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Technical Q&A

Technical Glossary

Why should the frozen CoolPacs not be placed next to the product load?

The liquid within a standard CoolPac changes phase from a solid to a liquid at approximately 0°C, during this change, the CoolPac is able to absorb large amounts of heat energy. If the CoolPac at 0°C or less is in direct contact with the product, then there is a risk that the product may fall below +2°C.

Why do we need to condition the CoolPacs at factory ambient temperature?

To ensure that the CoolPac is completely frozen, the temperature to which it is conditioned must be below its point of phase change. At the point of removal from the freezer, it can become necessary to allow the CoolPac to warm slightly at factory ambient, bringing it closer to its point of phase change, as this will lessen the impact of its introduction into the control temperature package. This conditioning period prevents the product falling below +2°C.

How are the temperature profiles used in the qualification created?

SCA Cool Logistics are happy to use customer-specified ambient profiles when qualifying your packaging. Alternatively, we can suggest profiles. We have over 3 years running trials with various companies, where the temperature of the TCP experienced during transit is logged. From this data, we are able to develop profiles to suit your requirements.

What are the differences in the styles of CoolPacs you offer?

There are two key differences in the styles of CoolPacs we offer. The first difference is simply a packaging material change and this could be from a very flexible gel-filled bag, to a rigid bottle pack presentation. The second difference would reference the coolant material contained within the pack and at what temperature it would change phase.

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Why shouldn’t I have my insulated shipping system placed in the fridge?

Control temperature packaging is designed to maintain product temperature at a given range of ambient or external temperatures. If a pack designed to maintain product at +2°C to +8°C for European Summer shipments is placed in a +2°C to +8°C fridge and not the expected +25°C warehouse, the deltaT will be considerably reduced. This reduction in the pack's ambient temperature can cause the product to go below the specified minimum temperature. Temperature controlled packaging can be designed to be placed into a fridge or coldstore if required, although this will affect other logistical parameters.

Is it ever sensible to put my +2°C to +8°C insulated shipping system in a fridge?

Yes. If you have a high understanding of your transportation route, you may be able to gauge at what point the frozen mass within the system has been fully depleted. At this point, placing the system into the fridge will prevent any temperature excursions. It is however, advised that laboratory qualification testing is undertaken prior to this, so as to fully understand the rate of exhaustion in varying temperatures. If there is a possibility of the system being placed into a +5°C environment during transportation, then this period can be developed into the test ambient temperature and the system can be developed accordingly.

Why do I always seem to have moisture on the CoolPacs?

If using a frozen CoolPac within a control temperature package, it is often noted that at the end of the shipping process there may be some moisture on the CoolPacs. This moisture is simply condensation that has occurred due to the warmer air within the system, coming into contact with the colder surface of the CoolPac and so some of the water vapour contained within the warm air has been released as the air temperature falls. We do offer a CoolDry heat stabilising pack that has an absorbent material to cope with this issue.

If I put dry ice into a shipper, will it burst as the dry ice sublimes?

Although during sublimation dry ice expands by approximately 800 times from its pelletised format into a gas, TCP containers do not provide an air-tight seal to their contents and so the gas is free to escape without the issue of explosion. Dry ice should never be loaded into a 6.2 dangerous goods secondary pack.

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Why do my temperature recorders always alarm at the start of shipping?

Best practice is to treat your temperature recorder as you treat your product. The excursions that you see will most likely occur whilst being transferred from desk drawer into control temperature package, where they would have stabilised at a comfortable office temperature, rather than a product one. Storing the temperature recorder within a +5°C environment prior to use and adding a 30 minute start-up delay would remove the high temperature excursions.

Why do my temperature recorders always alarm at the end of shipping?

An alarm at the end of shipping could simply be that the temperature monitor was removed from the system, but was not immediately stopped and so began measuring external temperature prior to download.

Do you take your used packaging back?

Yes. SCA Cool Logistics has the facilities to offer a disposal program. If you would like more information regarding this, please contact us.

How do I safely dispose of any packaging you have supplied after use?

All SCA Cool Logistics products are developed with environmental issues in mind. The majority of items supplied by SCA Cool Logistics can be thrown away with all other refuse. However, if you do have specific concerns regarding items, we can supply you with safety and disposal documentation.

Why don’t you put an inner (or core) carton in every design?

The benefits of an inner carton are simply that they offer a portable payload space that can be filled and loaded into the temperature controlled package at the very last moment. This is often handy if multiples of small products are being shipped in one package and many customers would rather supply their own and have the system developed around these. However, the inner carton can take up space. As it offers no real thermal benefit, it is a component that can be omitted in favour of cost saving. Also, many customers consistently pack their own bulk packs into our shippers, so they have a core pack already.

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Do I need to use an outer carton for my temperature controlled packaging?

No. The outer carton simply acts as a layer of protection for your insulated container, working simply as both a device to enable reuse and to maintain good product presentation at delivery. Knocks to the carton will not affect performance, but will defend against the performance-reducing chips that can be knocked off an insulated container.

Where is the best location for a temperature monitor in my shipment?

In the product specified location. A temperature controlled package, although designed to maintain product temperature between specified thresholds, may utilise components whose temperatures sit outside of the product temperature range and so by measuring these points, you are not gaining data from a useful location.

Why does the monitored temperature fluctuate more than is seen in the qualification?

The temperature monitoring devices used at SCA Cool Logistics connect directly to the product. When making real shipment, this type of probing becomes unrealistic due to the high level of product tampering that would be needed. These real shipment monitors simply measure the air surrounding the product and as air is more susceptible to temperature change, due to its lower thermal mass, its changes look more dramatic when compared to actual product reading.

Do you suggest any label text to alert the receiving site that the shipment is of temperature sensitive product?

This is a long-standing point of debate and in our experience, no one particular phrasing is any better than the other. The best method is to disassociate the temperature controlled package from the product inside, whilst mentioning the temperature of the contained product and asking that it be removed and then placed within a controlled temperature environment upon final receipt. Commonly used is, ‘Upon receipt remove product and place in a +2°C to +8°C store’.

Why should I use temperature controlled packaging for shipping ‘Temperate’ product?

What is Temperate? Our research into this leads us to believe that it is most commonly +15°C to +25°C or +2°C to +25°C. Much debate occurs over this issue and one thing that is certain, is that your product will need to be kept out of some temperature environments. If these environments are seen during your shipment, the need to use a control temperature package is created.

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Technical Glossary

Thermal Conductivity (k)

The Thermal Conductivity of a material is a measure of its ability to transmit heat. It is a specific property of that material and is defined as the quantity of heat in Watts, which will flow through one square metre of surface area of the material one metre thick, when there is a temperature difference of one degree Celsius between its faces, i.e;

Wm/m2°C
By cancelling out m above and below the expression becomes;

W/m °C
thus the units of k are expressed in Watts per metre per degree Celsius (W/m °C).

Thermal Resistance (R)

Thermal Resistance is a measure of the resistance to heat flow, either of a material of any given thickness, or of a combination of materials. It may be regarded as the number of hours required for the transmission of one Watt through one square metre, when the difference between the outer surfaces is one degree Celsius. The units of R are expressed in m2 °C/W. If the thickness of the material is increased, there is a corresponding increase in thermal resistance and if several materials are placed together in parallel layers, the total thermal resistance of that combination may be obtained by adding together the resistances provided by the particular thickness of each component. The unit of thickness to be used is the metre and if thickness is expressed in millimetres, then this must be converted to metres.

Thermal Resistivity (1/k)

Thermal Resistivity is the reciprocal of Thermal Conductivity and is expressed as m °C/W.

Thermal Conductance (C)

Thermal Conductance is the rate of heat flow through a material of any given thickness, or through a combination of materials. It is the reciprocal of total thermal resistance
i.e. C=1/R
and is the quantity of heat in Watts which will flow throughout a square metre of a material or a combination of materials, in one hour, when the difference between the two surface temperatures is one degree Celsius. The units of C are expressed in W/m2 °C. This term is normally used to express the insulating efficiency of a polished metallic surface such as aluminium foil, used in conjunction with an air space. The former may be used alone or stapled or glued onto building boards or some other type of insulation. However, to function effectively, the foil must have a cavity with a minimum depth of 19mm.
If the C value of a material or combination of materials is given, this can readily be converted to thermal resistance R units as follows:
1/C = R

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Thermal Transmittance (U)

The k, R and C values defined above, have been related to the temperatures at the surfaces of materials. The surface temperatures of a building are not usually known and for purposes of heat loss calculations, it is the inside and outside air temperatures that are used. The heat is first transferred from the inside air to the structure, then through the structure and finally, from the structure to the outside air. Both the inside and outside surfaces provide some resistance to heat flow and the thermal transmittance, or U value, takes into account these surface resistances.

Phase Change

The process by which a substance transforms from solid to liquid or liquid to gas, as well as transformations in the reverse direction. Most common is Temperature Controlled Packaging (TCP). A CoolPac would be placed into the shipper in a frozen state and allowed to change phase to a liquid, thereby absorbing energy in an isothermal manner and stabilising the internal temperature.

Heat Capacity

Heat Capacity is the amount of heat required to raise the temperature of a specific quantity of a substance by one degree Celsius. Symbol C (C p at constant pressure, C v at constant volume). This value is useful to calculate the temperature change in TCP when no phase change is taking place. The higher the value, the more stable the internal temperature.

Specific Heat Capacity

Specific Heat Capacity is the quantity of heat needed to raise the temperature of unit mass of a particular substance by one degree Kelvin (Units W/Kg K).

Latent Heat

Latent Heat is the energy required to change a substance from one state to another. Heat of fusion (Hf) = solid to liquid or liquid to solid. Heat of vaporization (Hv)= liquid to gas or gas to liquid. This is an important value for the design of Temperature Controlled Packaging (TCP), since it defines the amount of heat that can be absorbed isothermally.

Energy Density

Energy Density is the amount of energy per unit volume. The term is used commonly to refer to food or batteries. In TCP design, it is used commonly to refer to the sum of the Heat Capacity and Latent Heat.

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Enthalpy

Enthalpy is the quantity of heat necessary to raise the temperature of a substance from one point to a higher temperature. The quantity of heat includes both latent and sensible.

Delta T (δT)

This is short-hand for difference in temperature, usually referring to the difference between the ambient, or external temperature and the product temperature or system interior within the TCP. A high Delta T requirement, means that a system with a high performance is required.

Wall Thickness

Thickness of the shipper walls being used in the TCP.

EPS (Expanded polystyrene)

EPS is unlike other thermoplastic processes. The production of EPS products requires that the raw materials be pre-conditioned prior to their final "tooled" moulding process.The raw material (also known as "expandable polystyrene" or "bead"), has a spherical shape and is similar to sugar in appearance. This is the most commonly used material for TCP within Europe and has a thermal conductivity in the region of 33 mW/mK.

PU (Polyurethane)

PU is used in a foamed state within TCP design. PU foam is made by adding water to polyurethane plastics. The material foams up after mixing and spraying and a tool is used to define the finished shape. The thermal conductivity is lower than EPS, in the region of 23 mW/mK. The finished material is also more robust and therefore more suitable for packaging which is to be reused.

Vacuum Insulation Panel (VIP)

Vacuum Insulation Panels are made by placing a core into a bag of barrier material (film or foil) and evacuating and sealing the bag. The core provides a framework to give the panel thickness and the vacuum minimises the heat transfer by conduction and convection. The thermal performance and lifetime of the panel varies significantly with the materials used.

Closed Cell

This describes the nature of foamed material used in the manufacture of insulated containers. The closed cell structure reduces the convection within the wall thickness. Normally the smaller the cell size, the better the insulation.

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Thermal Mass

Thermal Mass is the amount of potential heat storage capacity available. This term is commonly used in architecture and has been adopted by the TCP industry. Usually, it refers to the idea that a high thermal mass will have high temperature stability, thereby requiring more energy transfer to change temperature.

Condition or Stabilise Product

To stabilise or condition products or CoolPacs they are stored at a temperature range. So, to condition CoolPacs, they are left at ‘factory temperature’ (typically in the range +15°C to +25°C) for a fixed period of time.

IQ OQ PQ (Installation Qualification, Operational Qualification & Performance Validation.)

The process through which equipment and instruments must go, for them to be acceptable for use by the pharmaceutical industry.

Ambient

The ambient profile is the temperature profile that any TCP is tested against, to show its performance. The ambient temperature is the temperature outside the packaging at any time. ‘Ambient product’ has been used in the past as a term for product which could be stored and shipped with no temperature control.

Temperate Product

A term for product to be stored and shipped between temperatures such as +15°C and +25°C or +2°C and +25°C.

Chilled Product

A term for product to be stored and shipped between +2°C and +8°C.

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Frozen Product

A term for product to be stored and shipped in a deep frozen state. Temperature ranges vary but generally below -18°C.

Volumetric Weight

Calculation used in the logistics industry to charge for large parcels that weigh little. Various formulae are used but generally,
Litres/6 = kg (volumetric).

Phase Change Materials (PCM)

A Phase Change Material is matter which undergoes a phase change at a specific temperature and gives off, or takes in, large amounts of energy in the process. They are usually engineered in order to achieve a certain amount of temperature consistency within a system. Common usage of this expression is normally for materials other than water, where the phase change does not happen at 0°C. These materials usually have a lower latent heat.

Isothermal

Isothermal means ‘at one temperature’. Ice will melt isothermically, thereby absorbing energy, but not increasing temperature.

Dry Ice

Solid Carbon Dioxide, used to maintain product in a frozen state. Dry Ice changes directly from a solid to a gas (or sublimes) in normal atmospheric conditions at -78.5°C, without going through a wet liquid stage. Therefore, it gets the name "dry ice". It does need to be shipped as a miscellaneous dangerous good UN1845.

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