Beware: Uncontrolled Heat, Humidity Can Damage Stored Materials
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maintenance | continued Excessive humidity can cause “container sweat” and drip con- densation on boxes and materials. SHIPPING CONTAINERS PART 2 Too hot for the box Don’t store the following in a shipping container Beware: Uncontrolled heat, without climate control: • Bonding agents humidity can damage • Solder • Epoxy and adhesives stored materials catalysts • Lubricants (grease and oil) by Preston Ingalls • Hydraulic fluids ou should be aware of two cal conditions, the ceilings of many • Glycols distinct downsides to repur- shipping containers will easily reach • Paints (aerosol and cans) posing shipping containers: well over 100 degrees in the summer. • Alcohol heat and humidity. The hot metal ceiling causes humid- • Soaps During the Vietnam conflict, ity in the air to begin to condense Yshipping containers were repurposed about 6 inches near the ceiling, • Water in plastic bottles by military units as storage for motor which is referred to as the “sweat • Solvents pool parts, aviation components and zone.” Droplets form on the ceiling • Gaskets ammo – the forerunner to their use and upper vertical band of the walls, • O-rings in construction. producing what is commonly called • Seals In Vietnam, they were commonly “container rain” or “container sweat.” • Belts known as “sweat boxes” because the This level of heat and humidity is heat from the tropical sun would pro- too much for a wide range of prod- • Circuit boards duce dripping condensation inside ucts and materials (see sidebar). • Filters where the average temperature was Even without any condensation, el- • Semiconductor devices 15 degrees hotter than the exterior. evated humidity over time can cause and electronics While most shipping containers in damage. Many metals will corrode or • Wood and leather items the United States won’t endure tropi- discolor at a humidity level of 60 per- EquipmentWorld.com | September 2018 33 maintenance | continued Powered climate control, such as window AC units or the ductless mini-split system shown here, are your best defense against hostile climate conditions. cent. At higher levels, say above $10 digital humidity and tempera- on furniture joints loses its bond 80 percent, molds can grow, ture monitor in the unit. Also, by and cracks. Moisture saturation labels peel, and corrugated boxes putting several items in your stor- from condensation or constant soften and delaminate. Most of age container and examining what thermal expansion and contraction these items should be kept at happens to them over time, you from heat has a wearing impact a temperature of less than 80 can determine if you need climate on many components. degrees Fahrenheit and a relative control. humidity of 50 to 60 percent. For example, oil-filter media Climate control comes The humidity of the air changes may dry and form cracks from in many forms only as a result of the change heat or excessive cold, or they These problems have solutions. A in temperature. When air cools, can become saturated with mois- common way to manage conden- it becomes more humid even ture from humidity. Cork, rub- sation is to control the air flow though the moisture content in the ber or silicone seals can become to keep the inside and outside of air remains the same. Warm moist brittle from high temperature and the container the same, or close air from the outside can also enter humidity ranges. Some estimate to the same, temperature. Re- into a container through “contain- that long-term storage of filters in member, temperature differential er breathing.” This is where the shipping containers will cut their causes the dewpoint problem. container “exhales” as air expands normal five-year life expectancy Since the main keys to condensa- during daytime heating and then in half. tion control are ventilation and/ “inhales” moist air through leaks Humidity can also cause solder or dehumidification, let’s look at and the seals when it cools at joints on printed circuit boards to eight solutions to the problem: night. The temperature does not become brittle and crack. Chemi- 1. Storage container vents have to change for this to happen. cals and lubricants begin to sepa- Adding two vents at each end A good suggestion is to mount a rate, like paints and inks. The glue of the container provides ample EquipmentWorld.com | September 2018 35 maintenance | continued airflow to keep contents dry. Vent 3. Exhaust fans As with kitty litter, they require peri- types include fixed, louvered Exhaust fans are available in odic monitoring and replacement. and rooftop turbines. While fixed sizes of 10 to 36 inches. They 7. Pole container desiccant vents are simple and effective, come standard with fan guards and Pole desiccants come in different they can’t alter airflow. Louvered gravity shutters. Variable speed configurations, can absorb up to vents are more expensive, but control is an option. three times their weight in mois- they allow some flexibility over 4. Dehumidifier ture and trap it as a thick gel that airflow. Both can be purchased With electricity, dehumidifica- will not spill or drip. Pole varia- online. Nonpowered rooftop tur- tion is an option. The addition of tions use calcium-chloride salts to bine vents that can be mounted a discharge line makes for efficient absorb moisture in a gel form that anywhere on the roof are the elimination of condensed water is permanently deposited into a most popular, effective and ex- and reduces maintenance and built-in “tank” for evacuation. It pensive nonpowered ventilation inspection. requires replacement once the salts option. 5. Kitty litter are exhausted. 2. Air conditioning units An open bag placed at each end 8. Painting the container white If you’re using the container of the container will absorb mois- Painting the outside of the con- for an office or workshop and ture. It’s inexpensive (a 40-pound tainer white reduces the breathing have a power source, consider bag costs around $25) but requires of the container during a 24-hour HVAC, such as a basic window air monthly monitoring and regular heating/cooling cycle by reflecting conditioner. Commercial through- replacement based on humidity the sun. As an extra precaution, wall HVAC systems from 1.5 to 5 level. consider using a zinc paint coating tons are primarily used in harsher 6. Commercial desiccants to slow rusting of the underlying climates or for specific applica- Products like Container Dri or steel. Quality zinc paint should tions when climate control is of DampRid can be placed inside the contain at least 90 percent dry zinc the utmostVMAC EquipWorld_Sept18_DTM70H.pdfimportance. 1 8/15/2018storage 2:57:35 PM container to collect moisture. powder. Untitled-3 1 8/16/18 8:49 AM 36 September 2018 | EquipmentWorld.com Additional pointers to reduce the • Regularly monitor humidity • Avoid storing anything inside temperature and humidity with a moisture meter or, bet- with a high moisture content. Ways to further reduce the tem- ter yet, a temp gun (for ceiling • Above all, use common sense perature and humidity within the temperature measurement). and check on your container shipping container include: • Set the container on gravel or just like you would check on • Place your shipping container in 6-inch pressure-treated blocks anything you own. the shade, but not under trees. for better air circulation. Remember the “doggy rule” • Build a roof over the container • Park on high ground to avoid when considering storing items to reflect the light. flooding and standing water. in the storage container. If you • Insulate the internal walls with • Keep the roof clear of leaves and wouldn’t put your dog in the traditional insulation or spray moss since they trap moisture. container with food and water foam. • Separate containers by 6 feet for a prolonged time, don’t store • Install cross ventilating win- for better air flow. items that would react to the heat dows. • Avoid trees since windy loca- and humidity over a prolonged • Install extractor fans to purge tions allow storage containers time. hot air. to dry out. • Arrange items for better air • Add a roof-mount- flow inside the container, such ed, peaked tarp Preston Ingalls as stacking them off the floor with a 2-foot over- consults with construction on shelves or clean pallets, hang that avoids industry fleets on equipment and avoid cramming the items roof contact, to uptime and cost improvements. tightly together. slow quick tem- He can be reached at • Mount a container on ConFoot perature changes. www.tbr-strategies.com. legs for elevation that inhibits • Keep air vents soil reactions and easier moving. unblocked. 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