Event: AGC Accumulator Stand Delivering Low Pressure

See the event “HPU – On” for previous steps in this sequence.

 

Note: This accumulator stand delivers pressurized hydraulic fluid, at one of two reduced pressure settings, to the Operator Side and Drive Side AGC circuits on each of the six Mill Stands (F1 through F6). During the rolling operation, pressure is delivered at 25 bar. Each Mill Stand is supplied by its own accumulator (236.06 through 236.12) supplied fluid through a directional control valve (313.01 through 313.06) for each Mill Stand. During Roll Change-over, this stand supplies fluid at a pressure of 60 bar.

 

1)    The pressure compensated pumps deliver flow to this accumulator stand. The fluid first flows to Accumulators 237.11 and 237.12 which provide flow during short-period flow demands while the pump compensators respond to the decrease in pressure caused by the flow demand.

2)    Pressurized hydraulic fluid flows through Pressure Reducing Valve 280.01 which reduces the fluid pressure to 60 bar.

3)    Next the fluid flows through Check Valve 157.12 after which it branches to the P ports of Pilot Operated Directional Control Valves 313.01 through 313.06. The second branch connects to the inlet port of Pressure Reducing Valve 280.01 which further reduces the pressure to 25 bar. This reduced pressure fluid supplied Accumulators 236.06 through 236.12 which are connected to the T ports of Pilot Operated Directional Control Valves 313.01 through 313.06.

4)    When each of the pilot operated directional control valves is actuated to the crossover flow pattern, low pressure fluid (25 bar) is supplied to each of the Mill Stands. Note that the T ports of the directional control valves may be pressurized because these valves are externally piloted and drained. Therefore, the T ports do not need to be connected to tank.

5)    Pressure Relief Valves 272.01 and 272.02 protect each of the reduced pressure circuits from overpressure.