Lessons Learned Implementing a Mechanical Infrared Program at an Aerospace Testing Facility

InfraMation 2015 Application Paper Submission

Dan Henley, Infrared Program Lead

Aerospace Testing Alliance, Arnold Engineering Development Complex

ABOUT AEDC

The product of Arnold Engineering Development Complex (AEDC) is aerospace test research,  development, test, & evaluation data for U.S. Department of Defense (DoD), NASA, and commercial  customers across not only this nation but also different parts of the world. Aerospace Testing Alliance  (ATA) at AEDC operates and maintains approximately 63 test facilities at Arnold Air Force Base, TN,  Tunnel 9 at White Oak, MD, and NFAC at NASA AMES Research Center in CA. AEDC is located on  Arnold Air Force Base and is the most advanced and largest complex of flight simulation test facilities in  the world. Established in 1951, the center includes 43 aerodynamic and propulsion wind tunnels, rocket  and turbine engine test cells, space environmental chambers, arc heaters, ballistic ranges, and other  specialized test units. The center’s test facilities simulate flight conditions from sea level to space and  speeds up to Mach 20, with 27 test capabilities unique within the United States and 14 worldwide. Every  high performance aircraft, missile, space launch system and most satellites in use by the DoD today have  been tested at AEDC as well as all of NASA’s manned spacecraft and many commercial aircraft and  spacecraft, including the Atlas, Titan, Minuteman and Peacekeeper ICBMs, the space shuttle, space  station, and Projects Mercury, Gemini and Apollo. As the prime contractor at AEDC, ATA’s mission is “to  be a trusted partner in delivering best value war fighter support and asset stewardship to AEDC.”

In order to accomplish this mission, ATA operates and maintains facilities & equipment valued at  approximately $11 Billion in Asset Replacement Value. The test center is much like a mid-size  metropolitan city, with its multitude of facilities, each with their various types of equipment within them.  This equipment ranges from very unique test cell-specific equipment to large compressors, coolers, and other plant equipment. Additionally, there are machine shops, utilities, and base infrastructure. To better  show the analogy of a mid-size metropolitan city with an equivalent population of about 150,000 people,  the center’s utilities and facilities necessary to accomplish this mission include 161kV and 13.8kV  electrical power, a dedicated lake & dam for raw water supply and distribution lines, potable water  production & sewage treatment plant, GN2 production plant, jet fuel storage and distribution system,  steam production facility, and hundreds of industrial and office buildings in addition to typical base  infrastructure such as office buildings, military family housing, commissary, healthcare dispensary, fitness  facilities, a golf course, hotel-style lodging, and club restaurant facilities.

ABSTRACT

While electrical infrared inspections are common at AEDC, just as any Reliability Centered plant, using  infrared for our mechanical equipment is a new focus area. Expanding our mechanical infrared  inspections can produce real savings and substantially lower unplanned down time as well. Does your  infrared program include mechanical systems? Are you providing asset owners valuable information to  help prioritize their maintenance budget dollars?

INTRODUCTION

At AEDC we have a countless amount of mechanical equipment and systems. Two of the primary ones  are hydraulic and lubrication systems. These systems have a fairly simple purpose in life; to provide  hydraulic pressure or muscle for the purpose of operating valves and lubricating large motor and  compressor bearings. We have also used infrared to verify tank fluid levels and indicator accuracy, check  accumulators, inspect test cell ducting and many other uses. Infrared inspections can re-assure  operations personnel that valves are working and that liquids or gasses are flowing properly. By  performing periodic infrared inspections and trending component temperature data we can respond to  equipment needs before they cause downtime and unplanned maintenance. Showing asset owner’s real  savings through planned repairs and lowered downtime cost is a good way to get them on board with  periodic infrared inspections. 

MECHANICAL INFRARED INSPECTION FOCUS POINTS

SERVO VALVES

Figure 1 is a typical servo valve diagram showing the small ports and slides that are susceptible to micron  size trash and varnish. As the slides become harder to move back and forth they naturally draw more  current. This in turn elevates their operating temperature which can begin the varnish process. As the  varnish builds up the current rises and the process just worsens. Figure 2 is an IR image of a servo valve  while in operation. The image shows the hottest section of the valve is the coil section.

Servo valves have a maximum operating temperature, we have found the best method to prevent us from  having unexpected failures due to temperature is to trend the operating temperatures in hopes of detecting when they begin to rise and responding on a scheduled basis. 

In Table 1 you can see that Servo Valve Pump 1 shows an upward trend in temperature that drops off in  September due to being replaced. Also, Table 1 shows that we are trending the case drain lines as well  as the water to oil heat exchanger.

ACCUMULATORS

Hydraulic system accumulators are used to supplement flow and are a valuable hydraulic system  component. IR inspections are a quick way to scan the accumulators for proper operation. We have  found that many times the accumulator’s nitrogen charge gage is broken or so discolored the gage is hard to read. We could simply feel of the accumulators by hand to see if they have a warm oil side and a  cooler gas side but we have found the quickest and safest method is a quick IR scan. The IR scan can  give a clear image of what is going on with the accumulator. The bladder could be discharged or leaking  and this information can be used to justify funding for repairs or replacement. We have even seen cases  where accumulators were inadvertently valved out which the IR camera can detect as well. In this case  we would make a note of it in the report so that the system engineer could confirm whether it needed to  be opened or closed.

PROCESS AIR FLOW

Ensuring that your process air is being properly conditioned is a critical way to protect sensitive  equipment within the flow path as well as reduce required run time needed to meet specified conditions.  Reducing run time can be an excellent way to drastically reduce operation cost. 

Figure 4 shows a cooling section of a Process Air Duct that is not getting enough cooling water flow.  While cooling water flow is often monitored remotely, it is not practical to instrument every section or  passage of the cooling system therefore it is possible that remote indicators appear normal when in fact  large sections of ducting are not flowing enough. The doubled wall sections of duct are equipped with  cooling passages all throughout. Our systems engineers are able to compare the water flow data through  these passages in the control room recorded at the same time the images were taken to prove that while  the control rooms are seeing the proper water flow rate and temperatures, they are in fact not cooling  large sections of the ducting as efficiently. Replacing some of the supply and return lines has helped to  improve the cooling efficiency of the hot gases flowing through the duct as well as extend the life of the  ducting sections that were being heated excessively. More extensive maintenance is needed to improve the cooling efficiency further decreasing energy cost, allow original design specifications to be reached,  and lowering the temperatures the upstream compressors are subjected to. To address this issue some  options are being considered such as flushing out the passages with rust and crude, removing solvents, and replacing sections of the ducting. This section of ducting is much larger and more complicated than  the images represent so unfortunately replacing the duct is too costly at this time.

TANK LEVEL

In most cases fluid filled tanks will have a site glass or float type level indicator or possibly even a digital level gage that can be monitored from a control room or remote location. But many times the gage may  need to be verified for accuracy. Another advantage of an IR inspection is that the tank level can be  checked very quickly from a long distance with an IR camera.

SUMMARY

Expanding your infrared program with a mechanical emphasis can be a great way to increase system  performance, reduce down time, repair cost, and operating cost. Showing real savings to asset owners is  a good way to get their approval for additional periodic infrared inspections.

ACKNOWLEDGEMENTS

The author wishes to thank his management team and the complex leadership for allowing the  opportunity to present these findings.

ABOUT THE AUTHOR

Dan is a Level II thermographer and has lead the ATA Infrared program for 5 years.