MOTOR CIRCUIT ANALYZER "RIGHT" STUFF FOR ASSURING QUALITY OF JOHNSON SPACE CENTER MAINTENANCE OPERATIONS
HOUSTON, TEXAS -- (September 26, 1996) -- Building 24, Central Heating and Cooling Plant, and Building 28, Auxiliary Chiller Facility, at the Johnson Space Center in Houston are critical to the day to day function of the Center. The primary role of the Johnson Space Center is Lead Center for NASA's manned space flight program.
The two buildings provide chilled water through 3.5 miles of tunnels to air conditioning systems in the main complex of the Center. Air conditioning systems include those which cool the main frame computers for NASA's Mission Operations Center and astronaut training simulators and systems serving life science laboratories.
Johnson Controls World Services Inc. is responsible for maintaining the chiller motors, water pumps, cooling tower fans and their critical spares in the cooling plant and motors, water pumps, cooling tower fans and their critical spares in the cooling plant and the chiller facility. The company has some 250 operators, pipe fitters, electricians, millwrights and insulators who perform a multitude of such critical maintenance functions at the center.
In the past, thermography and vibration analysis were the mainstay technologies of the quarterly predictive testing and inspection of the motors in these buildings. These motors range in size from five to 2,250 horsepower.
A revolutionary electric motor circuit analyzer was recently added to the mix. "The MCE tester was a new technology we wanted to evaluate for use in our preventive maintenance program," recalled Johnson Controls Senior Analyst Robert E. Guthrie.
The MCE Tester
The PdMA Corporation's self-contained, portable Motor Circuit
Evaluator (MCE™) System 3000 can be used as a quality
assurance tool or as a tracking and trending device for ac
induction, dc, synchronous and wound rotor motors. The tester can
help detect rotor anomalies, including broken bars or end rings,
warped or bowed shafts, eccentricity and porosity; and stator
defects, including turn-to-turn faults, phase-to-phase leakage,
improper winding and core grinding or damage.
In addition, the tester can be used to assess the condition of the windings and the insulation system.
The MCE tester evaluated by Johnson Controls was equipped with PdMA Corp.'s new WinVis™ software. WinVis' user-friendly, Windows interface and complete "Help" system permit quick database set-up based on the plant layout; fast entry or duplication of nameplate data; testing and assessment of a variety of motors in the field; the generation of graphs, charts and reports; and exporting data to other applications.
The MCE's testing capabilities have been expanded to include polarization index, dielectric absorption ratio and commutator bar-to-bar testing.
Limiting & Controlling Failures
"It's very user friendly, especially with the new
Windows software. It enhances our ability to limit motor failures
and to schedule maintenance for a convenient time," said
Guthrie of the MCE tester, which replaced an insulation breakdown
tester formerly used in Johnson Controls' predictive maintenance
program.
"Under the old system, the data was getting lost. There was no convenient location to store it. But the MCE tester has built-in storage," recalled Johnson Controls Analyst Greg McCracken. Building 28's chiller motors provide a classic example of how Johnson Controls is using the MCE tester. The chillers are critical to the chilled water systems that cool facilities providing vital support for manned space flights during Space Shuttle operation, flight simulators and the Mission Control Center.
Johnson Controls observed that Chiller #1, a 1,750 horsepower motor, was running hotter than expected and detected excessive vibration. The MCE tester was used to pinpoint the cause. A similar AC motor was tested at the same time and provided "normal" readings for comparison.Because the MCE test results on Chiller #1 did not suggest an immediate risk to the life of the motor and backups were available, trouble shooting was scheduled after a planned Space Shuttle mission. When MCE testing was conducted again, the results indicated that Chiller #1's circuit and a capacitor were suspect.
An inspection of cables inside the controller subsequently showed that there was a large hole in the insulation on the cable running from power factor capacitor #3 to the surge capacitor. Identification of this problem prevented expensive and unnecessary motor repairs or replacement, and extended the motor's life.
Other benefits of using the MCE tester realized by Johnson
Controls at the Johnson Space Center were troubleshooting
critical spares and quality checking motors sent out for repairs.
Also under evaluation by Johnson Controls is an MCE tester
purchased for use in launch-based support services at the Kennedy
Space Center in Cape Canaveral. Johnson Controls is in the
process of purchasing a second MCE tester for use in that
program, according to a company spokesperson.
Johnson Controls is a leading global provider of technology-driven integrated facility management solutions for government and commercial clients. Approximately 16,000 professional, technical and crafts personnel operate 325 contracts at more than 325 worldwide sites.Headquarters offices for the Integrated Facility Management unit of Johnson Controls are located in Atlanta and Cape Canaveral, Fla.
The PdMA Corporation, based in Tampa, is a predictive maintenance company which also offers advanced motor circuit evaluation, full lubricant analysis, maintenance program analysis, and predictive maintenance training.
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