कंपनी की खबर How to Evaluate Hydraulic Puller and Tensioner Performance During Factory Acceptance Testing

A factory acceptance test is the only point in the procurement cycle where you can watch the machine work while the consequences are still someone else's problem. Yet most FATs consist of a short run, a photograph and a signature. For a machine that will hold 250 kN sustained over a river crossing, that is not a test, it is a handover with the risk transferred to you.

The construction problem: specifications that do not survive site conditions

Contractors rarely discover a machine's real limits at the factory. They discover them on the third pull, when the oil temperature will not come down, the brake creeps under sustained load, or the pull at maximum speed turns out to be far below the datasheet. A properly staged FAT surfaces all three in half a day, with calibrated instruments and the manufacturer's engineers present.

Technical cause: what the staged load actually reveals

Machines are limited by thermal steady state, not by a single pressure reading. At 25 percent load the test reveals control stability and minimum speed behaviour. At 50 percent it shows efficiency and the rate of heat build-up. At 75 percent it shows whether the cooler can hold the approach to steady state. At 100 percent of sustained rating it shows whether the oil temperature plateaus or continues climbing. The final stage is the one that separates a genuine continuous-duty machine from one with an optimistic datasheet.

For a high-capacity machine the same staging applies to much larger numbers: the GS280 is published at 280 kN maximum tractive force and 250 kN maximum sustained traction at 2.5 km/h, so the 100 percent stage is 250 kN sustained and the peak check is 280 kN. On the tensioner side, the GL140TP is published at 140 kN maximum intermittent tension and the 8 ton twin-bundle tensioner at 2×45 / 1×90 kN intermittent against 2×40 / 1×80 kN continuous.

Field handling: running a FAT that means something

• Hold each stage to thermal steady state, typically 15 to 30 minutes at the top stages, and record pull force, speed, pressure, oil temperature and engine parameters at each.
• Test speed control: command a step change in set point and watch for overshoot, hunting or a dead band of several kN, which becomes conductor surge on site.
• Test the brake three ways: static holding at rated load for ten minutes with no creep, dynamic braking at the maximum expected load, and simulated total hydraulic pressure loss to confirm the spring-applied brake sets automatically.
• Verify tensioner behaviour at null speed, because that is what a stalled crossing requires and it cannot be checked on a static bench.
• Compare instrumentation against calibrated external instruments at every stage, and confirm the USB log exports and opens with the supplied software.
• Collect the paperwork: load-stage sheet with actual numbers rather than ranges, relief valve setting before and after, oil temperature curve, brake test record, instrument calibration certificates and a matched spare parts list.
• Photograph the instruments at each stage, not only the machine, so the readings are traceable to the report.

Two practical checks are often skipped. First, hold each stage long enough to reach thermal steady state rather than a fixed five minutes, because a cooler that looks adequate in five minutes may fail at forty. Second, witness the test with your own instrument: a handheld dynamometer or calibrated load cell in the line costs little and converts the manufacturer's claim into a number you can hold. If a supplier resists either request, that is itself information about the machine and about the support that follows delivery.

Reference configurations: the GS280 280 kN puller rated 250 kN sustained, the 280 kN hydraulic brake cable puller winch, the SA-QY120 120 kN puller and the 16 ton four-conductor tensioner.

FAQ

How long should a FAT take?

For a high-capacity puller or tensioner, plan a full day. Staged loads to thermal steady state consume three to four hours before brake and instrumentation tests begin.

Is a video of the test enough?

No. Video shows the machine running; it does not show pressure at each stage or the oil temperature curve. Ask for the data.

Can the FAT be repeated on site?

It should be, for critical crossings, but it cannot replace the factory test, where calibrated load is available, corrections are still possible and the manufacturer's engineers are standing next to the machine.