ICCT have produced a series of downloadable guidelines. These include:

Surveyors guidelines pdf and in word format (editable), pdfs of carriage instructions in English and Spanish and typical carriage temperature that can be achieved in containers and reefer ships. 

Please feel free to use these guidelines but ensure that you acknowledge the ICCT Group.

Recommendations Regarding Carriage Instructions for Refrigerated Cargoes

Introduction

Refrigerated cargoes are invariably perishable to a greater or lesser degree, and their safe carriage depends on maintaining suitable storage conditions during transportation. This is true for all modes of transport and all cargoes, though conditions are more critical for longer journey times and for more perishable commodities.

Refrigerated cargoes include both frozen and chilled goods, the latter including fresh fruits and vegetables. Generally, frozen goods do not suffer if over-cooled, whereas chilled goods can be damaged by low temperatures, either by freezing or by chilling injury to fresh produce. Much tropical and sub-tropical produce is liable to chilling injury if subjected to temperatures below those usually experienced in the growing area.

Successful transportation is dependent on the carriage instructions, which define the conditions in which the goods are to be carried. If these instructions are incomplete, inadequate, contradictory, or wrong, then problems can be expected. For the shipper, there is the risk of loss of cargo. For the carrier, there is the risk of a claim even if the goods are undamaged. Many shippers and carriers are prepared to accept inadequate instructions either through ignorance or through unquestioning acceptance of what has been accepted previously by themselves or others. Instructions may be based on goods of different origin, which may have different requirements.

The way in which cargo is stowed into holds or stuffed into containers is important for successful carriage, but is outside the scope of these recommendations.

These recommendations have been drawn up by ICCT to assist both shippers and carriers to re-assess their carriage instructions in order to improve the operation of refrigerated transport chains. Any suggestions for improving these recommendations would be welcome.

First, general requirements are considered. Thereafter, separate sections relate to containerised cargoes and to shipments in reefer vessels. For ease of reference, points that are the same for both types of transport are repeated in the appropriate sections.

General Requirements

The responsibility for specifying carriage instructions is that of the shipper, the owner of the goods. Only the shipper knows the full nature of the goods and their requirements. Frequently this responsibility is passed to the carrier, but in this case the shipper prior to shipment should agree the acceptability of the specified conditions. In either case, the exact nature of the cargo needs to be known - in the case of fruit, for example, carriage requirements may vary dependent on type, variety, maturity, origin and growing season conditions.

If mixed loads of differing commodities are to be carried in a single cargo space, it is necessary to consider compatibility of temperature, atmosphere (especially ethylene levels) and liability to taint. This will usually require specialist cargo care advice. It may be necessary to ensure that carriage conditions are specified to all carriers in the transport chain, as frequently an international journey may use different carriers at the start and end of the journey.

Items such as relative humidity and maximum time without refrigeration should not be over-specified but should meet the necessary requirements of the goods. Over-specification of requirements is to be avoided as it tends to lead to more, and sometimes spurious, claims regarding technicalities which have not actually affected cargo quality.

Many of the specific items listed below may be taken for granted with regular shipments, but may need to be specified if a new carrier is used

Specific Requirements for Containerised Cargoes

The parameters that may be included in carriage instructions for containerised refrigerated cargo include the following:

For Controlled Atmosphere shipments, additionally:

Each of these will be considered below.

Pre-stuffing sanitation - The proper cleanliness and lack of odour in containers to be used for refrigerated goods should be a matter of normal good practice, but any special or particular needs should be identified

Pre-cooling of containers - Pre-cooling is only useful when loading from temperature controlled loading bays; in other conditions, it can result in excessive moisture ingress from the atmosphere and is not recommended.

Cooling during part loaded conditions - Part loaded containers should be closed and temperature maintained if there is a delay before completing loading.

Prohibition of stuffing cargo at mixed temperatures - Properly pre-cooled cargo and substantially warmer cargo should not be mixed

Stowage requirements - Any special stowage requirements, such as a protected or underdeck stow, should be stated.

Ventilation - The rate of fresh air ventilation for fresh produce should be specified. This should be as an absolute figure in cubic metres per hour. The specification of a percentage rate of ventilation only has meaning if related to a specific container size and a specific model of refrigeration unit.

Carriage temperature - It is not physically possible to provide refrigeration in the absence of temperature differences, both between air and goods and within the bulk of the goods. The only temperature which can be controlled is the set point, which corresponds to air delivery temperature for chilled goods and to air return temperature for frozen goods. The term “carriage temperature” therefore has little meaning, and “set point temperature” should be specified. If appropriate, this may be augmented by a maximum allowable temperature during periods without refrigeration.

Although degrees Celsius are the international standard, in the USA degrees Fahrenheit are still commonly used. As zero C is a common chilled goods temperature and zero F is a common frozen goods temperature, great care is needed to avoid possible confusion of units.

For USDA and other cold treatment quarantine requirements, maximum pulp temperature may have to be maintained below a specified temperature throughout a continuous period of days or weeks, and only approved equipment may be used

Maximum time without refrigeration - Sometimes it may be necessary for statutory or other reasons to specify a maximum duration of time without refrigeration, either per event or in total for the journey. This should not be necessary if temperature limits are well defined.

Air circulation - Many containers have a high air circulation rate for chilled goods and a lower rate for frozen goods. If a speed change switch is fitted, low speed operation for chilled goods may be possible, but as this inevitably results in a wider range of cargo temperature, it is not recommended.

Relative humidity - When special equipment with humidity control is used, a range must be specified. It is difficult to measure humidity regularly to better than the nearest 2 to 3%, so an acceptable range of at least plus or minus 5% should be specified, albeit with a tighter target. Special equipment is available to maintain either high (e.g. 90%) or low (e.g.50%) humidity. Without such equipment, relative humidity is not controllable and should not be specified.

Measurement and reporting requirements - It is normal to record return air temperature in refrigerated containers, and some equipment also records delivery air temperatures. Any specific shipper requirement for reporting temperatures should be stated. When the refrigeration unit is not running, the recorded temperatures do not reflect cargo temperatures. Shippers may choose to put their own recording equipment within cargo, in which case they should inform both carriers and receivers

Special conditions for cold weather - Sometimes special requirements exist for exceptionally cold conditions. However, it should be noted that most transport refrigeration equipment will control temperature using either cooling or heating as necessary to maintain specified conditions.

Need to pass instructions to subsequent carrier - If there is uncertainty at the start of a voyage as to who will be the final carrier, it may be necessary to request the initial carrier to pass on carriage instructions.

Need to notify if limits exceeded - Procedures for notification of out of specification conditions should be established prior to acceptance of cargo for shipment. This could apply to warm loading, or to equipment failures, for example. Standard procedures and safe limits should be available.

Additional requirements for Controlled Atmosphere shipments - Controlled Atmosphere (CA) systems are designed to maintain an atmosphere different from normal, usually with low oxygen and increased carbon dioxide. They enhance the storage life of some produce when used in conjunction with refrigeration. There are additional requirements for such shipments, as follows:

• Levels (ranges) for O2, CO2, humidity, ethylene - For each of the atmospheric gases to be controlled, upper and lower concentration limits should be specified.
• Permitted time to reach specified levels - The maximum time allowed to reach the specified levels may be laid down.
• Procedure in event of CA system failure - The failure of a CA system will not necessarily have a drastic effect on the produce if the refrigeration continues to run. In these circumstances it will be necessary to introduce fresh air ventilation to fruit and vegetable cargoes. This should be specified.
• Safety requirements - CA produces an atmosphere which is deadly to humans - breathing an oxygen-depleted atmosphere produces immediate unconsciousness and fairly rapid death. Adequate safety systems must be in place, and these may need to allow for the possibility of stowaways in the cargo.
• Discharge atmosphere requirements - The safety requirements extend to those unloading cargoes. Proper ventilation prior to entering containers and training of workers are both necessary.

Containerised Transport of Perishables without Refrigeration

Some perishable commodities are carried without refrigeration, possibly for short-duration journeys, or in ventilated equipment. In these cases it is wise to consider which of the above requirements may still apply.

Products with limited temperature sensitivity may be carried under refrigeration for certain journeys only. The following guidelines suggest when this may be appropriate.

• For any goods requiring close temperature control, refrigeration is essential. If temperatures need to be maintained within a band of 2 degrees C or less, refrigeration should be virtually continuous.
• At the other extreme, for less sensitive goods with a maximum temperature tolerance of 30 degrees C or above, refrigeration is only necessary for storage on land at high ambient temperatures. For containerised shipments at sea, a protected stow may be requested.
• If the maximum permitted temperature is 25 degrees C or lower, refrigeration should be used for any journeys through the tropics and for any journeys anywhere in summer.
• If cargo requirements are marginal, either in terms of temperature tolerance or in terns of possible delays at high ambient temperatures, then the only safe option is to use refrigeration. Frozen foods may sometimes be carried without refrigeration for short journeys as long as the cargo does not rise above the specified maximum temperature. This should only be done with the consent of the owner of the goods.

Specific Requirements for Reefer Ships

The parameters that may be included in carriage instructions for refrigerated cargo include the following:

For Controlled Atmosphere shipments, additionally:

Each of these will be considered below.

Pre-loading sanitation - The proper cleanliness and lack of odour in compartments to be used for refrigerated goods should be a matter of normal good practice, but any special or particular needs should be identified.

Pre-cooling of cargo space - The pre-cooling of cargo spaces removes heat from steelwork and provides a check on the operation of the refrigeration system. However, an excessive pre-cooling time only wastes energy and time. Duration of 24 hours after the required temperature has been reached is sufficient. The required pre-cooling temperature may be a few degrees lower than the required transport temperature.

Cooling during part loaded conditions - Part loaded spaces should be closed and temperature maintained if there is a delay before completing loading. Care should be taken to ensure that under these conditions the temperature is not held at a pre-cooling temperature below the required transport temperature for long enough to damage the cargo

Prohibition of loading cargo at mixed temperatures - Properly pre-cooled cargo and substantially warmer cargo should not be mixed at loading.

Stowage requirements - Any special stowage requirements should be stated.

Ventilation (or lack of) during cooling - For most refrigerated cargoes, the cargo should be loaded at carriage temperature. For some cargoes, notably bananas and the less sensitive citrus varieties, cooling in transit is normal. In these cases a period of 48 hours should be specified, during which fresh air ventilation is stopped to allow maximum refrigeration. Reference is sometimes made to the “reduction period” which is the time from hatch closure to the air return temperature reaching within 4 degrees Fahrenheit of the requested air delivery temperature. This is a parameter which may usefully be measured and reported, but should not be specified.

Ventilation thereafter - After cooling, or throughout in the absence of cooling, the rate of fresh air ventilation for fresh produce should be specified. This may be as an absolute figure in cubic metres per hour, or as a rate in air changes per hour of the empty volume of the cargo space. Alternatively it may be linked to measured values of humidity, ethylene or carbon dioxide. Care is necessary to avoid requirements that conflict.

Carriage temperature - It is not physically possible to provide refrigeration in the absence of temperature differences, both between air and goods and within the bulk of the goods. Carriage temperature for chilled goods must therefore be specified as the air delivery temperature. Pulp temperatures may usefully be measured and reported. It may be required to specify a lower temperature for a limited period to ensure rapid cooling of warm cargo, known as “shock treatment”. Dual-temperature regimes, in which the delivery air temperature is changed after a specified period of days, may also be specified. For frozen cargo, it is usually sufficient to specify a maximum temperature that should not be exceeded. This may be subject to qualification for short periods. For example: Cargo temperature shall not exceed minus 18 degrees C, except for short periods during power disconnection or defrosting, when temperature shall not exceed minus 15 degrees C. A single specified “carriage temperature” is a meaningless specification that should never be accepted. Although degrees Celsius are the international standard, in the USA degrees Fahrenheit are still commonly used. As zero C is a common chilled goods temperature and zero F is a common frozen goods temperature, great care is needed to avoid possible confusion of units. For USDA and other cold treatment quarantine requirements, maximum pulp temperature may have to be maintained below a specified temperature throughout a continuous period of days or weeks, and only approved equipment may be used.

Air circulation rate - The rate of circulation of air around and through the cargo controls the range of temperature within the cargo, and also the rate of cargo cooling. Minimum rates may be specified, usually as multiples of the empty volume of the hold per hour. Often these multiples are misleadingly referred to as “air changes” per hour, or “ach”, a term best used for ventilation rather than circulation rates.

Relative humidity limits or target - Relative humidity is not specifically controllable in most shipments, and if there are critical requirements, either special equipment or special packaging or both may be required. A sensible specification is as follows. Relative humidity should be maintained at the maximum possible, after the delivery air temperature and fresh air ventilation requirements have been met. Over-specification of humidity requirements is likely to lead to conflicting instructions. When special equipment with humidity control is used, a range must be specified. It is difficult to measure humidity regularly to better than the nearest 2 to 3%, so an acceptable range of at least plus or minus 5% should be specified, albeit with a tighter target.

Carbon dioxide limits or target - For many fruits, a maximum level of CO2 may be specified, this to be the overriding parameter for ventilation rate control. Care is necessary to avoid conflicting ventilation requirements.

Ethylene limits - The measurement or specification of ethylene levels is rare, as accurate measurement at very low concentrations needs specialised equipment. If limits are to be specified, the measurement and control regime must also be specified.

Measuring and reporting requirements - It is normal for carriers to measure temperatures of the air in ships’ holds. Any specific shipper requirement should be stated, especially if it involves cargo rather than air temperatures. Shippers may choose to put their own recording equipment within cargo, in which case they should inform both carriers and receivers.

Special conditions for cold weather - Sometimes special requirements exist for exceptionally cold conditions. However, it should be noted that most transport refrigeration equipment will control temperature using either cooling or heating as necessary to maintain specified conditions.

Need to pass instructions to subsequent carrier - If there is uncertainty at the start of a voyage as to who will be the final carrier, it may be necessary to request the initial carrier to pass on carriage instructions.

Need to notify if limits exceeded - Procedures for notification of out of specification conditions should be established prior to acceptance of cargo for shipment. This could apply to warm loading, or to equipment failures, for example. Standard procedures and safe limits should be available.

Additional requirements for Controlled Atmosphere shipments - Controlled Atmosphere (CA) systems are designed to maintain an atmosphere different from normal, usually with low oxygen and increased carbon dioxide. They enhance the storage life of some produce when used in conjunction with refrigeration. There are additional requirements for such shipments, as follows.

• Levels (ranges) for O2, CO2, humidity, ethylene - For each of the atmospheric gases to be controlled, upper and lower limits should be specified.
• Permitted time to reach specified levels - The maximum time allowed to reach the specified levels may be laid down.
• Procedure in event of CA system failure - The failure of a CA system will not necessarily have a drastic effect on the produce if the refrigeration continues to run. In these circumstances it will be necessary to introduce fresh air ventilation. This should be specified.
• Safety requirements - CA produces an atmosphere which is deadly to humans - breathing an oxygen-depleted atmosphere produces immediate unconsciousness and fairly rapid death. Adequate safety systems must be in place, and these should allow for the possibility of stowaways in the cargo.
• Discharge atmosphere requirements - The safety requirements extend to those unloading cargoes. Proper ventilation prior to opening cargo spaces and training of workers are both necessary

Disclaimer

These recommendations are given in good faith after due consideration, but neither CRT nor ICCT nor any of its members nor any of the endorsing organisations or individuals accept any liability for the consequences of their use.

Endorsements

This document is endorsed by the following:

These recommendations may be freely quoted in whole or in part, as long as full reference to the source is given.

Comments or suggestions for improvements to future versions of these recommendations may be sent to:

Ian Lawson
ICCT
Cambridge Refrigeration Technology
140 Newmarket Road
Cambridge CB5 8HE
UK