INDUSTRIAL APPLICATIONS
The ultrasonic cross-correlation flow meter or USCCFM was developed originally as a tool set for nuclear applications. This was in part due to its capability to operate in very high temperature industrial environments all the while demonstrating accurate flow measurement capabilities.
Because the USCCFM is a non-intrusive technology flow measurements can be taken without the high cost of pipe cutting and then welding (breaching the pressure boundary). Non-intrusive technology flow measurements can also provide to the customer the benefit of not having to shut down a plant. In addition flow measurements can be made in pipes that have no existing flow measurement. Because nuclear applications require traceability to national standards, the USCCFM can also be used to calibrate existing flow elements in industrial applications for process optimization or reduced environmental emissions.
The USCCFM is thus ideally suited for applications in high temperature and caustic or corrosive processes in the chemical processing industry.
The USCCFM can also be used for water management volumetric metering for water utilities which have issues with accurate metering and scale build up inside the pipes.
NUCLEAR & FOSSIL APPLICATIONS OF THE ULTRASONIC CROSS-CORRELATION FLOW METER (USCCFM)
The ultrasonic cross-correlation flow meter or USCCFM has been used extensively for boiler feedwater flow calibration and monitoring. Feedwater pipes in CANDU-based nuclear plants have a diameter of between 12” and 16” at temperature of between 170 C and 180 C. Since feed-water flow measurements are used for calibrating reactor thermal power, there are particularly stringent requirements to the meter accuracy and reliability. In addition to the demonstrated accuracy of well within +1% and its high reliability, the ease of use of the USCCFM makes it an excellent tool for evaluating flows in other power plant systems. A few examples of such applications in CANDU-based nuclear plants, with a brief description of the systems are given below. It should be noted that accurate flow measurements in all the systems listed below, except for the moderator system, are just as important in fossil power plants as well. Since temperatures encountered in fossil plants are even higher than in CANDU nuclear plants, the USCCFM is uniquely positioned to provide accurate non-intrusive flow measurements in fossil plants.
HEAT RATE IMPROVEMENT (FOSSIL)
One of the cost effective ways of improving efficiency and thus meeting increasingly stringent environmental compliance of existing fossil power plants is to improve the accuracy of boiler feed-water flow measurements. This can be achieved by calibrating installed flow elements such as nozzles or orifices. Industry experience indicates that nozzle fouling can introduce as much as 4% measurement error, resulting in the corresponding reduction in plant efficiency. Calibration can be performed non-intrusively if the Ultrasonic Cross-Correlation Flow Meter (USCCFM) with special high temperature transducers is used, which can achieve better than 1% accuracy at temperatures of up to 600⁰F. Since the USCCFM transducers are mounted externally to the pipe, flow measurements can be taken without the high cost of pipe cutting and then welding (breaching the pressure boundary). The USCCFM has been extensively used in the nuclear industry for reactor thermal power calibration and power uprate.
The concept of this meter is totally different from the well known transit time meters and is based on directly measuring the time of flight of the turbulence eddies prevalent in a turbulent flow. More
Participants in Industry Forums such as the recent (Feb. 2013) Electric Power Research Institute (EPRI) Heat Rate Improvement Meeting in Scottsdale, AZ have noticed increased interest in accurate boiler feed-water flow measurements. Several presentations given at that meeting alluded to the fact that primary flow elements installed in feed-water lines go back to the original plant installation and have not been calibrated or inspected since then. Therefore, the original calibrations are no longer valid and the flow element accuracy is questionable. There were several discussions on the level of accuracy required for feed-water flow measurements, and the consensus seemed to be that around 2% would be beneficial.
With its high accuracy, the USCCFM can be used to calibrate the above mentioned primary flow elements. The USCCFM can be bought by a customer or a calibration service can be provided.
To get more details on how the USCCFM can improve the efficiency of your existing coal-fired power plant or combined cycle plant and/or to arrange for a demo Contact
MODERATOR SYSTEM (CANDU NUCLEAR)
The moderator system in CANDU nuclear plants is D2O-based and operates at temperatures between about 40 C (calandria inlet) and 60 C (calandria outlet). The system is designed so that moderator D2O flow is constant and its cooling is done by service water in the two heat exchangers. Moderator heat load contributes approximately 4% to the total calculated reactor thermal power. Stations use design values for the moderator load, which could result in a significant bias error in the reactor power. USCCFM was used at all 3 CANDU stations in Ontario to evaluate the moderator flow and thus to reduce the overall reactor power uncertainty. In addition, accurate knowledge of the moderator flow is required to ensure that the trip coverage on the moderator outlet temperature.
SECOND STAGE REHEAT (NUCLEAR & FOSSIL)
Reheater drains contribute about 3% to the total calculated reactor power. At Darlington NGS, a change in power error was noticed when reheater drains flow were isolated. USCCFM measurements identified that the actual flow were about 10-15% lower than station indication and resulted in 0.4% gain in production for all four units. The discrepancy was traced to incorrect installation of orifice flow elements in reheater drains piping. The piping is 6” carbon steel at about 250 C. Reheater drains flows were also measured in all other Ontario plants.
HIGH PRESSURE SERVICE WATER (CANDU NUCLEAR)
One of the uses of high pressure service water is to provide moderator heat exchanger cooling. The flow of the service water is controlled by the moderator outlet temperature controller; however, there is no flow measurement device installed to provide an indication of the actual flow. USCCFM has been used regularly on all the units of Pickering NGS to verify that the flow meets minimum requirements. Accurate knowledge of the flow also allows evaluation of the moderator heat exchanger performance.
LOW PRESSURE SERVICE WATER OR INTAKE COOLING WATER (NUCLEAR & FOSSIL)
Maintenance of low pressure service water pumps is usually done on a “call-up” basis and results in unnecessary unit shutdowns. As part of Condition Based Maintenance Program, USCCFM was used to perform monthly flow measurements in the low pressure service water system of Pickering NGS. This helped identify performance deterioration of one of the pumps. Subsequent pump inspection during a scheduled unit outage identified a cracked rotor which was immediately repaired. The piping is 30” carbon steel at about 20 C. Service water supply to other systems was also measured regularly to satisfy regulatory requirements that sufficient supply is available.
SEWAGE FLOW (NUCLEAR & FOSSIL)
Sewage flow was measured at Pickering NGS to evaluate extraction pump performance and to establish that the total discharge is within the environmental limits. The pump was operating in the on/off mode, and flow data were collected over extended period of time to determine the total discharge.
Please note that this application is an example of high turbidity resilience of the USCCFM.
TURBINE LUBE OIL FLOW (NUCLEAR & FOSSIL)
Turbine lube oil flow was measured at Bruce B NGS to indentify possible flow obstruction.
GENERATOR STATOR COOLING FLOW (NUCLEAR & FOSSIL)
Generator stator cooling flow was measured at Pickering NGS to indentify possible flow obstruction.
ASME PTC-6 TURBINE TESTING (NUCLEAR & FOSSIL)
ASME PTC-6 is the procedure for accurate testing of nuclear and fossil steam turbines. There is need for accurate boiler feedwater flow. ASME flow nozzles are in the feedwater train and they are subject to erosion and fouling. The USCCFM is used to obtain accurate boiler feedwater flow.
On most CANDU Nuclear stations the feedwater flow can also be obtained by a mass-energy balance of the Deaerator and since condensate ASME flow nozzles are located in the lower temperature / pressure of the cycle and therefore not as susceptible to erosion and fouling. The use of the mass-energy balance provides additional independent verification of the high accuracy of the USCCFM.
Deaerator Mass Energy Balance (DAMEB) is performed annually at Darlington NGS. Based on the test results and the USCCFM flow measurements vs DAMEB data the annual average data discrepancy was less than 0.2% (1994-2008)
Full PTC-6 tests were performed at Bruce NGS units 5-8 after the LP turbine upgrade. Based on these test results the data discrepancy was between 0.2%-0.5% (2005-2006). Once again providing additional independent verification of the high accuracy of the USCCFM.