15. Controlled Atmosphere

8/9/2019 15. Controlled Atmosphere

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CONTROLLED

ATMOSPHERE SYSTEM


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What is Controlled Atmosphere? Controlled Atmosphere:

The control of the chemical composition of the

atmosphere surrounding a commodity by thecontinualaddition or removal of gases.

Modified Atmosphere:

The one time surrounding of a commodity with

a mixture of calibrated gases prior to shipment.


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CA History

Apple

Storage

19981950 1966 1987

Modified

Atmosphere

Controlled

Atmosphere


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History

5 units

19971987 1992 1994

Series 1

25 units

Series 2

107 units

Series 3

Production

starts


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Gas Composition

Nitrogen 78%

Oxygen 21%

Carbon

Dioxide .03%

Nitrogen 96%

Carbon

Dioxide 2%

Oxygen 2%

Normal Atmosphere Typical Desired Atmosphere


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Respiration

Oxygen

21% +Sugar CarbonDioxide

Heat


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Reduces Respiration

O2


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Respiration and OxygenRespiration

0%

25%

50%

75%

100%

125%

2 4 6 8 10 12

% Oxygen

Rate


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Effects on Produce

Reduces respiration Ethylene production retarded

higher natural sugar content.

Retards senescence (ripening / aging) associated softening and compositional changes.

Alleviates certain physiological storage disorders.

Retards some pathogens and consequential decay.

Provides insect control.


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Retards Senescence


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Insect And Pathogen Control


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Ethylene - C2H4

Produce generated ripening hormone

Accelerates senescence - plant breakdown

Diluted by adding nitrogen

Absorbed naturally by potassium permanganate

Scrubber available from CTD


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Controlled Atmosphere Benefits Permits longer tree ripening

Better product quality at final destination

Less spoilage during transport

Broader range of cargo can be shipped

Permits extended post harvest shipping and

storage times


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15 - 19% O2- Co-ordination impaired

12 - 14% O2- Perception and judgement impaired

10 - 12% O2- Performance failure, poor judgement- Onset of Cyanosis

8 - 10% O2- Mental failure, unconsciousness

6 - 8% O2- 100% fatal after 8 minutes exposure

4% - Coma in 40secs, convulsions, death

SAFETY

Modified and Controlled Atmosphere


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Never assume the atmosphere is safe

Vent before entering 20 minutes minimum

Remain clear of open doors Remain clear of air vents

Even if safe yesterday

Work in pairs when entering

Modified Atmosphere Controlled Atmosphere Units

SAFETY DETAILS


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Integrated within CTDs proven reefer unit

Utilizes membrane separator technology

Operates anywhere without additionalsupport technicians or trucks

No schedule delays waiting for service

No additional usage charges or fees

System Features


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Creates and accurately maintains :

Oxygen 1 to 21%

Carbon Dioxide 0 to 25%

Automated Pretrip checks:

Integral safety lock

Internal oilless air compressor Membrane protected by two filters


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Uses the Micro-Link 2 controller

Easy to use

Identical operation logic Possesses self diagnostics

Built in alarm indicators

Requires only software change

Uses same keypad and display (except for text)


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High N2 output reduces leakage requirements

Improves pulldown times.

CA uses the Reefer Datacorder.

Design uses common parts to minimize spares Low weight :


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Carry out Reefer PTI test

Carry out Air Leakage Test

Carry out CA PTI Attach Ethylene Scrubber (If required)

Set Reefer Temperature Set point

Set O2 and CO2 Set point

General Operation 1


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Attach CO2bottles internally (If required)

Pick and pack premium cargo

Fit rear door curtain

Start Reefer and CA units

Attach external CO2bottles (If required)

Ensure temperature pulls down

Ensure CA starts and pulls down

General Operation 2


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N2

O2 CO2

CO2O2COCO22


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Overview


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Membrane Oxygen permeability (polymer specific)

Selectivity - The ratio of oxygen to nitrogen

permeability (polymer specific)

Surface area

Pressure differential across the membrane wall


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Safety Door Lock

Locks when O2 is less than19.8%

Unlocks when O2 is greater than 20.3%

Has manual override


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Safety Door Lock


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The operator inputs O2 and CO2 setpoints.

The system compares to actual levels.

Then uses one of three modes

Nitrogen addition

Oxygen addition

Null


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The nitrogen mixes with existing box atmosphere

Creating a slight positive pressure

Compensates for normal box leakage.

Continues until the set points are achieved

Unit into Null mode

External CO2 is required if CO2 respiration is low


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Successful Shipmentsr uct Fr m To R esults

Beans Dakar Rotterdam Good

Melons Dakar Rotterdam Good

Tomatoes Morrocco Montreal Good

Pineapples Ghana Rotterdam Very Good

Bananas Gen. Santos Hong Kong Excellent


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CA is not a panacea

Control is paramount

Preparation and packaging controlled

Temperature controlled

Atmosphere controlled

CA Cannot improve produce

Decreases senescence rate Not all product is equal

Documents

15. Controlled Atmosphere