Pipeline Operations and Integrity Management Colegi Colegio o de Ingene Ingeneiro iros s del Peru Peru - Capitulo de Ing Ingenieria Quimica - May 29th - 30th 2017 Dr Alan Murray P Eng FASME Calgary ,AB Canada
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Suggestions for a Successful Learning Experience •
Relax!
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Make notes
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Actively participate and share your thoughts/experiences thoughts/experiences
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Be respectful of others
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There are no stupid questions , so ask at any time. Write them down if you are really shy!
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Whatever else works for you.
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Alan Murray 2017
Introduction and Course Objectives •
Provide an introduction to the current best practices in operating and maintaining a modern Pipeline network.
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Provide background to some of the key issues in developing an approach to managing pipeline integrity
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Provide a good source of reference material for future use
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Outline
Where are we? we?
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Module 1 Pipeline Operations •
In this module m odule we have an overview of:
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The nominations process for gas and liquid Pipeline systems.
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Scheduling and batching multiproducts
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Metering and custody transfer
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Supervisory control and data acquisition (SCADA)
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Transportation Service Service The pipeline is the link between the product supplies and the market market including end customers. • Pipeline companies provide transportation service for shippers including suppliers s uppliers and customers. • Transportation service involves the receipt of the products, the transportation transportation through its pipeline network, network, and the the delivery delivery of the products products to the customers. s ervices are available: firm and • Two types of services interruptible. interruptible. A firm service is a guaranteed transportation service, while an interruptible service is not guaranteed if there is a capacity constraint. •
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Transportation Service Service Process Process The pipeline company and shippers negotiate the contract and tariff. • The shippers enter and modify monthly nomination, and the schedulers develop a monthly schedule using the inventory and facility constraints constraints together with wi th nomination data, out of which a daily schedule is created. de livery • The dispatcher controls the batch lifting and delivery according to the daily schedule, generating tickets. • The revenue accounting and invoice for each shipper is generated from the volume accounting and tariff. •
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Tariff Common carriers publish tariffs which are dictated by the government government regulator. regulator. • Tariffs cover the transportation rates and rules including nominations and minimum batch size requirements. requires that all shippers submit to the • The tariff requires pipeline company their intended shipping volumes and other information on a certain date before before the cycle lifting date. •
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Business Process Nomination Management
Revenue accounting
Transportation requests
Shipper
Invoicing
Nomination validation
Contract management
Inventory analysis
Nomination confirmation
Nomination Monitoring
Volume allocations
- Batch scheduling - Operation Operation planning
Volume accounting
SCADA: SCADA: Operation & Me Measurements asurements
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Transportation Request •
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The transportation starts with a request for product movement, usually in the form of nomination, by shippers to the pipeline company for a quantity of product for a specified period of time. On gas pipelines nomi nominations nations are made several times daily. For liquid pipelines a nomination can be effective effective for the current or future shipping period. The period can be based on either a month or a batch cycle. Nominations are accepted or changed at receipt and delivery points. The result of the nomination process is a confirmed nomination. Shippers are allowed to change their nominations until a specified date and time without incurring additional charges. CPTI DOPCO 2017
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Scheduling •
After the final changes are made, the pipeline company develops a transportation transportation schedule s chedule to accommodate the shippers’ nominated volumes. • Scheduling is an internal process that validates nominations for contractual levels, determines pipeline capacity, capacity, puts products or batches in a pumping sequence, etc. with pipeline facility and hydraulic hydraulic constraints taken into account. • When nominations exceed available capacity, the volume is prorated prorated to meet the capacity according to the preassigned prorating rules defined in the agreements between shippers and the pipeline company. CPTI DOPCO 2017
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Confirmation •
The nominations are accepted or changed through a confirmation process.
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Receipt quantities and market deliveries are scheduled and confirmed.
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Pipeline control is operationally set up for physical physical flow after confirmation.
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Products are measured and necessary necessar y data are transmitted to the pipeline control system such as SCADA.
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Allocation •
Allocation is the process by which physical volumes that actually flowed at a point are allocated to confirmed nominations.
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Allocated Allocated volumes volumes are used used for cashout, cashout, balancing balancing and billing purposes.
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Prorata Prorata allocation allocation - measured measured volume is allocated allocated to to all confirmed nominations on a prorated prorated basis.
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Natural gas gas is homogenous so mixing of product from different sources is allowed Gas can enter and leave the pipe line at any point. Figure I-1
Producing Wells
Natural Gas Pipeline Pipeline System Transmission Line
Gathering Lines Processing Plant
Compressor Stations LNG Plant
City Gate
Underground Storage
Large Volume Customer
Meter
DISTRIBUTION SYSTEM
Regulator
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Different Liquids have to be shipped in Batches Batch interface Buffer
Gasoline Gasoline
Kerosene
Diesel
LPG
Gasoline
Batch cycle
Batch Cycle & Interface Interface CPTI DOPCO 2017
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Interfacial Mixing •
Interfacial Interfacial mixing takes takes place at the interface interface boundaries between two adjacent batches.
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The commingled product that does not meet the shipper’ shipper ’s product specifications is called slop. This off spec product is accumulated in a slop tank and then sent to a refinery for reprocessing or blended with other tolerable product.
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The interface mixture may be cut into one or the other product, or divided between the two adjacent products at the mid-gravity mid-gravity point. CPTI DOPCO 2017
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Mixing Size Mixing size depends on product properties such as gravity and viscosity, fluid velocity, pipe diameter, and travelling distance. minimize interfacial mixing mixi ng length, batches are sized si zed • To minimize large and lifted in a pre-determined batching sequence. For this reason, the tariff specifies the minimum batch size. Normally, the sequencing of batches is such that • Normally, products closely related are adjacent in descending or ascending order of quality or gravity to minimize batch interfaces. • A buffer may be used to separate two expensive products. CPTI DOPCO 2017 17 •
Mixing Profile 99%A-1%B mixing
90%A-10%B mixing
50%A-50%B mixing
Product A
10%A-90%B mixing
1%A-99%B mixing
Product B
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Batch Tracking Display MAOP
Elevation Pressure
LAOP
Batches
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Density
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Measurement Accurate Accurate Measurement is critical to the safe safe and efficient operation of a pipeline •Measurement issues • Measurement errors • Types of flow meter •
Pressure and temperature measurement
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Meter Stations
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Measurement Issues •
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Why measure? – A change in ownership or responsibility for the transported fluid – Monitor or control facilities (Safety considerations) considerations) – Fluids are transported across national boundaries (Trade (Trade figures) What to measure? – Flow rate or volume – Pressure – Temperature – Density or composition – Quality How to measure? – Various instrumentation using many different techniques
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Measurement Errors •
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Errors Errors are inherent in all measurements. The total error includes errors errors from a primary primary device, auxiliary devices devices and electronics. The errors are combined by statistical methods. Accuracy is specified over an applicable range of values. Errors Errors are random or biased, and change with time and environmental factors such as humidity and temperature Errors are expressed in terms of accuracy, systematic error, bias, repeatability, resolution, and precision. ANSI ASME and ISO definitions include only accuracy, accuracy, bias error and precision. Accuracy is the combination of bias and precision errors.
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Accuracy and Repeatability •
Accuracy is defined as the closeness of agreement between the result of a measurement measurement and the true value of the measurand. It is the combination of bias and precision errors.
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The measurement of a variable requires a primary device and auxiliary devices. To determine measurement accuracy of the variable, the accuracy of the primary device must be combined with the individual accuracies of additional measuring devices and then properly weighed in the accuracy a ccuracy calculation.
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Accuracy is specified over an applicable range of values. The errors errors are combined by statistical methods.
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Repeatability Repeatability is essential to ensure quality and credibility of data
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Bias and Precision A bias error is the difference between the average and true values. A bias error is directional and must be added or subtracted from the instrument reading. Bias error, error, if known, can be eliminated by correction. • A precision error is random about the bias. Precision can be improved only by selecting another measuring device. • Three cases regarding regarding accuracy: – Bias error is not negligible, but precision is good. – Bias error is negligible, but precision is poor. – Bias error is small and precision is good; this is an accurate device. •
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Bias , Precision and Repeatability
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Total Error •
Primary device errors
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Secondary device errors errors
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Electronic errors:
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Current/voltage conversion error
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Amplification error
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A/D conversion error
Influence quantity errors (departures from reference conditions such as homogeneity and single phase flow)
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Calibration •
Calibration is a process to ensure that the measuring instrument is accurate and in good operating condition.
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The frequency of the calibrations depends on the application and accuracy requirements.
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The frequency of calibrations is a contractual obligation if the measurement involves a custody transfer transfer (change of ownership of the fluid)
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Shippers on the pipeline system system pay in proportion to volumes shipped hence the need for accuracy.
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Measurement Devices A flowmeter is a device that measures the rate of flow or quantity of a moving fluid in an open or closed conduit. It usually consists of a primary and a secondary device. • A primary device is the device mounted internally or externally to the fluid conduit which produces a signal with a defined relationship to the fluid flow in accordance with known physical laws relating the interaction interaction of the fluid to the presence of the primary device. • A secondary device is the device that responds to the signal from the primary device and converts converts it to a display or to an output signal that can be translated relative to flow rate or quantity. • Meter influence quantities should be properly defined to achieve accuracy conditions. They include fluid properties, installation method, interference, and pulsation and vibration. •
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Influence Quantities •
The measurement of flow rate requires additional instruments to measure temperature, pressure and/or differential pressure, density, chromatograph, etc.
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The sensitivity of a flow meter depends on each of these measurements.
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Accuracy for flowmeters flowmeters are based on the steady flow of a homogeneous, single-phase newtonian fluid. Departures from these reference conditions are called influence quantities, which include velocity profile deviation, non-homogeneous flow, flow, pulsating flow, non-newtonian flow, and cavitations.
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Flow/Volume Measurement •
The primary flow measuring devices are classified either as differ differential ential producing flow meters meters or linear flow meters. meters. • For differential producing flow meters, flow rate is expressed as a square-root relationship among measured differential differential pressure, density and flow rate. Orifice and venturi meters are popular. • All linear flow meters are based on the principle that the speed of a measured variable increases linearly with flow velocity. Turbine, positive displacement and ultrasonic flow meters are widely used, and the applicable flow range is wide (10:1 ratio). 30
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Differential Flow Meter
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Differential Differential flow meters are based on the Bernoulli equation, in which the flow rate is proportional to square root of pressure differential.
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The applicable flow measurement range or turndown t urndown ratio is narrow: 3:1.
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Frequently used differential differential flow meters include: –
Orifice flow meter
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Venturi Tube flow meter
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Annubar flow meter
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Nozzle flow meter
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Orifice Plate
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Linear Flow Meters Turbine meter • Positive displacement meter mete r • Vortex meter • Ultrasonic flow meter •
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Linear Flow Meter •
Linear flow meters are based on different different measurement principles. • The applicable flow measurement range is wide: Over 10:1 ratio. • Linear flow meters frequently used in the pipeline industry are: – – – – –
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Turbine meter Positive Displacement meter Ultrasonic flow meter Coriolis mass meter Vortex flow meter
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Turbine Meter •
The speed of a turbine flowmeter’s flowmeter’s rotor increases linearly with flow velocity. Blade rotation is a measure of velocity and detected by noncontacting external magnetic detector.
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AGA-7 Standard is adopted in North American gas industry and ISO 9951 for other parts of the world.
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A permanent magnet embedded in wheel generates pulses and a small coil mounted on the housing picks up pulses.
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Pressure drop is negligibly small, small, but floating debris and back flow can damage the rotor. rotor.
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Accuracy is in the order of o f 0.25% of flow range, and the applicable flow range is wide (10:1 ratio).
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Turbine Meter Magnetic detector Rotor support assembly
Flow
Magnet
Retaining Ring
Rotating axis Turbine Wheel
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Turbine Meter
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Turbine urbine Meter Meter (Cont (Cont’’d) •
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Advantages –
Large flow range (about 10:1)
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Accurate (0.5% error)
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Small pressure drop
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Ease of calibration and maintenance
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Proven Proven and widely accepted in pipeline industry
Disadvantage –
Highly susceptible to damage from solids or liquids in gas stream
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Susceptible to friction loads which can cause measurement error
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Require an upstream strainer
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Not economical for low flow ranges
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Turbine Meter Characteristics Characteristics • • • • •
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The relationship between line velocity and rotor speed is linear over a range of 10:1 to 20:1, depending on viscosity. viscosity. Liquid turbine meters can attain an accuracy of +/-0.25 +/ -0.25 percent and a precision of +/-0.05 percent. The meter coefficient is expressed expressed as a K factor in units of pulse per unit volume. Pressure drop is low, but it is applicable to low viscosity clean fluids. Floating debris can damage rotor, and extreme temperatures, temperatures, corrosion, abrasion, and pressure transients can shorten bearing life.
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Turbine Meter Run
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Positive Displacement (PD) Meter
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PD flow measurement consists of a class of devices which measure a specific amount of fluid for each cycle. Meters of this design divide the fluid stream into unit volumes and totalize these unit volumes by means of a counter.
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A rotary meter belongs to the PD meter class. The fluid flow against against the rotating impellers impellers results in a volume of fluid being alternately trapped and discharged in a complete revolution of these impellers.
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The volume displaced during the revolution is multiplied by the number of revolutions to give the accumulated volume volume passed by the meter.
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PD Meter Characteristics •
PD meters can attain an accuracy of +/-0.5 percent
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Flow range is 10:1 and pressure drop is low.
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PD meters are subject to mechanical wear due to large number of moving parts with mechanical contact.
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PD meters are suitable for highly viscous fluid such as heavy oil.
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Applicable standards standards are API MPMS 5.2 or ISO 2714.
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Rotary Meter Diagram
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Rotary Vane PD Meter Rotary Vane Meter
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Coriolis Flow Meter Meter
Fluid is being pumped through the mass flow meter tubes which are continuously vibrating at between 80 and1000Hz. When there is mass flow, each tube twists slightly and the angular motion is measured very accurately accurately..
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Ultrasonic Flow Meter
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The ultrasonic flow meter operates on the principle that the acoustic velocity in a fluid in motion is the result of the acoustic velocity in the fluid at rest plus or minus the acoustic velocity itself. itself.
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The transmitters send acoustic waves to the receivers in the opposite ends, and acoustic waves waves propagate upstream and downstream of the flow direction.
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The basic principle is applied by several several different techniques using a wave wave that interacts interacts with the flowing fluid. Time difference, difference, Doppler shift, or frequency difference is used to determine flow velocity.
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The latest ultrasonic meters meters use multiple acoustic beams that allow the meter to construct the flow velocity profile which is then used to determine more accurate flow rate.
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Velocity Profile
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Ultrasonic Flow Meter •
The flow range is greater than 10:1.
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The applicable standard in North America is AGA 9.
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tras traso on c Station
et eter
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Ultrasonic Meter Characteristics •
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Ultrasonic flow meters can attain an accuracy of +/-0.5% with flow range greater than 10:1 for intrusive type meters and 2% for clamp-on type. Pressure drop is negligible and maintenance cost is low because there is no moving part. In order to increase accuracy and repeatability, repeatability, multiple beams are used to determine velocity profile, over which an average flow is calculated. Multi-path ultrasonic meters are suitable for almost any a ny types of fluid, including high viscous fluids. Applicable standards standards are ASME MFC-5M or ISO 12765.
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Pressure Measurement •
Pressures are used for pipeline system control and flow rate calculation.
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Pressure measurements measurements are most widely available for most of pipeline systems.
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Piezoelectric Piezoelectric pressure transducers are popular for pipeline applications. - Pressure causes causes elastic deformation deformation of certain certain crystals, which is converted converted to proportional electric signal. - Accuracy is in the order of 1 % and rangeability is up to to 20,000 psi.
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Piezoelectric Pressure Transducer
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Temperature Measurement •
Temperatures are seldom used for liquid pipeline system control, but used for flow calculation.
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Therefore, temperature measurements are not widely available for most of pipeline systems.
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Resistance Resistance temperature temperature detectors detectors (RTD) are popular for pipeline applications. - The electrical resistance resistance of metals varies directly directly with temperature temperature and is reproducible to a high degree of accuracy. - Good accuracy (0.5 % of range) over wide spans up to 870 oC
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RTD Device
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Meter Station with Prover
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Volume Accounting •
A volume accounting system should cover the following major functions: –
Collect measurement data from the host SCADA
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Store the collected data in a historical database database
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Manage gas quality data
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Correct volume to a base condition
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Totalize flows
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Validate measurement data with audit trails
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Provide failure recovery capability
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Measurement Measurement Collection •
Collect measurement data automatically by providing the capability to upload to and download from the host h ost SCADA.
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Collect data on hourly and daily basis.
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Establish a procedure for data collection in the event of communication outage.
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Provide the capability to download manual data to RTU, FC or PLC.
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Provide the capability to manually enter missing data, override the measurement, measurement, and enter gas quality data.
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Provide the capability to edit measured data and parameters parameters and record history of manual data entry for audit trails.
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Measurement Data Storage •
Store meter data including time stamp, corrected volumes and energy, meters meters and operating time, gas quality and status.
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Provide a historical database to store all the measurement related data. The stored data and storage storage period depend on the regulatory requirements.
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Record all measurement measurement related changes including configuration and gas quality.
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Record all download and upload history of gas compositions.
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Provide data modification, alarms and event event history for audit aud it trails.
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Control Centre • Operation is remotely controlled 24/7 through the use of a
supervisory control and data acquisition system Pipeline Control Room Management addresses pipeline control room related issues.
• API RP 1168 –
Control Centre Security • API Standard 1164 – Pipeline SCADA Security provides guidance on SCADA security to the operators of pipeline systems. • The control center is so critical that its security has to be fully protected. • Control consoles are manned 24 hours a day, so no separate protection is required. • The access of unauthorized personnel has to be limited to protect the integrity of the system and to maintain the confidentiality of the data.
Backup Control Centre • A backup control center can be set up to recover the SCADA system system and fully function even if a disaster occurs to the primary control center. Still, the primary control center is primarily responsible for monitoring and controlling the pipeline system. • Usually, Usually, the backup control center is equipped with the same SCADA system system as the primary primar y control center . • One option is that the backup system system receives the real time data directly from the field devices each cycle, so that it is the exact replica replica of the primary system. system. • The other option is that the entire backup system system is refreshed with the required data received from the primary system in a regular interval. 61
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Disaster Recovery PRIMARY CONTROL CENTRE
T1 Leased Line
Frame Relay Service
ROUTER
TERMINAL SERVER
BACK-UP CONTROL CENTRE
Control Requirements • Control is required in normal conditions: – Liquid/Gas – Liquid/Gas receipt and delivery changes – Pump/Compressor – Pump/Compressor startup and shutdown – Flow – Flow and pressure set point changes – Valve – Valve open/close operation – Batch – Batch changes – Tank – Tank or storage changes – Coordination – Coordination with shippers including other pipelines • Control problems occur due to abnormal conditions: – Pump/Compressor – Pump/Compressor trips – Emergenci – Emergencies es such as line rupture – Loss – Loss of supply and delivery changes – Violation – Violation of limits such as MAOP
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SCADA Overview •
SCADA is an abbreviation of Supervisory Control and Data Acquisition. • A SCADA system is a computer-based control and data acquisition system system designed to gather and transmit operating data from geographically remote field locations via communication links to a control center (s). Operators at the control center monitor the data and can issue • Operators control commands to the field devices in the remote locations in response to the incoming data. • A basic SCADA system system consists of instrumentation, instrumentation, remote terminal units (RTU) or programmable logic controller controller (PLC), communication system, and host SCADA computer system with operator interface.
SCADA A SCADA system has a master – master – slave slave relationship between the control center and field site.
Hardware / Physical Physical
Supervisory Control Master (Host)
Remote Terminals
and Data Acquisition Software/Protocol
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SCADA Functions Data telemetry: gather and transmit analog values such as flow or volume, gas composition, pressure and temperature, temperature, and digital values such as on-off and open-close status • System control: control flow or pressure, start or stop pump/ compressor, change set points, and open or close valves generate alarms and event • Alarm annunciation: generate messages, monitor controlling actions, help solve problem situations situations before they occur, occur, and dispatch personnel to deal with specific problems •
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SCADA Network Main Dispatching and Control Centre
Backup / Regional Regional Dispatchin g and Control Centre
User Terminals
User Terminals
OPC
SCADA Master Servers
Pipeline Application Servers
Pipeline Application Servers
Pipeline LAN/WAN network infrastructure
SCADA Master Servers
Corporate LAN (1 of X)
(X of X)
Pump/Compressor Station Master/ RTU
Pump/Compressor Station Master/ RTU
OPC
Firewall
Modem
OPC
Modem RTU Fire & Gas
Fire & Gas Station PLC RTU
at Valve Stns
Modbus or OPC
Station ESD
RTU
at Valve Stns Station PLC Station ESD
at Valve Stns
(Courtesy of ABB)
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Questions? Time for a Break!
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