Dehumidification, ductwork ‘keep the powder dry' in AZ
Lt. Col. Pete Cullum, the base engineer who handles maintenance and repair of all operational systems, said the project was a three-phase process involving two different mechanical contractors. The first phase started with six dehumidification units in early 1998, but Cullum said these initial units had insufficient capacity to maintain the desired environment and maintain an even climate for the ammunition materials.
Bringing A Whole New Meaning To ‘Critical'Because of these special concerns, Mechanical Service and Systems (MSS, Midvale, UT) made accommodations for the unique climate demands of the storage facility during second phase. From late 1998 to early 1999, MSS handled phase two of the project to install 27 HCD800 vertical dehumidification units manufactured by PoolPak International. Randy Karren, MSS project manager, worked closely with the local PoolPak representatives at Trane/Salt Lake City to ensure project specifications were met.
Karren said that every storage site needed to have a new mechanical room constructed to house the dehumidification systems. These mechanical rooms were originally designed for horizontal dehumidification units but the vertical orientation of PoolPak equipment fit the existing space. Karren said the installation process went smoothly because PoolPak's supply and returns were easily reconfigured to mate with the existing ductwork. Ductwork was necessary to provide even air distribution into the ammunition storage area for all unit installations.
"The units matched project specifications, offered fair pricing and allowed for a better overall fit," Karren said. Each of the HCD800 units were also equipped with electric heat for precise temperature regulation and a TD2000 programmable microprocessor control system for remote monitoring. Cullum said inline heaters were also utilized in the ducting to assist with additional regulation of temperature controls not handled by the PoolPak systems in order to provide optimum conditions for the unique demands of the ammunition storage environment.
Another important aspect of the installation process was presenting necessary submittal papers to meet critical government specifications. "All the initial criteria passed inspection on the first try and units were delivered on time so we could start work right away without any delays. I'm very happy with their overall performance to date," Karren said. Eighteen of PoolPak's HCD800 units were selected and installed during the final phase of the project from 2001 to 2002.
Low Moisture, High ExplosivesEach of the storage/mechanical areas needed to maintain a 45% rh with 70°F winter temperatures and 80° during summer months. Brian Boyer, vice president, Boyer Metal (Flagstaff, AZ), said PoolPak International's high capacity dehumidification (HCD) units satisfied these requirements. The HCD800 has a supply airflow of 1,100 to 2,400 cfm, with a maximum outside airflow of 800 cfm. Ideal for high-moisture locations, the standard HCD operates as a reheat unit that dehumidifies and returns warm, dry air to a conditioned enclosure through a hot gas reheat coil.
Boyer's installation concerns involved the ducting. "We had to cut into concrete buildings dating back to the 1940s and 1950s in order to place the return air ducts between the two structures. The other difficulty came from the ducting itself, which was too thin for supporting the weight of dirt on the outside wall and crushed the piping." Because of that, Boyer said they had to replace 1/4-in.-thick fiberglass reinforced spiral pipe with 1/2-in.-thick FPR to rectify the problem.
Cullum is pleased with the final result, now that the PoolPak International dehumidification systems have been operating from two to five years without any downtime thus far. "From a maintenance point of view, the units are easy to work with on a regular repair schedule and offer optimal efficiency." ES