Video: AGRU-8

Video transcript

Where the AGRU-8 fits, how it recovers, stores and weighs the gas, and how it is operated with a single selector valve. Some jobs outgrow a hand cart, but do not justify a skid or a trailer unit. The AGRU-8 is built for that middle ground: breakers and switchgear up to 256 kilovolts, with enough storage on board for the gas of a large breaker. The figures. Up to 51 kilograms of gas an hour. A residual pressure below one millibar, which means 99.9% of the gas recovered.

Up to 208 kilograms in 4 bottles on board, or 300 with the optional tank. And a vacuum pump of up to 40 cubic metres an hour. The unit, from the top: the operator panel with its gauges, weight display and emergency stop. The drier and filter housings. The vacuum pump. Here, the optional 300 litre tank. The load cell that weighs the gas. And casters, to move it around the substation.

On the panel, 7 things do almost all the work. The emergency stop. The charging regulator. The equipment pressure and vacuum gauge. The digital vacuum gauge. The selector valve V one. And the equipment and auxiliary connections. The circuit is simple to follow. From the equipment, through the selector valve and the filter module, to the compressors, the condenser and the bottles on the scale. The way back to the equipment passes an evaporator and the charging regulator.

And the vacuum line works on its own. Recovery: V one to equipment to bottles. The compressors draw the gas through the drier, the purifier and the filter, the condenser liquefies it, and it lands in the bottles, where the scale weighs every kilogram. When the pressure falls to 0.2 bar, the vacuum compressor starts by itself, and pulls out the rest. Step by step: every valve closed and the main switch on.

The hose from the equipment connection to the breaker. V one to equipment to bottles, and the bottle valves open. Then start the compressors, and follow the recovery on the equipment gauge and on the scale. The scale is what turns a recovery into a measurement. A load cell under the bottle rack, a display on the panel that can be zeroed at any moment, and a lever that lifts the rack off the load cell for transport, so the cell is not damaged on the road.

Before filling, the equipment is evacuated with the vacuum pump. The hose goes to the vacuum connection, the isolation valve is opened, and the pump starts from the panel, with the digital gauge following the vacuum. If the power fails, a solenoid valve closes, so no oil is drawn into the equipment. Charging: V one to bottles to equipment, and the bottle valves open. An evaporator turns the liquid back into gas, between 18 and 24 degrees, and the charging regulator sets the pressure, read on the equipment gauge. While the bottles are at a higher pressure the gas flows on its own;

after that, the compressors take over. At the filling pressure, close the valve on the equipment and stop the compressors. The gas left in the hose is recovered back into the bottles, leaving a slight pressure in it. Then disconnect, and zero the regulator until the next use. The gas is purified twice on every routine, on the way in and on the way out. Activated alumina takes the moisture, a molecular sieve holds the arcing by-products, and a filter stops particles down to 0.1 micron.

The elements change without disconnecting any piping. And the rules that protect the unit and the people. Every hose, fitting and vessel rated for at least 34 bar. No bottles with check valves. Above 10 bar at the inlet, only through a regulator. Gloves and eye protection, and a ventilated area. And the specification, in one table. SF₆ gas handling, from Amperis.