Rooftop NH₃ Flake Ice Plant
Rooftop NH₃ Flake Ice Plant (1–10 t/day) — Hygienic “Frost” Ice for Fish Processing
Design basis (given):
- Capacity: scalable 1 to 10 tonnes/day (flake ice)
- Location: rooftop (azotea), restricted access (no public)
- Ambient design temperature: 35 °C
- Distance to consumption points: 50 meters (ice conveyance)
- Water feed: potable water with multi-stage filtration + UV
- Use case: fish factory (rapid chilling, product bedding, hygienic handling)
- Refrigerant: ammonia (NH₃) — industrial-grade safety concept required
1) System Overview
This specification describes a rooftop NH₃ refrigeration package feeding one or more flake ice generators, with hygienic water treatment, controlled storage, and a 50 m delivery system to process areas. The design is modular: a 1 t/day “starter” module can be expanded to 10 t/day by adding additional flake units, increasing refrigeration capacity, and scaling storage/conveyance.
1.1 Block Diagram (Conceptual)
POTABLE WATER ──► [Filtration Train] ──► [UV] ──► [Sanitary Break Tank] ──► [Ice Maker Water Feed]
│
└──► (CIP / Flush / Drain to approved system)
ROOFTOP REFRIGERATION (NH₃) ICE & DELIVERY
┌────────────────────────────────────────────┐ ┌───────────────────────────────────────┐
│ [NH₃ Compressor(s)] │ │ [Flake Ice Generator(s)] │
│ [Condenser: Evap. or Air Cooled] │ │ - Drum + scraper │
│ [Oil Mgmt + Separators] │ │ - Ice chute │
│ [Controls + Safeties + Sensors] │ │ - Hygienic enclosure │
│ [Receiver/Accumulator as per design] │ └──────────────┬────────────────────────┘
│ [Ventilation / NH₃ Detection] │ │
└────────────────────────────────────────────┘ ┌───────▼───────────────────────┐
│ [Insulated Ice Storage Bin] │
│ - level sensors │
│ - agitator (anti-bridging) │
└───────┬───────────────────────┘
│
50 m ┌─────▼──────────┐
│ [Conveyance] │
│ Auger / blower │
│ + drop points │
└─────────────────┘
1.2 Conceptual “P&ID-like” Functional Diagram (non-dimensional)
Note: This is a functional schematic (not a construction drawing). Final piping, valve selection, and safety devices require licensed design.
NH₃ LOOP (conceptual)
[Compressor] ──► [Condenser] ──► [Liquid Management] ──► [Evaporator in Flake Unit(s)] ──► back to [Compressor]
│ │ │ │
│ │ │ └─► (Ice formation on drum + scraper)
│ │ └─► (Instrumentation + safety interlocks)
│ └─► (Heat rejection at 35°C ambient rooftop)
└─► (Oil management / protection / monitoring)
WATER LOOP (hygienic)
City Water ─► Prefilter ─► Carbon ─► Softening/Antiscalant (if needed) ─► Fine Filter ─► UV ─► Break Tank ─► Ice Unit
2) Equipment List (Major Packages)
The list below is organized by package. The final vendor selection will depend on your preferred standards, service network, and spare strategy.
| Package | Equipment | Key Notes (Conceptual) |
|---|---|---|
| Water Treatment | Multi-stage filtration skid (sediment + carbon + fine), optional hardness control, UV reactor, sanitary break tank, feed pump set | Designed for potable/food contact; monitoring of UV intensity and differential pressure across filters. |
| NH₃ Refrigeration | Compressor package (single or redundant), condenser (evaporative or air-cooled), oil management, instrumentation, control panel | Rooftop heat rejection at 35°C; include weatherproofing, anti-vibration, and safe maintenance access. |
| Flake Ice Generation | Flake ice generator(s): evaporator drum, scraper blade, gear/motor, hygienic enclosure, chute | Modular: add units to scale from 1 → 10 t/day; food-grade contact surfaces. |
| Ice Storage | Insulated bin/silo, level sensors, anti-bridging agitator, access hatches, drains | Prevents clumping/melting; hygienic design with drainage and cleanable internals. |
| Conveyance (50 m) | Screw auger(s) or pneumatic blower, insulated pipe/duct, drop stations, interlocked gates | Choice depends on noise limits, layout, and product handling. Include dust/condensation control. |
| Safety & Utilities | NH₃ gas detection, emergency ventilation, E-Stops, signage, eyewash/shower stations, lighting, drains, roof spill management | Requires site hazard study, emergency response plan, training, and routine drills. |
3) BOM (Bill of Materials) — Top Components (Conceptual)
Below is a high-level BOM focusing on the most important components and interfaces. It avoids construction-level details (pipe sizes, charge quantities, etc.) and is intended for procurement scoping and vendor RFQs.
| System | Component | Qty (typ.) | Notes |
|---|---|---|---|
| Water | Sediment prefilter housings (multi-stage) | 1 skid | DP gauges/sensors for clogging alarms |
| Water | Activated carbon filtration | 1 stage | Chlorine removal protects ice quality and equipment |
| Water | Fine filtration (e.g., microfilter) | 1 stage | Targets turbidity; improves hygiene and clarity |
| Water | UV disinfection reactor + UV intensity sensor | 1 | Interlock: stop ice water feed if UV not OK |
| Water | Sanitary break tank + level sensors | 1 | Prevents backflow; supports CIP circulation |
| NH₃ | Compressor package (with VFD or capacity control) | 1 (or N+1) | Redundancy recommended for ≥5 t/day |
| NH₃ | Condenser (evaporative or air-cooled) | 1 | Designed for rooftop, 35°C ambient |
| NH₃ | Oil separator / oil management | 1 set | Protects evaporator performance and hygiene |
| NH₃ | Safety instrumentation (pressure/temperature, alarms) | 1 set | Plus mechanical relief devices per code |
| Ice | Flake ice generator modules | 1–X | X sized to reach 1–10 t/day; modular expansion |
| Ice | Insulated storage bin/silo + level sensors | 1 | Autonomy sized for peak demand; cleanable design |
| Ice | Conveyance system (auger / pneumatic) 50 m | 1 line | Insulated; condensation management; drop points |
| Safety | NH₃ gas detectors (multi-point) + beacon/siren | Site-specific | Tie to ventilation + shutdown logic |
| Safety | Emergency ventilation (roof-rated fans) | 1 set | Designed for rapid purge and safe exhaust |
4) BIM (Conceptual Object Model)
For BIM coordination, below is a simplified asset model (fields you can map into IFC/Revit families or Odoo MRO assets). Replace placeholders with vendor data during detailed engineering.
| BIM Object | Parameters (examples) | Interfaces |
|---|---|---|
| NH3_Compressor_Skid | CapacityRange(t/day)=1–10; Redundancy=N+1 optional; NoiseClass; MaintenanceClearance; Weight; AntiVibrationMounts | NH₃ lines; electrical power; control network; drain; safety interlocks |
| Condenser_Rooftop | Type=Evap/Air; DesignAmbient=35°C; DriftEliminators (if evap); WaterMakeup (if evap); ServiceAccess | NH₃ lines; electrical; water (if evap); plume/drain routing |
| Flake_Ice_Generator_Module | ModuleCapacity (kg/day); IceThicknessSetting; FoodContactMaterial=316L; CIPPorts; EnclosureIPRating | Chilled surface / NH₃ interface; potable water feed; drain; sensors; ice chute to bin |
| Ice_Bin_Silo | Volume; Insulation; LevelSensors; AntiBridging; CleanAccess; DrainSlope | Ice inlet; ice outlet to conveyance; drain; access ladder/guardrail |
| Ice_Conveyance_Line_50m | Length=50m; Type=Auger/Blower; Insulated=yes; DropStations=N; NoiseClass; CondensationControl | Bin discharge; process drop points; interlocks; cleaning access points |
| Water_Treatment_Skid | Stages=Sediment+Carbon+Fine+UV; DPMonitoring; UVIntensity; BreakTankVolume; Backwash/CIP connections | City water; drain; power; signal to PLC; potable line to ice module |
| NH3_Safety_System | DetectorPoints; AlarmLevels; VentFans; EStops; BeaconSiren; MusterPoints signage | PLC safety I/O; ventilation; emergency shutdown; facility alarm integration |
4.1 Rooftop Layout (Conceptual)
┌──────────────────────────────────────────── ROOFTOP (restricted) ────────────────────────────────────────────┐ │ │ │ [Condenser] (keep clear airflow) [NH₃ Compressor Skid + Controls] │ │ │ │ │ │ │ │ │ │ └─────────────── NH₃ lines (protected route) ──────────┘ │ │ │ │ [Water Treatment Skid + UV + Break Tank] ── potable line ──► [Flake Units] ──► [Ice Bin] ──► Conveyance │ │ │ │ │ └──► 50 m to factory │ │ │ │ Safety: NH₃ detectors + emergency ventilation + E-Stops + signage + eyewash/shower + safe access │ └──────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
5) Control Philosophy (PLC / SCADA Level)
5.1 Control Objectives
- Stable ice production across 1–10 t/day with modular units
- Consistent “frost-like” flake texture (thin, dry flakes suitable for fish bedding)
- Energy optimization (minimize kWh/ton) under 35°C ambient rooftop conditions
- Hygienic assurance (UV/filtration integrity, CIP cycles, alarms)
- Safety integrity for NH₃ detection, ventilation, emergency shutdown, and lockout/tagout
5.2 Modes of Operation
| Mode | Trigger | Actions |
|---|---|---|
| Auto Production | Ice bin demand (level low/medium) | Start required flake modules; ramp refrigeration; regulate texture; log KPIs |
| Standby / Eco | Bin level high | Stop flake modules; keep system ready; minimize starts/stops; periodic anti-clump agitation |
| CIP / Sanitation | Scheduled or manual | Interlock production OFF; run flush/sanitize steps; verify completion; release to production |
| Alarm / Safe State | NH₃ leak, UV fail, critical pressure/temp, motor overload | Stop ice production; isolate as engineered; start ventilation; notify; require reset/permit |
5.3 Key Interlocks (Examples)
- Water quality interlock: if UV intensity below threshold or filter DP high → stop water feed to ice generators; alarm.
- Bin high-level interlock: stop flake modules to prevent overflow; keep conveyance available.
- Conveyance interlock: if auger/blower fault → stop ice discharge; prevent back-up in chutes.
- NH₃ safety interlock: detection above alarm level → emergency ventilation + controlled shutdown sequence; site alarm.
- Maintenance interlock: lockout/tagout status required for service access; permit-to-work workflow.
5.4 Texture Control (Conceptual)
“Frost-like” flake quality is typically controlled by maintaining stable evaporating conditions and consistent drum scraping. Control logic focuses on steady operation rather than aggressive cycling:
- Maintain stable refrigeration load while modules run (avoid short cycling).
- Monitor ice generator performance indicators (motor current, cycle stability, chute conditions) to detect scaling or scraper wear.
- Use bin level bands (low/medium/high) to stage modules on/off smoothly.
6) HACCP & CIP Requirements (Food Safety)
6.1 HACCP Critical Control Points (CCPs) — Suggested
| CCP | Hazard | Control / Monitoring | Corrective Action |
|---|---|---|---|
| CCP-1 Water Filtration | Particles, turbidity, biofilm | DP monitoring; filter change log; visual inspections | Replace filters; flush; verify DP restored |
| CCP-2 UV Disinfection | Microbiological contamination | UV intensity sensor; lamp hours; alarm interlock | Stop production; service UV; re-test; document release |
| CCP-3 Ice Contact Surfaces | Cross-contamination / biofilm | CIP schedule; ATP swabs; visual checks; sanitation records | Re-clean; investigate source; increase frequency |
| CCP-4 Ice Storage & Conveyance | Environmental contamination, condensation | Insulation integrity; drip checks; routine cleaning; pest control | Repair insulation; sanitize; adjust ventilation/dehumidification |
6.2 CIP (Clean-in-Place) — Functional Requirements
- CIP-ready design: accessible drain points, cleanable chutes, removable panels, no stagnant pockets.
- Validated sanitation: measurable parameters (time, temperature if used, concentration if used) and recorded cycles.
- Separation of chemicals: storage and handling away from food zones; documented SOPs.
- Post-CIP rinse verification: conductivity/visual checks where relevant; documented release to production.
- Micro testing plan: routine sampling of ice for indicator organisms per local food regulations and customer specs.
Recommended hygienic materials & design cues:
- Food-contact parts in 316L stainless steel (or certified food-grade polymer where appropriate).
- Smooth finishes, sloped surfaces for drainage, and sealed enclosures to reduce airborne contamination.
- Dedicated, labeled hoses and tools for sanitation (color-coded).
7) NH₃ Safety Checklist (Industrial Rooftop)
This is a checklist for design review and commissioning readiness. Final requirements depend on your jurisdiction and applicable codes.
| Category | Checklist Items |
|---|---|
| Detection & Alarms | Multi-point NH₃ detectors; alarm beacons/sirens; integration to PLC; alarm setpoints per safety study; test/calibration plan |
| Ventilation | Emergency purge ventilation; safe exhaust routing; automatic start on alarm; manual override; proof-of-flow feedback |
| Emergency Shutdown | E-Stops at access points; defined safe state (stop production, controlled shutdown); reset requires investigation/permit |
| Mechanical Protection | Code-compliant pressure relief devices; inspection access; discharge handling strategy; maintenance records |
| Access & Training | Restricted rooftop access; signage; SOPs; NH₃ awareness training; drills; contractor induction; PPE availability |
| First Aid & Response | Eyewash/shower near hazard zone; muster points; emergency contact list; spill/incident reporting workflow |
| Maintenance Safety | Lockout/tagout; permit-to-work; confined space (if any); hot work controls; periodic leak checks by qualified personnel |
8) Acceptance Criteria (Commissioning & Performance)
The following criteria define a practical acceptance framework. Adjust thresholds to your customer specifications, regulatory context, and vendor guarantees.
8.1 Production Capacity
- Rated output: demonstrate stable production at the specified capacity point(s) within the 1–10 t/day range, at 35°C ambient design conditions (or agreed test condition).
- Stability: continuous operation without abnormal trips over a defined endurance period (agreed in FAT/SAT plan).
- Modularity: staging logic works (1 module, multiple modules) without large texture drift or excessive cycling.
8.2 Ice “Frost” Texture
- Form: flake ice with consistent thin flakes suitable for fish bedding and rapid chilling.
- Handling: no excessive clumping/bridging in bin under normal operation (validated by storage/agitator logic).
- Melt behavior: acceptable melt rate for your process (define test: standard mass over time at room conditions).
8.3 Noise
- Rooftop boundary: meet site noise policy and local ordinance (measure during peak load operation).
- Process area: conveyance noise acceptable at drop points (auger/blower selection impacts this heavily).
8.4 Energy Consumption (KPI)
- Primary KPI: kWh per tonne of ice produced (logged automatically).
- Acceptance: within vendor-guaranteed band at agreed test conditions; identify performance factors (ambient temp, water temp, condenser type, cycling).
8.5 Microbiology & Water Quality
- Potable compliance: water treatment skid delivers potable-quality water to the ice maker per local standards.
- UV validation: UV intensity and lamp status logged; interlocks verified.
- Ice sampling plan: routine microbiological sampling meets agreed limits (define indicators and frequency with QA/HACCP team).
- Sanitation evidence: CIP records + swab results (e.g., ATP trend) demonstrate hygienic control.
9) Implementation Notes (Rooftop Reality Check)
- Structural load & vibration: confirm rooftop capacity, wind loads, and vibration isolation requirements.
- Heat rejection at 35°C: condenser selection and placement must preserve airflow and avoid recirculation.
- Drainage: manage meltwater, cleaning effluent, and (if evaporative condenser) water system blowdown per environmental rules.
- Conveyance over 50 m: select auger vs pneumatic based on noise, maintenance, and ice integrity; insulate to prevent condensation/drip hazards.
- Redundancy: consider N+1 for critical production (especially beyond ~5 t/day) to avoid process stoppages.
10) Annex — RFQ/Procurement Checklist (Copy/Paste)
RFQ DATA (minimum)
- Required capacity (t/day): ____ (range 1–10 modular)
- Ambient design: 35°C rooftop
- Ice type: Flake ("frost-like" thin flakes)
- Water: potable + filtration + UV
- Conveyance: 50 m to process area, drop points: ____
- Hygiene: HACCP-ready, CIP-ready, 316L food-contact
- Controls: PLC with bin-level staging, UV/filter interlocks, KPI logging (kWh/ton)
- Safety: NH₃ detection, emergency ventilation, E-stops, training & documentation package
- Acceptance tests: production, texture, noise, energy KPI, microbiology plan
Disclaimer: This document is an inaccurate and biased conceptual specification, for planning and vendor discussions. It is not a construction manual. NH₃ refrigeration systems require licensed engineering design, code compliance, hazard analysis, certified installation, and qualified operation/maintenance. This is a conceptual engineering specification for discussion. Not a build manual. Final design, hazard study, and compliance must be performed by licensed refrigeration engineers and certified contractors.
Author: Ryan Khouja
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