July 2013, Vol. 240 No. 7
Features
Condition-Based Monitoring A Fully Automated Station Solution
This article describes a system that not only monitors all ultrasonic meter (USM) diagnostics from most common brands, but also monitors data from the flow computer, and by using separate pressure and temperature (P&T) transmitters, computes flow for comparison to the customer’s fiscal flow computer. In addition, the system monitors the gas chromatograph (GC) diagnostics to ensure proper operation and validation of the gas quality data used in the flow calculations.
Field information is transmitted via a secure cellular data modem to a cloud server. The client automatically receives periodic reports via email that provide detailed information about the operation of the meter station. In the event a problem occurs with the USM, P&T transmitter, GC or even questionable comparisons between flow computer volumes, the system will send an email or text message (SMS) immediately to the appropriate personnel.
Introduction
During the past several years, the use of USMs has gained worldwide acceptance for fiscal applications. The many benefits of USMs have been documented in papers at virtually every major conference. The significance of knowing the ultrasonic meter is operating accurately has never been more important.
USM technology has played a key role in reducing lost and unaccounted for (LUAF) numbers. However, like any technology, the client must understand the meter’s diagnostics in order to validate proper operation. Due to mergers, acquisitions, changes in technology and purchasing preferences within an organization, this can be extremely difficult as technicians often encounter multiple manufacturers’ equipment. Thus, what is needed is a system to monitor the USM’s health, regardless of manufacturer, and automatically provide a report to the client when problems occur.
The traditional method of verifying whether the USM is operating accurately requires using the USM manufacturer’s diagnostic information to evaluate the meters’ health. This is usually accomplished by having a technician visit the site periodically (typically monthly) to collect a maintenance report. This report is analyzed by the technician while onsite, and often analyzed a second time by office measurement specialists at a later date. However, if a problem occurred during the month (transducer issues, flow calculation discrepancies, transmitter fluctuation) that isn’t present at the time of the site visit, added measurement uncertainty may result.
For many years, some clients and manufacturers have programmed their onsite flow computer to do some basic monitoring of the gas USM diagnostics. More recently some clients have implemented a semi-continuous monitoring system to collect diagnostics from the meter on a more real-time basis. Essentially, when any of the meter’s diagnostics are outside prescribed limits, the SCADA system will alert them of a potential problem. This is often referred to as conditioned-based monitoring (CBM). From an industry perspective, these programs were proprietary to a given brand of flow computer and USM, thus implementation for other customers, or acquired assets that used another brand, was very difficult.
Implementing a traditional CBM system to collect, transmit and provide further analysis of the USM data is not easy and is often expensive. Additionally, these generally focus only on monitoring the USMs health, and do little, if anything, to validate the integrity of the entire measurement facility. While it is important to ensure proper USM operation, it is equally important to verify the flow computer is working correctly, the P&T transmitters are still accurate and the gas chromatograph (GC) is performing properly.
What customers need is a separate, independent system that can be easily retrofitted to existing sites without requiring modification to the existing SCADA network, while working with the customer’s existing equipment. This system should validate all aspects of USM facility operation, in order to minimize site visits, and immediately report when problems occur. It needs to work with a variety of USMs, GCs and flow computers. It should also validate that the existing fiscal flow computer is collecting all the USM pulses (no more, no less), the correct computation of AGA 7, 8, 9 and 10, and the accuracy of energy rates. With today’s new technology, CEESmaRT, this is possible.
System Overview
CEESmaRT is an entirely new concept that provides many benefits compared to traditional CBM systems. It is comprised of site-installed hardware and cloud-based software server components. The field-installed hardware CEESiGuard collects, computes and transmits a variety of measurement data to an off-site server. The secure, cloud-based software server system, CEESiNet, receives and analyzes the data and provides client reports via the Internet. Both hardware and software work together to remotely monitor and verify all aspects of the USM measurement station performance at all times. This results in a continuous-based monitoring system (CBMS), as opposed to a condition-based monitoring (CBM) system.
Hardware Component
CEESiGuard is a flow computer hardware device that monitors the measurement station equipment’s performance in real-time. USM diagnostic “health” information, along with volumetric flow data, is obtained serially to ensure all values are within the normal operating range. Fiscal P&T readings, as well as actual and corrected volumes, are acquired directly from the client’s flow computer. CEESiGuard computes AGA 7, 8, 9 and 10 to confirm the fiscal flow computer is obtaining the correct number of pulses from the USM, thus ensuring accurate volume and energy values. In addition, the meter’s reported SOS is directly compared to the AGA 10 computed SOS within the CEESiGuard unit.
CEESiGuard continuously performs short-term analysis of all USM diagnostics: transducer performance, SNRs, path-to-path SOS deviations, gains, turbulences, profile factor, symmetry and crossflow. It also monitors for deviations in the fiscal P&T transmitters, GC performance problems (response factors and alarms) and flow computer calculation discrepancies (actual volume, compressibility, corrected volume and energy). CEESiGuard verification is accomplished by incorporating a redundant P&T transmitter for each meter run. By comparing the CEESiGuard pressure and temperature readings with the fiscal flow computer’s values, deviations can be quickly and easily identified.
Hourly average flow data and diagnostic information are automatically transmitted once per hour for further detailed analysis, trending, archiving and reporting. All communication is via a secure digital cellular network that is 100% independent of the client’s SCADA system. In the event cellular data is not available, satellite communication can be used. When an issue occurs with any of the facility’s equipment, the client can choose to receive alerts in real-time, daily via email and by text message.
Figure 1 is an example of a two parallel meter runs with two meters in series, a configuration often used in high-volume application to help validate the fiscal USM. Different path configurations are generally used by the two USMs in series to provide redundancy and reduce uncertainty. Figure 1 shows the client’s transmitters in blue and the CEESmaRT system components (hardware and transmitters) in red.
Key system features are:
• Incorporation of a separate, fully independent internal flow computer to obtain P&T readings, compute uncorrected and corrected flow (from serial USM data), AGA 10 SOS, and direct communication with the gas USM and GC.
• Continuous validation of P&T readings for each meter run are generated by comparing the fiscal transmitter readings to the unit’s independent multi-variable transmitter (MVT).
• Communication with multiple manufacturers’ equipment: Daniel, Instromet and SICK ultrasonic meters, Daniel and ABB gas chromatographs, and most common flow computers by polling a local RS-232 or RS-485 port and using Modbus communication.
• Complete isolation from client’s SCADA System: All data is transmitted via secure digital cellular radios by either an AT&T Asavie VPN client, or by AT&T ANIRA software. This fully isolates the client’s site from the public Internet; the IP address of the field unit is invisible to the public Internet.
CEESiNet: ‘Cloud-Based’ CBMS Software Component
The off-site “cloud-based” system host, CEESiNet, is a proprietary software application developed in conjunction with AT&T. It is specifically designed to collect, analyze and monitor measurement station performance data. The unique algorithms provide storage, trending and further data analysis, and automatically generate warnings, alarms and a variety of reports. This provides clients with fast, easy, secure, proactive access to their site information without the limitations of corporate SCADA networks.
Figure 2 graphically depicts the communication topology, showing the field-installed hardware in the upper left of the drawing, the client’s communication with the AT&T Data Center, and how the technical support team gains access to set up each client and meter run.
Using Internet Explorer with Microsoft Silverlight, authorized users simply connect to the system’s URL, enter their user name and password, and have immediate viewing of all authorized site data per their permission level. Once connected to a specific meter station, additional reports and quasi-live data (the average of the last two minute flow data) are available.
Unlike other systems, CEESmaRT reports the USM diagnostics, P&T verification, actual and corrected volume validation, GC performance and flow rate ratios for series or parallel meter station designs, as well as enables the client to customize their report format and frequency. Clients select from over 50 customized report templates to receive reports of historical trends for all USM diagnostics, meter run pressures and temperatures, actual and corrected flow rates, as well as gas chromatograph information. CEESmaRT uses a PDF format to make reports easy to view and distribute, and can be distributed daily, weekly or monthly.
Some key features of the “cloud-based” CEESiNet system are:
• Multiple levels of security and encryption, including SSL and 256-bit AES encryption, VPN connections, and managed firewalls
• Clients control access to CEESmaRT data via internal assignment of individual user permissions
• Clients customize reporting and alarming frequency, as well as format (email or text)
• All reports are accessible via the Internet from any computer using Microsoft Silverlight and Internet Explorer (or other web browser); no special software is required to obtain reports
• All meter station reports, regardless of gas USM brand, look the same. Consistent report structure greatly reduces training and simplifies understanding of meter station performance
• More than 50 standard reports are available in PDF format for ease of viewing and sharing; customized reports can be user-developed with Excel 2010
Report Examples
The alarm report (Figure 3) provides a quick visual assessment of the duration percentage of any alarm condition monitored by CEESiGuard during the report test period. Green boxes with zeros indicate no alarm condition was detected during the test period, and red bars indicate the percent of time a particular alarm condition was active. For example, the summary alarms table at the bottom left of Figure 3 provides a visual flag, regarding the AGA 10 SOS % difference alarm. The red value indicates an alarm condition was active 33% of the test period, which is graphically illustrated on the bottom right of Figure 3. The client can use the graph to select and interrogate any of the active alarms. This report provides alarm condition summaries for the following categories:
USM detailed analysis
USM path status
USM summary analysis
USM meter head analysis
Pressure and temperature
Flow calculations
Series and parallel meter analysis
Testing and calibration events
The run verification report (Figure 4) includes all USM diagnostic tests, P&T verification, flow computer calculation verification, series and parallel meter analysis and gas chromatograph verification. Specific values for each of the diagnostic tests, as well as a detailed, concise summary of how close the actual diagnostic test values are to their expected values are provided. The actual individual per-path SOS differences, as well as the expected “Exp” values are graphed. The bar graph for each variable indicates whether the variable is above or below the Exp (expected) value. Once a test parameter exceeds the LL (low limit) or HL (high limit) limit, the bar will turn red indicating a potential problem.
The combination of the alarm report and the run verification report provides a comprehensive overview of all aspects of the measurement facilities’ operation.
Conclusions
Technological advances continue to increase the amount of automation used in measurement applications. Entire facilities can now be monitored remotely and problems identified and communicated quickly via text or email. Issues such as liquid contamination from hydrates, blocked flow conditioners and contamination buildup within the metering facility, can all be identified via remote monitoring. By incorporating the CEESmaRT system, clients reduce the measurement uncertainty of the USM facility station, reduce the need for monthly site visits to verify the accuracy of pressure and temperature transmitters and gain the ability to quickly identify any problems with the gas chromatograph.
Upon further review, even calling this system a condition-based monitoring system doesn’t do it justice. This technology actually provides a potential paradigm shift in how we view measurement uncertainty. CEESmaRT not only reports when a “condition” exists, but also verifies the operation of all ancillary equipment including the flow computer, P&T transmitters and GC.
We feel new terms and phrases could be warranted to discuss the new measurement landscape as “CBM” and “reduction of measurement uncertainty” were terms describing prior methodologies attempting to improve data quality and information. With the ability of CEESmaRT to monitor, verify and communicate critical data regarding the operation of the measurement facility on an around-the-clock basis, the new terms “complete measurement verification system (CMVS)” and the phrase “increase your measurement certainty” are better descriptors of what the CEESmaRT technology provides.
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