Many shippers and carriers are prepared to accept inadequateinstructions either through ignorance or through unquestioningacceptance of what has been accepted previously

IntroductionRefrigerated cargoes are invariably perishable to a greater or lesserdegree, and their safe carriage depends on maintaining suitable storageconditions during transportation. This is true for all modes of transport andall cargoes, though conditions are more critical for longer journey timesand for more perishable commodities.

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

Successful transportation is dependent on the carriage instructions, whichdefine the conditions in which the goods are to be carried. If theseinstructions are incomplete, inadequate, contradictory, or wrong, thenproblems can be expected. For the shipper, there is the risk of loss ofcargo. For the carrier, there is the risk of a claim even if the goods areundamaged. Many shippers and carriers are prepared to acceptinadequate instructions either through ignorance or through unquestioningacceptance of what has been accepted previously by themselves orothers. Instructions may be based on goods of different origin, which mayhave different requirements.

The way in which cargo is stowed into holds or stuffed in containers isimportant for successful carriage, and is dealt with later.

These recommendations have been drawn up to assist both shippers andcarriers to re-assess their carriage instructions in order to improve theoperation of refrigerated transport chains. Any suggestions forimproving these recommendations would be welcome.

Carefully to CarrySEPTEMBER 2006

UK P&I CLUB

Carriage instructions forrefrigerated cargoes

Carefully to CarryAdvisory Committee

This report was produced by the Carefullyto Carry Committee – the UK P&I Club’sadvisory committee on cargo matters.The aim of the Carefully to CarryCommittee is to reduce claims throughcontemporaneous advice to the Club’sMembers through the most efficientmeans available.

The committee was established in 1961and has produced many articles oncargoes that cause claims and other cargorelated issues such as hold washing,cargo securing, and ventilation.

The quality of advice given hasestablished Carefully to Carry as a keysource of guidance for shipowners andships’ officers. In addition, the articleshave frequently been the source ofexpertise in negotiations over thesettlement of claims and have also beenrelied on in court hearings.

In 2002 all articles were revised andpublished in book form as well as on disk.All articles are also available to Memberson the Club website. Visit the Carefully toCarry section in the Loss Prevention areaof the Club website www.ukpandi.com formore information, or contact the LossPrevention Department.

“The carriershall properlyand carefullyload, handle,stow, carry,keep, care forand dischargethe goodscarried.”

Hague Rules,Articles iii, Rule 2

First, general requirements are considered. Thereafter,separate sections relate to containerised cargoesand to shipments in reefer vessels. For ease ofreference, points that are the same for both types oftransport are repeated in the appropriate sections.

General requirementsThe responsibility for specifying carriage instructions isthat of the shipper, the owner of the goods. Only theshipper knows the full nature of the goods, their priorhistory and their requirements. Frequently thisresponsibility is passed to the carrier, but in this casethe shipper should agree the acceptability of thespecified conditions prior to shipment. In either case,the exact nature of the cargo needs to be known – inthe case of fruit, for example, carriage requirementsmay vary dependent on type, variety, maturity, originand growing season conditions. ● If mixed loads of differing commodities are to be

carried in a single cargo space, it is necessary toconsider compatibility of temperature, atmosphere(especially ethylene levels) and liability to taint. Thiswill usually require specialist cargo care advice.

● It may be necessary to ensure that carriageconditions are specified to all carriers in thetransport chain, as on occasions an internationaljourney may use different carriers at the start andend of the journey.

● Items such as relative humidity and maximum timewithout refrigeration should not be over-specified butshould meet the necessary requirements of thegoods.

● Over-specification of requirements is to be avoidedas it tends to lead to more, and sometimes spurious,claims regarding technicalities which have notactually affected cargo quality.

Many of the items listed here may be taken for grantedin the case of regular shipments, but may need to bespecified if a new carrier is used.

Specific requirements for containerised cargoesThe parameters that may be included in carriageinstructions for containerised refrigerated cargo arelisted below:

● Pre-stuffing sanitation.

● Pre-cooling of containers.

● Cooling during part-loaded conditions.

● Prohibition of stuffing cargo at mixed temperatures.

● Stowage requirements.

● Ventilation.

● Carriage temperature.

● Maximum time with refrigeration.

● Air circulation rate.

● Relative humidity.

● Measurement and reporting requirements.

● Special conditions for cold weather.

● Need to pass instructions to subsequent carrier.

● Need to notify if limits exceeded.

For controlled atmosphere shipments,additionally:

● Levels (ranges) for O2, CO2, humidity, ethylene.

● Permitted time to reach specified levels.

● Procedure in event of CA system failure.

● Safety requirements.

● Discharge atmosphere requirements.

Each of these is considered below:

Pre-stuffing sanitationThe proper cleanliness and lack of odour in containersto be used for refrigerated goods should be a matterof normal good practice, but any special or particularneeds should be identified.

Pre-cooling of containersPre-cooling is only useful when loading fromtemperature-controlled loading bays; in otherconditions, it can result in excessive moisture ingressfrom the atmosphere and is not recommended.

Cooling during part-loaded conditionsPart-loaded containers should be closed andtemperature maintained if there is a delay beforecomplete loading.

Prohibition of stuffing cargo at mixedtemperaturesProperly pre-cooled cargo and substantially warmercargo should not be mixed.

Stowage requirementsAny special stowage requirements, such as a protectedor underdeck stow, should be stated.

VentilationThe rate of fresh air ventilation for fresh produce shouldbe specified. This should be as an absolute figure in

cubic metres per hour. The specification of apercentage rate of ventilation only has meaning ifrelated to a specific container size and a specificmodel of refrigeration unit.

Carriage temperatureIt is not physically possible to provide refrigeration inthe absence of temperature differences, both betweenair and goods and within the bulk of the goods. Theonly temperature which can be controlled is the setpoint, which corresponds to air delivery temperature forchilled goods and to air return temperature for frozengoods. The term ‘carriage temperature’ therefore haslittle meaning, and ‘set point temperature’ should bespecified. If appropriate, this may be augmented by amaximum allowable temperature during periods withoutrefrigeration.

Although degrees Celsius (oC) are the internationalstandard, in the USA degrees Fahrenheit (oF) are stillcommonly used. As zero degrees C is a commonchilled goods temperature and zero degrees F is acommon frozen goods temperature, great care isneeded to avoid possible confusion of units.

For USDA and other cold treatment quarantinerequirements, maximum pulp temperature may have tobe maintained below a specified temperaturethroughout a continuous period of days or weeks, andonly approved equipment may be used.

Maximum time without refrigerationSometimes it may be necessary for statutory or otherreasons to specify a maximum duration of time withoutrefrigeration, either per event or in total for the journey.This should not be necessary if temperature limitsare well defined.

Air circulationSome containers have a high air circulation rate forchilled goods and a lower rate for frozen goods. If aspeed change switch is fitted, low speed operation forchilled goods may be possible, but as this inevitablyresults in a wider range of cargo temperature, it is notrecommended.

Relative humidityWhen equipment with humidity control is used, a rangemust be specified. It is difficult to measure humidityregularly to better than the nearest 2 to 3%, so anacceptable range of at least ±5% should be specified,albeit with a tighter target. Special equipment isavailable to maintain either high (e.g. 90%) or low (e.g.50%) humidity. Without such equipment, relativehumidity is not controllable and should not bespecified.

Measurement and reporting requirementsIt is normal to record air temperature in refrigeratedcontainers, and some equipment also records deliveryair temperature. Any specific shipper requirement forreporting temperatures should be stated. When therefrigeration unit is not running, the recordedtemperatures do not reflect cargo temperatures.Shippers may choose to put their own recordingequipment within cargo, in which case they shouldinform both carriers and receivers.

Special conditions for cold weatherSometimes special requirements exist for exceptionallycold conditions. However, it should be noted thatmost transport refrigeration equipment will controltemperature using either cooling or heating asnecessary to maintain specified conditions.

Need to pass instructions to subsequent carrierIf there is uncertainty at the start of a voyage as to whowill be the final carrier, it may be necessary to requestthe initial carrier to pass on carriage instructions.

Need to notify if limits exceededProcedures for notification of out of specificationconditions should be established prior to acceptanceof cargo for shipment. This could apply to warmloading, or to equipment failures, for example.Standard procedures and safe limits should beavailable.

Additional requirements for controlledatmosphere shipments

Controlled atmosphere (CA) systems are designed tomaintain an atmosphere different from normal, usuallywith low oxygen and increased carbon dioxide. Theyenhance the storage life of some produce when usedin conjunction with refrigeration. There are additionalrequirements for such shipments, as follows:

Levels (ranges) for O2, CO2, humidity, ethyleneFor each of the atmospheric gases to be controlled,upper and lower concentration limits should bespecified.

Permitted time to reach specified levelsThe maximum time allowed to reach the specifiedlevels may be laid down.

Procedure in event of CA system failureThe failure of a CA system will not necessarily have adrastic effect on the produce if the refrigerationcontinues to run. In these circumstances it will benecessary to introduce fresh air ventilation to fruit andvegetable cargoes. This should be specified.

Safety requirementsCA produces an atmosphere which is deadly tohumans – breathing an oxygen-depleted atmosphereinduces rapid unconsciousness and may result indeath. Adequate safety systems must be in place, andthese may need to allow for the possibility ofstowaways in the cargo.

Discharge atmosphere requirementsThe safety requirements extend to those unloadingcargoes. Proper ventilation prior to entering containersand training of workers are both necessary.

Containerised transport ofperishables without refrigerationSome perishable commodities are carried withoutrefrigeration, possibly for very short-duration journeys,or in ventilated equipment. In these cases it is wise toconsider which of the previous requirements may stillapply.

Products with limited temperature sensitivity may becarried under refrigeration for certain journeys only.The following guidelines suggest when this may beappropriate:

● For any goods requiring close temperature control,refrigeration is essential. If temperatures need to bemaintained within a band of 2oC or less, refrigerationshould be virtually continuous.

● At the other extreme, for less sensitive goods with a

maximum temperature tolerance of 30oC or above,refrigeration is only necessary for storage on land athigh ambient temperatures. For containerisedshipments at sea, a protected stow may berequested.

● If the maximum permitted temperature is 25oC or

lower, refrigeration should be used for any journeysthrough the tropics and for any journeys anywhere ina summer season.

● If cargo requirements are marginal, either in terms oftemperature tolerance or in terms of possible delaysat high ambient temperatures, then the only safeoption is to use refrigeration.

● Frozen foods may sometimes be carried withoutrefrigeration for short journeys as long as the cargois not subjected to more than the specified maximumtemperature. This should only be done with theconsent of the owner of the goods.

Specific requirements for reefershipsThe parameters that may be included in carriage

instructions for refrigerated cargo are listed below:

● Pre-loading sanitation.

● Pre-cooling of cargo space.

● Cooling during part-loaded conditions.

● Prohibition of loading cargo at mixed temperatures.

● Stowage requirements.

● Ventilation (or lack of) during cooling.

● Ventilation thereafter.

● Carriage temperature.

● Air circulation rate.

● Relative humidity limits or targets.

● Carbon dioxide limits or targets.

● Ethylene limits.

● Measurement and reporting requirements.

● Special conditions for cold weather.

● Need to pass instructions to subsequent carrier.

● Need to notify if limits exceeded.

For controlled atmosphere shipments,additionally:

● Levels (ranges) for O2, and CO2, humidity, ethylene.

● Permitted time to reach specified levels.

● Procedure in event of CA system failure.

● Safety requirements.

● Discharge atmosphere requirements.

Each of these is considered below.

Pre-loading sanitationThe proper cleanliness and lack of odour incompartments to be used for refrigerated goods shouldbe a matter of normal good practice, but any special orparticular needs should be identified.

Pre-cooling of cargo spaceThe pre-cooling of cargo spaces removes heat fromsteelwork and provides a check on the operation of therefrigeration system. However, an excessive pre-cooling time only wastes energy and time. Duration of24hours after the required temperature has beenreached is sufficient. The required pre-coolingtemperature may be a few degrees lower than requiredtransport temperature.

Cooling during part-loaded conditions

Part-loaded spaces should be closed and temperaturemaintained if there is a delay before completingloading. Care should be taken to ensure that underthese conditions the temperature is not held at aprecooling temperature below the required transporttemperature for long enough to damage the cargo.

Prohibition of loading cargo at mixedtemperaturesProperly pre-cooled cargo and substantially warmercargo should not be mixed at loading.

Stowage requirementsAny special stowage requirements should be stated.

Ventilation (or lack of) during coolingFor most refrigerated cargoes, the cargo should beloaded at the required carriage temperature. For somecargoes, notably bananas and the less sensitive citrusvarieties, cooling in transit is normal. In these cases aperiod of 48 hours should be specified, during whichfresh air ventilation is stopped to allow maximumrefrigeration.

Reference is sometimes made to the ‘reduction period’which is the time from hatch closure to the air returntemperature reaching within 18oF of the requested airdelivery temperature. This is a parameter which mayusefully measured and reported but should not bespecified.

Ventilation thereafterAfter cooling, or throughout in the absence of cooling,the rate of fresh air ventilation for fresh produceshould be specified. This may be as an absolute figurein cubic metres per hour, or as a rate in air changesper hour of the empty volume of cargo space.Alternatively it may be linked to measured values ofhumidity, ethylene or carbon dioxide. Care is necessaryto avoid requirements that conflict.

Carriage temperatureIt is not physically possible to provide refrigeration inthe absence of temperature differences both betweenair and goods and within the bulk of the goods.Carriage temperature for chilled goods must thereforebe specified as the air delivery temperature. Pulptemperatures may usefully be measured and reported.

It may be required to specify a lower temperature for alimited period to ensure rapid cooling of warm cargo,known as ‘shock treatment’. Dual-temperatureregimes, in which the delivery air temperature ischanged after a specified period of days, may also bestipulated.

For frozen cargo, it is usually sufficient to specify amaximum temperature that should not be exceeded.

This may be subject to qualification for short periods.For example:

Cargo temperature shall not exceed -18oC, except forshort periods during power disconnection ordefrosting, when temperatures shall not exceed -15oC.A single specified ‘carriage temperature’ is ameaningless specification that should never beaccepted.

Although degrees Celsius (oC) are the internationalstandard, in the USA degrees Fahrenheit (oF) are stillcommonly used. As 0oC is a common chilled goodstemperature and 0oF is a common frozen goodstemperature, great care is needed to avoid possibleconfusion of units.

For USDA and other cold treatment quarantinerequirements, maximum pulp temperature may have tobe maintained below a specified temperaturethroughout a continuous period of days or weeks, andonly approved equipment may be used.

Air circulation rateThe rate of circulation of air around and through thecargo controls the range of temperature within thecargo, and also the rate of cargo cooling. Minimumrates may be specified, usually as multiples of theempty volume of the hold per hour. Often thesemultiples are misleadingly referred to as ‘air changesper hour’, or ‘ACH’, a term best used for ventilationrather than circulation rates.

Relative humidity limits or targetRelative humidity may not be specifically controllablein shipments; if there are critical requirements, eitherspecial equipment or special packaging or both will berequired. A sensible specification is as follows:

Relative humidity should be maintained at the maximumpossible, after the delivery air temperature andfresh air ventilation requirements have been met.

Over-specification of humidity requirements is likely tolead to conflicting instructions. When specialequipment with humidity control is used, a range mustbe specified. It is difficult to measure humidity regularlyto better than the nearest two to three percent, so thatan acceptable range of at least plus or minus fivepercent must be specified, albeit with a tighter target.

Carbon dioxide limits or targetFor many fruits, a maximum level of carbon dioxide maybe specified, this to be the overriding parameter forventilation rate control. Care is necessary to avoidconflicting ventilation requirements.

Ethylene limitsThe measurement or specification of ethylene levels is

UK P&I CLUBIS MANAGEDBY THOMASMILLER

For further information please contact:Loss Prevention Department, Thomas Miller P&I LtdTel: +44 20 7204 2307. Fax +44 20 7283 6517Email: lossprevention.ukclub@thomasmiller.com

rare, as accurate measurement at very lowconcentrations needs specialised equipment. If limitsare to be specified, the measurement and controlregime must also be specified.

Measuring and reporting requirementsIt is normal for carriers to measure temperatures of theair in ships’ holds. Any specific shipper requirementshould be stated, especially if it involves cargo ratherthan air temperature. Shippers frequently choose toput their own recording equipment within thecontainer/cargo in which case they should inform bothcarriers and receivers.

Special conditions for cold weatherSometimes special requirements exist for exceptionallycold conditions. However, it should be noted thatmost transport refrigeration equipment will controltemperature using either cooling or heating asnecessary to maintain specified conditions.

Need to pass instructions to subsequent carrierIf there is uncertainty at the start of a voyage as to whowill be the final carrier, it may be necessary torequest the initial carrier to pass on carriageinstructions.

Need to notify if limits exceededProcedures for notification of out of specificationconditions should be established prior to acceptanceof cargo for shipment. For example, this could apply towarm loading, or to equipment failures. Standardprocedures and safe limits should be made available.

Additional requirements for controlledatmosphere shipments

Controlled atmosphere (CA) systems are designed tomaintain an atmosphere different from normal, usuallywith low oxygen and increased carbon dioxide. Theyenhance the storage life of some produce when usedin conjunction with refrigeration. There are additionalrequirements for such shipments as follows:

Levels (ranges) for oxygen, carbon dioxide,humidity and ethyleneFor each of the atmospheric gases to be controlled,upper and lower limits should be specified.

Permitted time to reach specified levelsThe maximum time allowed to reach the specifiedlevels may be stipulated.

Procedure in the event of CA system failureThe failure of a CA system will not necessarily have adrastic effect on the produce if the refrigerationcontinues to run. In these circumstances it will benecessary to introduce fresh air ventilation, whichshould be stated.

Safety requirementsCA produces an atmosphere that is fatal to humans –breathing an oxygen-depleted atmosphereatmosphere induces rapid unconsciousness and mayresult in death. Adequate safety systems must be inplace, and these should always admit the possibility ofstowaways in the cargo.

Discharge atmosphere requirementsThe safety requirements extend to those unloadingcargoes. Proper ventilation prior to opening cargospaces and training of workers are both essential.