PETRONAS TECHNICAL STANDARDS DESIGN AND ENGINEERING PRACTICE
MANUAL
LIQUID HYDROCARBON CUSTODY TRANSFER AND ALLOCATION MEASUREMENT
PTS 32.32.00.43 JANUARY 2010
© 2010 PETROLIAM NASIONAL BERHAD (PETRONAS) All rights reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the permission of the copyright owner
PTS Circular 2009-SKG14/PTS-012
PTS No: Publication Title:
32.32.00.43 Liquid Hydrocarbon Custody Transfer and Allocation Measurement Revision 13
Base PTS Version:
This New PTS 32.32.00.43 - Liquid Hydrocarbon Custody Transfer and Allocation Measurement has been developed incorporating: 1. 2. 3. 4.
PETRONAS Lessons Learnt Best Practice New information issued by relevant industry code and standards. Replacement of Current PTS 20.221 (deleted).
All updates in the document are highlighted in Summary of Changes.
Document Approval Name
Designation
Date
Initiator
Aneeta Kajah Ahmad
Instrument Engineer
Reviewed
Razali Ibrahim
Principal Engineer & COP Measurement
Approved
V.R. Harindran
Verified
Saifol Mualim B Ahmad Yahaya Pau Kiew Huai
Custodian Engineer (Technical Authority), Instrument & Control, PA&O - GTS Senior Manager, Engineering - GTS General Manager, Engineering - GTS Senior General Manager, GTS
Verified Endorsed
Pramod Kumar Karunakaran
Signature
Revision History Date
Version
Description of Updates
Author
PREFACE PETRONAS Technical Standards (PTS) publications reflect the views, at the time of publication of PETRONAS OPUs/Divisions. They are based on the experience acquired during the involvement with the design, construction, operation and maintenance of processing units and facilities. Where appropriate they are based on, or reference is made to, national and international standards and codes of practice. The objective is to set the recommended standard for good technical practice to be applied by PETRONAS' OPUs in oil and gas production facilities, refineries, gas processing plants, chemical plants, marketing facilities or any other such facility, and thereby to achieve maximum technical and economic benefit from standardisation. The information set forth in these publications is provided to users for their consideration and decision to implement. This is of particular importance where PTS may not cover every requirement or diversity of condition at each locality. The system of PTS is expected to be sufficiently flexible to allow individual operating units to adapt the information set forth in PTS to their own environment and requirements. When Contractors or Manufacturers/Suppliers use PTS they shall be solely responsible for the quality of work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, it is expected of them to follow those design and engineering practices which will achieve the same level of integrity as reflected in the PTS. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the owner. The right to use PTS rests with three categories of users: 1) PETRONAS and its affiliates. 2) Other parties who are authorised to use PTS subject to appropriate contractual arrangements. 3) Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) and 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards. Subject to any particular terms and conditions as may be set forth in specific agreements with users, PETRONAS disclaims any liability of whatsoever nature for any damage (including injury or death) suffered by any company or person whomsoever as a result of or in connection with the use, application or implementation of any PTS, combination of PTS or any part thereof. The benefit of this disclaimer shall inure in all respects to PETRONAS and/or any company affiliated to PETRONAS that may issue PTS or require the use of PTS. Without prejudice to any specific terms in respect of confidentiality under relevant contractual arrangements, PTS shall not, without the prior written consent of PETRONAS, be disclosed by users to any company or person whomsoever and the PTS shall be used exclusively for the purpose they have been provided to the user. They shall be returned after use, including any copies which shall only be made by users with the express prior written consent of PETRONAS. The copyright of PTS vests in PETRONAS. Users shall arrange for PTS to be held in safe custody and PETRONAS may at any time require information satisfactory to PETRONAS in order to ascertain how users implement this requirement.
TABLE OF CONTENTS 1.
2.
3.
4.
5.
6.
INTRODUCTION ....................................................................................................................1 1.1
SCOPE.....................................................................................................................1
1.2
DISTRIBUTION, INTENDED USE AND REGULATORY ........................................1
1.3
DEFINITIONS...........................................................................................................1
1.4
ABBREVIATIONS ....................................................................................................4
1.5
CROSS-REFERENCES...........................................................................................5
1.6
ORDER OF PROCEDURES....................................................................................5
GENERAL REQUIREMENT................................................................................................6 2.1
UNIT OF MEASUREMENT......................................................................................6
2.2
APPROVAL REQUIREMENT ..................................................................................6
2.3
DOCUMENTATION .................................................................................................8
DESIGN OF METERING SYSTEM .....................................................................................9 3.1
GENERAL REQUIREMENT ....................................................................................9
3.2
METER RUN DESIGN AND PIPE WORK METERING SKID ...............................10
3.3
FLOWMETER TYPE..............................................................................................11
3.4
METER PROVING SYSTEM DESIGN ..................................................................12
3.5
METERING SKID AND CONTROL ROOM INSTRUMENTATION .......................16
3.6
METERING COMPUTERS AND CONTROL SYSTEM REQUIREMENTS...........18
3.7
SAMPLING AND ANALYSIS REQUIREMENT......................................................21
3.8
METERING DATA AND REPORTING ..................................................................22
TESTING, CALIBRATION AND COMMISSIONING .........................................................23 4.1
GENERAL REQUIREMENT ..................................................................................23
4.2
CALIBRATION .......................................................................................................23
4.3
TESTING................................................................................................................25
4.4
COMMISSIONING .................................................................................................29
OPERATION, VALIDATION AND ACCOUNTING ............................................................31 5.1
GENERAL REQUIREMENT ..................................................................................31
5.2
SYSTEM OPERATION ..........................................................................................31
5.3
SYSTEM VALIDATION ..........................................................................................32
5.4
SYSTEM MAINTENANCE .....................................................................................34
5.5
SECURITY .............................................................................................................34
5.6
ACCOUNTING/ALLOCATION MANUAL ...............................................................35
5.7
METERING STATION RECORD KEEPING..........................................................35
5.8
SYSTEM REPORTING ..........................................................................................36
REFERENCES ..................................................................................................................37
APPENDIX 1
LIQUID HYDROCARBON METERING SYSTEM TYPICAL SCHEMATIC DIAGRAM ...............................................................................................................1
APPENDIX 2
TYPICAL FLOW CHART – APPLICATION FOR ACCEPTANCE OF CUSTODY TRANSFER METERING SYSTEM (IN MALAYSIA) ...........................1
PTS 32.32.00.43 January 2010 Page 1 1.
INTRODUCTION
1.1
SCOPE This PTS (guidelines) specifies the minimum requirements in the design, installation, testing, commissioning, operation and maintenance of Liquid Hydrocarbon Custody Transfer and Allocation Metering System, for installations in Malaysia or in any other countries. It is intended for use by the Principal and Contractor when preparing a specification for equipment packages and also during the operation and maintenance of the system. For specifications on metering system using turbine meters, please also refer to PTS 32.32.00.11 and also Requisition Sheet PTS 32.32.00.93.
1.2
DISTRIBUTION, INTENDED USE AND REGULATORY Unless otherwise authorised by PETRONAS, the distribution of this PTS is confined to companies forming part of PETROANS or managed by a Group company, and to Contractors and Manufacturers nominated by them. It is intended for use in oil refineries, chemical plants, gas plants and, where applicable, in onshore and offshore exploration and production facilities and supply/marketing installations. If national and/or local regulations exist in which some of the requirements may be more stringent than in this PTS the Contractor shall determine by careful scrutiny which of the requirements are the more stringent and which combination of requirements will be acceptable as regards safety, environmental, economic and legal aspects. In all cases the Contractor shall inform the Principal of any deviation from the requirements of this PTS which is considered to be necessary in order to comply with national and/or local regulations. The Principal may then negotiate with the Authorities concerned with the object of obtaining agreement to follow this PTS as closely as possible.
1.3
DEFINITIONS
1.3.1
General definitions The Contractor is the party that carries out all or part of the design, engineering, procurement, construction, commissioning or management of a project or operation of a facility. The Principal may undertake all or part of the duties of the Contractor. The Manufacturer/Supplier is the party that manufactures or supplies equipment and services to perform the duties specified by the Contractor. The Principal is the party that initiates the project and ultimately pays for its design and construction. The Principal will generally specify the technical requirements. The Principal may also include an agent or consultant authorised to act for, and on behalf of, the Principal. The word shall is a requirement. The word should is a recommendation.
PTS 32.32.00.43 January 2010 Page 2 1.3.2
Specific definitions Accuracy The measure of the closeness of a measurement to the true value. Allocation Metering System (for liquid hydrocarbon) A measuring system comprising mechanical, instrument and computer parts whose registered measured quantity is used for allocation between two or more Contractors which involved in sharing the same facilities for their operation. This system normally has an uncertainty of +/- 1%. Automatic Sampler A system which when installed in a pipe and actuated by automatic control equipment, enables a representative sample to be obtained from the liquid flowing in the pipe. The system generally consists of a sampling probe, a sample extractor, an associated controller and a sample receiver. Normally it is also equipped with a sampler performance monitoring device. Computer Part The part of the metering system that consists of digital computers and receives digital signals from A/D converters or from digital instrument loops. Control Chart A graphical chart of the constancy measurement used for evaluating whether meter proving operations are in or out of statistical control. On it are shown the +/- 3 sigma limits of dispersion from the average system factor, x (standard deviation), within which the measurement system considered to be in control (API Chapter 13). Custody Transfer Metering System (for liquid hydrocarbon) A measuring system comprising mechanical, instrument and computer parts whose registered measured quantity is used for sale where there is a change in ownership. This system normally, has an uncertainty of +/- 0.25% of standard volume. Density The density of a quantity of a homogeneous substance is the ration of its mass of its volume. The density varies as the temperature changes and is therefore generally expressed as the mass per unit of volume at a specific temperature. Displacement Prover Prover which operate on the principle of the repeatable displacement of known volume of liquid from a calibrated section of pipe between two detectors. These include prover that was commonly referred to as either “conventional” pipe prover or “small volume” prover. Flow computer It is an arithmetic processing unit and associated memory device that accepts electrically converted signals representing input variables from a liquid measurement system and performs calculations for the purpose of providing flow rate and total quantity data. Flow meter Flow measuring device which, indicates the measured flow rate. In some cases, it is also a device that indicates the total amount of fluid passes during a selected time interval. Instrument Loop Includes all elements that form part of the measurement of each individual quantity from sensor to input of the A/D converter or input of digital signal to the computer part.
PTS 32.32.00.43 January 2010 Page 3 Linearity The deviation or spread of calibration data points from an acceptable straight line over the defined flow range. Linearity of a Meter The ideal accuracy curve of a volume meter is a straight line denoting a constant meter factor. Meter linearity is expressed as the total range of deviation of the accuracy. Maximum Meter Flow Rate The maximum rate of flow recommended by the meter manufacturer or authorised by a regulatory body. The maximum rate is determined by considerations of accuracy, durability, pressure drop, repeatability and linearity. Meter Proving An exercise carried out in accordance to the proving procedure in order to determine the relationship between the volume of liquid passing through a meter at one set of conditions and the indicated or reference volume at the same conditions. Meter Run A flow measuring device complete with associated strainers, entry/exit pipework, upstream and downstream straight lengths, flow meter and flow straighteners. Minimum Meter Flow Rate The minimum rate of flow recommended by the meter manufacturer or authorized by a regulatory body. The minimum rate is determined by considerations of accuracy, repeatability and linearity. Online Density Meter A density meter also known as densitometer operating on a representative sample of the process material withdrawn continuously from the process line or vessel via a sampling system. Positive Displacement Meter A meter in which the measuring element is the discrete volumetric segments in the meter and volume is directly measured by continuous separating (isolating) a flow stream into discrete volume segments and counting them. Prover Computer It is an arithmetic processing unit and associated memory device which consists only the proving function for the proving of meters and calculation of meter factors. Pulse Interpolation Any of the various techniques by which the whole number of meter pulses is counted between two events (such as detector switch closures) and any remaining fraction of a pulse between the two events is calculated. Repeatability The quality which characterize the ability of a measuring instrument to give identical indications or responses, for repeated applications of the same value of the measured quantity under stated conditions of use. Sampling An exercise in accordance to the procedure that is carried out either automatically or manually to obtain a sample that is representative of the contents of any pipe, tank or other vessel and to replace that sample in a container from which a representative test specimen be taken for analysis.
PTS 32.32.00.43 January 2010 Page 4 Small Volume Prover Any pipe prover used to calibrate a meter, having a volume between detectors that does not permit a minimum accumulation of 10,000 whole (unaltered) pulses from the meter. Small volume provers require meter pulses discrimination by pulse interpolation or other technique to increase the resolution. Standard Reference Conditions The conditions of temperature and pressure to which measured volumes are to be corrected. Standard reference conditions for pressure and temperature shall be 101.325 kPa (abs) and 150C respectively, in accordance with ISO 5024. Station Computer It is an arithmetic processing unit and associated memory device which sends commands and accepts calculated data from Flow Computer and Prover Computer for Station Totalisation computation and archiving. Turbine Meter A meter in which the measuring element is a multi bladed rotor or impeller to which the metered stream imparts a rotational velocity that is proportional to the mean velocity of the stream. Measured volume is registered by counting rotor revolutions. Uncertainty The part of the expression of the result of a measurement which states the range of values within which the true value of, if appropriate, the conventional true value is estimated to fall within stated confidence level as defined in ISO 5168. For the purpose of this PTS, all uncertainty quoted, are stated at 95% confidence level. Validation The process of confirming or substantiating the accuracy of input variables to a measurement system at normal operating conditions, using reference equipment traceable to certified standards.
1.4
ABBREVIATIONS AC
-
Alternating Current
A/D
-
Analogue to Digital
AGA
-
American Gas Association
API
-
American Petroleum Institute
BS
-
British Standard Institution
CCR
-
Central Control Room
DC
-
Direct Current
DP
-
Differential Pressure
FAT
-
Factory Acceptance Test
GHV
-
Gross Heating Value
IP
-
The Institute of Petroleum
PTS 32.32.00.43 January 2010 Page 5
1.5
IEC
-
International Electrotechnical Commission
ISA
-
Instrument Society of America
ISO
-
International Organization of Standardization
LCR
-
Local Control Room
MPMS
-
Manual of Petroleum Measurement Standard
NBS
-
National Bureau of Standard
NEC
-
National Electricity Code
PID
-
Piping and Instrument Drawings
RTD
-
Resistance Thermal Detector
SI
-
International System of Unit
SIRIM
-
Standard Industrial Research Institute of Malaysia
STC
-
Site Testing and Commissioning
CROSS-REFERENCES Where cross-references to other parts of this PTS are made, the referenced section number is shown in brackets. Other documents referenced by this PTS are listed in (6).
1.6
ORDER OF PROCEDURES In case of conflict between documents, the following priority of documents shall apply: 1. 2. 3. 4. 5.
National or legal codes or regulations or binded contract between buyer and seller. The Purchase Order. The requisition, see PTS 32.32.00.93. This PTS Other PETRONAS, industry, national and international standards referenced herein.
Any conflict of requirements that cannot be resolved by the above order of precedence shall be referred to the Principal for resolution.
PTS 32.32.00.43 January 2010 Page 6 2.
GENERAL REQUIREMENT
2.1
UNIT OF MEASUREMENT The base (reference of standard) conditions for metering system shall be in SI units in accordance with the ISO 1024 latest revision whose base conditions are defined as pressure of 101.325 kPa (abs) at temperature 15oC. Where imperial units such as barrel are required, it shall be converted from the base SI unit and referenced to 14.696 psia and 60oF. Liquid hydrocarbon measurement shall be either in volumetric, mass or energy units. The units shall be SI units.
2.2
APPROVAL REQUIREMENT Host country authority or the respective country petroleum resource manager’s approval may be required for measurement and allocation concept and metering project implementation as per items 2.2.1 and 2.2.2, respectively for the oil and gas production facilities. Item 2.2.3 specifies the government approval that is required to be compiled by Contractors.
2.2.1
Measurement and Allocation Concept
2.2.1.1
Proposed Measurement and Allocation concept has to be submitted for the host country authority or their petroleum resource manager’s evaluation and approval for the oil and gas production facilities. The concept shall be submitted and agreed during the field Development Plan Stage. Contractor shall carry out the financial exposure and cost benefit analysis during the evaluation of the concept and to determine the location for the installation of the metering system, metering system configuration and level of accuracy required. To facilitate the above approval, the preliminary submission to the host countries authority shall include but not limited to the following items: • • • • • • • • •
Measurement philosophy. Product allocation principles. Measurement methods and standards. Proposed system accuracy. Production accounting exposure analysis. Metering project cost estimates. Field area and installation layout with main pipelines. Proposed sizing of the metering system. Preliminary system configuration.
The metering system can either be used for Custody Transfer or Allocation purpose. 2.2.1.2
Two categories of metering system fall under the preview of these guidelines. a)
Custody Transfer Metering System This type of system is shall be of high accuracy and designed with an uncertainty of +/- 0.25% of standard volume, used for custody transfer application i.e. transfer of ownership. The figure registered from this system is used for sales determination.
PTS 32.32.00.43 January 2010 Page 7 b)
Allocation Metering System This type of metering has slightly lower accuracy than Custody Transfer Metering and shall be designed with an uncertainty of +/- 1%. This type of system is commonly used in oil and gas production facilities, used for allocation of liquid between field s of different ownership sharing a common facility or facilities. The allocation method normally used is by “full allocation” i.e. where metering systems are installed in all fields of different ownership involved in sharing the same facilities. However, the uncertainty of the metering system shall be designed to be of custody transfer quality standard e.g. +/- 0.25% if “measurement by difference” allocation concept being adopted. Lowest level quality of Allocation Metering system can be of a well test system’s standards (+/- 10%). Factors such as oil reserve, investment cost and impact to the related parties are to be considered and agreed by those involved before this allocation concept is adopted. This is applicable for oil and gas production facilities only.
2.2.1.3
Generally two main measurement and allocation concept are currently acceptable for the above purpose namely, a) b)
Measurement by different method Full allocation
Only upon the host country authority agreement or the respective country petroleum resource manager on the measurement and allocation concept, Contractor can proceed on procuring of the relevant metering systems in accordance to these guidelines. It is the responsibility of the Principal to obtain agreement from their equity partner and the interested party or parties that will be affected with the metering system installation, before the concept is submitted for host countries authority or the respective country petroleum resource manager’s agreement. 2.2.2
Metering Project Implementation
2.2.2.1
Host country authority or the respective country petroleum resource manager may also request the following information to be submitted for approval for the oil and gas production facilities prior to the release of bid package: a) b) c) d) e)
System specifications Design formula calculations Calculation of overall accuracy and uncertainty of the system Relevant drawings Other relevant information
They may also request the Project Definition Manual be submitted prior commencing fabrication of the metering system. 2.2.2.2
Prior to the official use of the metering system, Contractor hall submit an application together with all relevant data for the respective host country to review and data submitted or after visiting the installation site. Metering system installed shall be traceable to the national and international standards. For the case of the system in Malaysia, SIRIM Berhad’s directive is applicable. Contractor shall also submit to the respective host country authority or their petroleum resource manager for approval, the hydrocarbon and accounting procedure and as well as the validation procedure. The operation procedure will be requested on the need basis.
PTS 32.32.00.43 January 2010 Page 8 2.2.3
Government Regulatory Requirement
2.2.3.1
Custody Transfer Metering System that registered flow quantity that is also used to calculate the crude oil relevant tax needs to be agreed by the respective countries government authorities. For the system in Malaysia, it will be the Malaysian Authorities i.e. SIRIM Berhad and Customs and Excise Department. System to be installed shall be first agreed by the authorities and certification from them is necessary prior official use. See Appendix 2 for typical flowchart of the application.
2.2.3.2
Contractor shall also ensure that the necessary safety approval is obtained by their Vendors from the Government Safety Department should the fabrication and testing of the metering system be carried out in the country that requires this approval. Approval may also need to be obtained if the system is to be installed and operate onshore in certain countries. The government regulatory requirement may vary from country to country and Contractor shall ensure that the respective country regulatory requirements are being met.
2.2.3.3
Any deviations form these guidelines with respect to the measurement and allocation concept, design, operation and maintenance of the metering system requires Principal prior approval.
2.3
DOCUMENTATION
2.3.1
Contractor shall establish and maintain an up-to-date file containing all specifications, calculations and drawings (AS-BUILT). The file should also contain reports concerning verification revisions, design, fabrication, installation and commissioning including inspection and testing programs and operation manual for all fixed and temporary phases and other relevant documentation.
2.3.2
Contractor shall ensure that all documentation during the metering project implementation are timely available such as the project definition manual including the uncertainty analysis, factory and site acceptance test procedures and its result and as well as validation procedures.
2.3.3
The Contractor should maintain up-to-date lists of current documentation and documentation under preparation. Contractor’s internal control system including the documentation should also be made available to ensure qualities of the metering systems are maintained.
PTS 32.32.00.43 January 2010 Page 9 3.
DESIGN OF METERING SYSTEM
3.1
GENERAL REQUIREMENT
3.1.1
The metering and proving systems shall be designed, fabricated, inspected and tested in accordance with the latest agreed editions and addenda to the technical specifications, codes, standards and references mentioned in (6).
3.1.2
Contractor shall request the vendor to quote for the design, manufacture, testing, calibration and documentation of a fully integrated skid and associated control panel. The metering system shall comprise the following major component parts: a)
Field mounted skid, meter proving equipment and instrumentation. •
• • • •
b)
The minimum number of parallel meter runs required from the specified maximum and minimum flow rates at the specified accuracy with one complete spare meter run. For allocation metering system having less critical availability, the spare run may not be required. It is on case-to-case basis. A meter proving equipment and its instrumentation for regular proving and calibration of the meter. Flow proportional automatic sampling system. Refer to Section 3.7 for details. All associated pipe works, valves and fittings, access stairs, walkways for operation, maintenance and validation, lifting pad eyes and drip pans. All transducer and instrumentation necessary for automatic meter proving prover operation and continuous measurement of mass and volumetric quantities and flow rates of liquid together with its temperature, pressure, density and water content prior to delivery.
Metering control panel and computing facilities in the Control Room •
• •
The computer system consisting of the respective stream flow computing functions, meter proving computing functions, station computing functions and communication bus that will perform the calculation and computation of quantities, reporting and metering system control functions. Station computer and communication bus shall be provided with full redundancy. For allocation metering system will depends on the availability and criticality requirement of the system. All other items not specifically mentioned but necessary for the functioning of the systems, including equipment for testing and calibration. The control panel shall include all termination, computing devices, indicators and controls necessary for operation from the panel location.
3.1.3
All equipment within the skid shall be ergonomically arranged such that it is safe and easily accessible for operation, maintenance and validation. Facilities to ease the validation shall be included in the system. Platforms, gratings, stairs etc. be provided as required for easy movement within the skid area. For metering system that required heat tracing, all equipment and components that will be accessed periodically shall be provided with removable insulating covers fitted with quick release fasteners. All equipment and material supplied shall be brand new and suitable to be used for its intended operating conditions.
3.1.4
The system shall be designed to allow subsequent re-calibration of the displacement prover (either sphere or piston displacer) on site with a portable master displacement prover – master meter calibration equipment, tank prover-master meter or calibration can. The flange connection size for the tie ins of the prover system must be suitable with the respective parties facility providing such recalibration services. For allocation metering system where a master meter being used, a calibration facility for proving the master meter shall be made available. Suitable process and electrical equipment and connections shall be provided for the above purpose.
PTS 32.32.00.43 January 2010 Page 10 3.1.5
No bypassing of the metering system is allowed for normal operations after commissioning and start up. For the purpose of commissioning and start up, should a bypass line is required, it shall be provided with a blind or a positive shutoff double block and bleed valve with telltale bleed for verifying shutoff integrity. This valve shall always be sealed.
3.1.6
Other designs can be accepted provided that the Contractor can demonstrate and document equivalent or better accuracy and integrity of the above mentioned system. A typical flow schematic diagram is shown in Appendix 1 of this guideline.
3.2
METER RUN DESIGN AND PIPE WORK METERING SKID
3.2.1
The meter runs shall be designed in accordance to the ISO2714, ISO 2715 and API Manual of Petroleum Measurement Standards Chapter 5 - Metering and other chapters as specified in (6). Materials selected shall conform to applicable codes, pressures and temperature ratings, process conditions, corrosion resistance, ingress protection and electrical safety classification.
3.2.2
Each parallel meter run shall be provided with an inlet, outlet stream control and prover inlet valves, thermal relief valve, flow meter with required upstream and downstream straight length or flow straightening vane as required and a strainer with differential pressure indicator and draining facility. The strainer shall be able to handle the highest flow capacities of the meter with a minimum pressure drop. Temperature transmitter and thermowell, pressure transmitter and pressure gauge shall also be provided. The number of parallel meter runs shall be such that the metering system throughput with one meter runs on standby and the remaining meters still operating within their working range. For allocation metering system that is less critical, standby meter run may not be required.
3.2.3
A full bore through conduit or ball valve should be fitted upstream, downstream and prover inlets of each meter run.
3.2.4
Double block and bleed valves configuration with positive shut off for meter proving or meter calibration and prover system calibration shall be fitted at the following places: •
Meter runs outlets to prover inlet header
•
Meter run outlets to outlet header
•
Prover outlet to outlet header
•
Prover drains line.
These valves (with exception of the meter run inlet valve) shall have instrumentation for cavity pressure relief and shutoff integrity verification. Drain connections from double block and bleed valves configuration shall have an isolation valve and pressure gauge, for verification of tight shut-off. All drains and vents system downstream of the meter shall be of high integrity. For offshore metering systems, suitable arrangement for the valves to meet the safety standards is to be followed. 3.2.5
Flow control valves shall preferably be located at the following points: •
On each meter run outlet between the tee and the outlet double block and bleed valve.
•
On the prover outlet between the 4-way diverter valve and the outlet double block and bleed valve.
PTS 32.32.00.43 January 2010 Page 11 The valves shall be capable to achieve a stable flow rate control at a flowrate required during meter proving and calibration over at least the normal linear range of the meter. Valve and actuator sizing calculations shall be required as part of the documentation. Should during operation, a stable flow could not be achieved over normal operating range of the meter, the interest parties including the host country authority may agree on an acceptable reduced range for meter proving. However, the meter shall not be operated below 20% of the meter maximum rated flow rate. 3.2.6
Thermal relief valves shall be provided for all sections of pipe work capable of isolation and possible over-pressure. All connections shall be self-draining. The total pressure drop of each meter run at the maximum linear operating conditions shall be provided.
3.2.7
Maximum pressure drop across the metering system shall be 2 bar and 2.5 bar when meter when calibration is in progress. The operating pressure of the metering system shall be above the vapour pressure of the liquid and a single liquid phase is to be maintained throughout the measuring process. It is necessary to check further with the process engineers that the designed pressure drop will not caused any problem to the downstream equipment of the metering system.
3.3
FLOWMETER TYPE Careful considerations such as the liquid viscosity, flowrate and the liquid conditions need to be taken in selecting the appropriate flowmeter. Some meter is only limited to certain viscosity ranges and not suitable for high viscosity. Other factor such as the ability for in situ proving shall be considered. The authority in certain countries may approved certain types of flowmeter only and should the flowmeter intended to be used has not been approved for Custody Transfer and Allocation purpose, it is the responsibility of the Contractor to get prior approval prior of the project implementation. The meter shall be calibrated initially, preferably on the liquid with the viscosity for which the system is designed, or if unavailable, on water at the factory and a certificate is to be issued.
3.3.1
Turbine Meters For technical specification of turbine meter metering system, please refer to PTS 32.32.00.11. The turbine meters shall be equipped with two pick up coils each of which shall be fitted with a preamplifier and is independent of each other, in accordance with Level A of the IP 252/76 Code of Practice. This is to indicate whether the signal is good or bad and to alarm the operator of a possible meter or pulse transmission failure. The repeatability of the meter factor shall be better than 0.05% (band) within linear range from five (5) consecutive runs. The linearity of each meter shall be within +/- 0.25% over the specified “Normal operating flow range” and for the full range of viscosities specified i.e. the complete family of calibration curves for all viscosities within the specified “Normal operating flow range” shall lie within the envelope of +/- 0.25% of the average between the highest and lowest meter factor at the specified viscosity. The vendor shall provide, in his proposal, typical meter test reports for the type and size of meter offered over the specified viscosity range.
PTS 32.32.00.43 January 2010 Page 12 3.3.2
Positive Displacement Meter The positive displacement (PD) meter is to be used when the turbine meters could not meeting the conditions of the medium such as high viscosity for it to operate. Double casing type of PD meter should be used for high pressure application to minimize the effect of pressure in volume of the measuring chamber of the meter. The required repeatability and linearity for the meter is similar to that of a turbine meter. Alternatively, a helical turbine meter can also be considered to be used at high viscosity medium. The proving requirement for the PD meter is also similar to that of the turbine meter. The pulse generator selected must be capable to provide sufficient pulses required i.e. 10,000 pulses (unaltered) for a single trip when proving using conventional pipe prover.
3.3.3
Other types of Meter The use of other types of meters such as the Coriolis Mass flowmeter and Liquid Ultrasonic meter may require the Principal to be consulted. Proving of this meter at site need to be taken into consideration when this type of meter is to be selected.
3.4
METER PROVING SYSTEM DESIGN A permanent meter proving facility shall be provided and be designed as per ISO 7278 Liquid Hydrocarbons - Dynamic Measurement - Proving Systems for Volumetric Meters and API MPMS Chapter 4 - Proving Systems and Chapter 4 of API Manual. Meter proving facility can be using any of the following methods. The capacity or size of the prover shall correspond to the maximum flow range of the flow meter.
3.4.1
Displacement Prover A displacement prover includes a calibrated section in which a displacer (sphere or piston displacer) travels with the flow, activating detection devices (mechanical switches or the optical switch). All types of displacement prover systems operate on the principle of the repeatable displacement of the known volume of liquid are achieved by an oversized sphere or a piston travelling through the pipe. The liquid flow is not interrupted during meter proving. This uninterrupted flow permits the meter to be proved under specific operating conditions and at a uniform rate of flow without having to start and stop. Generally, displacement prover can be categorised as follows: • •
3.4.1.1
Conventional pipe prover Small volume prover
Conventional Pipe Prover For detail technical requirement on technical specification of turbine metering system, please refer to PTS 32.32.00.11. The Conventional Pipe Prover shall preferably be of the bi-directional type with quick opening closure for sphere removal, sized and manufactured in accordance with ISO 72782 Liquid Hydrocarbon - Dynamic measurement - Proving systems for volumetric meters Part 2: Pipe Provers, API MPMS, Chapter 4.2 - Manual of Petroleum Measurement Standards Chapter 4 - Proving System Section 2 - Displacement Provers and the following criteria: •
Number of meter pulses generated over calibrated volume to be not less than 10,000 whole pulses (unaltered) per trip i.e. 20,000 pulses (unaltered) total round trip volume.
PTS 32.32.00.43 January 2010 Page 13 •
Resolution of detector/displacer system shall be compatible with requirement (1).
•
Displacer velocity shall not exceed 3 m/s to avoid slippage around the displacer.
•
Length between detector switches to be at least 20,000 times detector repeatability.
•
Prover connection shall be downstream of the meters.
•
The prover shall be designed such that the repeatability during calibration of the volumes, where five calibration trials i.e. 5 consecutive round trips are performed and be within +/-0.01% of the average volume.
•
Connections shall be provided on the prover loop to facilitate recalibration with a portable master pipe prover-master meter or tank prover-master meter. Drain at the lowest point and vent at the highest point shall also be provided. The prover system should also equip with temperature and pressure measuring element.
•
Other considerations for the design including the followings: a.
Detector switches The pipe prover shall have two detector switches at each end of the prover with preferable four independent calibrated prover volumes. The prover volumes from the cross-sectional installed detector switches shall be very similar and these calibrated volumes are to be independent of each other where at any one time if either one of the detector switches fails, it does not invalidate the other prover volume. The detector should be designed such that the contacting head of the detector protrudes far enough into the prover pipe to ensure switches takes place at all flow rates during calibration and normal operation. Detectors and switches should be weather proofed against corrosive marine environment and suitable for the electrical safety classification of the installation.
b.
Prover Internal and Coating Internal diameter of the prover loop shall have the same diameter throughout and there shall be no tapping or drain points between the calibrated volumes of the prover. The internal coating of the pipe prover shall provide a continuous level, durable and smooth surface for the application. The vendor shall provide full details of the coating, surface preparation, method of surface preparation, method of application, maximum allowable fluid temperature and method of repair. Porosity and explosive decompression of the lining shall also be avoided.
c.
Four-way Diverter Valve The four way diverter valve shall be motorized and provided with a local and remote actuation together with a manual override handwheel. Limit switches shall be provided for remote status of valve. Necessary instrumentation to detect leakage on the valve is also to be equipped. The 4-way flow diverter valve in the bi-directional prover shall be full seated and sealed before displacer meets the first detector.
d.
Freedom from Shock When the prover is operating at its maximum design flowrate the displacer shall come to rest safely at the end of its travel without shock.
PTS 32.32.00.43 January 2010 Page 14 e.
Guide Bars/Tees Careful consideration shall be given to the design of the guide bards or tees to avoid damage to displacers.
3.4.1.2
Small Volume Prover
3.4.1.2.1 “Small Volume” is one type of prover which the volume is insufficient to accumulate a minimum of 10,000 whole meter pulses between detector switches for each pass of the displacer. Small volume prover requires meter pulse discrimination by pulse interpolation or another technique to increase the resolution. 3.4.1.2.2 The performance of this type of prover is critically dependent on the mechanical precision of the tube bore and movement element position detecting system, the measurement accuracy and stability of temperature and pressure, tightness of the moving parts and the ration between the diameter of the tube and the actual displacement of the moveable elements. 3.4.1.2.3 Should the host country authority accept the use of “small volume” prover, there may be applied. For offshore applications, where space and weight are important considerations, a “small volume” prover will provide a smaller and lighter solution for a given meter capacity. 3.4.1.2.4 Small volume prover shall be designed and manufactured in accordance with ISO 7278-2 Liquid Hydrocarbon - Dynamic Measurement - Proving systems for volumetric meters - Part 2: Pipe provers and API MPMS, Chapter 4.2 - Manual of Petroleum Measurement Standards Chapter 4 - Proving Systems Section 2 - Displacement Provers and also with the following criteria: •
Small Volume Prover inlet connection should preferably be downstream of the operation meters.
•
Connection shall be provided at the small volume prover system to facilitate recalibration by Water Draw Method at site.
•
Piston seal leakage check kit shall be delivered together with the small volume prover.
•
Water Draw Assembly or Test Measures should be delivered together with the small volume prover and the test measure shall be traceable to national and international standards.
•
The prover shall be designed such that the repeatability during calibration of the volumes, where five calibration trials i.e. 5 consecutive runs are performed and be within +/- 0.01 of the average volume.
•
Vertically installed.
3.4.1.2.5 Test Measures for the calibration of the small volume provers shall comply with the requirements given in the API Manual of Petroleum Measurement Standards Chapter 4 Proving Systems, Section 7 - Field Standards Measures and shall be supplied by the vendor, certified with certificate issued. Prior calibration of small volume provers using the Test Measures at site, the Test Measures shall be first calibrated and certified by the respective country authority. As minimum requirements, the following elements shall forms parts of the small volume prover: •
A precision cylinder.
•
A displacer piston, spheroid, or other fluid separation device.
PTS 32.32.00.43 January 2010 Page 15 •
A means of positioning and launching the displacer upstream of the calibrated section.
•
A displacer detector(s).
•
A valve arrangement that allows fluid flow while the displacer is travelling from one position to the opposite position.
•
Pressure measurement and indication devices.
•
Temperature measurement and indication devices.
•
Instrumentation with timers counters and pulse interpolation capability.
3.4.1.2.6 During proving of Turbine and Positive Displacement meters, the displacer velocity should not exceed 1.5 m/s. The internal diameter of the prover flow tube shall have the same diameter throughout the flow tube. The calibrated or swept volume of the prover, located between the displacer-position sensors shall be free from any tapping, vent or drain points. 3.4.1.2.7 The small volume prover should be installed downstream of meters. The small volume prover shall allow the displacement to come to rest safety without shock at the end of its travel when operating at its maximum design flow rate. There shall be no sign of cavitations in the small volume prover, the valves or any other apparatus within the specific temperatures and pressure ranges when operating at its design maximum flow rate. The internal coating of the small volume prover shall have uniform bore, durable and smooth lasting surface. Block valve shall be installed to isolate the small volume prover from line pressure during maintenance, removal of displacer, replacement of seals, cleaning etc. Drain at the lowest point and vent at the highest point shall be provided. Pressure relief valves and leak detection facilities shall be installed with discharge piping to control thermal expansion of the liquid in the small volume prover while it is being isolated from the main stream. 3.4.2
Master Meter Prover A Master-meter is an indirect prover that uses the concept of transfer proving. A flowmeter with exceptional linearity and repeatability is selected to serve as a master meter (Intermediate Standard) for the proving of another meter or prover operating in the field. A comparison of the two outputs is the basis of the master-meter proving method.
3.4.2.1
The master-meter prover shall be manufactured in accordance with ISO 7278 Liquid Hydrocarbons - Dynamic Measurement - Proving Systems for Volumetric Meters and the API Manual of Petroleum Measurement Standards Chapter 4 - Proving Systems, Section 5 - Master-Meter Provers.
3.4.2.2
Master-meter proving, of which satisfactory results can be achieved, is used in situations in which proving by direct method cannot be accomplished because of logistic reasons, such as unavailability of provers. However, the Master-meter method introduces uncertainties between the meter being proved and the prover that is used to calibrate the master meter. Master-Meter Provers shall be used on a less critical metering system.
3.4.2.3
The master meter should be placed downstream of the meter to be proved and shall be connected in series and close enough to minimise corrections for volume during proving. All fluid diverting valves between the meters shall provide a positive seals.
PTS 32.32.00.43 January 2010 Page 16 The master-meter provers shall be manufactured in accordance with the API Manual of Petroleum Measurement Standards Chapter 4 - Proving Systems, Section 5 - MasterMeter Provers. If the master-meter is in portable service, it should be protected against damage during transportation, installation and handling.
3.5
METERING SKID AND CONTROL ROOM INSTRUMENTATION
3.5.1
Field Instrumentation
3.5.1.1
Location of Sensors Temperature and pressure shall be measured in each meter runs and at the inlet and the outlet of the pipe prover.
3.5.1.2
Installation of Instruments A thermowell shall be installed adjacent to every electronic temperature sensor or group of sensors for calibration. It shall be possible to connect test instruments in parallel with all pressure sensors in the metering system. Temperature, pressure and density, where specified, measuring points shall be representative of conditions at the meter and situated as follows:
3.5.1.3
•
In volumetric measurement systems: as close to the meter as possible without infringing the requirements of the API Measurement manual or other standards as specified in this guideline.
•
In mass measurement systems: as close to the densitometers as possible, which should also be located as near the meter as possible, without infringing the API Measurement Manual or other standards as specified in this guideline.
Instrument Loops The instrument loops shall be kept separate from other types of instrumentation and power supply cabling in the area of use. Cables and junction boxes shall not be shared with instrument loops that are not part of the metering system. Cables and other part of the instrument loops shall be designed and installed so that they will not affected by electromagnetic fields.
3.5.1.4
Transmission of Pulse Signal Pulse signal transmission and treatment from the turbine meter shall be designed in accordance with guidelines in IP252 or ISO 6551. A pulse comparator shall be installed which signals an alarm when a pre-set number of error pulses occurs on either of the transmission lines in accordance with the above code. The pre-set level should be adjustable and when an alarm occurs it should be recorded on a non-resettable comparator register. Where the pulse error alarm is determined by an error rate, the error threshold shall be less than 1 count in 100,000. Pulse discrepancies that occur during the low flow rates experienced during meter starting and stopping should be inhibited. The pulse transmission to the prover counter should be from one or both of the secured lines to the pulse comparator and precautions should be taken to avoid any signal interference in the spur from the comparator line.
PTS 32.32.00.43 January 2010 Page 17 Internationally accepted pulse interpolation methods for the pulse signals from the turbine meters may be used if it can be proved that the accuracy of the metering system satisfies the requirement in this article and satisfactory documentation of the reliability for the interpolation is produced. 3.5.1.5
Conversion of Signals from Analog to Digital Form The A/D conversion shall not contribute systematic errors to the measurements. Total inaccuracy in the analog to digital conversion, including resolution, drift, linearity, repeatability and other random errors shall be less than +/- 0.025% of full scale. Where a signal A/D conversion is used, back up converter is required.
3.5.1.6
Temperature Measurement The temperature measuring element shall be a platinum resistance element Pt-100 Platinum RTD element 100 ohms at 0oC with temperature transmitter in accordance with guideline in IEC 60751 “Tolerance Class A” or equivalent. The accuracy for the complete circuit shall be better than +/-0.15oC.
3.5.1.7
Pressure Measurement The accuracy for the complete pressure loop shall be better than +/-0.25% of span.
3.5.1.8
Density Measurement The density measurement where specified, shall be designed in accordance with IP Petroleum Measurement Manual Part VII Section 2 or API Manual of Petroleum Measurement Standard, Chapter 9. For mass measurement, two density transducers should be installed. The installation shall be such that the liquid passing through the density meter is representative of the line density and no gas can be trapped in the density meter that could cause the error on the density reading. They should both be installed at the inlet to the metering system, within the fast loop arrangement. Insertion type densitometers may be installed in the inlet or outlet of the metering system. The densitometers installation should be in such that one can remain online for density measurement continuously while the other one is taken out for maintenance/validation. Necessary correction to meter conditions shall be carried out. The built-in temperature sensor in the densitometer shall only be used for indication purpose. The accuracy for the complete loop shall be better than +/- 0.5 kg/m3.
3.5.1.9
Control Room Instrumentation Environmental Instruments which are sensitive to temperature or other environmental factors shall be installed in locations where these factors can be controlled.
PTS 32.32.00.43 January 2010 Page 18 3.6
METERING COMPUTERS AND CONTROL SYSTEM REQUIREMENTS
3.6.1
General Metering and meter proving shall be managed by a computer system. Manual proving shall also be incorporated as a backup. This system shall be installed in the CCR, LCR or local equipment room. Flow computers shall be dedicated for each meter run for Custody Transfer Metering System. The station computer and the prover computer shall be able to perform the station function and also the proving function. However, the number of computers may be reduced if it can be demonstrated that the required reliability, availability and redundancy standards will be met. For detail technical requirement on technical specification of turbine metering system, please refer to PTS 32.32.00.11.
3.6.2
Computer System Design The computer system is to be designed as follows:
3.6.2.1
The computer in the metering system shall have no functions other than those related to the metering. The metering system shall be designed in such a way that the maximum liquid flow will be measured.
3.6.2.2
The computer part shall have the capability of displaying continuously the number of pulses received from the meter during proving.
3.6.2.3
The system should include at least two independent registers for storing accumulated fiscal quantities for each meter run and the station total. It shall not be possible to delete or change these registers by operator encroachment or power failure.
3.6.2.4
The computer shall also be designed to ensure that flow quantity measured during validation/calibration i.e. simulation quantity are registered separately from the actual measured amount (during maintenance mode).
3.6.2.5
Manually entered parameter shall be displayed without rounding off or truncation of digits. The display on the computer shall have sufficient resolution to enable the verification or the calculation accuracy as in Section 3.6.4 be carried out.
3.6.2.6
Computer system shall be designed such that the transfer of data to DCS/SCADA/Plant Information (PI) System is permissible and all interfacing requirement such as the handshaking and necessary software is provided.
3.6.2.7
The computer part shall have automatic watch over for differences between readings for continuous monitoring of measurement data the computer shall, for each meter run, automatically log and store for at least one year the following data; At internals of 1 hour cumulative quantities, meter factor and average values of pressure, temperature and density. At intervals of 24 hours: cumulative quantities. This information shall be accessible on printout in a clearly set out format using standard computer printer and paper. Access to the logs shall not be possible without the use of key operated switch.
3.6.2.8
The flow computer shall (standard feature and without further modification) be able to receive at least 2 pulse trains from a turbine meter to perform the pulse security check in accordance with the guidelines stated in the IP 252 or ISO 6551.
3.6.2.9
Report facility for computer constants, keypad setting should be available.
3.6.2.10 The computer will have the ability to perform meter curve (foot-print) interpolation for minimum of 8 calibration points.
PTS 32.32.00.43 January 2010 Page 19 3.6.3
Data Security The data transmission of the computer shall be designed in accordance with Level A of the IP Standard 252/76, Part XIII Section 1. The computer shall have a self diagnostic capability. It shall monitor that the program loops are executed at the correct intervals by means of a watchdog function. The parts of a memory that contain permanent data shall have a periodical check sum control. The algorithms and the fixed parameters important for accurate computation of fiscal quantities shall be stored in non-alterable memory. Security system shall be provided for manual entering of data. The computer system shall be designed and features provided for sealing. Program version number shall be assigned to identify the current program used and this can be determined directly from Visual Display Unit (VDU) or print out. The version number can be updated every time permanent program is altered.
3.6.4
Calculation The computer routines for fiscal measurement calculation shall satisfy API MPMS Chapter 12 - Calculation of Petroleum Quantities and IP 201 Petroleum Measurement Manual Part 1 - Calculation of Oil Quantities. a.
Update time to changes of input signals shall not be more than 2 seconds and parameters having response time such as density and temperature shall not exceed 5 seconds.
b.
The interval between each cycle for computation of instantaneous flowrate and accumulated flow shall be less than 10 seconds.
c.
The algorithms for calculation of meter factor at reference condition shall contain all correction factors given in API 2534 1st edition 1970.
d.
Algorithm and rounding off error for computation of fiscal quantities in the flow computer shall be within +/- 0.001 % for totalisation and +/- 0.01% for flowrate of the computed value. Rounding or truncation shall only be carried out at the end of final computation.
e.
Temperature reading in degree Fahrenheit (deg F) shall be corrected to 1 decimal point and 2 decimal points for reading of temperature in degree Celcius (0C).
f.
For meter factor and volume prover computation purposes, the decimal points used shall follow the API PMS Ch. 12. However, the requirement of some countries would differ e.g. in Malaysia. • Ctl, Cpl, Cts and Cps - 6 decimal points • Prover volume calculation - 4 decimal points • Meter factor - 6 decimal points • Final prover volume shall be corrected to 3 decimal points.
Deviation from the respective country requirement would require approval from the respective country authority or the respective country petroleum resource manager.
PTS 32.32.00.43 January 2010 Page 20 3.6.5
Printouts and Hardcopies The computer system shall have dedicated printers for alarms and reports. Supervisory computer should be able to electronically archive all the alarms and reports. Common printer can be used if an acceptable priority routine is established. Automatic logging on the following information is to be provided:
3.6.5.1
•
Alarms for faults detected by the computer (date, time).
•
Inserted parameters/constant, both fixed and changeable. Old and new manually entered by operator shall also be printed out.
•
Quantity report.
•
Instantaneous values of rate and measured input parameters. Fixed values, which are used instead of live signals, shall be identified.
•
Meter proving report. All data required for manual checks of calculated correction factors and meter factor shall also be included.
•
The Contractor shall consult the respective country authority to establish a system for reporting of agreed data.
Printouts for continuous measurement system The computer system shall automatically generate the following reports intervals but shall also be able to suppress the printing of the reports. •
Current status (instantaneous values)
•
Hourly report
•
Daily sales and production report (Normally daily sales report is at 00.00 hrs and 06.00 hrs for production report).
The generated quantity report shall consists of the following information as minimum:
3.6.5.2
•
Current flowrate current process data and average process data (average values shall be flow weighted)
•
All totals.
Printouts for batch measurement system The computer system shall automatically generate the following reports intervals: •
Current status (instantaneous values)
•
Hourly report
•
Batch start and end report.
Other reporting requirement, similar to 3.6.5.1.
PTS 32.32.00.43 January 2010 Page 21 3.6.6
Meter Proving Algorithm Routine During designing the computer routine for meter proving operations, the followings shall be followed:
3.6.7
a.
All meter runs outlet and prover inlet valves and status check for meter proving sequencing shall be automatic.
b.
All proving calculations shall be carried out by the computer system and printed automatically. Sufficient data shall be available on the printout such that meter proving calculations can be verified externally. Repeatability limits and the required number of consecutive run for repeatability acceptance shall only be changeable with highest security level (meters repeatability shall be such that they can be calibrated against a permanent meter prover with a sequence of 5 consecutive runs, where the difference between the highest and lowest meter factor does not exceed 0.05% of the average meter factor).
c.
Maximum trial runs before the computer aborts the proving operation shall also be made changeable with highest security level (default number of trial runs is 10).
d.
Prover stabilization period for process conditions i.e. temperature, flowrate, pressure parameters of the stability limit shall be user changeable with appropriate security level (supervisor/engineer).
e.
Automatic loading of meter factor to flow computer upon confirmation from operator. Acceptable meter factor shall be within the meter factor high and low limit of the respective meter.
Power Supply The computer shall be equipped with an uninterruptible power supply (UPS) system for back up purposes. Normal operation of the metering system shall not be affected if there is any change from one power source to another.
3.7
SAMPLING AND ANALYSIS REQUIREMENT
3.7.1
The metering system shall be provided with automatic flow proportional sampling system to collect representative sample for the determination of BS&W, average density and for other analysis purposes. Manual spot sampling for back up purposes shall also be made available. The sampling system shall be designed in accordance with guidelines in IP Petroleum Measurement Manual Part VI Sampling Section 2, ISO 3171 and API MPMS Chapter 8 of latest edition.
3.7.2
As sampling system for the determination of water content is critical especially in upstream activities which eventually determined the net production, due attention must be given to the design and operation in ensuring a representative sampling.
3.7.3
For Custody Transfer System, sampler controller and sample monitoring unit shall be installed. It is also recommended to be installed on allocation metering system especially where the sampling system become more critical. The control unit should be able to monitor the sample volume collected continuously. Receiver to be sized to allow 10,000 grabs per sample period with 80% filling range with minimum grab size of 1 ml. The sampling cylinders or receivers should be installed in a cabinet and be located as close as possible to the sampling point.
PTS 32.32.00.43 January 2010 Page 22 3.7.4
Selection of sampling point shall be such that the pipeline condition at the selected point is homogeneous. Contractor need to demonstrate by calculation whether additional mixing requirement such as static or jet mixer is required to ensure homogeneity of the liquid prior sampling. Additional precautionary measures are to be taken if the amount of water presence in the fluid is quite high.
3.7.5
The sampling system should be located near to the metering station. Where slugs of water may be experienced, inline water detection probe shall be fitted to detect abnormal levels of water content. For sampling of pressurized liquids, the following should be observed.
3.8
•
Pressurized cylinders shall be lightweight.
•
Prior extracting of the liquid either for further transportation or analysis, the samples shall be representative and can be achieved through internal mixing in the cylinder. Integrity of the samples is to be maintained throughout the exercise.
•
For pressurized manual sampling, appropriate sample point and sampling cylinder for pressurized liquid is to be used and to ensure that no lighter components of the fluid able to be liberated out of the cylinder.
METERING DATA AND REPORTING All the metering data should be made available at hourly/daily and on request basis.
PTS 32.32.00.43 January 2010 Page 23 4.
TESTING, CALIBRATION AND COMMISSIONING
4.1
GENERAL REQUIREMENT
4.1.1
Prior to site installation, a Factory Acceptance Test (FAT) shall be conducted to check the integrity of both the computer software and the mechanical/skid instrumentation. FAT procedures shall be agreed between Contractor and the Vendor prior to the test.
4.1.2
During FAT, the electronic and the mechanical instrumentation shall be tested together. Prover system need to be first calibrated and witness by a third party before flow integration test be carried out. It is essential that the vendor shall demonstrate that the equipment was internally tested and in good working order before the Contractor’s representative are invited for the test.
4.1.3
All FAT results are to be fully documented. Only after successful completion of the FAT can the metering system be accepted and shipped out to the site. On site, further testing shall be carried out prior to the commissioning of the system. All calibration equipment used for the SAT shall be traceable to the respective country’s National and International standard. In Malaysia, it has to be traceable to Malaysia’s standard where SIRIM Berhad is the Custodian. It is the responsibility of the Contractor to ensure that the FAT and Site Acceptance Test (SAT) procedure be made available prior to the tests. The host country authority may request these procedures to be submitted for review and also to witness the test. The host country authority shall be notified at least three weeks prior to both tests.
4.2
CALIBRATION
4.2.1
General Liquid Hydrocarbon Custody Transfer and Allocation Metering Systems shall be calibrated with test equipment having certified traceability to international or national standards. The uncertainty of this equipment shall be better than the uncertainty of the metering equipment it used to calibrate. Secondary standards or instruments used for calibration of all relevant parts of the metering system shall be calibrated and certified by the respective country’s Metrology unit (SIRIM Berhad for equipment to be used in Malaysia) or any other independent laboratory which can prove such traceability.
4.2.2
Instrument Calibration All relevant instruments used in the metering system shall be calibrated and certified by the manufacturer which can prove such traceability.
4.2.3
Prover Calibration The proving system shall be calibrated at the vendor’s works as part of their system checks and after installation on site, immediately prior to start up. Comparison on these two volumes will be done for checking purposes. The detail calibration method used will depend on the type of meter proving system. Prover calibration procedure shall be made available prior to the exercise.
PTS 32.32.00.43 January 2010 Page 24 4.2.3.1
Conventional Pipe Prover Calibration
4.2.3.1.1 The pipe prover shall be calibrated using waterdraw or master-meter method at vendor’s workplace as part of their system checks. The pipe prover shall also be calibrated by using waterdraw or master-meter method upon installation on-site for SAT before it is put into service. If master meter method is used, the meter shall be calibrated at site using waterdraw. Similar method of calibration should be done both at the vendor’s factory and at site prior to officially use of the metering system. After in operation, this prover shall be calibrated on yearly basis or at any frequency as agreed by the respective host country authority. 4.2.3.1.2 Both calibrations shall be in accordance with the standards as specified in (6). All pipe prover calibrations at the factory shall be witnessed by an independent certification authority or the Contractor and attested to in writing. The calibration at site normally being witnessed by the respective host country authority and other interested parties. 4.2.3.1.3 Test Measures used for the pipe prover volume calibration shall be certified traceable to international or national standards. 4.2.3.1.4 The pipe prover shall be calibrated with at least two separate volumes. Four volumes is preferred. The pipe prover shall be capable of producing corrected volumes for five consecutive runs in any given direction within +/- 0.01% of the average. The average of the five (5) consecutive round trips volumes shall be used as the base volume of the pipe prover. 4.2.3.1.5 Pipe prover volume calibration process shall be repeated at a flow rate change of at least 25% to verify the possible leak during the base volume calibration. The corrected volumes for 3 consecutive runs at any given direction shall repeat within +/-0.01% of the average. The average volume of these three (3) round trips volumes shall not deviate from newly established prover base volume by more than 0.02%. 4.2.3.1.6 Copies of the calibration certificates for each of these and all subsequent calibrations shall be documented in the validation report. These certificates shall show the reference numbers of the sphere detectors. The calibrated volume shall be in SI units at Standard Reference Conditions. 4.2.3.2
Small Volume Prover Calibration
4.2.3.2.1 The small volume prover shall be calibrated physically using waterdraw method at vendor’s place as part of their system checks for both the upstream and downstream volumes. The small volume prover shall also be calibrated by using the same method i.e. waterdraw method upon installation on-site before it is put into service. 4.2.3.2.2 Both calibrations shall be in accordance with the standards as specified in (6). 4.2.3.2.3 A small volume prover calibration shall be witnessed by an independent certification authority and attested to in writing. 4.2.3.2.4 Test Measures used for the small volume prover calibration shall be certified traceable to international or national standards. 4.2.3.2.5 The small volume prover shall be calibrated physically for both upstream and downstream volume if these volumes are used for meter proving. The small volume prover shall be capable of producing corrected volumes of these volumes are used for meter proving. The small volume prover shall be capable of producing corrected volumes for five (5) consecutive runs in any given direction repeatable within +/-0.01% of the average.
PTS 32.32.00.43 January 2010 Page 25 The average of the five (5) consecutive volumes shall be used as the base volume of the small volume prover. Small volume prover calibration process shall be repeated at a flow rate change of at least 25% or greater to verify the possible leak during the base volume calibration. The corrected volumes for 3 consecutive runs in any given direction shall repeat within +/-0.01% of the average. The average volume of these three (3) volumes shall be within 0.02% with the newly established base volume. 4.2.3.2.6 Copies of the calibration certificates for each of these and all subsequent calibrations shall be sent to the host country authority or the petroleum resource manager upon request. These certificated shall show the reference numbers of the optical detectors used in the calibration. 4.2.3.2.7 The calibrated volume shall be in SI units at Standard Reference Conditions. 4.2.3.3
Master-Meter Prover Calibration The master meter prover shall be calibrated on the same liquid or other liquid as appropriate that will be used during operation of the meter. Any linearity curve of the master meter prover should be developed at minimum 8 points over the range of the meter to operate. The linearity limit shall be within +/-0.25% for up to 2 inch meter and +/- 0.15% for meter size greater than 2 inch. The meter factor that is applied to the master meter should be the average value of five (5) consecutive runs repeating within +/-0.01% of the average.
4.2.4
Meter Calibration
4.2.4.1
The first calibration test on each meter shall be performed at Vendor’s premises. For each type of meter used, the performance of the meter shall prior to FAT, be demonstrated by the Vendor by initial calibration with a suitable medium at minimum 8 points. 5 of these points shall span the “Normal operating range” and 3 points shall span low flow to “Design minimum”. The Vendor shall issue calibration certificates for the meter calibrated.
4.2.4.2
Each point shall consist of five (5) consecutive runs, the results of which the difference between the highest and lowest meter factor does not exceed 0.05% of the average meter factor.
4.2.4.3
The linearity must be within +/-0.25% over the specified “Normal operating flow range”. The vendor or Contractor shall perform final test and calibration during SAT with hydrocarbon against meter prover.
4.3
TESTING
4.3.1
General Testing General testing shall include checking against drawings, flushing, cleaning, hydrostatic pressure testing, electrical earthing and be done on an individual item basis. Vendor shall perform its own test prior to FAT and provide the necessary evidence if required via filled test sheets.
PTS 32.32.00.43 January 2010 Page 26 4.3.2
Factory Acceptance Test (FAT)
4.3.2.1
General Check Prior to further test in the factory, a general check on the system is to be carried out. This includes checking of the following items.
4.3.2.2
a.
Dimension check as per approved drawings and standards.
b.
Instrument installation and quantity check as per approved drawings and bill of quantity respectively.
c.
Availability of all documents.
Metering Panel and Instrumentation Equipment Tests
4.3.2.2.1 All panel and field mounted instrumentation, cabling and the connectors shall be visually inspected for compliance with specifications with regard to segregation of cables, satisfactory access, vents, drains and general good quality of installation work. 4.3.2.2.2 Calibration checks using precision test equipment shall be performed on all transducers, transmitters, converters, indicators, recorders, gauges and switches etc. supplied for use with the system. 4.3.2.2.3 All safety and relief valved shall be tested, set and tagged with the set pressure. 4.3.2.2.4 An insulation test shall be made on all power supply and instrument cables and panel wiring using voltage tester. Instruments shall be disconnected during this test which may cause internal damage. All resistance thermometer elements shall be tested for insulation resistance to BS-1904. 4.3.2.2.5 A sample of the power circuit breaker shall be tested by simulating a short circuit failure. 4.3.2.2.6 The control panel shall be fully functionally tested before connection to the skid using appropriate simulators and other test equipment. These tests shall include: •
Panel mounted receiving indicators etc.
•
Outputs from panel mounted controls.
•
Meter run and prover instruments.
•
Computer functional test.
•
Verification of computer calculation and integration accuracy as specified in item 3.6.
•
Interlock and alarms.
•
Checking of power distribution circuits and breakers for correct wiring.
•
Analogue functions shall be calibrated at a minimum of five points rising and five points falling in the range (0%, 25%, 50%, 75% and 100%).
PTS 32.32.00.43 January 2010 Page 27 4.3.2.2.7 All remotely operated valves shall be checked after installation in the metering skid by: •
Manual stroking of the valves to check limit switch actuation and to ensure full operating.
•
Local operation to verify phase of electrically operated actuators rotation and functioning of local controls.
•
Remote operation and checking of remote position indication and interlocks.
•
Noting the time for each valve to fully stroke in each direction.
4.3.2.2.8 After connection between the panel and skid, loop checks shall be made on all circuits to check correct wiring and calibration of the system. This shall include checks if all alarms, interlocks, digital and analogue inputs and outputs. 4.3.2.2.9 A check shall be made on effects of power supply variation by setting all instruments in a normal operating mode and varying the output voltage to upper and lower limits and noting the effect by repeating functional checks. 4.3.2.2.10 The panel should be heat soaked for a minimum of 100 hours. Records shall be made of temperature at selected points on the panel. Following completion of the heat soak, the loop checks as in 4.3.2.2.8 shall be repeated at ambient temperature to ensure that none of the equipment has suffered any thermal effects. A check of microprocessor functional performance shall be made during the soak test (after internal panel temperatures have stabilized). 4.3.2.2.11 Measurement and records shall also be made on panel maximum power consumption (AC & DC). 4.3.2.2.12 Data transfer to another system shall be checked for data accuracy, data correctness and redundant switching of communication channel. 4.3.2.2.13 Spares, if possible should be tested. 4.3.2.2.14 The simulation test among other thing shall include simulating with at least five different values that cover the minimum and maximum level in the working range of the skid instrument and the computers using test simulators. The simulators shall simulate signals connected to the computers input or in any other way to secure a controlled, constant input to the computers. Testing or simulating the different functions of the computers shall include but not be limited to manually input data, printouts, alarms and data transmission between the computers. All calculations by the computers shall be verified by injecting known values to the computers and to compare the result using manual calculation e.g. flow calculation software. 4.3.2.3
Flow Testing Calibration
4.3.2.3.1 Prior to flow test at the vendor’s location, all the individual equipment inclusive if mechanical, instrument and computing system has first to be tested. The system shall be connected to suitable pump and test equipment where the following tests be carried out using water or other suitable test medium.
PTS 32.32.00.43 January 2010 Page 28 a.
All meters shall be individually flow tested and proved against the prover at their rated maximum and minimum flows on five points at specified intervals between maximum and minimum. Each point shall consist of five consecutive runs, the results of which the difference between the highest and lowest meter factor does not exceed 0.05% of the average meter factor.
b.
The linearity must be within +/-0.25% over the specified “Manufacturer design flow range”. Observations shall also be made and recorded of: • Pressure drop across strainer. • Pressure drop across meter run. • Pressure drop across prover. • Density measurement (if applicable).
c.
Checks shall be made during testing for tightness of shut-off high integrity and the four-way diverter valves.
d.
All meter runs shall preferably be flow tested simultaneously (i.e. one metering and one proving) and preferably up to the normal maximum linear capacity of each meter.
e.
Checks shall be made on the functioning of the flow control valves.
f.
Checks shall be made on the correctness of the meter proving algorithms.
g.
Checks shall be made to ensure correct reports such as meter proving report and metering report (hourly or batch report) generated by the computing system.
h.
Checks on the correct functionality of the sampling system to ensure volume collected and accuracy as per number of grabs, accuracy of sampling system, alarms and switching of sampling cylinders.
4.3.2.3.2 Following completion of the flow testing, the liquid test medium shall be drained and a thorough inspection be carried out on the condition of prover lining and other equipment where possible. 4.3.2.3.3 Computer simulations shall be carried out whereby all calculations by the computing system shall be verified. 4.3.2.4
Site Acceptance Test (SAT)
4.3.2.4.1 The Contractor shall provide test procedures for punch list items arriving on site. Other items to be provided shall include but not limited to the following: •
Loop diagram and loop checkout sheets
•
Full print data base checking
•
System functional test procedure and schedule
PTS 32.32.00.43 January 2010 Page 29 4.3.2.4.2 The onsite acceptance test shall be considered as an extension of the FAT. Prior to SAT, all wiring termination to be checked and powering of the panel should be carried out by the vendor or authorized vendor’s representative. Some tests carried out during FAT shall also be repeated during SAT. SAT on Custody Transfer Metering System that involved export tax computation which the government have interest in, should be witnessed by the government or the host country representative e.g. SIRIM for the installation in Malaysia. SAT shall concentrate more specifically on the following: a. Inspection of material and equipment on arrival at site including spares and documentation. If damage occurred during transport, it is important to establish without delay, the extent of the damages and whether it is repairable onsite or necessary to order new materials. Suitable storage of material and equipment should be provided. b. Field calibration of the pipe prover shall be in accordance with API Manual of Petroleum Measurement Standard Chapter 4 – Meter Proving and the requirements stated in these guidelines. All calibration equipment used for prover and other metering equipment shall be traceable to National standard. All prover calibration on Custody Transfer Metering system that involved export tax computation shall be witnessed by Contractor and SIRIM for metering installation in Malaysia. c.
The metering panel and instrumentation equipment test shall be repeated which also includes the computations check carried out by the computer system. The calibration exercise carried out on the instrument in this exercise is considered as Validation No 1.
d. The completed meter skid and panel shall be subjected to operational functional test during actual flow condition to demonstrate satisfactory performance at the design flowrates. 4.3.2.4.3 Contractor shall submit project completion report, which should include the first official validation report to the host country authority should it be required within 30 days after system has been commissioned. Before the system is put in operation for official use, approval from the respective host country authority shall be obtained.
4.4
COMMISSIONING
4.4.1
General The installation, commissioning and start-up of the metering system shall be carried out in accordance with the requirements in this section.
4.4.2
Installation Quality Assurance The Contractor shall set up an installation and commissioning plan of a system of activities, the purpose of which is to provide assurance and show evidence that the overall quality control shall be effectively maintained. The plan shall be applied systematically to all metering systems, and deviations will not be tolerated.
PTS 32.32.00.43 January 2010 Page 30 4.4.3
Commissioning Commissioning shall include running-in of all rotating equipment, checking alignment, testing control loops, stroking valves, flushing, hydrotesting, final testing of electrical instrumentation systems, purging, drying, inerting etc which usually carried out sequentially on a system basis. Commissioning is completed when the metering system is ready for start-up.
4.4.4
Start-up It begins with the introduction of process hydrocarbon into the system excluding the period where hydrocarbon may have been used previously for pressure testing/purging.
PTS 32.32.00.43 January 2010 Page 31 5.
OPERATION, VALIDATION AND ACCOUNTING
5.1
GENERAL REQUIREMENT Contractor shall operate and maintain the metering system to the highest degree of engineering standard in order to maintain its accuracy and integrity. As such, operating, validation and accounting procedures/manuals shall be prepared by the Contractor and approved by the respective host country authority or the host country petroleum resource manager wherever applicable before start-up. (In Malaysia, the approval party is PETRONAS being the petroleum resource manager and authority of the Production Sharing Contract) These procedures shall document all activities that influence the measurement system.
5.2
SYSTEM OPERATION Contractor is required to carry out the following essential activities:-
5.2.1
Metering stations shall be operated and maintained in accordance with the manufacturer recommendations and approved operation, validation and hydrocarbon allocation/accounting procedures. Metering validation is to be performed as per the agreed validation procedure using equipment that is traceable to National and International Standard. All factors, constant, key pad values and limits used in the metering system either used for computations, checks or alarms shall be updated regularly. When the metering equipment e.g. the density meter and the flowmeter is changed, all the respective factors for density calculation, Meter K Factor, Meter Factor etc. Need to be updated. Upon successful meter proving, the new meter factor shall be updated in the computer accordingly. During meter proving, particular attention shall be given to flow stabilization prior to meter proving, checking of block and bleed valves for leaks and venting at high points. a) Meter Proving Operations for continuous Flow Measurement System For a newly commissioned metering station with a dedicated meter proving facility in a continuous production system (as distinct from tanker loading), meters shall be proved twice a week at approximately equal intervals between proving. Provided the meter factor scatter is acceptable and until a meter factor control chart is established, the frequency may be reduced to once a week or on monthly basis. The frequency for proving may be further reduced upon agreement between the host country and Contractor where applicable. Where meter factor linearization curve is being used, the curves linearity shall be within the normal meter operating flow range and is within +/- 0.25%. b) Meter Proving Operations for Batch Measurement System For tanker loading systems, any meter onstream shall be proved at least once regardless of the duration of loading. Additional proving is required on stream(s) where conditions of loading. Additional proving is required on stream(s) where conditions such as the flow rate have changed and a ‘prove required’ alarm is triggered and this new factor shall only be used on the new flowrate.
5.2.2
Where meter types other than mentioned in this guideline, the type and frequency of meter proving by the Contractor shall be determined on an individual basis by the host country authority after consultation with the Contractor. Account shall be taken on the meter type, process fluid and operational load cycle. Where meters employing novel technology are to be used, extra evaluation periods and tests will usually be required before a long-term operational schedule can be determined.
PTS 32.32.00.43 January 2010 Page 32 5.2.3
Meter factors that are acceptable for use shall be based on the repeatability acceptance criteria of not more than 0.05% of five consecutive runs. Meter factor control chart is to be developed and Meter Factor High and Low limits be established used to verify the acceptability of the meter factor.
5.2.4
Pipe provers and small volume provers shall be calibrated at least once a year. Where this is not possible for operational or whatever reasons, longer calibration interval may be considered by the respective host country authority. Inspection of the sphere, checking of sphere size, concentricity etc should take place prior to calibration. After calibration, the sphere detectors and switches shall be sealed. Any maintenance work on the prover that could affect the swept volume e.g. changes of sphere detectors and switches should not be undertaken without prior consultation with the host country authority who will advice if a calibration is required.
5.2.5
Operating Manual The Operating Manual shall be prepared for the purpose of providing operational guideline for the operators in performing metering activities. It shall then be describe the operation of the system which includes the computers, the skid instrumentation, sampling activities and other operation of the metering system. The manual among other things shall also include what actions to be taken in case of malfunction or alarm on the metering system. The minimum content of the manual shall consist of the following:• Overall process description. • Metering system description. • Metering instrument specification. • Computer system operation (including the computer read codes) and actions taken on alarms. • Metering system operation. • Metering sealing procedure. • Sampling procedure.
5.3
SYSTEM VALIDATION In order to maintain the reliability and accuracy of the metering system, Contractor shall conduct a periodic calibration and validation of the metering system at a frequency agreed by the respective host country authority. For new systems, a monthly validation shall be performed. A new validation frequency can be agreed with the host country authority after such time the system is stable. The calibration/validation shall be performed in accordance with the agreed system Validation Manual. Contractor should consider installing the validation software application in its computer system which will facilitate further the validation exercise.
PTS 32.32.00.43 January 2010 Page 33 All validation result shall be recorded on the format agreed in the Validation report. The report shall include but not limited to the following:• • •
As found and as left result of the calibration exercise. System uncertainty in accordance with ISO 5168 latest revision. Findings and recommendations.
Metering irregularities occurred since then and between the last validations. Validation reports shall be prepared after each validation and submitted to the host country authority within 1 month. Any irregularity on the figures generated, resulting from the validation shall be endorsed by the respective host country authority. 5.3.1
Validation Manual The validation Manual shall be prepared for the purpose of providing guideline for the verification of the metering system instrumentation. Contractor may consider including the scope for the metering vendor to also provide the validation manual in its documentation submission. This manual shall be ready prior to the official use of the metering system and approved by Principal and also the host country authority. The content of the validation manual shall consist of, but not limited to the following:
5.3.1.1
Brief description of the metering system. This shall include a concise description of the design concept of the system and its instrumentation including the computer system. Description as to the function of each individual instrument in the system, its accuracy and location in the system layout, system capacity, flow operating condition and the schematic drawing of the system, instrument description shall include manufacturer’s name and model number, range, accuracy, input/output signal and tag number.
5.3.1.2
Calibration Procedures The step-by-step calibration procedures for the instruments shall be detailed out for each individual instrument in the system. A set of validation check sheets shall also be included and all readings obtained during each calibration shall be recorded on the check sheets. Adjustment shall be made when a reading is out of tolerance. After any adjustment the complete test shall be repeated.
5.3.1.3
Frequency of Calibration and Inspection Contractor shall detail out the frequency of validation/calibration of each of the metering instruments.
5.3.1.4
Flow Calculation Calculations/formulae used to arrive at the volumetric, mass and heat throughput shall be clearly laid out. All flow constants that are to be used shall be shown in actual units they are used. Where the flow constants are fixed, the actual values and their derivations shall be shown.
5.3.1.5
Metering Irregularity Calculation All types of irregularities on the metering system and methods for the corrections shall be clearly stated.
PTS 32.32.00.43 January 2010 Page 34 5.3.1.6
Calibration/Validation equipment A list of the calibration/validation equipment to be used in the validation exercise shall be provided in the validation manual. All information related to the equipment specification such as its accuracy, repeatability, serial no., and range shall also be provided. The accuracy of the calibration equipment shall be better than the accuracy of the instrument to be validated. The equipment shall be traceable to any National Standard or National Bureau of standard acceptable to the National Standard body.
5.3.1.7
System Uncertainty Calculation System uncertainty calculation shall be listed in the validation man ual and shall be in accordance with ISO 5168 latest revision.
5.4
SYSTEM MAINTENANCE The metering system shall be maintained in order to maintain its accuracy and integrity. The host country authority approval shall be secured before any change or modification is made on the metering system. Drawing(s) and sufficient data shall be submitted together with the request for approval. The host country authority representative(s) shall be invited to witness the maintenance activities on the system modification. All results pertaining to these activities shall then be properly documented. The contractor shall also obtain the vendor’s recommended comprehensive spare parts list and priced quotation for parts commissioning and two years operation.
5.5
SECURITY All software and all flow factors, status and alarm information stored in the system shall be protected to prevent loss of information by inadvertent operator action or input power failure. In order to ensure security of data in the computers and other critical instrumentation in the metering system, sealing procedures shall be adhered to. The procedure shall be prepared by the Contractor. Critical instruments such as the computers and critical valves shall be sealed where practically possible to prevent unauthorized entry or manipulation of the computer system and opening or closing of critical valves at the metering skids. The sample cans of the sampling systems shall be sealed. The seals shall have serial number for easy identification. The last valve downstream of the outlet header or offloading valve shall be sealed for system that is exporting crude oil or condensate in a batch loading system. The sealing-of these identified critical instruments shall be carried out by Contractor’s authorized person and be recorded in a dedicated /sealing Log Book. This logbook shall be kept in the metering control room where the host country authority personnel will review it on the need basis.
PTS 32.32.00.43 January 2010 Page 35 5.6
ACCOUNTING/ALLOCATION MANUAL The Accounting/Allocation Manual shall be prepared by Contractor and approved by the Principal and the host country authority which is applicable to the metering system in the oil production facilities. The manual define the method and procedure on how the metered and other data are to be used for determination of sales, allocation and production quantities. The minimum content of this manual shall consist of the following:a. b. c. d. e. f. g.
Accounting and allocation concepts. Allocation procedure and algorithm. Production measurement system. Product sampling and analysis. Data requirements. Mass, volume and heating value calculations. Methods to account for irregularities in quantity.
5.7
METERING STATION RECORD KEEPING
5.7.1
Log books/Records Contractors shall maintain electronic/manual logbook and records of power system, metering system, meter proving and metering print-out. Records of parameters such as meter flow rate, liquid temperature and density shall be kept at the metering station for at least 3 months. All of the logbook/records shall be made available within reasonable time for inspection by host country authority. Electronic or manual logbook and records shall be maintained comprising information of the following systems:
5.7.2
Metering system Log Book A dedicated log book for the metering system shall be kept preferably for each metering station
5.7.2.1
Metering Log The metering system log shall include the metering skid and its associated equipment showing details of: •
Type, stream and Tag No. Particulars including location and production measured.
•
Totaliser reading(s) where applicable on commencement and cessation of metering.
•
Validation and calibration activity on the metering system and its related equipment.
•
All mechanical or electrical repairs or adjustments made to the meter or its readout equipment and other parts of the metering system.
•
Metering errors due to equipment malfunction, incorrect operation, etc. Including data, time and totaliser readings; both at the time or recognition of an error condition and when remedial action is completed.
•
Alarms, together with reasons and operators response.
•
Any breakdown of meter or withdrawal from normal service, including time and totaliser readings.
•
Replacement of security seals when broken.
PTS 32.32.00.43 January 2010 Page 36 5.7.2.2
Proving system log Log detailing the prover system including the calibration activity, sphere detector details during maintenance work done on proving facilities loop and its associated equipment.
5.7.2.3
Metering Record A manual / automatic recording should also be kept, at intervals of not more than hour, of the following parameters: • All meter totaliser readings; • Meter flow rates (also relevant meter factors), pressure and temperature, and (if measured continuously) density. One of these sets of readings should be recorded at 2400 hours on the billing period and also at other agreed time for taking daily closing figure. Other parameters such as liquid density and percentage of BS & W content should be recorded at agreed interval.
5.7.3
Meter Proving Record A Meter Proving Record for each meter giving the details of each proof run such as prove flow rate, pressure, temperature, meter factor etc. This record shall include a running plot, or similar control chart, so that any undue change or fluctuation in meter actors may be easily detected (see API Chapter 13).
5.8
SYSTEM REPORTING Any major maintenance, re-calibration work on the metering and proving systems and also other operational related activities work shall be officially notified, when any abnormal situation or error occurs which could require significant adjustment to the totalized meter throughputs. If a meter is required to be removed for maintenance work or replacement, host country authority shall be officially informed detailing the serial number of the meter concerned and the reasons for the action taken. When correction to meter totalized figures are required due to known metering errors, a formal report shall be submitted to the host country authority where applicable detailing the time of the occurrence, tantalizer readings, and suspected causes for the errors occurring.
PTS 32.32.00.43 January 2010 Page 37 6.
REFERENCES In this PTS reference is made to the following publications: NOTE
Unless specifically designated by date, the latest edition of each publication shall be used, together with any amendments/supplements/revisions thereto.
PETRONAS STANDARDS Turbine Fiscal Metering System for Liquid hydrocarbon
PTS 32.32.00.11
STANDARDS (APPLICABLE FOR OPERATIONS WITHIN MALAYSIA) Malaysia’s SIRIM’s Berhad Criteria Circular – AFLA 1991/01 and 1991/02. (Applicable for operations within Malaysia. Weights and Measure Act 1972 (Applicable for operations within Malaysia) Custom Exercise Act 1976, P. U(A) 161 (Applicable for operations within Malaysia)
API STANDARDS API Manual of Petroleum Measurement Standards Chapter 1
Vocabulary
Chapter 4
Proving Systems Section 1 – Introduction Proving Systems Section 2 – Displacement Provers Proving Systems Section 5 – Master-Meter Provers Proving Systems Section 6 – Pulse Interpolation Proving Systems Section 7 Field – Standard Test Measures Proving Systems Section 8 – Operation of Proving Systems Proving Systems Section 9 – Methods of Calibration for displacement and Volumetric Tank Provers
Chapter 5
Metering Section 1 – General Considerations for Measurement by Meters Metering Section 2 – Measurement of Liquid Hydrocarbon by Displacement Meters Metering Section 3 – Measurement of Liquid Hydrocarbon by Turbine Meters Metering Section 4 – Accessory Equipment for Liquid Meters Metering Section 5 – Fidelity and Security of Flow Measurement Pulsed-Data Transmission Systems Metering Section 6 – Measurement of Liquid Hydrocarbon by Coriolis Meters Metering Section 8 – Measurement of Liquid Hydrocarbon by Ultrasonic Flow Meters using Transit Time Technology
Chapter 6
Metering Assemblies
Chapter 7
Temperature Determination
Chapter 8
Sampling
PTS 32.32.00.43 January 2010 Page 38 Chapter 9
Density Determination
Chapter 10
Sediment and Water
Chapter 11
Physical Properties Data
Chapter 12
Calculation of Petroleum Quantities
Chapter 13
Statistical Aspects of Measuring and Sampling
Chapter 15
Guidelines for the Use of the International System of Units in the Petroleum and Allied Industries
Chapter 20
Allocation Measurement
Chapter 21
Flow Measurement Using Electronic Metering System
BRITISH STANDARDS BS 5233: -1975 ‘Glossary of Terms used in Metrology’, 1st edition 1975. BS 1904 ‘Specification for Industrial Platinum Resistance Thermometer elements’.
IEC STANDARDS IEC 751 : 1983 ‘Industrial platinum resistance thermometer Sensor’, 1st
IP PETROLEUM MEASUREMENT MANUAL IP Petroleum Measurement Manual, Part VI Section 2 A Guide To Automatic Sampling of liquid from pipelines July 1987. IP 252/76 Petroleum Measurement Manual, Part XIII Section 1 Fidelity and Security of measurement – Data Transmission for fluid metering system. IP Petroleum Measurement Manual, Part VII Section 2 Continuous Density Measurement tentative Sept. 1979. IP 201/64 Petroleum Measurement Manual, Part 1 – Calculation of Oil Quantities. IP Petroleum Measurement Manual, Part VI1 Section 2 – Guide to Automatic Sampling.
ISA STANDARDS ISA Standards S 5,1 1983 ‘Instrumentation Symbols and Identification’ 3rd edition.
ISO STANDARDS ISO 1000 : 1981 ‘ SI Units and recommendations for the use of their multiples and of certain other units’ – 2nd edition 1981. (Latest 3rd Edition 1992-11-01 Amendment 1 199811-01) ISO 1998-6 Petroleum Industry – Terminology – Part 6: Measurement – First Edition ISO 2714 Liquid hydrocarbons – Volumetric measurement by displacement meter systems other than dispensing pump. ISO 2715 Volumetric measurement by turbine meter systems
PTS 32.32.00.43 January 2010 Page 39 ISO 3170 Petroleum liquids – Manual sampling ISO 4124 Liquid Hydrocarbons – Dynamic measurement – Statistical control of volumetric metering systems ISO 4267-2 Petroleum and liquid petroleum products – Calculation of oil quantities – Part 2: Dynamic measurement. ISO 5024 Petroleum liquids and liquefied petroleum gases – Measurement – Standard reference conditions ISO 5168 Measurement of fluid flow – Evaluation of uncertainties ISO 6551 Petroleum liquids and gases – Fidelity and Security of dynamic measurement – Cabled transmission of electric and/or electronics pulsed data ISO 7278-1 Liquid hydrocarbons – Dynamic measurement – Proving systems for volumetric meters – Part 1: General principles ISO 7278-2 Liquid hydrocarbons – Dynamic measurement – Proving systems for volumetric meters – Part 2: Pipe provers ISO 7278-3 Liquid hydrocarbons – Dynamic measurement – Proving systems for volumetric meters – Part 3: Pulse interpolation techniques ISO 7278-4 Liquid hydrocarbons – Dynamic measurement – Proving systems for volumetric meters – Part 4: Guide for operators of pipe provers ISO/TR 9494 Petroleum liquids – Automatic pipeline sampling – Statistical assessment of performance of automatic samplers determining the water content in hydrocarbon liquids ISO 10790 Measurement of fluid in closed conduits – Guidance to the selection, installation and use of Coriolis meters (mass flow, density and volume flow measurements)
PTS 32.32.00.43 January 2010 Appendix 1 APPENDIX 1
LIQUID HYDROCARBON METERING SYSTEM TYPICAL SCHEMATIC DIAGRAM
PTS 32.32.00.43 January 2010 Appendix 2 APPENDIX 2
TYPICAL FLOW CHART – APPLICATION FOR ACCEPTANCE OF CUSTODY TRANSFER METERING SYSTEM (IN MALAYSIA)
Letter to SIRIM/CUSTOMS – Request for Approval
Presentation to SIRIM/CUSTOMS, Detailed spec, Diagram
Not agree
More information or change design
Agree
Detail design, procedure/FAT
SIRIM/PMU (Host Authority) present at site – SAT/ Prover Calibration/Validation No 1 - Witness
Issue temporary approval letter subject to further test
Fail
Pass with condition
Issue temporary approval letter subject to further test
Pass
PMU Issue approval letter for use/ SIRIM issue calibration certificate
System is officially used
Last Page of this PTS
