result in crossovers that will damage the cable and fill the winch
drum before the tower is fully raised.
Lift the tower about 1 m (3 feet) off the ground while checking side guy tensions. The lifters are set up to produce a
slight bow in the tower, with the
top 0.15 m to 0.3 m (6” to 1 foot) higher than the middle (we refer to this as a
“positive curve”). This is normal, and it needs to be maintained throughout the entire lift to avoid tower buckling or
collapse. Adjust the side guy wire tensions to prevent the tower from either falling off to one side or bowing which
could damage the tower.
Warning:
The tower must remain straight side to side and maintain a positive curve as described above. Failure to
maintain the proper shape can cause the tower to collapse, endangering the crew and equipment. This is the
highest stress point of the lift.
Watch the winch anchors for movement.
The maximum lifting force will be experienced when the tower is first
lifted a few feet off the ground. If the winch anchors will not hold, either the anchor was not installed correctly or
another type of anchor is needed. See Appendix B: Anchoring Guidelines for more information.
Watch the tower baseplate for movement toward the winch
. If either the winch anchors won‟t hold or the
baseplate slips, immediately lower the tower.
If everything looks OK, continue to lift the tower a little at a time, checking side guy tension along the way. At times,
it may be necessary to adjust the side guy wire tension. Do this ONLY when the winch is stopped. Readjust with
wire rope clips, letting cable out or pulling loose cable in
(see “inchworm” technique). Work slowly and smoothly.
Fast, uneven movements tend to make the tower bounce, shake or swing.
Be sure that communication
between all
members of the lifting team is clear and concise.
Continue lifting and adjusting until the tower is about 60 degrees
above horizontal (just above half way).
STOP
.
Beyond 60 degrees above horizontal, it is absolutely essential that tension is maintained on the back guy wires
during the last part of the lift, particularly the guy wires at levels 2 and 3. Excess tension on level 4 will remove the
pos
itive curve shape from the tower and potentially cause a collapse. So don‟t do it. The tower will lift very easily at
this point because the weight of the ginpole and winch will be enough to tip the tower without powering the winch,
causing total loss of tower control. Any wind blowing in the direction of the lift will also help reduce the load on the
winch.
Therefore, the crew must control the lift from this point on using the back guy wires.
Before continuing the lift, adjust the back guy wires to take out the excess slack.
Continue the lift by alternately powering the winch and smoothly and incrementally (a few feet of guy wire at a time)
letting out on the back guy wires (in order from top to bottom) using the inchworm technique. Do not completely
remove slack in back guy wires by running the winch too long. Continue this process until the
top
of the tower is
directly over the base (sight with a carpenter‟s level).
Warning:
Avoid winching in too much cable (to the point where the pulley collides with the winch). If the pulley and
winch are winched tightly together, the winch cable can break, causing total loss of tower control. Please note that
the winch‟s motor has a slightly delayed response after the switch is released, and while coasting to a stop may
produce enough force to break the winch cable.
Re-check that the tension in the back guys and in the side guy wires is set up correctly to about 23 kgf (50 pounds) of
tension, allowing some slack in each guy wire. Check that wire rope clips are secure.
