0405_002

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					Saudi Aramco 7180 (5/89)
                                                                                             G.I. NUMBER
                                                                                                            405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                                  ISSUE DATE         REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                               19 FEB 1995         15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                                 APPROVAL           PAGE NUMBER
                                                                                                   VP, ES          1    OF   8


         CONTENT:
         1.     PURPOSE AND SCOPE
         2.     RESPONSIBILITIES
         3      METERING EQUIPMENT
         4.     OPERATION
         5.     INSPECTION & CALIBRATION
         6.     SEALING REQUIREMENTS
         7.     CALCULATION & BILLING
         8.     RECORD KEEPING
         9.     PROCEDURE FOR FOLLOW-UP
         10.    APPROVALS

         1.0       * PURPOSE AND SCOPE
                  These instructions shall be followed for all custody transfer of natural gas and ethane for proper
                  accountability and measurement control.

         2.0      RESPONSIBILITIES
                  2.1      Operating Department Responsibilities

                           2.1.1   Each Operating Department involved in the custody transfer of natural gas and/or ethane
                                   shall be responsible for the implementation of this instruction. The operating department
                                   shall assign competent personnel whose responsibilities shall include, but not be limited
                                   to, the following:
                                   A.    Apply identifiable seals as necessary to meters, bypass valves and other
                                         equipment that have an effect on measurement accuracy.
                                   B.    Monitor and keep records, as required for control and auditing purposes.

                           2.1.2   The Operating Department shall ensure that the operating instruction manuals are
                                   prepared, or if already in existence, revised, to reflect accuracy and accountability in the
                                   custody transfer of gas. These operating instructions and any subsequent revision shall
                                   be reviewed by the Custody Measurement Unit of Electrical Systems Division/
                                   Consulting * Services Department (CMU/ESD/CSD) for concurrence prior to their
                                   approval and implementation.
                           2.1.3   The Operating Department shall also maintain accurate records of gas transferred to each
                                   customer.

                  2.2      Maintenance Department Responsibilities

                           2.2.1   The Maintenance Department involved shall ensure that all instrument reference
                                   standard test equipment (e.g., dead-weight tester, decade box, volt-ohm-ammeter, gauge


* CHANGE                   ** ADDITION               NEW INSTRUCTION                 COMPLETE REVISION                  8
Saudi Aramco 7180 (5/89)
                                                                                            G.I. NUMBER
                                                                                                          405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                                 ISSUE DATE        REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                              19 FEB 1995       15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                                APPROVAL          PAGE NUMBER
                                                                                                 VP, ES          2   OF   8


                                    tape, etc.) being handled by Saudi Aramco (or outside contractors) are recalibrated/
                                    checked and certified by a third party calibration agency duly accredited by an
                                    authoritative body such as NIST or SASO.

                                    NOTE: Note: The optimum mean time between calibration/checking will be
                                              determined using the recommendation of the calibration agency, usually only
                                              after conducting at least two or more consecutive years of calibration or
                                              checking.
                           2.2.2    The Maintenance Department shall ensure that all operating instruments used are
                                    properly maintained and calibrated at predetermined intervals against the applicable
                                    reference standards mentioned in item 2.2.1 above, and sufficient number of calibrated
                                    and certified test equipment are available, to ensure continuity.

                  2.3      * Custody Measurement Unit/ESD/CSD Responsibilities

                           2.3.1    * CMU/ESD/CSD shall conduct surveys of the custody transfer metering stations to
                                      check proper implementation of this instruction and the operating instructions and to
                                      assure good measurement control. The period between surveys of a custody transfer
                                      point shall not exceed five years.
                           2.3.2    A survey report will be submitted to the Operating Department, and if there are action
                                    items, the Operating Department shall advise the action plan for implementing the action
                                    items. Refer to Section 9 for follow-up procedure on survey recommendations.

         3.0        METERING EQUIPMENT
                  3.1      Meters

                           Custody transfer measurement of natural gas and ethane shall be through orifice meters. The
                           orifice plate shall be removable concentric type with single or double chamber fittings.

                  3.2      Flow Computer

                           3.2.1    On-line data gathering and flow calculation for net volume at standard conditions shall
                                    be by flow computers. Manual calculation using recording charts, chart integrators etc.,
                                    shall only be used on a temporary basis in case of failure ofthe flow computer.
                           3.2.2    The flow computer shall be capable of directly receiving the signals from the
                                    temperature, pressure and differential pressure transmitters.
                           3.2.3    The flow computer shall be used to calculate the total energy content, if on-line gas
                                    composition data is available.

                  3.3      Temperature Measurement

                            Temperature shall be measured using Resistance Temperature Detector (RTD) probes.


* CHANGE                    ** ADDITION              NEW INSTRUCTION                COMPLETE REVISION                8
Saudi Aramco 7180 (5/89)
                                                                                            G.I. NUMBER
                                                                                                          405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                                 ISSUE DATE         REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                              19 FEB 1995        15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                                APPROVAL           PAGE NUMBER
                                                                                                 VP, ES           3   OF   8


                  3.4      Low & High Differential Pressure & Static Pressure Measurement

                           Only orifice flange taps shall be used for pressure measurement. The static pressure shall be
                           measured at the downstream flange tap.

                  3.5      Heating Value and Relative Density Determination

                  *        Heating value and relative density (specific gravity) shall be determined either by an on-line gas
                           chromatograph, or by analysis of the gas sample obtained from the automatic sampler of the
                           metering station. Samples shall be collected at least once a week.

         4.0      OPERATION
                  Metering station instruments shall normally be operated within the following ranges to maximise the
                  accuracy of measurements:

                      Differential Pressure : 10 to 95% of full scale
                      Static Pressure      : 60 to 80% of full scale
                      Temperature          : 50 to 75% of full scale

         5.0      INSPECTION & CALIBRATION
                  Inspection check, maintenance and calibration schedule shall be as follows:

                  5.1      * Calibration Frequency

                           Simultaneous calibration of temperature, pressure and differential pressure instruments is
                           recommended. The maximum duration between calibration shall not exceed six months.

                  5.2      Temperature Instruments

                  *        The temperature transmitter shall be calibrated using a resistance decade box properly certified,
                           as stated in section 2.2 above. The maximum allowable deviation shall not be more than 0.2%
                           of the span or 0.03 mA for a 4 to 20 mA output signal. The complete loop (RTD, transmitter and
                           the flow computer) shall be checked against an ASTM glass thermometer certified by Saudi
                           Aramco Laboratory and placed in the test thermowell. Necessary corrective action shall be taken
                           If the reading differs by more than 1 deg F.

                  5.3      Pressure Instruments

                           5.3.1   All pressure instruments shall be checked against a reference standard (test equipment)
                                   traceable to NIST or its equivalent. Dead-weight testers, if used, shall have the NIST
                                   stamped on the weights, indicating the local gravity at which they were calibrated.


* CHANGE                    ** ADDITION              NEW INSTRUCTION                COMPLETE REVISION                 8
Saudi Aramco 7180 (5/89)
                                                                                               G.I. NUMBER
                                                                                                             405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                                    ISSUE DATE         REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                                 19 FEB 1995         15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                                   APPROVAL           PAGE NUMBER
                                                                                                    VP, ES           4    OF   8


                           5.3.2    * Full range calibration shall be performed on the static pressure and the differential
                                      pressure instruments. The maximum allowable error shall not be more than 0.25%
                                      of span or 0.04 mA for a 4 to 20 mA output signal. All sensing lines shall be checked
                                      for leaks and blown to clear any blockage.
                           5.3.3    The differential pressure instrument shall be checked for zero differential at operating
                                    condition. Any error determined at zero may be applied to the average differential
                                    pressure recorded from the date of last check to adjust the billing if required by
                                    contractual agreement or management request.

                  5.4      Orifice Plates

                           Orifice plates shall be checked during instrument calibrations. The plate shall be free of rust,
                           deposit and the edge shall have no nicks or roundness sufficient to reflect a beam of light when
                           viewed without magnification. The meter plate shall be inspected for flatness per AGA Report
                           3. Any damaged plate shall be rejected and a standard plate, identical to the original one, shall
                           be installed.

                  *        If process conditions have changed, either the differential pressure transmitter must be
                           recalibrated or the plate is re-sized for the new conditions. If the differential pressure or the beta
                           ratio exceeds the limit set forth in the Saudi Aramco Standard SAES-J-101, then a waiver is
                           required to be submitted to CSD for approval. Pertinent data shall be revised in the flow
                           computer after installing the new plate.

                  5.5      Meter Tubes & Straightening Vanes

                           Meter tubes and straightening vanes shall be inspected for any blockage or damage during a
                           consumer plant shutdown for an extended period or whenever required due to a certain metering
                           problem. Replacement shall be of the same standard as the original installation.

                  5.6      Gas Chromatograph

                           The gas chromatograph shall be checked every month using a gas mixture of known
                           composition (primary standard gas mixture). The gas chromatograph shall be recalibrated if the
                           peak area of the major component differs by more than 0.5%.

         6.0       SEALING REQUIREMENTS
                  6.1      All bypass piping shall be blinded. Bypass valves shall be sealed closed.

                  6.2      Flow computers shall have a key lock and/or password protection to prevent unauthorized entry
                           of orifice coefficients or any calibration data which affect billing.




* CHANGE                    ** ADDITION               NEW INSTRUCTION                  COMPLETE REVISION                  8
Saudi Aramco 7180 (5/89)
                                                                                            G.I. NUMBER
                                                                                                          405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                                 ISSUE DATE         REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                              19 FEB 1995        15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                                APPROVAL           PAGE NUMBER
                                                                                                 VP, ES           5   OF   8


                  6.3      If the metering station is accessible to unauthorized personnel, all equipment which may affect
                           the accuracy of measurement (e.g. temperature and pressure transmitters,etc.) shall be sealed to
                           prevent unauthorized adjustment.

         7.0      CALCULATION AND BILLING
                  7.1      Net Volume

                           Net volume shall be reported as Standard Cubic Feet (SCF) at 60 degree Fahrenheit and 14.73
                           psia.

                           7.1.1   Natural Gas

                                   The calculation for natural gas shall be based on the American Gas Association (AGA)
                                   Report 3, Part 3 (issued 1992) and Report 8 (issued 1992). The equation and the
                                   applicable constants are given below:

                                   7.1.1.1    *   The following flow equation shall be used for the natural gas supply to all
                                                  customers in the Jubail Industrial area, replacement of the existing flow
                                                  computers and new customers in other areas:

                                          *       Qv = Fn Cd. Y2.Ftf.Fgr.Fpv.Fwl. Pf2.hw
                                                  Where:
                                                  Qv = Flow rate in Standard Cubic Feet per Hour (SCFH)
                                                  Fn = Numeric conversion factor
                                                      = 338.196 Ev.D**2.Beta**2


                                                  Ev = Velocity of approach 1/ 1 – Beta 4
                                                  D     = Pipe diameter at flowing temperature
                                                  d     = Orifice diameter at flowing temperature
                                                  Beta = d/D , Beta ratio
                                                  Cd = Coefficient of discharge for Flange taps
                                                  Y2 = Expansion factor for downstream tap location
                                                  Ftf = Flowing temperature factor
                                                  Fgr = Relative Density Factor
                                                  Fwl = Gauge location factor, applied to correct for the local
                                                           gravity    effect on dead weights. See note a below
                                                  Fpv = Supercompressibility factor, AGA Report 8.             See
                                                           note b below
                                                  hw = Differential pressure in inches
                                                  Pf2 = Static pressure in psia (down stream)



* CHANGE                    ** ADDITION              NEW INSTRUCTION                COMPLETE REVISION                 8
Saudi Aramco 7180 (5/89)
                                                                                            G.I. NUMBER
                                                                                                          405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                                 ISSUE DATE        REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                              19 FEB 1995       15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                                APPROVAL          PAGE NUMBER
                                                                                                 VP, ES          6   OF   8




                                   7.1.1.2    The following flow equation is used for customers having Jiskoot or UGC flow
                                              computers: (Reference: AGA Report 3, 1985.)
                                          * Qv = Fb.Fr.Y2.Ftf.Fgr.Fa.Fpv.Fwl._/Pf2.hw
                                             Fb = Basic orifice factor
                                             Fr = Reynolds no. factor
                                             Fa = Thermal Expansion Factor,
                                                    1 + 0.0000185 (deg. F - 68.0 )
                                             All other factors are defined in Section 7.1.1.1 above.

                             Notes:
                             a.   Fwl = 0.9986, based on latitude of 25 deg F at sea level and the dead weight testers that
                                are generally used by Saudi Aramco for the differential pressure (Ametek unit, g = 980.0
                                cm/sec**2) and static pressure (EG & G Chandler units, g = 980.665 cm/sec**2)
         *                   b. Presently, the super compressibility factor (Fpv) is calculated using AGA Report 8
                                equations for all Jubail             Industry custody transfer points. Implementations at
                                other locations shall be based on economics and mutually agreed upon by CMU/ESD/
                                CSD and Pipelines Department. Meanwhile, these locations shall continue to use AGA
                                Report NX-19.

                           7.1.2   Ethane Gas

                             *     Net volume calculations shall be based on the same equation for natural gas as per
                                   paragraph 7.1.1.1 or 7.1.1.2. However, AGA Report 3 is not applicable for the
                                   supercompressibility factor (Fpv) for ethane. It shall be derived from proper equation of
                                   state for ethane gas. Consult CMU/ESD/CSD.

                  7.2      * Heating Value and Total Energy content

                           Based on an on-line gas chromatograph or laboratory analysis of the gas and its component, the
                           heating value of the ideal gas mixture shall be calculated. The ideal heating value of the gas
                           mixture shall be converted to real gas heating value by applying compressibility factors of each
                           component. The heating value shall be reported in BTU/SCF on dry basis.

                           Total energy content shall be obtained by multiplying the total volume with the heating value
                           and reported in BTU.

         8.0      RECORD KEEPING
                  The following records shall be maintained for each station:
                  *     - Records of physical data of all equipment, including instruments and flow computer for each


* CHANGE                    ** ADDITION              NEW INSTRUCTION                COMPLETE REVISION                8
Saudi Aramco 7180 (5/89)
                                                                                                 G.I. NUMBER
                                                                                                                405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                                      ISSUE DATE         REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                                   19 FEB 1995         15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                                     APPROVAL           PAGE NUMBER
                                                                                                      VP, ES           7    OF   8


                                  custody metering station. Data shall be kept current by recording any changes made.
                                  (permanent)
                  *         -     Copy of the flow computer program version loaded at each station. (permanent)
                            -     Orifice Coefficient Record. (permanent)
                            -      Monthly Gas Record (minimum of one year).
                            -     Maintenance record of all instruments including flow computer (minimum of one year)

         9.0      PROCEDURE FOR FOLLOW-UP ON SURVEY RECOMMENDATIONS
                  9.1       * CMU/ESD/CSD shall submit a survey report to the Department Head of the surveyed
                              metering station and shall include the following items:

                                  a)      A list of violations to this GI found during the survey.
                        *         b)     CMU/ESD/CSD recommendations and suggested corrective action(s) to be taken by
                                         the proponent.

                  9.2       The proponent shall respond, within one month, stating his corrective action(s), providing a
                            schedule for implementing the recommendations. The proponent shall also provide reasons for
                            any disagreement with the recommendations.

                  9.3       * CMU/ESD/CSD shall review the response and evaluate the implementation plan and
                              schedule. If there is a disagreement, it shall be discussed with the proponent.

                  9.4       At the end of the agreed upon implementation period, a follow up visit to the surveyed station
                            shall be made to ensure that corrective actions have been taken by the proponent.

                                a. If there are items that are not completed, a letter shall be sent to the proponent listing these
                                   items and the follow-up will continue until completion.
                                b. When all items are completed, a memo to file shall be issued in this regard.

                  9.5       If there is a disagreement over items that cannot be resolved between the proponent and
                            Consulting Services Department, they shall be elevated to an appropriate level of management
                            to decide either to implement or waive these recommendations.

         10.0 APPROVALS
                  Originated by:              Manager., CSD.

                  Concurred by:               General Manager, Pipelines
                                              Vice President, Yanbu Operations




* CHANGE                        ** ADDITION             NEW INSTRUCTION                  COMPLETE REVISION                  8
Saudi Aramco 7180 (5/89)
                                                                                      G.I. NUMBER
                                                                                                    405.002
 SAUDI ARABIAN OIL COMPANY (Saudi Aramco)
 GENERAL INSTRUCTION MANUAL                                                           ISSUE DATE       REPLACES
 ISSUING ORG.     CONSULTING SERVICES DEPARTMENT                                        19 FEB 1995      15 SEP 1991
 SUBJECT:         CUSTODY TRANSFER OF NATURAL GAS AND ETHANE                          APPROVAL         PAGE NUMBER
                                                                                          VP, ES          8   OF   8


                  Approved by:           Vice President, Engineering Services




* CHANGE                   ** ADDITION              NEW INSTRUCTION             COMPLETE REVISION             8