Video: ARFU-2

Video transcript

What the ARFU-2 does, how its gas circuit is built, and how to evacuate and fill a compartment with it, step by step. Before a switchgear compartment or a circuit breaker is filled with SF₆, the air and the moisture inside it have to come out. Left in, they spoil the gas that insulates the equipment. So every filling starts with a vacuum, and ends with gas at a controlled pressure. The ARFU-2 brings both jobs together on one cart. Its own vacuum pump empties the compartment,

and a pressure regulator then fills it from a standard gas cylinder. A single three-way valve switches from one job to the other, without moving a hose. The figures that matter. A 10 CFM pump, that is 17 cubic metres an hour. A sealed vacuum below 0.03 millibar. And a cart of 31 kilograms, on large wheels, that runs on an ordinary single-phase supply. On the cart: the cylinder, carried on its own rack. The gauges and the regulator of the filling line.

The vacuum gauge, just above the pump. The pump itself, permanently mounted. The 3 metre equipment hose. And the large wheels that take it across a gravel yard. This is the whole circuit. On top, the cylinder line: an isolation valve, the cylinder hose, the regulator with a gauge on each side, and a relief valve set at 10 bar. In the middle, the selector valve V one, which connects the equipment hose either to the cylinder or to the pump.

Below, the vacuum line, with its gauge and the pump. The vacuum pump has 3 controls, and it always starts the same way. Open the isolation valve, close the gas ballast, and switch on. For the first moments the ballast is cracked open while the pump clears the initial air; once it quietens, it is closed again. To evacuate: check the pump oil, it must be above half the sight glass. Make sure the compartment holds no pressure.

Fit a vacuum gauge on the equipment, connect the hose to the equipment and to the DN8 port of the cart, and turn V one to evacuate. Then start the pump, and open the valve on the equipment. The air leaves the compartment through the hose, crosses the selector valve, passes the vacuum gauge and goes out through the pump exhaust. Keep going until the gauge on the equipment shows the vacuum you need: the pump can reach below 0.03 millibar. When the vacuum is reached, close the valve on the equipment,

and stop the pump the right way: close the isolation valve, open the gas ballast, let it run for two or 3 seconds, switch off, and only then close the ballast. Then disconnect the hose. For filling, start with the regulator backed right out, at zero. Connect the hose from the equipment to the DN8 port, and the cylinder to the CGA5 90 connection, with its valve still closed. A shut-off valve and a gauge on the equipment are recommended,

to follow the fill where it matters. Now turn V one towards the equipment and open the cylinder. The gas passes the cylinder gauge, the regulator sets its pressure, read on the second gauge, and the selector valve sends it down the hose. Open the valve on the equipment and watch its own gauge until the filling pressure is reached. At the filling pressure, close the valve on the equipment, turn V one to off, and close every other valve.

Remove the hose, and zero the regulator for the next job. One tip from the manual: a cylinder kept warm fills faster. A few habits keep the cart working. Read the pump instructions before first use. Depressurise the hoses before evacuating. Keep it out of the rain. Check the pump oil regularly, and keep fresh oil at hand. Move it upright, so the pump keeps its oil. And soap-test the cylinder connection from time to time.

And the specification, in one table. Where it is used: evacuation before any SF₆ filling, regulated filling of switchgear and breaker compartments, and commissioning and maintenance in the field. SF₆ gas handling, from Amperis.