ISO 16079-2-2020 pdf free download – Condition monitoring and diagnostics of wind turbines — Part 2: Monitoring the drivetrain.
5Failure mode and symptoms analysis (FMSA)
5.1 General
The FMSA process is essentially an extension of the FMECA process with a focus on the symptomsproduced by the identified and ranked possible failure modes that were the outcome of the FMECAanalysis.
The FMSA methodology is designed to assist with the selection of monitoring techniques and strategiesthat provide the greatest sensitivity to detection and rate of change of a given symptom, thusmaximizing the confidence level in the diagnosis and prognosis of each of the failure modes identifiedfor each of the components of the wind turbine drivetrain.
Where the confidence in a technique’s sensitivity and resulting diagnosis/prognosis accuracy isquestionable, then the use of additional techniques for further correlation is recommended.
Refer to ISO 16079-1 which gives guidance on applying FMECA analysis to wind turbines.5.2The process of the FMSA analysis
The FMSA analysis shall be a team effort with participation of condition monitoring experts as well asparticipation of staff with an in-depth knowledge of the machine under analysis.
The essential elements of the FMSA process are:
— listing the components involved;
— listing the possible failure modes for each component;
— listing the effects of each failure mode;
— listing the causes of each failure mode;
— listing the symptoms produced by each failure mode;
— listing the most appropriate primary and feasible monitoring technique;
— listing the estimated frequency of monitoring – monitoring interval;
— listing the most appropriate correlation techniques. Increased diagnosis and prognosis confidence can be gained by using “correlation techniques” when monitored at a given frequency.
The FMSA analysis shall be performed for each component/failure mode, which can be prioritized by using the monitoring priority number (n MP ) of the FMECA analysis.
A practical approach is to use copies of Table 2 to structure the FMSA process.
Refer to the example in Annex B which shows an FMSA analysis for the most common failure modes of the wind turbine drivetrain.
6 Descriptors for fault detection6.1 General
The FMSA process provides a list of potential fault indicators – the descriptors; this clause describeshow some of those descriptors may be derived.
NOTE In some literature, the term “characteristic value” is used instead of ” descriptor”.
The format of a descriptor is a single scalar value and a timestamp. This makes descriptors verysuitable for long term trending against time.Changes in the measured value of descriptors are veryeasily detected and correlation between different descriptor values such as vibration-based values and process parameters is straightforward. Any database historian can store descriptor values due to the simple format.
Regardless of the technique, the capability of a condition monitoring system relies upon the followingbasic elements: the number of sensors, the type of sensors, and the associated signal processing and simplification methods utilized to extract important information in the form of descriptors from the various signals and observations.
A symptom indicating a fault is expressed by the behaviour of one or more descriptors with respect to:
— presence,
— absence,
— increase or decrease,
— rate of change,
— location(s) of the change of descriptor,
— operating conditions.ISO 16079-2 pdf download.