Resolution of US-NRC Technical Issues with Enhanced CROSSFLOW Technology
The assumption that laboratory calibration results are transferrable to an in-plant configuration without additional in-plant calibration, without a complete uncertainty evaluation, and without traceability to a national standard. Alternatively, if in-plant calibration is used to eliminate this assumption, the weaknesses of in-plant calibration without a complete uncertainty evaluation and without traceability to a national standard may remain.
Improvements in the CROSSFLOW system over the ten year period since the Topical Report was compiled include the following:
- Hardware redesigns include the use of up to eight sets (sixteen pairs) of ultrasonic transducers, located at the same or different pipe cross-sections.
- Processing capability which implements up to twelve software and eight hardware channels.
- This enables the collection of up to twelve sets of demodulated signal and consequently twelve different measured values with twelve sets of criteria.
- Each signal pair is obtained by using different frequency windows and therefore produces data related to different sections of the turbulence spectrum.
- As a result, the enhanced CROSSFLOW system:
- Provides very detailed information about flow conditions at the location of the meter which may affect flow rate readings, and can generate output signal which is not affected by flow conditions.
- Recognizes the influence of hydraulic effects from feed water piping configurations and/or correlated noise effects.
- Provides the analytic capability to support the transference of laboratory calibration to an in-plant installation.
- Implements the capability to correct for differences in the fluid dynamic condition.
- Implements the capability to determine whether the meter is operating within the domain to which its calibration factor applies.
Other Considerations include:
- AMAG will follow the ISO guidelines for the uncertainty calculation as defined in the Guide to the Expression of Uncertainty (GUM). This will address the statistical validity of the traceability and uncertainty calculation.
- The approach to the uncertainty calculation has been modified to include CROSSFLOW commissioning data such as power and plant configuration changes to obtain an uncertainty envelope encompassing variation in CROSSFLOW readings.
The treatment of the impact of acoustic noise on CROSSFLOW and the ability to detect and remove the effects, including determination of residual uncertainty.
Various methods have been developed and validated to mitigate the impact of correlated noise. These noise detection methods are as
Offline TDA evaluation (software)
Online Zero Peak noise removal (software)
Online Signal Rejection Unit (hardware)
Alarms have been introduced that will detect effects of noise during system operation based on the changes in the parameters (peak/RMS, CCV, Symmetry) of the CROSSFLOW system and/or changes in the number of rejected points.
The additional uncertainty associated with each method is quantified and is included in the uncertainty calculation.
The lack of periodic in-plant calibration using an instrument traceable to a national standard and lack of assurance that CROSSFLOW operation remains within the claimed uncertainty.
The CROSSFLOW system contains various internal calibration checks to ensure that the key elements of the system remain valid.
Deviation alarms associated with CROSSFLOW system (uncertainty and lower bound) also detect significant shifts in the CROSSFLOW
Once a baseline is established, trending analysis can provide information on changes in plant parameters which can be related to
CROSSFLOW system performance. Analytical tools of known accuracy, for specific applications, are available to perform this analysis.
CROSSFLOW in-plant performance accuracy is assured by the following means:
In place Calibration Parameters (internal timing calibration check, signal conditioning unit check traceable to national standards)
Monitoring and corroboration of other Plant Processes and Parameters
Continued validation of correction factor during plant power and configuration changes
On-line monitoring and alarming functions
- Periodic measurements of pipe internal diameter