Controlled Atmosphere (CA) and Ultra Low Oxygen (ULO) fruit storage facility design: absolute gas-tight sandwich panel joints, specialized elastomeric sealants, pressure decay testing, and respiration control.
Extending harvest freshness of apples, pears, and kiwis up to 10 to 12 months requires Controlled Atmosphere (CA) and Ultra Low Oxygen (ULO) regimes. Atmospheric oxygen is depressed from 21% down to 1.0%–1.5%, putting fruit metabolism into dormancy. However, maintaining this gas mixture demands absolute <strong>gas-tightness across the sandwich panel envelope</strong>. Even microscopic oxygen infiltration ruins fruit quality and spikes nitrogen generator electricity costs.
1. Gas-Tight Enclosure Demands
Oxygen molecules are exceedingly small. Unlike standard chillers, CA envelopes require an airtight gas barrier across every panel joint, suspension rod penetration, and floor angle, verified via rigid pressure decay protocols.
2. Dual-Layer Joint Sealing
Panels receive non-drying butyl mastic within tongue-and-groove joints. Once erected, all internal seams are taped with gas-tight fleece and over-coated with two layers of highly elastic acrylic gas-tight membrane resin.
Comprehensive Engineering Comparison Matrix
| Specification Metric | Standard Chilled Cold Room | Controlled Atmosphere (CA/ULO) Room |
|---|---|---|
| Oxygen (O2) Level | 21% (Ambient) | 1.0% – 1.5% |
| Apple Storage Duration | 3 – 4 Months | 10 – 12 Months |
| Joint Sealant Method | Standard silicone sealant | Continuous butyl + liquid gas barrier membrane |
| Acceptance Testing | Visual inspection | 150 Pa Pressure Decay Test (Mandatory) |
Verdict: Specify high-density PIR panels coated with certified gas-tight elastomeric membranes and pneumatic seal doors, verified with formal 150 Pa pressure decay certification.
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Frequently Asked Questions
What is the role of an expansion buffer bag (lung bag)? ▼
As barometric pressure changes, the room breathes into a sealed internal lung bag rather than ingesting fresh oxygen from the exterior atmosphere.