Hydro-Loop Pressure

Definition

Hydro-Loop Pressure (HLP) is the gauge pressure, in bar, of the closed-loop hydroponic distribution header that feeds nutrient solution to all cultivation benches and spheres. It is read directly from redundant transducers at the loop manifold and is a two-sided control variable: too low and emitters starve, leaving root zones under-irrigated; too high and seals, fittings, and drip lines are stressed toward failure. The nominal band represents the pressure at which every emitter on the loop delivers its rated flow.

Why it matters

The hydro-loop is the facility's circulatory system. A pressure sag can dry a bench within an irrigation cycle and depress turgor and vitality (VC-MET-001) before any soil sensor reacts; an over-pressure event can burst a line and flood a containment cell. Because the failure modes are fast and bidirectional, HLP samples every 30 seconds and carries hard safety interlocks. It is a front-line infrastructure metric on the Operations Dashboard and a direct trigger for pump-control and isolation logic.

Formula

HLP is a directly measured signal; the model below covers transducer voting and calibration:

HLP = median( P_a , P_b , P_c )      [bar, gauge]

where P_a, P_b, P_c are three redundant manifold transducers.
Median voting rejects a single faulted transducer; if two
disagree by > 0.15 bar, the loop flags SENSOR_DISCORD and the
worst outlier is excluded.

Calibration:
  zero offset trimmed against atmospheric reference at each
  maintenance window; span verified at 4.0 bar dead-weight.
  transducer accuracy ± 0.02 bar over 0–6 bar range.

Rate guard (two-sided):
  if |dHLP/dt| > 0.4 bar/min  →  flag PRESSURE_TRANSIENT
     (possible line breach or pump runaway).

No smoothing on the alarm path; a 5-sample median is published
for trend display only.

Inputs

Units & Scale

HLP is reported in bar (gauge) to two decimal places. It is a point measurement at the loop manifold, not an aggregate; sub-loop branch pressures are monitored separately where the distribution tree splits. The published trend uses a 5-sample median for readability, but thresholds act on the unsmoothed voted value. A SENSOR_DISCORD flag is raised when redundant transducers disagree beyond 0.15 bar, degrading confidence until reconciled.

Sampling & Source

• Sampled every 30 seconds from triple-redundant manifold transducers over the PhytoSense Mesh.
• Median voting across three transducers rejects a single faulted unit; discord > 0.15 bar flags SENSOR_DISCORD.
• Rate guard trips PRESSURE_TRANSIENT on changes > 0.4 bar/min.
• Stale handling: no valid frame for 90 s → last value held, marked STALE, and pump control reverts to fail-safe set-point.

Thresholds

Recent Trend

Loop manifold pressure in bar, last 14 thirty-second samples:

Interpretation Guidance

Related Metrics

Related SOPs

• SOP Library — hydro-loop operation, isolation, and breach-response procedures.
• Branch isolation & relief-bypass response on CRIT — see the SOP Library.
• Pressure interlock & pump-control monitoring — Monitoring Systems.