An inspection that happens on the morning of the pull is a formality. An inspection that happens a week before is maintenance. On high-voltage stringing, the difference shows up as a brake that will not hold, a load indicator reading 8 percent low, or a groove worn past its shoulder that nobody measured. This checklist is the one worth running before mobilisation, because every item on it has caused a real incident somewhere.
Brake failures, load indicator errors and groove wear are rarely sudden. They develop over months and become urgent at the worst moment: the crossing, the night shift, the last pull before the energisation date. A pre-mobilisation inspection converts those latent faults into planned maintenance, which is the only kind that costs one day instead of one week.
Spring-applied, hydraulically released brakes hold by spring force and release by hydraulic pressure. They fail in two directions: a weak spring or contaminated oil reduces holding force, and a partially stuck release circuit leaves the brake dragging, which shows up as heat and oil temperature rise rather than as an obvious fault. Load indicators drift because pressure sensors age and because temperature changes the reading. Grooves wear slowly and invisibly until the conductor sits below the shoulders and contact pressure climbs.
| Item | Test | Accept criterion |
|---|---|---|
| Spring-applied, hydraulically released brake | Release pressure, then simulate loss of hydraulic pressure | Brake sets automatically and holds rated load |
| Overload protection | Preset maximum pull, pull against a fixed anchor | Machine stops at preset without exceeding it |
| Load indicator | Compare against a calibrated dynamometer at 25, 50 and 75 percent | Within 5 percent across the range |
| Pressure hold | Hold set pressure with the pull stalled for five minutes | Decay of no more than a few bar per minute |
| Emergency stop | Operate at working speed | Engine and hydraulic drive stop immediately |
| Safety interlocks | Attempt operation with a guard or control interlock open | Machine refuses to drive |
Use the machine's own published figures as the reference. For an 18 mm rope machine such as the GX60 or SA-QY60 class, measure rope diameter at three points and reject anything below the discard diameter for that rope specification; a stretched rope also sits deeper in the groove and changes friction. For a 24 mm rope machine such as the GL140TP, check the same way against the 24 mm limit. For bull-wheels, gauge grooves against the unworn end of the wheel: 1300 / 1500 mm wheels with seven grooves on the 60 kN class, 960 mm with eleven grooves on the GS280 class, 1500 mm on the 25 kN and 45 kN puller-tensioners.
Also verify hydraulic specifications rather than assuming them: the SA-QY60 and SA-QY120 classes list 2.5 km/h at maximum pull and 5 km/h maximum speed, with 25 kN and 50 kN respectively available at maximum speed. If the machine cannot reach those points in a no-load or light-load test, the fault is in the hydraulic circuit, not in the operator's technique.
Machines this applies to include the GS220 puller with preset overload protection, the SA-QY60 six-ton puller with spring-applied hydraulic-release brake, the SA-QY40 4 ton OPGW puller and the 5 ton hydraulic tensioner with real-time force and length display.
Before each project mobilisation and after any incident. Between projects, the daily pre-start check covers fluid levels, brake feel, guards and instrumentation only.
No. Indicators drift with sensor age and temperature. Compare against a dynamometer at the start of every project.
Groove wear. It is slow, invisible at a glance, and directly responsible for both conductor damage and slippage.
Người liên hệ: Mr. Marble Wu
Tel: 8613301534008
Vietnamese
