Major maintenance project nears completion

  • Published
  • By Philp Lorenz III
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  A major Engine Test Facility-focused (ETF) renovation and maintenance project at the U.S. Air Force's Arnold Engineering Development Center (AEDC) is nearing completion and checkout ahead of a heavy ground test schedule in August.

A primary focus of the project involves replacing a number of cooling coils in the Aeropropulsion System Test Facility's (ASTF) RC1 Cooler, the largest of the facility's three pressurized air supply units that dry and cool air to provide the required conditions simulating flight at altitude and at sea level in the jet engine test cells, which can test jet engines under simulated flight conditions to altitudes above 100,000 feet and speeds above Mach 3.

"This effort will allow AEDC to operate until the next phase of an improvement which is still several years out," said Navy Commander Frank Moulds, 704th Maintenance Squadron commander.

Commander Moulds said the next phase of the project will improve the test effort and allow the center to introduce new technologies that will be more environmentally friendly. He emphasized that the current maintenance project, especially on the RC1 Cooler, is a vital part of the ongoing effort.

"The RC1 Cooler is one of those critical systems we have to continuously maintain to ensure it is available when required to meet our test customer's needs," said Warner Holt, deputy branch manager of plant operations and maintenance for Aerospace Testing Alliance (ATA) - the center's prime contractor. "It is also a one-of-a-kind system.

"The RC1 Cooler is showing wear after 25 years of service, and it's not a system that is easily maintained - the components are heavy and bulky - you can't just go out and buy these parts off the shelf when they need replacing."

Center Commander Col. Art Huber was among three of the center's senior leaders who recently suited up with personal protection equipment to check on the progress of the project. Colonel Huber, Col. Raytheon Scott, commander of the 704th Maintenance Group and Col. James Jolliffe, commander of the 704th Test Group, entered the RC1 Cooler in full protective gear and traced the steps the craftsmen take on a daily basis to get a feel for the challenges they are facing. The experience of climbing vertical ladders, climbing across narrow mezzanines in cramped quarters and climbing back down scaffolding in a tight space was revealing.

After exiting the cooler, Colonel Scott said, "I now have a much greater appreciation for what the craftsmen are experiencing on this job."

Cold air is necessary to simulate high altitude conditions and the air must be dry to prevent icing and condensation from severely damaging test equipment and jet engines during testing at those conditions. The RC1 Cooler supports engine developments and upgrades for all U.S. fighter aircraft and is the only place in the world to conduct full flight envelope testing for F-22A Raptor and F-35 Lightning II Joint Strike Fighter-class engines.

According to Holt, the RC1 cooler and supporting work to the high stage compressors and other components is being managed as a scheduled system outage.

"We've got this narrow window of opportunity to accomplish all this work that needs to be done," he said.

Holt said the work on the RC1 Cooler presents the most significant challenge of the project, especially when all of the other work on supporting systems and components is added to the workload.

"We've done this all in-house labor supplemented by Jacobs Industrial Services, Inc., craftsmen," he said. "This project takes a lot of our people to get the work accomplished, including engineers, schedulers/planners and craftsmen. All must work together toward a common goal to meet the tight schedule.

"They've also been doing a lot of significant preventative maintenance work on ETF's airside and exhaust-side compressor rotors - all of that complicates a project of this scale. The key to our success is our world-class craft work force. They have overcome challenge after challenge on this project."

The maintenance project is only meant as an interim step pending approval for a $120 million project to repair the existing RC1 Cooler, according to Kent Lominac, the deputy director for the 651st Test System Squadron.

"AEDC has exercised an aggressive program to keep RC1 operational and this latest maintenance project has been critical to the success of that effort," said Kirk Rutland, deputy director of the 704th Maintenance Group. "However, the repair and maintenance costs have more than tripled in the last few years. Also, the maintenance reliability of RC1 has decreased significantly over the last decade."

According to Larry Roberts, ATA turnaround manager with the center's Mission Operation Control Center, the major ETF-focused maintenance project included a wide range of work. He said to fully appreciate the work done on the RC1 Cooler alone, it help to understand how it works.

"The RC1 Cooler consists of multiple banks of finned tubes," he said. "Cooling fluids including raw water, glycol and trichloroethylene (TCE) flow through the tubes while the air to be conditioned flows across the banks of tubes. The scope of this project included draining and temporarily storing the several thousands of gallons of coolants, except for the water. While the fluids were removed, they opened the hatches, drained the fluids, and installed air conditioning equipment for adequate air flows for personnel safety from the heat and residual gases."

Roberts said hatches were opened throughout the cooler to provide access to personnel and allow coils to be removed and replaced from inside the cooler shell. All the internal piping was thoroughly flushed to remove debris normally found in the raw water supply. Water strainers were added to reduce the likelihood of debris finding its way into the newly installed cooler banks of coils.

"Three TCE coils and 12 water coils were replaced," he continued. "Each coil weighed about a ton. Internal sheet metal drains for condensate collected by the coils were removed and remanufactured as necessary to maintain the performance of the cooler. The total system was pressurized with air and checked for leaks. Minor repairs were made to leaks discovered in the check process.

"Thirty-two external vertical supply lines that had degraded over time due to interaction of the TCE and water vapor were systematically replaced, concurrently with the coil replacements. Minor weld repairs were made to associated supply and drain piping in the vicinity of the RC1 cooler. All the fluids will then be pumped back into the system, hatches closed, and final checkouts performed in conjunction with the rest of the plant equipment"

He said a major amount of work was also done on plants that supply conditioned air for testing - all part of the project and much of the work is ongoing.

"This included a 50,000 man-hour effort involving multiple ATA craftsmen, supervisors, engineering, planners, schedulers and multiple subcontractors," he explained. "The turnaround included a multi-million dollar investment project for replacing electrical breakers and switchgear. The ASTF medium voltage breaker replacement effort will replace 30-year old electrical circuit breakers used for the main air compressor motors and other facility electrical machinery."

A 72-inch diameter water valve was installed during a base-wide water outage. One 108-inch or nine-foot diameter process air isolation valve was installed for improved access to process air heating. Five additional valves, on the order of an average of five feet in diameter were disassembled, inspected, rebuilt and reassembled in place. Each valve contained shaft sections of eight to 10 inches in diameter.

Shaft materials and bearings were upgraded as needed to improve the service life of the valves. Infrared windows were installed in breaker cabinets throughout C Plant to enable inspectors to examine infrared profiles of energized electrical equipment and prevent possible arcing due to loose or worn connections. Approximately 2,500 gallons of hydraulic oil were removed from three systems, cleaned and pumped back into the systems. The oil was cleaned to improve performance of the large servo-controlled valves. We are currently in the checkout phase of the turnaround when all systems are checked for proper operation and delivery of properly conditioned air for the test cells.

According to Gary Casteel, ATA manager of plant operations and maintenance, significant preventive maintenance work was performed on four major compressors in the ETF plant area. The compressors, weighing up to 70 tons, were disassembled, cleaned, non-destructively inspected and reassembled. 

These compressors provide the required process air for the engine test cells. "This was the first time that we've had as many as four compressors down for preventive maintenance in the same maintenance turnaround period, at least that I am aware of," he said.

Casteel added, "During this period, we completed preventive maintenance on 14 large drive motors for compressor drives and refrigeration units. Electrical utility preventative maintenance for large transformers, including maintenance that is only performed every nine years, was also completed."