Emergency Response · Controlled Procedure
VC-SOP-0402 — Hydro-Loop Overpressure Response
The emergency procedure for detecting, isolating, and safely relieving overpressure in the nutrient hydraulic loops that feed the greenhouse grid — protecting personnel, equipment, and stock from rupture and toxic nutrient release.
⚠ Overpressure is a rupture and exposure hazard. Nutrient loops can carry concentrated alkaloid-laden solution. A burst line is both a flooding and a toxin-exposure event. Do not approach a pressurized leak. Isolate remotely first. Manual relief is permitted only after the loop is isolated and confirmed below the safe-approach threshold.
1. Purpose
To define the immediate and controlled response to a hydro-loop overpressure condition such that the affected loop is isolated and depressurized before rupture, no personnel are exposed to nutrient or toxin solution, and unaffected zones continue irrigation without interruption.
2. Scope
Applies to all pressurized nutrient hydraulic loops (H-Loop A through H-Loop F) and their pumps, accumulators, and relief manifolds. Routine dosing and pH control is governed by VC-SOP-0118; climate impact by VC-SOP-0102; facility-wide emergencies escalate to VC-SOP-0204-adjacent response under VC-SOP-0401. CHLORA override during response follows VC-SOP-0409.
3. Definitions
| Term | Definition |
|---|---|
| Overpressure | Loop pressure exceeding the maximum allowable working pressure (MAWP) control band. |
| Isolation Valve | A remotely actuated valve that seals a loop segment from the pump and reservoir. |
| Relief Manifold | The controlled depressurization path that vents to a neutralant-lined catch tank. |
| Safe-Approach Threshold | The residual pressure (≤ 0.5 bar) below which manual inspection is permitted. |
| MAWP | Maximum Allowable Working Pressure — the engineered ceiling for a loop segment. |
| Hammer Event | A transient pressure spike from sudden valve closure or pump trip (water hammer). |
4. Responsibilities
| Role | Responsibility |
|---|---|
| Hydraulics Engineer (Owner) | Directs the response; authorizes manual relief and re-pressurization; owns this SOP. |
| Watch Commander | Declares the event tier; clears affected zones of personnel; coordinates escalation. |
| Hydraulics Technician | Executes valve actuation, relief, and inspection under engineer direction. |
| CHLORA | Auto-isolates on threshold breach; arms relief manifold; logs pressure history. |
| Safety Officer | Verifies PPE and exposure controls; manages any spill per VC-SOP-0307. |
5. Pressure Thresholds
| Loop Class | Normal | Warn | Critical / Auto-Isolate | MAWP |
|---|---|---|---|---|
| Standard nutrient (A–D) | 2.0–3.5 bar | > 4.0 bar | ≥ 5.0 bar | 6.0 bar |
| High-pressure toxin feed (E) | 4.0–6.0 bar | > 7.0 bar | ≥ 8.0 bar | 9.0 bar |
| Reclaim / return (F) | 1.0–2.0 bar | > 2.5 bar | ≥ 3.0 bar | 4.0 bar |
6. Procedure
6.1 Detection & Declaration
- On a Warn pressure alarm, the Hydraulics Technician confirms the reading against the redundant transducer; rule out a sensor fault per VC-SOP-0501.
- On confirmation, or on any Critical alarm, the Watch Commander declares a hydro-overpressure event and clears the affected zone of personnel.
- CHLORA auto-isolates the loop at the Critical threshold; verify the isolation valves report closed.
6.2 Isolation
- Command the upstream isolation valve closed and trip the feed pump for the affected segment.
- Confirm unaffected loops remain in service; cross-feed valves stay closed to prevent pressure migration.
- Do not approach the segment while pressurized. Verify isolation by a falling, then stable, pressure trace.
6.3 Controlled Relief
- With Hydraulics Engineer authorization, arm the relief manifold to the neutralant-lined catch tank.
- Vent in controlled steps; target a decay rate ≤ 1.0 bar/min to avoid a hammer transient.
- Continue relief until the segment reaches the safe-approach threshold (≤ 0.5 bar) and holds for 2 minutes.
- Confirm the catch tank level and neutralant capacity remain within limits; if exceeded, escalate spill control per VC-SOP-0318.
6.4 Inspection & Recovery
- In Safety-Officer-approved PPE, inspect the segment for cracked fittings, accumulator failure, or a stuck check valve.
- Replace failed components; record the root cause (e.g., pump overspeed, blocked return, hammer event).
- Re-pressurize slowly under engineer authorization in ≤ 0.5 bar/min steps; hold at each step to confirm no leak.
- Return the loop to automatic control only when pressure is stable within the normal band for 10 minutes.
6.5 Quality Checkpoints
- Affected zone cleared before any manual approach
- Loop isolated and confirmed below safe-approach threshold before inspection
- Relief decay rate held ≤ 1.0 bar/min — no induced hammer event
- Root cause identified and recorded before recovery
- Stable 10-minute hold within normal band before auto-control restored
7. Escalation Matrix
| Condition | Tier | Action |
|---|---|---|
| Warn pressure, sensor-confirmed | Tier-1 | Engineer-led local response; monitor. |
| Critical / auto-isolate | Tier-2 | Watch Commander declares; zone cleared; controlled relief. |
| Line rupture / nutrient release | Tier-3 | Spill + exposure response per VC-SOP-0307 / VC-SOP-0318. |
| Toxin-feed (Loop E) rupture | Tier-4 | Facility response under VC-SOP-0401; Directorate notified. |
8. Records
- Pressure history and isolation/relief actuation log (CHLORA, retained 10 years)
- Event declaration, tier, and zone-clearance record
- Root-cause and component-replacement report
- Any spill or exposure record (cross-filed to Monitoring and VC-SOP-0307)
9. References
- VC-SOP-0118 — Hydro-Loop Nutrient Dosing & pH Balance
- VC-SOP-0307 — Dermal & Inhalation Exposure First Response
- VC-SOP-0318 — Toxic Waste Neutralization & Disposal
- VC-SOP-0401 — Containment Breach Emergency Response
- VC-SOP-0409 — CHLORA Auto-Response Override & Manual Reversion
- VC-SOP-0102 · VC-SOP-0501
- Operational Metrics · Monitoring Systems
10. Revision History
| Rev | Date | Author | Summary |
|---|---|---|---|
| A–B | 2087–2089 | Hydraulics Engineer | Initial issue; isolation and relief manifold defined. |
| C | 2090-06-20 | Hydraulics Engineer | Auto-isolate thresholds and controlled-relief decay rate added. |
| D | 2091-04-10 | Hydraulics Engineer | Toxin-feed Loop-E tier-4 escalation and hammer-event controls. CBO approval. |