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Innovative Manhole Protection Affords Many Benefits at Redstone Arsenal

By Gretchen Jacobson

Pictured above are corroded pipes and missing insulation before a manhole has been upgraded. Below, a manhole contains new insulation and jacketing after it has been improved. Photos courtesy of the Army Corps of Engineers ERDC-CERL.

a manhole contains new insulation and jacketing after it has been improved.

Redstone Arsenal, located in northern Alabama’s rural Tennessee Valley, has been the heart of the Army’s rocket and missile programs for more than 40 years. Today, Redstone is home to the Army Aviation and Missile Command, the Space and Missile Defense Command, major components of the Defense Intelligence Agency and the Missile Defense Agency, and numerous program executive offices.

The Redstone facility is charged with conducting basic and advanced weapons system research and development. It also places the right missile and aviation systems with U.S. troops and provides weapons systems, services, and supplies to U.S. allies, among other critical tasks essential to military readiness.

At U.S. military facilities throughout the world, maintaining infrastructure is a crucial part of the daily operations required to fully support the DoD mission. In recent years, Redstone Arsenal has identified its heat distribution system as a vital infrastructure component that needs to be managed with better protective systems because of serious corrosion problems. In particular, corrosion of the steel manhole piping is causing leaks, flooding, and costly heat loss from the distribution system.

In 2005, the U.S. Army Engineer Research and Development Center (ERDC), Construction Engineering Research Laboratory (CERL) initiated a proposal to address corrosive environmental effects and improve energy efficiency in heat distribution manholes at Redstone Arsenal.

"During their normal service life, pipes in heat distribution system manholes routinely experience an environment that is both hot and humid," said Charles Marsh, a project leader at ERDC-CERL. "This results in an ongoing, severely corrosive environment to which bare and often uninsulated steel piping is exposed."

Corrosion-related failures are causing multiple occurrences of leaking valves, pinhole leaks in condensate lines, ground water ingress, and occasional flooding. In addition, flooded manholes are at a near optimal temperature for nucleate boiling, resulting in excessive heat loss.

"We estimate that a boiling manhole can lose from $50,000 to $125,000 worth of heat per year if not repaired," said Marsh. "Unfortunately, boiling manholes can easily go uncorrected for many years. Long-term exposure to such conditions significantly shortens the life of the pipe, eventually requiring expensive repair and replacement."

Based on both experience and investigation at Redstone Arsenal, the ERDC-CERL project team came to the conclusion that using an innovative thermal barrier coating that has been successfully used for more than 10 years in industrial settings was the best option for protecting newly constructed, bare manhole piping at Redstone. This liquid ceramic coating, while providing strong protection to the metal, has the added benefit of reducing the temperature of pipe exteriors and thus protecting maintenance personnel from burns. An application of 180 mils of the ceramic coating, for example, will render a 350°F pipe non-painful when contacted with bare skin.

A new thermal barrier pipe coating developed by the Army Corps of Engineers improves safety for people who work near manholes by reducing the external temperature.

Another advantage is that depending on the specific application, an indicator coating may be incorporated into the system to alert maintenance personnel when recoating is required. This can be either a distinctively colored intermediate layer that shows through when the outer layer is worn, or a thermal indicator coating that changes color above a specific temperature. In addition, a fiber reinforcement is selectively used in some areas to improve durability by creating a ceramic matrix composite coating.

Up to 25 manholes are being upgraded at the facility using the liquid ceramic coatings. The team is also drafting contract language and writing specifications that include surface preparation criteria, product acceptance requirements, and safety procedures for use on additional applications and at other Army, Navy, and Air Force facilities.

"We are confident that the outcome of this project will be enhanced thermal efficiency, improved life-cycle costs, lower ongoing operational costs, improved worker safety, and increased system-wide reliability for these heat distribution systems," concluded Marsh. "The intent of this project is also to implement the corrosion control technology at multiple Army regions and installations in the future, as well as other military sites."