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Communications and External Relations
ORNL instrument can help keep U.S. military planes in air
OAK RIDGE, Tenn.,
May 5, 2003
Using an instrument and technology developed at Oak Ridge National Laboratory, mechanics can know in seconds if a fuel pump of a military transport plane like the C-141 Starlifter is excessively worn and could fail.
That information is vital to maintaining combat readiness, which is especially important with today's conditions, said Don Welch, a co-developer of the instrument and a researcher in the Department of Energy lab's Engineering Science and Technology Division.
"While the C-141 has 20 fuel pumps, if even one is bad it may ground the plane," Welch said. "And applying this tool is a crucial first step in identifying operating fuel pumps that are on the verge of failure."
The payoff is increased reliability and maintenance efficiency of the C-141, regarded as the workhorse of the Air Force's Air Mobility Command. The plane, powered by four turbofan engines, can haul 200 soldiers, 155 paratroopers or nearly 69,000 pounds of cargo.
The instrument is a personal computer-based system with menu-driven software and is housed in a rugged case that fits within the size restrictions of carry-on luggage. The unit is battery powered and can be used either in the hangar or on the flight line by maintenance personnel.
ORNL's current signature analysis works either remotely or locally by connecting probes to electrical lines carrying current to the fuel pump.
"Our system measures changes in the electric current drawn by a motor as an indicator of changes in the mechanical load that it is driving," said Howard Haynes, one of the pioneers of the technology. "In this case, the changes in current reflect wear in either the pump or motor assembly."
By using the instrument, mechanics can identify wear in the fuel pump that has exceeded allowable tolerances - remotely and under harsh environments such as those with the C-141, where the pumps are submerged in the fuel.
The technology has a number of other applications and has been demonstrated as an effective tool for diagnosing conditions of rotor and gear train in helicopters, Army portable power generators, Navy fire and seawater pumps, NASA propellant control valves, heat pump and air conditioning systems, air compressors, Army ammunition delivery systems, diesel engine starter motors, and electric vehicle motors and alternators.
Haynes and colleagues trace the roots of electrical signature analysis to work in the mid-1980s for the Nuclear Regulatory Commission to monitor aging and service wear of nuclear power plant motor-operated valves. Then, the goal was to develop diagnostic techniques that used the motor's running current because they could acquire it remotely and non-intrusively. The techniques provided a breakthrough in detecting load and speed variations generated anywhere within the motor-operated valves and converted them into signatures that revealed problems and potential failures.
Electrical signature analysis represents ORNL research that started two decades ago and includes current, voltage and power analysis. Test results of prototype systems on C-141s have been extremely positive, and ORNL expects to turn over two prototypes to the Air Force later this month.
ORNL is a DOE multiprogram research facility managed by UT-Battelle.