A PSA nitrogen generator requires tight cycle timing control and continuous purity monitoring. The booster integration adds pressure management complexity. Here's the control architecture.
PSA Cycle State Machine
Each PSA tower cycles through three states: adsorbing (producing nitrogen by adsorbing oxygen), equalising (pressure equalisation between towers), and regenerating (depressurising to desorb oxygen). A cycle controller tracks each tower's state and elapsed time since the last switch, typically running a 60-second adsorption phase, a brief 5-second equalisation, and a 55-second regeneration phase for the opposite tower.
The controller adjusts adsorption time dynamically based on purity feedback: if measured purity drops below the 99.5% target, the adsorption phase is extended (up to a clamped maximum of 120 seconds) to allow more complete oxygen removal before switching, trading flow rate for purity. Once the elapsed time in the adsorbing state reaches this adjusted threshold, the controller triggers a tower switch, incrementing the cycle count and resetting the timer. Each state maps to specific solenoid valve commands — inlet and outlet valves open during adsorption, the exhaust valve opens during regeneration — so the controller's core job is translating tower state into valve position for each half-cycle.
Purity Monitoring and Booster Control
The hydraulic booster only runs when its permissive conditions are met: PSA output pressure at or above a minimum threshold (typically 5 bar) and nitrogen purity at or above the 99.5% specification floor. This prevents the booster from compressing under-spec or insufficiently pressurised gas into the high-pressure circuit.
Booster on/off control follows simple pressure-band logic. If the surge tank pressure falls below the minimum PSA input threshold, the booster stops — there isn't enough feed pressure to run safely. Once the output cylinder reaches the target pressure (200 bar in this system), the booster also stops, since the fill is complete. Between those two conditions, the booster runs, boosting incrementally from current pressure toward the 200 bar target.
Every cylinder fill also generates a traceability record: cylinder serial number, fill date and time, operator ID, initial and final pressure, fill duration, measured nitrogen purity, and a boolean flag indicating MIL-PRF-27401 compliance (purity at or above 99.5%). This record ties directly back to the Neometrix Manual N2 Generation Plant system identifier, giving each filled cylinder an auditable record for quality and defence-spec compliance purposes.
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