会社のニュース How to Plan Puller and Tensioner Positioning for Overhead Transmission Line Stringing Sites

Most stringing problems blamed on the machine are actually layout problems. A puller set thirty metres too far from the first block, a tensioner aligned five degrees off the conductor path, a drum stand crowded against a fence: none of these appear in a specification, and all of them appear as slip marks, uneven tension and lost hours. Positioning deserves the same engineering attention as machine selection, and it is far cheaper to get right on paper than on site.

The construction problem: what a bad layout looks like

The symptoms are consistent. Conductor enters the bull-wheel at an angle and climbs one groove wall, so one side of the groove wears twice as fast and the conductor shows a polished stripe. Tension readings between subconductors drift apart because one path is longer or one drum pays out harder. The tensioner operator fights the brake all pull because the conductor is dragging over a flange. On crossings, a badly placed machine means the abort decision arrives too late to recover the span. All four symptoms come from three layout variables: fleet angle, anchor geometry and working space.

Technical cause: fleet angle and load path

Fleet angle is the angle between the rope and the centre line of the sheave or bull-wheel. Beyond about 2 to 3 degrees, the rope rides up the groove wall, contact pressure concentrates, effective wrap falls and slip risk rises. On a long pull the entry angle changes as sag develops, so the machine must be placed for the worst case, not the starting case. Correcting a persistent fleet angle with the machine anchor is a common error: it twists the frame, loads the brake unevenly and does nothing for the geometry at the groove.

The second variable is the load path. Puller and tensioner load in opposite directions. Anchoring both to a shared point transmits one machine's load into the other's structure, and anchoring off the pull axis introduces bending into a frame designed for axial load. Keep anchor line, machine axis and conductor path in one vertical plane, and set each anchor independently at not less than 1.5 times the working pull.

Parameter examples: footprint and space planning

The 45 kN machine also illustrates a second layout figure: its bull-wheel groove bottom diameter is 1500 mm and the trial traverse diameter 34 mm, so the conductor must enter and leave without rubbing the groove edge. Allow at least 2 m of clear space on the cooler side of every machine. A vehicle parked against the radiator removes cooling capacity exactly when the pull needs it most.

Tensioner side: where sag is actually made

The tensioner brake sets the back-tension that becomes sag. Place it so conductor leaves the last groove horizontally and passes to the first block without crossing another conductor or rubbing a flange. Drum stand height should keep the conductor roughly level into the tensioner; a conductor dragged upward from a low drum loads the groove edge and abrades the outer strands. Where geometry cannot be made level, use a lead sheave rather than accepting an angle. Machines with a hydraulic power pack controlling up to four reel stands or winders simplify this, because stand height and payout tension can be adjusted from one control position instead of improvised on site.

Field handling: the planning sequence that works

• Survey the span and crossing constraints first, then fix block positions, then place the puller relative to the first block, then the tensioner relative to the last block, then the drum stands relative to the tensioner.
• Work backwards from the block line, never forwards from where the machines can park.
• Check ground bearing capacity and level; a 3.5 tonne puller settles on soft ground under load and quietly changes the line of pull.
• Confirm the operator has sight of the bull-wheel and a radio link to every block watcher.
• Leave an access route behind the tensioner for drum changes and recovery, not in front of it.
• Record the final geometry: distances, anchor positions and entry angles, so the next section can repeat it.

Reference machines for these layouts: the GX60 seven-slot 60 kN puller, the 45 kN puller-tensioner, the 25 kN puller-tensioner with 1500 mm bull-wheel and the 5 ton hydraulic tensioner.

FAQ

How far should the puller be from the first block?

Enough to keep entry angle under 3 degrees, normally 30 to 60 m. If space is short, add a corner or lead sheave rather than moving the machine closer.

Can puller and tensioner share an anchor?

No. They load in opposite directions, and a shared anchor transmits one machine's load into the other's frame.

Does machine orientation affect braking?

Yes. Spring-applied, hydraulically released brakes are sensitive to mounting and level, and an off-level machine will not set or release evenly.