DIVIN MADAKKARA Engineer Loss Control, KOC B. Tech in Instrumentation and Control. 8 years experience in process automation and custody metering. Working in Export Tech Service Team, KOC Worked as Metering Engineer in Daniel. Worked as DCS Engineer with Emerson. Worked in projects like RLOC in Qatar, MOIP and NOP in KNPC, Crude Metering System at NPP in KOC and Bunker Metering System at KNPC.
Custody Measurement Control System
Introduction Custody transfer using dynamic measurement of fluid with flow meters offer accuracy of 0.25% or better. Devices and instrumentation installed play an important role in the measurement performance. Its the overall system that brings all the equipment together to ensure the required accuracy, sustainability, and reliability of the custody transfer measurement.
What is a Custody Metering System? Metering system is an engineered solution to a measurement problem, with unique requirements. Different fluid properties, flow rates, measurement requirements, physical locations. Custody metering is not just about having a flow meter, components of a custody metering system include multiple meter runs, Quality systems, proving and calibration facilities and metering control system.
What makes it Special? Metering system could be rendered inaccurate by a failed component, internal damage caused by foreign material in the flowing stream, build-up of solids, calibration drift over time, or a number of other factors. Periodic maintenance on custody metering systems is critical to maximize overall accuracy and uptime. The frequency of scheduled maintenance on custody metering systems is often mandated in custody transfer contract agreements.
Even though there is established routine maintenance practices, still there are many who do not follow or follow less-than-optimal practices. A number of factors will affect the best possible maintenance practices for a custody metering system including: contract requirements, OEM recommendations, practical experience, and amount of financial risk to which improperly maintained measurement equipment might expose the operator. Custody Metering is special and requires special attention.
Metering Control System Components Flow Computers PLC Supervisory Computers
Metering control systems Legacy Single Stream Flow computers. Separate Prover Flow computers. Supervisory computers.
Flow Computers - Primary Function Actual Cash register of custody transfer system. Industry standard flow calculations. Retains the true fiscal totals. Directly connected to measurement devices. Generation of fiscal reports. Alarms and event handling.
Flow Computers - Current Multi Stream Capability. Fast Processors with 32 Bit Math Co processor. Configurable or Programmable. HART Connectivity. WEB-Enabled interfaces.
Supervisory Computers The Metering Supervisory Computer is normally customized to each Fiscal Metering Station. The Concepts, the Hardware, software and the Functions differ from System to System.
Supervisory Computers
Supervisory Computers Challenges PC hardware and associated software drivers are frequently revised / updated. New operating systems are regularly released. Software patches are regularly released. Customized programming.
Redundancy Stand Alone Dual Redundant Hot Standby
Typical System Configuration RS232 or Ethernet Flow Meter Inputs Turbines Temperature Pressure Supervisory Ethernet HUB DCS / SCADA Communications Ethernet Ethernet HMI Flow Computers Digital I/O PLC Alarms Reports
RS232 or Ethernet Flow Meter Inputs Turbines Temperature Pressure Supervisory Ethernet HUB DCS / SCADA Communications Ethernet Ethernet HMI Flow Computers Digital I/O Alarms Reports PLC
DanPac Measurement and Control System
DCS Embedded Metering Control System ERP SYSTEMS Distributed Control System (DCS) Field Instruments
Benefits of New technology Advanced network integration, scalability and ability to embed various standalone applications, helps in real time interpretation of data for performance monitoring, quantitative and qualitative analysis. Enhanced real time diagnostic features, using benefits of smart instrumentation & various validation techniques. Use of controller based distributed architecture with standard hardware and software enhances the stability, redundancy features and makes it easier for upgrades and maintain.
What We as an End User Looks For? 1. Not just another HMI in the control room. Typically MSC systems are like any other control system, keeping focus on normal operation, process data and access to historical reports. A system which can be used to monitor and control the quality of measurement. A system which can seamlessly embed the various standalone applications related to flow metering, supporting our maintenance, audit and management.
2. Ability to integrate the smart metering devices. Use of smart devices in metering, provide lots of information on their own health, ability to communicate with other device and more. MSC normally acquire process data required for operation, generate alarm if something is wrong with measurement, requiring specialist to travel to site and troubleshoot issue. A system which can provide remote access to wealth of diagnostic information provided by the smart devices, with ability to use this information in real time.
3. Ability to store Measurement Data. Measurement data is about both quantity and quality. FCs store these data for a particular period, then flush these information and lost for ever. A System which can archive all crucial measurement data, including the periodic quantity reports or batch reports, calibration and validation reports, changes in configuration settings and any events related to metering system. A System which can encrypt these measurement data.
4. Ability to detect the measurement deviations. A System which can continuously monitor the health of metering equipment and validate measurement data in real-time, e.g. by cross-checking redundant and parallel measurements and applying statistical control. A System which can apply self-diagnostics on both device and system and can warn the user in real-time for measurement issues.
5. Ability to provide auto correction for error. Quantifying the measurement error and correcting the meter ticket is a time consuming and a specialist job. A system which can automatically replicate the flow computer calculations, using the concepts of virtual flow computer with high resolution metering data and sophisticated correction method and can quantify the loss or gain caused due to the error in measurement.
6. Measurement Management Track the measurement management process and build a traceable measurement system. A System which can track the periodic validations for the instruments as per the standards or company policies, reports the abnormalities to the responsible persons in the hierarchy in case of deviations beyond the tolerance limits. A System which can help our Ship Shore difference investigations, with consolidated reports for all the events happened during a particular vessel loading and associated validation reports.
7. Customized with Standardized Metering Package. Standardized metering packages with customized solution for our operational and fiscal requirements. A System which uses standard programming languages and avoid using custom scripting at the supervisory level. A System with inbuilt redundancy features. A System which can effectively control batch operations. Preference to integrated supervisory and flow metering technology.
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