Snam
GAS MEASUREMENT
"GAS MEASUREMENT" PROCEDURE
INTRODUCTION AND DEFINITIONS
This document defines the procedures and the criteria adopted by Snam Rete Gas in order to determine the measured gas quantities at the REMI plants utilising volumetric and/or Venturi meter types.
The correct application of the procedures included in this document is a necessary but not sufficient condition for a precise determination of gas quantities.
In order to achieve this objective, it is essential that the owner of the measurement plant carries out all the actions necessary for guaranteeing correct operation of the plant.
For this reason, the owner of the measuring plant, or an appropriate qualified operator nominated by him, must perform periodic inspections and calibration interventions on the equipment following the relevant criteria for ensuring correct measurement (as specified in Attachment 4 of the “Sizing of REMI plants” Procedure)
These interventions should be performed at least once a year.
For the purposes of this document, the following definitions apply:
Owner/manager = owner/manager of the REMI plant;
Shipper = a gas system user who, via confirmation of the assigned capacity, acquires booked capacity for its own use or for trading;
Centre = Snam Rete Gas maintenance centre;
REMI = regulation and measuring plant (including the measuring plant which is considered in this document);
S.I. = the Transporter's IT system, i.e. the REMIGAS system;
1. AOP = (Homogeneous Area) this is the portion of a national pipeline for which the average monthly PCS value of the natural gas redelivered is the same for all redelivery points and, compared to the average monthly PCS values of the natural gas of the adjacent AOPs, differs by no more than ± 2%;
Measurement Report = a document produced on a monthly basis by Snam Rete Gas, documenting the validated measurement data for a REMI plant;
other parameters are defined within the text.
Formulae and criteria used for the calculation of REMI plant capacities and volumes
1 Introduction
The determination of gas quantities and the processing of information relating to the regulation and measurement plants takes place via a combination of automated procedures (S.I.)
The S.I. provides measurement data for the following types of measurement plants:
➢ automatic and telemetered
These plants have equipment which directly, or in the case of electronic volume correctors via processing by the S.I., provides the flow and/or volume data.
The collation and transmission to the S.I. of measurement data for such plants is totally automated, using telecommunication networks.
➢ automatic
These plants are similar to the ones described in the previous point where the processed data is gathered and manually entered into the S.I. or via a lap-top computer.
➢ traditional
These plants have equipment providing primary data which must be entered manually into the S.I. and processed data needed to derive flow and/or volumes.
A measurement plant can comprise one or more measurement lines characterised by a specific “Structure”.
2 Objective
The objective of this procedure is the combination of operations which, as a result of the measurement data produced in the REMI plant, lead to the drafting of the Measurement Report.
The quantities contained in the Measurement Report refer to the month that begins at 06.00 on the first day of the month to 6.00 on the first day of the following month with daily indications (always 6.00 to 6.00) where the equipment allows. The reference hour used is always the solar hour (GMT).
3 Scope
The scope of this procedure is to illustrate the methods of data processing used to obtain measurement capacities and volumes.
The criteria for the gas data analysis used by the S.I for the traditional plants, and programmed in the processor software for the automatic plants are highlighted.
4 Volumetric measurement
1 Basic formula
In order to determine the volume in m3 (at 15 (C and 1.01325 bar), measured by the meter over the relevant period, the following formula is used:
(1) [pic]
where:
[pic] = Volume in m3 (at 15 (C and 1.01325 bar).
[pic] = Final meter reading.
[pic] = Initial meter reading.
[pic] = Total coefficient for volumetric measurement (see paragraph 1.4.2.).
2 KTvo calculation
The [pic] is given by the following formula:
[pic]
where:
[pic] = Absolute operating pressure (bar), for the relevant period:
[pic]
[pic] = Relative operating pressure (bar).
[pic] = Local barometric pressure (bar) calculated using the following formula:
[pic]
where:
[pic] = Barometric pressure.
[pic] = Barometric pressure at sea level (1.01325 bar).
[pic] = Average air temperature in °C, fixed for gas measurement purposes at the average value of 15°C.
[pic] = Altitude of the location (in metres) above sea level (for practical purposes the altitude may, in some cases, be defined to the nearest (100 m).
[pic] = Operating temperature, for the relevant period, expressed in K:
[pic]
[pic] = Operating temperature in °C
[pic] = Absolute reference pressure = 1.01325 bar.
[pic] = Reference temperature = 288.15 K.
[pic] = Coefficient of deviation from ideal gas law at operating conditions (see paragraph 1.6.1), relative to both the type of gas (see paragraph 1.7) and [pic] to [pic].
[pic] = Coefficient of deviation from the ideal gas law at reference conditions (15 (C and 1.01325 bar) (see paragraph 1.6.2), dependent on gas type (see paragraph 1.7).
3 Volume calculation
The method of volume calculation is as follows, dependent on the type of measurement plant:
➢ Automatic plants
The calculation of volumes is carried out by the processor using the formula (1), on the basis of pulse data taken from the meter and from the pressure and temperature transmitters. This data is processed and then either manually inserted in the S.I. or gathered and automatically sent via the telemetry system.
➢ Traditional plants
The calculation of volumes is carried out by the S.I. using the formula (1), on the basis of monthly volume meter readings or daily/meter units provided by the printer and the pressure and temperature values determined in accordance with paragraph 4.2.
N.B.:
For measurement plants without a printer and without telemetry, and where measurements are only available on the basis of aggregated readings, a reading is needed obtained from linear interpolation between the last reading and the previous one used to determine the volumes recorded in the previous month. The objective is to determine the volume withdrawn in the reference time period (from 6.00 on the first day of the month to 6.00 on the first day of the following month).
5 Venturi meter measurement
1 Basic formula
In order to determine the flow in m3/h (at 15 °C and 1.01325 bar), measured by a Venturi meter containing a diaphragm, the following formula is used:
(2) [pic]
where:
[pic] = Coefficient that combines the conversion constants of the measurement units and the coefficients of compressibility and emission (calculated using the rules described in paragraph 1.5.2).
[pic] = Diameter of the aperture in mm.
[pic] = Differential pressure in mbar.
[pic] = Total coefficient for the Venturi meter measurement:
[pic]
[pic] = (see paragraph 1.4.2).
[pic] = Volume mass at reference conditions (15 (C and 1.01325 bar) in kg/m3, dependent on gas type (see paragraph 1.7).
2 Reference standards
The calculation of the quantities is carried out according to one of the following standards:
➢ UNI EN ISO 5167 – 1 plus amendment A1
➢ UNI EN ISO 5167 – 1
➢ CNR UNI 10023
3 Volume calculation
The method of volume calculation is as follows, dependent on the type of measurement plant:
➢ Automatic plants
The calculation of volumes is carried out by the processor using the formula (2) on the basis of the magnitude of the following data collected in the field and provided by the transmitters:
[pic] = Operating pressure
[pic] = Operating temperature
[pic] = Differential pressure
and, where present
[pic] = Volume mass at reference conditions.
This data is processed and then either manually inserted in the S.I. or gathered and automatically sent via the telemetry system.
➢ Traditional plants
The calculation of volumes is carried out by the S.I. using the formula (2) on the basis of data measured by the recorder, aggregator or Venturi meter printer, as specified in paragraph 4.2.
For measurement plants with an aggregator, the information is as described in paragraph 1.4.3 above.
6 Calculation of the coefficient of deviation from the ideal gas law (Z)
1 Operating conditions
In volumetric and Venturi meter measurements, the calculation of [pic] is derived using the standard ISO 12213-3 or the most current version of the American method AGA NX 19 Mod. depending on the settings of the processor.
2 Reference conditions (15°C and 1.01325 bar)
In volumetric and Venturi meter measurements, the calculation of [pic], is derived using the ISO 6976 standard.
7 Gas quality parameters used in measurement
In order to derive gas volumes and capacities the following quality data is used:
➢ the composition for the calculation of [pic] (see paragraph 1.6.2) and of [pic];
➢ depending on the standard used for the calculation of [pic] (see paragraph 1.6.1), 3 or 4 quality parameters will be required from the following list:
[pic] : volume reference mass or [pic] density relative to the air ([pic])
[pic] : molar percentage of carbon dioxide
[pic] : molar percentage of nitrogen
[pic] : molar percentage of hydrogen
[pic] : gross calorific value
➢ [pic] for the volume calculation in the case of Venturi meter measurement.
These parameters are determined on the basis of gas samples analysed for each AOP (Homogeneous Area) with which the REMI is associated.
For reasons of availability, data relating to a gas sample for a particular month is used in the calculation of the quantities for the month after next.
The application of the parameter [pic] does not follow the aforementioned criteria in the case where the measurement plant has a mass volume transmitter at reference conditions connected to the processor.
For automatic volumetric measurement with a measurement pressure of ( 5 bar, the quality parameters are those calculated on the average values for the solar year preceding that of the application.
Where the measurement plant is equipped with a gas chromatograph connected to the processor, provided it is allowed under the existing legal metering regulations, the quality parameters can be updated in a continuous manner.
In this case, the gas chromatograph must operate in accordance with the procedures and requirements specified in Attachment 11/B.
8 Quality data planning for automatic measurement plants
1 Volumetric measurement
The quality data stored in the processor is used to determine the compressibility factor at operating conditions [pic] and therefore the total coefficient for the volumetric measurement [pic].
The update frequency of the data is determined in accordance with the measurement pressure:
➢ for plants with [pic] ( 5 bar, values are entered into the processor at the beginning of each year, as soon as average values for the preceding solar year are available;
➢ for plants with [pic] > 5 bar, values are entered into the processor each month and refer to the most recent monthly average value available.
The programming of some simplified electronic volume correctors does not require the insertion of the individual quality data, but of the value [pic]. This is calculated and entered each year, and every time the average measurement pressure changes. The calculation is carried out as described in paragraph 1.4.2 using:
[pic] : average pressure measurement value;
[pic] : reference temperature
[pic], [pic] : calculated on the basis of the average gas quality for the preceding solar year.
2 Venturi meter measurement
The gas quality data of the programmed gas in the processors is used to determine the compressibility factor at operating conditions [pic] and therefore to determine the total co-efficient for the Venturi meter measurement [pic]. In particular [pic] (or [pic]) is used to calculate the quantities in volume.
The updating of the programmed analysis data is carried out in the event that this deviates significantly from that actually observed, in any event, at least once every two years.
The S.I. will recalculate the quantities provided by the processor using the daily analysis data of the composition referring to the same month.
At the request of the measurement plant owner who will bear any additional costs, an alternative approach can be adopted as described below.
The frequency with which updating is carried out is monthly and refers to the last monthly average analysis available.
The multivariable transmitter is programmed with the same frequency (where it is used as the reserve and control instrument) by entering the following quality data:
➢ [pic]
➢ [pic]
➢ [pic]
In measurement plants with equipment that directly provides the value [pic] (Densimeters), it is necessary to programme the remaining analysis values into the processor with the same criteria and frequency described above, to allow for the compressibility factor [pic]to be processed.
Security of telemetered data
The Transporter will operate a telemetry system on the basis of the equipment available.
For the reasons given above, with the exception of future technological developments, the Transporter is not responsible for the operation of telemetry systems installed by third parties at the measurement plant.
The Shipper must inform its Customers that, should they wish to restrict access to their measurement data to themselves only, and if they have communicated the relevant telephone number (or password) to parties other than the Transporter, they must change the telephone number (or password).
The details of any such change should be provided to the Transporter and any other relevant parties by whom they may be telemetered.
The Shipper must inform its Customers that, if they wish to have highly secure telemetered data, they should install appropriate equipment, including a password management system.
The Transporter declares that its programme for telemetry upgrading allows it to interact with the aforementioned equipment described and make the telemetered data, nominated by the Owner/manager, available to Shippers who insist on the use of telemetered systems as well as any other third party nominated by them.
Determination of quantities in case of anomalies
If any anomalies, malfunctions or breakdowns should occur, Snam Rete Gas will draft an intervention report documenting the nature of the anomaly and the procedure for its resolution.
This report is to be countersigned by Snam Rete Gas and the Owner/manager (or his nominee).
Revised measurement quantities following the new report, will only be obtained and used when the causes and the start date of the anomaly have been objectively verified.
The maximum period for which such retroactive revisions may apply is determined by the availability of the relevant fiscal documentation as specified in paragraph 5.2.
The Measurement Reports, detailing the revised quantities, will be sent both to the Owner/manager and the relevant Shippers depending on the relevant period.
1 Criteria
Whenever a measurement equipment failure or calibration error occurs on one or more instruments that make up the measurement chain, the processing of the gas quantities can be guaranteed by primary data provided by the reserve equipment where present, provided that this is calibrated and functioning correctly.
In the event that there is no reserve equipment present, the off-take volumes can be taken using the procedure below:
a) if, during the month of verification of the anomaly there are valid measurements representative of the true off-takes, a daily average is calculated and applied to the invalid or missing daily measurements;
b) otherwise, a coefficient is calculated which is representative of the increase/decrease of the off-takes, which is then multiplied to determine the monthly volumes for the missing measurement, multiplying by the corresponding monthly volumes for the preceding year; this coefficient is the ratio between the average daily m3/d of the 90 days prior to the anomaly and the average daily m3/d of the corresponding day of the previous year: in the calculation of the average daily m3/d zero off-take days are excluded;
c) if the Owner/manager is able to provide production data relating to the flow of gas and when it has been verified that the ratio derived between this data and the relative quantity measured is constant, it is possible to apply this ratio to the production data (daily if possible) for the measurements of the missing periods.
If the period of missing measurements is greater than one month, the quantities which will be forfeited and recorded will have an ever greater degree of uncertainty.
For other unexpected scenarios or significant variations from those dealt with or where particular anomalies recur, Snam Rete Gas will determine the most appropriate solution on a case by case basis, agreed, whenever possible, with the Owner/manager.
2 Substitution of data
In automated plants where there exists a partial lack of telemetered data during the month, the S.I. will calculate estimates for the missing or not measured quantities following criteria provided for in paragraph 3.1 and will then proceed with the next validation of the respective Measurement Reports.
Following these Reports, new processed and validated data will be used for the relevant period:
➢ data taken directly from the processor or printer, if this data has not arrived automatically due to problems with the telemetry system;
➢ data provided by the reserve equipment after verification of its functioning and calibration, in the case where the automatic measurement equipment has broken down or cannot be utilised;
➢ according to the criteria described in point c) of paragraph 3.1, only in the event that neither of the above options is viable.
3 Off-takes falling within the valid measurement range
In order to ensure the correct operation of the measurement equipment within valid ranges and as anticipated in the Introduction of this procedure, the Owner/manager performs:
➢ regular equipment inspection and calibration;
➢ continuous monitoring of off-takes in order to ensure optimal functioning of the measurement equipment, via timely and appropriate actions such as changes of measurement discs, modifications to the regulated pressure and meter inversion.
4 Off-takes falling outside the valid measurement range
Where off-takes fall outside valid measurement ranges, Snam Rete Gas will provide the observed source data to the Owner/manager, identifying as appropriate the following:
➢ for the volumetric measurement, the greatest measurement error from a constant off-take below the operational minimum, or near or above the maximum nominal capacity of the meter which, in this last case, could cause it to break;
➢ for the Venturi meter measurement, the greatest error resulting from the use of low percentage off-takes and the greatest uncertainty in the area to be measured in case of traditional measurement plants. If off-take levels approach the full scale, notify the possible application of the procedure described in paragraph 3.6.
6 Cut-Off
For automatic Venturi meter plants with a high full scale flow, it is possible that even where there have been no off-takes, quantity processing may still occur. This is due to the fact that the differential pressure transmitters, even though they may be calibrated and operating correctly, may still send a small signal to the processor even where there is no off-take.
In such cases, a minimum off-takeable volume in m3/h is determined (set at a maximum of 1% of the full scale) confirmed on the basis of documentation provided by the Owner/manager and by a plant inspection.
The corresponding value in %[pic] is programmed in the processor as the Cut-Off value so that below this value, the quantity is not processed.
New inspections and the corresponding reports are carried out every time this is deemed necessary by the parties. An electric recorder on the plant will print if and when the valve downstream from the measurement plant opens and closes.
7 Off-takes exceeding the valid measurement limit of the Venturi meter
If the measurement is automated, any possible overflow of the off-takes outside the valid measurement range lead to the addition of a specific quantity in m3 obtained by correlating the full scale hourly flow with the actual minutes of overflow, multiplying by a coefficient of K equal to 1.3.
In cases where the plant Owner/manager believes that the real off-take during the overflow period is greater than that determined, the actual quantity off-taken is documented in the intervention report drafted together with the plant Owner/manager.
Criteria for the GATHERING and determination of parameters needed for the measurement
1 Method used for the gathering of parameters
1 Volumetric measurement
For traditional measurement plants, meter readings are obtained at each site visit and transcribed onto the manothermograph diagram together with the date and time and which must contain the authentication stamp of the Owner/manager.
At the end of each month the diagram paper containing the readings for the month is retrieved and if necessary renewed (with reference to the pressure pen).
In cases where only the pressure and temperature values are recorded, values of at least [pic] and [pic] are obtained from the manometer and thermometer.
For automatic measurement plants, during station visits, readings from the processor aggregators (m3 e U.C.) are taken.
2 Venturi meter measurement
In traditional plants, once all the diagrams have been collected relating to the relevant period and renewed if necessary (for the triplex with reference to the [pic]pen, for the manothermographs with reference to the pressure pen). In the case of a Venturi meter aggregator the reading is transcribed, with the date and hour, to the triplex diagram.
For automatic plants the m3 aggregator reading is obtained during a site visit, and transcribed, together with the date and hour, onto the printer output.
Where the plant also has a reference densimeter, the diagram paper of the electric recorder or volume mass reading will also be retrieved.
Where a flow transmitter with multivariable module is installed (providing reserve and control equipment as back-up to the triplex recorder), average and maximum values are recorded for differential pressure, temperature, pressure and total volume. This data retrieval is performed with the aid of a lap-top computer running appropriate software.
In all cases the triplex and recorder diagrams must have the authentication stamp of the Owner/manager.
2 Parameter determination
The determination is related to data obtained from traditional equipment, in its use both as traditional measurement equipment and when it is used as back-up for automatic measurement.
1 Volumetric measurement
The determination of pressure and temperature from the manometer and thermometers is taken from their relative value on the instruments; normally a monthly reading cycle of the meter/s is sufficient.
The determination of pressure and temperature from the manothemograph is taken by visually evaluating the average percentage values of pressure and temperature in the period in question.
In plants were the determination of daily measurements is called for, (eg. UC/d printers), the relevant recording diagrams are extracted at 06.00 each day, and the average pressure and temperature values transcribed.
If the plant does not require the determination of daily values, the values are detected visually by unrolling the entire diagram paper for the month; if the linear traces are insufficient to allow a single evaluation of the percentage, the periods in which there were significant changes in pressure and temperature are identified and the respective percentages are determined separately.
2 Venturi meter measurement
Initially, the recordings retrieved will be validated and then the following are determined and transcribed on each diagram:
➢ the average percentage values of pressure and temperature,
➢ the area on the diagram,
➢ ( of the length in mm of the abscissae of permanence of the recordings:
- at full scale of the upper limit instrument,
- at the beginning of the scale (0%) of the instrument with the lowest [pic],
- relating to the periods in which the recording of the low instrument is considered [pic].
After having assessed the correct calibration of the planimeter, the measurement of the area of the diagrams is performed following the trace for any recording periods below 10%.
3 Anomaly verification
If, during the parameter determination process described above, any of the following occur:
➢ lack of diagram paper,
➢ lack or scarce visibility of the diagram traces,
➢ lack of the Owner’s/manager’s authentication stamp and date,
➢ incorrect colouring on the diagrams (flow rate: red, pressure: blue and temperature: green),
➢ instrument timing errors,
the Shipper and the Owner/manager will be immediately informed so that the Owner/manager can provide improved maintenance of the relevant equipment and if necessary, an agreement will be reached for the inspection of these instruments.
Documentation management
1 Consistency of the documentation
The documentation relating to the technical management of REMI plants, includes:
➢ the approval letter for the plant which is drafted following a new connection and includes the plan of the measurement plant, a list of the equipment and the verification form;
➢ any further letters covering plant modifications or updating required by the Owner/manager including the same details as the approval letter;
➢ the witnessing and equipment verification report which is drafted following approval/modification of the plant, and includes the plan of the plant, the list of equipment and details of communications with the Owner/manager;
➢ the intervention reports that are drafted following Snam Rete Gas undertaking work on the plant, such as changes of measurement disc, meter inversion, investigation of anomalies, etc. - these reports include dates, aggregator readings and other relevant information relating to the intervention;
➢ all other correspondence concerning the REMI plant.
The documentation and data relating to gas measurement includes:
➢ the documentation that provide primary data such as recorders’ diagrams, printers’ output, etc.;
➢ the Measurement Report that is produced on a monthly basis by the S.I. and represents the document that certifies the off-take from the REMI plant;
➢ technical information included in the report requested by the Owner/manager containing detailed measurement data (for the relevant period);
➢ primary measurement data obtained via the telemetry system;
➢ primary measurement data obtained from the flow transmitter with multivariable module.
These documents are produced in hard copy and in part, on the information system processes.
2 Retention period
All the documents and data listed above must be retained for a period that allows the reconstruction of all relevant financial events during the last 5 complete years plus the current year.
The management of the data archived on the S.I. provides for on-line archiving of monthly data for the current year and the preceding year, whereas the remaining data must be archived for 4 years.
Primary data supplied by flow transmitter with multivariable modules is archived on magnetic media on a monthly basis.
4 Documents relating to primary measurement data
Documents providing primary data are those documents from which measurement data which is input to the S.I. is obtained in order to allow the derivation of quantities documented in the Measurement Report, including those documents produced by reserve and control equipment.
These documents are of the following type:
➢ recorder diagrams of [pic], [pic], [pic],
➢ recorder diagrams of [pic] and [pic] or [pic] (usually as reserve and control),
➢ printer output,
➢ discs containing the data held on flow transmitter with multivariable modules,
➢ documentation detailing the gas consumption of Snam Rete Gas.
5 Archiving of primary measurement data
These documents are archived at the Centres.
➢ The documents are grouped by equipment type and date. The storage disc containing the multivariable data is labelled with the REMI code and the month/year.
➢ All the material relating to an individual REMI plant is collected in an envelope.
Where documentation is missing (in whole or partially), an explanatory note should be included.
This main REMI envelope should also contain the Owner’s/manager’s declaration in respect of a downstream REMI.
Each such envelope will display the Centre’s Code (2 alphanumeric characters), the REMI code, the month/year of off-take and, if applicable, the name and location of the plant.
6 Document availability
The documents are made available as follows:
➢ to Public Bodies entitled to have access,
➢ to Customers, in the case of disputes or inspections, with any costs incurred being borne by the losing party,
➢ to Customers (and to Shippers with prior authorisation of the relevant Owner/manager) for its own purposes, provided prior payment has been made of the relevant costs.
All relevant measurement data will be made available following specific technical and commercial agreements between the parties.
Inspection and control of measurement data
In order to ensure the quality of measurement data, periodic inspections are performed both on the primary data inserted into the S.I. and on the documents that contain this data. The method and time schedule of these inspections is described briefly below.
Should anomalies be detected, they will be dealt with as described in paragraph 3.
1 Inspection of data provided by automatic information systems
Inspections are performed via S.I. on automatic REMI plants with automatic measurement with a frequency that depends upon the annual off-take volume.
The inspection procedure is based on a comparison between the data provided by automatic measurement for both volumetric and Venturi meter types, and the data provided by the corresponding reserve and control equipment.
The objective of this process is to evaluate the reliability of the gas measurement equipment.
For non automatic volumetric plants with printers only, this process also provides a comparison between the measurement data provided and that of the associated meter.
2 Control of the process for determining measurement quantities
This check entails the verification of:
➢ characteristic data of the measurement plants,
➢ documentation provided by such plants (diagrams, prints, etc.),
➢ monthly volumes contained in the Measurement Report.
In order to obtain, periodically, a complete picture of measurement quality, a sample is taken periodically of plants which represents a meaningful percentage of total measured gas.
3 Documentation inspection
This activity is performed using an information system which contains all the documentation relating to individual REMI plants.
The inspection consists of:
➢ an assessment of whether or not the plant’s sizing and functional planning, taking into account any plant modifications, are compliant with the existing rules and procedures;
➢ checking the consistency of the details contained in the intervention reports and equipment inspection reports with the details held in the S.I.
Inspection and control of measurement plants
Snam Rete Gas reserves the right to perform whatever measurement plant control visits it deems necessary.
The main objective of the control visit is to check the correct functioning of the equipment installed on the REMI plant, insofar as it impacts on measurement quality.
During such visits the following activities are undertaken, in addition to checking the functional elements of the equipment:
➢ for volumetric plants:
- check of the meter’s capacity taking as reference a period of at least 5 minutes;
- check of the instantaneous control of pressure and temperature values, against the values measured by the control and reserve equipment;
➢ for Venturi meter plants:
- check of the instantaneous control of pressure, temperature and differential pressure values, against values measured by the control and reserve equipment;
- check of the recordings produced by the reference densimeter, with the hourly values of volume mass held on the S.I. for the most recent day.
These control processes can be carried out using portable measurement systems which can be connected to the REMI plant.
Further inspections of measurement plants will only be undertaken as a result of a specific request.
Validation of Measurement Reports
1 Introduction
Validation is defined as the carrying out of inspection and control activities which the Transporter has the right to perform in order to verify accuracy and correctness of the measurement data for its own transportation purposes. For this purpose, data is considered “validated” when it is considered usable by the Transporter for transportation balancing and the invoicing of transportation charges and penalties.
Measurement data is usually obtained:
➢ directly from the measurement plant, for automatic plants (for example, via the telemetry system);
➢ for non-automatic plants, via the processing of the primary data provided at such plants.
The operations which must be performed in order to gather and validate the measurement data are carried out at the end of the month to which the Measurement Report refers, with the exclusion of some plants where operations can only begin from the last day of the month.
2 Priority code
The Transporter performs measurement validation according to a series of priority codes.
With equal codes, the priority reduces in line with the reduction of the m3 reported in the last 12 months.
3 Automatic validation
For automatic and telemetered plants, following verification of the completeness of the measurement data and the absence of diagnostic signals that could compromise the validity of the data, the S.I. will provide the automatic validation of the Measurement Reports.
The verification process described in paragraph 6.1 will then be followed.
4 Semi-automatic validation
For plants and scenarios not covered in paragraph 8.3, semi-automatic validation is adopted.
Before this validation, the verification process described in paragraph 6.1 will be followed. The semi-automatic validation, performed via S.I., requires the confirmation of the operator.
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