Exhaust plants upgrade increases reliability

  • Published
  • By Shawn Jacobs
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  Refurbishment of the A and B Exhaust Plants continues to pay dividends to Arnold Engineering Development Center (AEDC) in the form of greater reliability and efficiency.

In addition, the project - completed in September 2009 - came in at more than $55,000 under budget and with no lost testing time.

The overhaul of the A/B Exhaust mechanical and electrical systems was the subject of an end-of-project brief at a "lunch and learn" Dec. 12 in the large Directorate of Operations conference room, presented by Tony Medley, an Aerospace Testing Alliance (ATA) project manager in the Investments and Design group. Medley, a resident of Decherd, has worked at AEDC for nearly 24 years.

The A/B Plants provide support for J and T test cells. Test cells J-1 and J-2 are altitude cells sized for medium and large turbine engine testing, while the J-6 facility provides ground test capabilities for solid-propellant rocket motors. Altitude test cells T-3 and T-4 are diverse cells with multiple test applications for testing small and medium turbine engines and cruise missile engines.

Medley said the project came about as part of a long-range plan to shut down A/B Exhaust and tie in to the C Plant, but maintenance became an issue as the timeline for the replacement continued to be delayed.

"As that project got pushed out, this project was put in to bring A/B Plant back up to its capabilities to make sure it could still function the next however many years it needs to," Medley said. "There was a team of people who ... looked at the maintenance records to see what we really needed to focus on, so this project was put together based on all the needs to keep those plants surviving."

One of the biggest improvements on the B side was replacing 50-year-old deteriorating cables in the control room that controls the exhaust machines.

"It was in conduit; it was underground," Medley said. "It had water in the conduit, and it was just worn out. They had a lot of problems getting machines on line for operations to do a test and had a lot of downtime due to that, so this project was to replace all those control cables.

"They had some problems with the exhaust machine themselves, and we took advantage of those downtimes and did as much work as possible without taking the plant out of service. The craft guys did an excellent job on working and supporting. As soon as an exhaust machine had problems and it was down, we went ahead and did our part while they were refurbishing the motors."

On the A Plant side, a major part of the upgrade involved XS1 and XS2, the exhaust machines that control the pressure ratio of the test cells. Medley said the 50-year-old machines were prone to trouble even though their maintenance was kept up-to-date.

"The pieces that support those machines - like lube oil systems, heat exchangers, the electrolyte system - there are a lot of failures due to that," he said. "The synchronous starting system [which gets the motors on line] was old and outdated, so we put in new 'sync' motors, starter systems and ran all new cable."

Medley said finding the proper cable was especially problematic. Not only was copper expensive, they could not locate the 3,000 feet of 1,500 thousand circular mil (KCM, an area measurement for cable) cable that was originally part of the system. Instead, they had to use much larger 3,500 KCM cable. The diameter of the copper wire strand in the new cable equates to a diameter of 1.87 inches. Add the insulation and the rubber sheath, and the diameter increased to about 3 inches.

"We replaced all the heat exchangers, the electrolyte heat exchanger and the lube oil heat exchangers," he said. "We had to run new pipe to the lube oil heat exchanger to bring us up-to-date in getting more capacity out of those. We replaced all the lube oil pumps that keep the XS1 and XS2 lubed."

In addition, Medley said the concrete electrolyte tanks were relined because they leached and allowed bits of the deteriorating lining into the pumps, which caused problems.

Despite these challenges, Medley said the five-year project actually ran very smoothly, thanks in part to excellent cooperation from AEDC's craft workers.

"They helped me by making decisions in the plant that needed to be made by doing what they felt like they needed to do to make sure everything worked right," he said. "We actually used the model shop electricians and ... mechanical guys on pieces of this project. There are also parts of this project [on which] we used plant craft guys - the plant electricians, pipefitters and other craft guys. Being able for those groups to come together and everybody work like they did was really just amazing."

Medley said the J and T cells will definitely benefit from less unscheduled maintenance and downtime at the A/B Exhaust Plants, but a cost savings is difficult to estimate.

"Any one of those pieces would have cost us tremendous downtime," he said. "On some of the equipment we could have been crippled where we ran half plant, or we could have ended up down for six months ... due to the fact that it would take that long to order and replace some of the equipment."