REG NASA-LLIS-0847-2000 Lessons Learned Ultrasound Testing.pdf

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1、Best Practices Entry: Best Practice Info:a71 Committee Approval Date: 2000-04-20a71 Center Point of Contact: KSCa71 Submitted by: Wil HarkinsSubject: Ultrasound Testing Practice: Use ultrasound as a technique for detection of air/fluid leaks, electrical shorts and bearing wear in Ground Support Equi

2、pment (GSE). Ultrasound is a technique of listening for audible frequencies outside the normal range of human hearing. This differs from ultrasonics, which is the technique of inducing sound frequencies into a medium to measure distance or thickness.Programs that Certify Usage: This practice has bee

3、n used on Automobiles, Power Industry, Hospitals, Aircraft.Center to Contact for Information: KSCImplementation Method: This Lesson Learned is based on Maintainability Technique number AT-10 from NASA Technical Memorandum 4628, Recommended Techniques for Effective Maintainability.Benefit:Timely dete

4、ction and elimination of air/fluid leaks, electrical shorts, and bearing wear will result in substantial cost savings in equipment operation and maintenance. Examples: Elimination of air/fluid leaks would produce savings in power consumption, and equipment wear and tear. Detection and elimination of

5、 conditions causing arcing in electrical systems would result in increased system availability and repair time associated with downtime and damage that would have resulted from Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-electrical shorts.Impleme

6、ntation Method:Ultrasounds, by definition, are beyond the limits of normal human hearing, an operator using a sophisticated detector translates ultrasound signals to the range of human hearing.Ultrasound detection is the number of times a sound wave cycles from trough to crest. This is expressed in

7、cycles per second and measured in hertz. One kilohertz is 1000 cycles per second. The best human ears can generally hear noises in the range of 20 to about 20,000 Hz (20 kHz). Many ultrasound detectors start at approximately 20 kHz and can work upward to sounds as high as 100 kHz. Operators using th

8、e ultrasound instrument can tune to and “hear“ what is going on in operating machinery (figure 1).refer to D descriptionD Figure 1. Use of Ultrasound Gun to Detect Leaks in Pipe Flanges Fluid and gas systems and other working machinery have constant ultrasound patterns. When a leak occurs, fluid pas

9、sing through an opening produces turbulence with strong ultrasound frequencies. Changes in the “sound signatures“ can readily be recognized as wear in components. An ultrasound detector senses subtle shifts in the signature of a component and pinpoints potential sources of failure before they cause

10、costly damage. The longer wavelengths of lower-pitched sounds easily penetrate solid; yet they slip through minute openings. Ultrasound detectors are used for isolating such leaks.Operators use lightweight, battery-powered pistol-shaped instruments which can easily be moved from machine to machine.

11、The instrument circuitry translates the high-pitched ultrasounds to those in the human hearing range. Some instruments feature a frequency-adjust dial to provide tuning capability, enabling operators to hear the ultrasounds through headphones and determine their Provided by IHSNot for ResaleNo repro

12、duction or networking permitted without license from IHS-,-,-intensity by the definitions registered on an analog meter.The instrument is used to establish sound patterns, which compared at a later date become useful in locating and diagnosing bearing failure, vacuum and pressure leaks, valve blowby

13、 and faulty electrical circuits.References:1. Plant Engineering, June 18, 1987.2. Maintenance Technology, January 19943. P/PM Technology, March/April 1991.4. P/PM Technology, Reprint 1986-1988.5. Predictive Engineering, LSOC/KSC.May 3, 1996.Impact of Non-Practice: The testing provides cost savings t

14、hru detection of leaks in air/fluid systems that are not normally audible. Compressors and fluid pumps may run at above normal requirements to make up for the loss caused by leaks creating unnecessary costs to power the equipment. Bearing problems can be evaluated over a period of time to detect pro

15、gressive wear by changes in the ultrasound intensity level, thus protecting the bearing from sudden failure. Testing of electrical systems for sounds of arcing is easily accomplished enabling loose connections and openings to be found. Ultrasound testing is one of the least complex and less expensiv

16、e maintenance detection methods, requiring a hand held detector and associated meter.Related Practices: N/AAdditional Info: Approval Info: a71 Approval Date: 2000-04-20a71 Approval Name: Eric Raynora71 Approval Organization: QSa71 Approval Phone Number: 202-358-4738Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-