By Michael Hastings
Which condition monitoring method is right for you? Now, you can confidently turn to ISO 19283 for the best solution. The new standard touches on all aspects of condition monitoring and diagnostics of the hydro unit in a comprehensive overview. This was necessary, partly because of the unique design of the hydro unit, where a wide range of monitoring techniques are available but not well-understood by many end users. Moreover, these have not always been adequately covered by standards in the field, as some are overlapping, lacking in coverage or only partially relevant to hydro unit applications.
ISO 19283, Condition monitoring and diagnostics of machines — Hydroelectric generating units, clears up the confusion by bringing everything that is relevant under one umbrella.
Why is condition monitoring important for hydro units?
Traditionally, hydroelectric generating units (or simply hydro units) have been overdesigned, well-staffed for maintenance and often continuously operated at only baseload conditions over many years. As a result, there were few maintenance issues and shutdowns could be planned at fixed intervals. Therefore, there was little need for condition monitoring of the units. Simple machine protection systems sufficed, if used at all.
Nowadays, there are more stringent requirements for operational regimes, availability and reliability. Disruption to consumers’ needs has to be minimized and cash generation for the utilities maximized. The operating regimes for many hydro units have been extended to include synchronized compensation, load-following and peaking, which means there are many starts and stops and partial-load operation, sometimes in the rough zones. Many applications are based on pumped storage, which provides its own maintenance and operation challenges. Moreover, new units are designed to be more streamlined to the application and less robust, and older units are often refurbished to extend life or to increase rating. This means that machines are more stressed, which can lead to premature or unpredictable failure of the components. Some of the new failure modes are even different than before.
At the same time, there is a trend for fewer maintenance staff and specialists to look after the machines. That means there is a significantly greater need for an effective condition monitoring strategy, not just a protection system. Moreover, the condition monitoring solution of these machines should be more than just basic vibration monitoring. Due to the complex nature of the hydro unit components, a number of potential failure modes now become apparent under the current stressful conditions, which require a number of different, specialized monitoring techniques and diagnostic expertise.
There are few standards for monitoring the hydro units and a general lack of understanding of the monitoring techniques. Even for hydropower stations that have a legacy condition monitoring system installed, the existing condition monitoring requirements for the hydro units are sometimes no longer valid as a result of changing operating conditions or refurbishment of the units. Condition monitoring and diagnostics therefore play an important role in reducing downtime and the life-cycle costs of hydro units today.
What does ISO 19283 offer and who is it intended for?
ISO 19283 focuses on recommended condition monitoring techniques for detecting and diagnosing developing machine faults associated with the most common potential failure modes for hydro unit components. It is intended to improve the reliability of implementing an effective condition monitoring approach for hydro units. It is also intended to help create a mutual understanding of the criteria for successful hydro unit condition monitoring and to foster cooperation between the various hydropower stakeholders.
This standard is not only intended for service provider maintenance operators and managers, but also for contractors, consultants, machine manufacturers and instrument suppliers.
Which type of hydro units and components are relevant?
The standard is primarily intended for the monitoring and diagnostics of potential failure modes of medium- to large-sized hydro units with more than 50 MVA installed capacity, but it is equally valid for smaller units in many cases. It is applicable to various types of turbines, such as Francis, Kaplan, Pelton or Bulb, to name a few.
ISO 19283 focuses on condition monitoring and diagnostics of the following hydro unit components:
- Shaft/bearing assembly
- Runner (and impeller for pumped storage applications)
- Penstock (including the main inlet valve)
- Spiral case
- Upper draft tube
Auxiliary systems, such as for lubrication and cooling, are briefly mentioned but are not a focus area. ISO 19283 focuses on the hydro unit. Therefore the foundation, civil works, transformers, substations and transmission systems are outside the scope.
What type of condition monitoring is covered?
The standard essentially covers online (permanently installed) and, to a more limited degree, portable instrument condition monitoring and diagnostic techniques for operational hydro units. Monitoring during operation is the key, so offline machine testing (i.e. that which is only done during shutdown), although very important, is not part of the scope of ISO 19283. Nor is one-time acceptance and performance testing within the scope.
ISO 19283 presents time-proven condition monitoring techniques that are used for detecting and diagnosing the most important potential failure modes of hydro unit components. Collating best practice from existing standards in the field, it gives general guidelines on how to establish an effective condition monitoring strategy, select the relevant monitoring techniques and determine the system that provides them. These techniques cover a wide range of continuous and interval-based data collection methods for a wide range of applications.
Michael Hastings is senior application engineer with Brà¼el & Kjà¦r Vibro. He is the ISO TC108/SC5/WG17 convenor and ISO 19283 project leader.