ISO 29821-1-2011 pdf free download

ISO 29821-1-2011 pdf free download.Condition monitoring and diagnostics of machines Ultrasound Part 1:General guidelines
Surveillance des conditions et diagnostic d’etat des ma chines — Ultrasons — Partie 1: Lignes directrices générales.
secondary technique for diagnosis and prognosis when these processes are carried out in accordance with ISO 133791l2l and ISO 13381-1t), respectively.
8.2 Comparative ultrasound
When starting an inspection route for the first time, it is important to be able to identity anomalies, especially those that can be in a failure state. The most common technique is to use the comparative method. It is the best method to use when there are no established baselines set and a series of points on a machine needs to be assessed with no previous assessment criteria. As with all technologies, the confidence level of the information obtained is dependent on the equipment used, training arid experience of the inspector and detection method applied.
Comparative ultrasound can be either quantitative or quahtative. The quantitative method is the most often used method for many ultrasound applications. This method uses the strength of the signal, expressed in decibels, (commonly called decibel value”) to determine the severity of a component’s condition. The resultant decibel value is compared to that of similar component or equipment baseline.
Many applications do not require quantitative data to monitor the condition of components of a machine. In the case of compressed air leaks and electrical discharges, qualitative techniques are usually the preferred methods, as these conditions do not produce ultrasound if they do not exist.
A typical example of the qualitative technique is where there are multiple electrical components operating at the same voltage under the same load and where one component is discharging, producing an ultrasonic signal. This is usually an indication of a deteriorating condition. In this instance, an evaluation of the demodulated or heterodyned sound pattern would be a better indicator of severity than change in signal level (decibel value). The sound analysis provides information that identifies the type and severity of the condition. This is where qualitative measurements can help locate the source of the emission by the increase in the signal level and the sound quality indicates the degree of severity.
Each application would require a plant or an individual to establish their own set of criteria for degradation levels. As an example, a compressed air leak that has an extremely low decibel value may not require repair, while a larger leak with a high decibel value would require repair. A detectable air leak at 1 x 1O2 cm3/s may not justify repair, while a leak at 100 cm3ls would.
8.3 Baseline method — Quantitative ultrasound
The most common structure-borne ultrasound method in use for condition monitoring is the baseline or quantitative method. This is important when critical plant components are monitored on a routine basis for diagnostic reference. When subsequent inspections or surveys indicate an increase in the decibel value or a change in sound characteristics, these baselines can be used for a comparison. This is useful to identify deteriorating conditions before they require any major maintenance or become catastrophic. The baseline method can include decibel value and baseline sound samples. The advantage of a baseline sound sample is the ability to review and analyse any changes in the subject equipment based on spectral and or time series views that might not be apparent with just a decibel value.ISO 29821-1-2011 pdf free download.