Thermal covers, blankets, shrouds and quilts… What’s the difference?

• Covers: Thin (usually single layer)  and low cost designed for single trip use. viz-es-futes Primarily a reflective material protecting against direct sunlight during temperature spikes. Usually supplied in preformed sizes.
• Blankets: Thicker (usually multi layer with a layer of insulation) and more expensive designed with more durability for repeat use and closed loop operations. Should provide higher protection against convection temperature threat (see ‘Temperature Threats’ below). Usually supplied in preformed sizes.
• Shroud: A single rectangular piece or layered piece of materials designed to lie over the goods to be protected.
• Quilt: Similar to blanket apart from the design of stitching, which is formed in a diamond criss-cross shape to ensure that there is not insulation slippage within the enclosure.  zarban

Temperature Control vs. Temperature Protection – What’s the difference?

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• Typically, epit-esz thermal covers etc. do not ‘hold’ temperature between limits. This is in contrast to TCP (Temperature Controlled Packaging) that utilises insulating and phase change materials to hold temperature for a validated duration (e.g. 72hrs). For this reason, thermal covers would be considered as ‘temperature protection’ rather than ‘temperature control’ packaging. villanyt-szerel

What is the performance expectation of thermal covers / blankets etc?

• • Thermal covers will generally allow passage of temperature exchange as soon as there is a difference between the inside and outside temperatures. receptek

• • The rate of change will depend on many variables so it’s very difficult to predict the performance. These variables include: skyemetalcoating

• 1. Size of load mass (the larger the load mass, the slower the temperature change e.g. an air cargo PMC pallet will have better thermal performance than a Euro skid pallet).
  2. How condensed the load mass is (a barrel of liquid will keep better temperature than a pallet of small bottles of liquid with lots of packaging between)
  3. The type of load mass (liquid, powder and solids will react differently).
  4. Type and design of packaging (bottles of liquid in shrink wrap packs will be more exposed than well packaged liquid protected by polystyrene and cardboard)
  5. The balance between ambient air temperature and direct sunlight (pallets exposed to similar levels of sunlight can perform quite differently if the ambient temperatures vary.
  6. Generally, the larger the temperature differences between the pallet load and ambient, the quicker the rate of thermal change.
  7. A pallet exposed to harsh sunlight in Dubai may rise 5-10C even when protected by a cover or blanket. In European sunlight the same pallet may only rise by 3-6C in the first hour.
  8. In each additional hour, the temperature will rise less than the previous.

Do covers/blankets work the same in cold weather?

• They will certainly slow down the temperature exchange in cold weather, often better than in hot conditions. In chamber testing and live trails, we see that it takes longer for the freight temperature to come down than it did to rise!

What are thermal covers and blankets best suited for?

• It comes down to COST!
• When the majority of a transit route is within safe operating temperatures, companies are obviously reluctant to spend more than necessary on thermal protection.
• The irritation is when there are a couple of very short temperature spikes during the supply chain that can threaten the freight. This is normally during loading and off-loading from aircraft, or during cross-docking etc.
• These durations can be quite short (no more than a few hours) and can be protected against with cost effective thermal covers.
• Typically, the nature of the protection lends itself well to ambient pharmaceuticals that have wide temperature limits proved through stability data.

Examples:

1. 2-25C where the goods don’t start too close to the temperature limits (e.g. don’t expect goods at 22C to keep under 25C when exposed to 4hrs of tarmac time in Dubai – if they come out of the aircraft at 5-10C, they may stand a chance)
2. 15-25C where the ambient isn’t too aggressive (note that there is often a desire to protect between 15-25C due to ‘storage’ rules, but these can sometimes be waivered during transit, allowing temporary wider tolerances)
3. 2-40C is the most common tolerance with normal ambient goods, and should be ideal for thermal cover protection.
4. 2-8C for VERY short durations of exposure, defiantly less than 1 hr – less than 20 minutes if harsh ambient environment.

How do you assess if covers or blankets will provide sufficient protection?

• It’s a case for balance between cost and performance. The goods should be shipped with the best performing protection affordable. The reason thermal covers are even a consideration is because there is no or very little budget.
• Ideally, each route should be assessed and managed accordingly and given a risk profile depending on the season.
• We would recommend live trials carried out by a professional quality assurance manager to assess performance.

WARNING: Trials carried out by untrained or inexperienced personnel can result in data that has little or no value. We have witnessed staff testing:

• A pallet load of wooden pallets
• A PMC load of PMC pallets
• All temperature monitors on the outside and none on the inside of the cover
• All temperature monitors on the inside and none on the outside
• Temperature monitors not switched on or just lost.

Are thermal covers easy to fit and remove?

• Yes, they usually come preformed and fit over the pallet like a hat, then sealed into place using tape. This should take no more than a few minutes. Removal should be just as quick.
• The only exception to this may be the rolls of silver backed bubble wrap often used. This can take two people up to 20 minutes if not using the preformed solution.

What difference does a thermal base make?

• • If operationally possible, adding a thermal base on the pallet before loading the freight will provide approximately 10% improvement on thermal performance.

• • Having the load fully enclosed will have the following benefits:

• 1. Reduce ambient air exchange (convection) temperature threat
  2. Reduce influx of rising air from hot airfield tarmac
  3. Create a sealed unit to prevent contamination

What if a thermal base can’t be fitted?

• When freight comes out of manufacturing fully palletised there is often no opportunity to fit a thermal base. The only option is to ‘double pallet’ using a second pallet fitted with a thermal base on top.
• Alternatively, a second cover can be used to boost performance.

Will adding a second cover double the performance?

• No, but it will improve performance quite considerably by an estimated 40-60% depending on various conditions.
• A third cover would only add around 5-15% performance.

Will using gel packs or phase change materials help performance?

• Potentially yes, live testing would provide an indication of how much. The main considerations would be practicality, operational and cost. A layer of gel packs could be placed on top of the product, under the cover, therefore providing an additional barrier to direct sunlight.
• If using reusable thermal blankets, pockets can be stitched in to hold the gel packs on the side panels.

When is the best time to fit thermal covers during the shipping process?

• Covers should be fitted at the point where the freight is at the correct temperature. The covers should also be at the same temperature.
• Fitting warm covers outside of the controlled temperature area will have the effect of warming up the freight (like a coat), so should be avoided.

Additional Notes

Operational Warning

• Ground handling teams can confuse thermal covers for permanent protection and decide to leave pallets on the tarmac thinking it’s protected. Ensure that your ground handling colleagues give priority to temperature sensitive freight whether it’s covered or not.

The Shippers Dilemma re Cost vs. Quality

• Understandably, there is resistance for shippers to pay any additional costs for ambient goods that have historically been sent through standard freight lanes. With more ambient goods being shipped with temperature limits, it’s a risk to allow sensitive freight to be exposed to delays on the tarmac. If there is a requirement for temperature control, there is naturally a cost to providing this protection, whether it’s through priority service, or thermal protection, or both.