Desiccants and Molecular Sieves (Adsorbents)
For Sensitive Internal Components, Moisture Is the Enemy
Moisture control technology, critical to the defense, aerospace, electro-optical and many other industries, moves from inside containers to inside the equipment
From missiles and munitions to engines, transmissions, cameras, imaging systems and optical guidance systems, moisture has long been the enemy of high-tech equipment during storage, transportation and field usage. Sensitive electro-optical equipment is particularly susceptible to moisture damage. Not only can moisture corrode wiring and metal parts, it can also cause condensation and fog lenses and mirrors, thereby compromising mission-critical performance.
In order to prevent the moisture that exists naturally in the air from getting into equipment during transport and storage, military and civilian engineers historically designed airtight shipping containers which could withstand large pressure, temperature, and altitude differences. However, as these heavy, bulky, steel containers were costly to build and ship, so called "controlled breathing systems" were introduced to allow for lighter, less bulky containers. Because of the cost and logistics advantages of lighter containers, many modern shipping containers employ some, if not all, elements of a controlled breathing system.
"The key elements of a controlled breathing system are: a breather valve, which controls pressure, vacuum and moisture entry; a desiccator, which removes moisture; and a humidity indicator, which indicates when to replace a desiccator when it's saturated and humidity levels begin to rise," explains Jim McCorry, Director of Business Development at AGM Container Controls Inc., a leader in the design and fabrication of moisture control and monitoring products. "The breather valve basically allows a sealed enclosure to 'burp' a little air in and out, to equalize internal and external air pressure."
While the moisture problem in shipping containers has long been solved with the use of these controlled breathing systems, the field of battle is evolving again. For mission-critical functionality, reliability, and longevity, the leading edge of moisture control is moving from inside the container to inside the equipment.
The continual pressure to improve the functionality, reliability, and longevity of mission-critical, electro-optical devices is now resulting in controlled breathing systems being used for moisture control directly in the equipment. After all, what is a camera housing or missile casing other than a container for the sensitive components inside?
"Reducing moisture in the presence of electronics and optical imaging systems is critical for performance and longevity," says James Weaver, a Mechanical Engineering Manager at Flir Systems, a world leader in thermal imaging with a growing presence in government, military, and defense. "With superior moisture control in the shipping container and even the equipment enclosure itself, you can operate longer and more reliably in harsher and harsher environments."
"Everything is demanding higher definition, more functionality, and more processing capability in a smaller, more rugged package," adds Weaver.
Having originally turned to AGM when a supplier was unwilling to make a necessary change in moisture control equipment, Weaver was pleased with their willingness to collaborate on a series of projects.
While a traditional shipping container has plenty of room for a separate breathing valve, desiccant, and humidity indicator, space was at a premium for Flir's Star Safire® HD system, which features megapixel thermal, daylight, and low-light cameras with high magnification optics, laser payloads, and a fully-integrated IMU to precisely locate targets.
"For us, every inch and every ounce must provide functionality," says Weaver. "We didn't have the luxury of using a large panel to put three separate, controlled breathing system modules in our device. To free up space for enhanced capabilities on the Star Safire® HD system, we sought to combine the moisture control modules."
Flir and AGM jointly designed and developed a controlled breathing system, called the TA340, with a combined breather valve, desiccator, and humidity indicator for space-efficient moisture control.
Incorporating a humidity indicator and two-way breather valve all in the same aluminum housing not only saved space, but also helped to avoid drilling an additional hole in the case. With only one mounting hole in the equipment, potential leak paths in the equipment were reduced, which makes its moisture control capabilities even more reliable.
Since the TA340's desiccant cartridge is mounted on the back end of the valve, when it breathes air in, the air goes directly over the desiccant bed to efficiently capture moisture on entry. For ease of desiccant replacement, the system is also designed to accept an externally accessible replacement desiccant cartridge, which pleases Weaver.
"It's critical for anyone servicing a controlled breathing system to have an externally accessible replacement desiccant cartridge," says Weaver. "Besides being easier and quicker, it minimizes moisture entry from outside air since the entire enclosure does not have to open. I'm glad we were able to include this in its compact design."
Above all, Weaver appreciated the controlled breathing system's space saving capability, which allowed Flir to pack even more functionality into its compact enclosure. "Since the TA340's 3-in-1 controlled breathing system reduced its 'footprint' by two-thirds compared to separate moisture control systems, we had more space to enhance our thermal imaging, visible imaging, and laser elimination capabilities," says Weaver.
On a more recent project, the two companies did themselves one better: they added RFI/EMI shielding to their compact, controlled breathing system. "RFI/EMI shielding enables an electronically tighter enclosure, with even less susceptibility," says Weaver. "It should allow its use on installations with higher emissions, and should shield customers from noise made on more sensitive equipment."
Weaver plans to collaborate with AGM on future projects where moisture control must be customized for specific purposes.
"AGM understood what we were after and helped us achieve it," says Weaver. "By jointly developing the compact, controlled breathing systems with us for use in the actual equipment, not just the storage container, they helped us deliver more value to our customers, while they delivered more value to us."
AGM Container Controls, Inc. is a leader in the design and fabrication of moisture control and monitoring products (desiccators, dry gas purge systems, humidity indicators); pressure and vacuum changes (breather valves); and shock and vibration (tie down systems and shock overload indicators and recorders). Its products are used in defense, aerospace, electronic, electro-optical, industrial and commercial markets to protect and extend the life of critical equipment by creating/or maintaining the best environments to guard against moisture, corrosion, pressure, and shock. Its facilities are approved by Army, Navy, Air Force, AEC, and NASA.
For more info, call 1-800-995-5590 or 520-881-2130; visit agmcontainer.com; email controlledbreathing@agmcontainer.com; or write to AGM Container Controls, Inc. at 3526 East Fort Lowell Road, Tucson, AZ 85716.
By Del Williams
