For the energy of displaced gas 5 2. Periodic instruments recalibration 6 2. Use of gauge tables 6 3. Correction tables 6 3. Approval by authorities 12 3. Inaccuracy of the table 12 3. Main liquid level gauging devices 12 3.
Timing of the level measurement 16 3. Readings 16 3. Correction of readings 16 3. Use of spare level gauge 17 3. Complete unloading tank stripping 17 3. Cargo Liquid Lines 23 4. Device 23 4. Testing and accuracy 25 4. Main devices 29 6. Description of vaporising devices 29 6. Auxiliary vaporisation control devices 29 6. Operating parameters 31 6. Gas sample bottles 32 6. Direct piping to gas analyser 32 6. Read also. Total Comments: 0.
Besides, accuracy GCV 0. GCV both variables are obtained from the LNG composition is taken into account negative For the purposes of Custody Transfer Handbook, correlation in this case: increase of density When a number is given without any further the unloaded or loaded energy is calculated with implies decrease of GCV, and vice versa , the information, it is generally interpreted so that the following equation: above figures decrease slightly.
Rounding shall not be parameters to obtain an equal number of replaced by truncation i. Uncertainty of the energy transfer determination impact of rounding of numbers is shown in Appendix Ship-to-ship LNG transfer operations Ship-t o-shi p transfer operati ons Ship-to-ship STS LNG transfer operations The method to obtain the energy transferred in done by an independent third party as enhance the transfer of LNG from one vessel to a STS operation depends on the contract for instance the independent surveyor.
This option does not take into without receiving facility on shore. Regasification Unit is used. This is also not the best responsible to provide and maintain the custody option, as it is not always possible to and to send the natural gas to a shore gas determine if the gas in the pipeline has pipeline.
In this case there compatibility, ship-to-ship communication and are some alternatives to be considered: For ship-to-ship LNG transfer operations from a cargo management in particular sloshing limits, regular LNG vessel into another regular LNG boil-off management and cargo transfer rate. It is connection to a shore jetty or pipeline. Otherwise one of the above mentioned methods might be used. In this case the gas sampling system installed on the pipeline s of the receiving terminal are to be used to determine the LNG quality transferred.
It is recommended to use the sampling system which is installed as close as possible to the unloading vessel in case more than one sampling system is available.
Loading and unloading of small scale vessels Loa ding a nd unloa ding of small scal e vess els performing small ship operations at a terminal on board a small scale vessel consists of a level Small scale vessels can be defined by various designed for large scale carriers, and modified to gauge and calibration tables.
As described in characteristics, such as vessel capacity, flow rate accept small scale vessels, e. The typical cargo compatibility of the small scale vessel with the an LNG volume as determined in the cargo tank capacity range for a small scale LNG vessel is large scale terminal. Furthermore, whilst large tables.
Most of the small scale for LNG bunkering operations. Many of the newly constructed vessels These loading or unloading operations will have previous cargo may differ from LNG.
Older small scale vessels designed measurement see section In this manifolds with hard arms or cryogenic hoses Although be required.
One difference is the number of This must be considered when managing the temperature sensors per tank, as the smaller return vapor flow during un loading operations. Volume type C tanks will have less than 5 temperature Un loading of small scale carriers brings some probes per tank as normally required for large The volume of the LNG transferred on a small additional considerations when compared to scale LNG vessels. In addition, many of the small scale operation is dependent on the classical large scale ship-to-shore transfers.
Both of these points may terminal. The agreements. Unlike the traditional large scale performed at pressures higher than the limitations of the RKM method in regard of the LNG vessel tank design, the smaller type C tanks atmospheric pressure, corresponding to the LNG components do also apply to this method.
Please note these measurements known as the Enhanced Revised Klosek and systems and accuracy ranges are subject to ship McKinley ERKM Method [22] which can be with an estimated uncertainty of: design and may vary among the global fleet. The uncertainty of the well- known RKM method [9] was reported to be 0. These may contribute to the calculated with the GERG equation of state general industry acceptance of in-line flow [23]. Afterwards, the performance of the ERKM meters for custody transfer use see section method was verified by means of highly The The uncertainty rises to 0.
Loading and unloading of small scale vessels : density of the LNG according to the These operations may be : density of the LNG according to the determination for small scale LNG operations is summarized into the following categories: 1. Closed operations: many small scale Revised Klosek and McKinley Method, see tables identical to those used in large scale un loading vessels are able to operate at much A to A of Appendix 16 for the molar operations.
The GCV measurement and higher cargo tank pressures than volumes vi and the correction factors k1 and k2 calculation methods as specified in sections 6, 7, traditional large scale carriers. As such, according to the extended temperature range of 8 and 10 of this document can be fully applied to there may be occasions where a vessel the Enhanced Revised Klosek and McKinley small scale LNG operations, but special care elects to un load without the vapor Method should be taken to ensure the proper location return connected.
Forced gas return: during re loading Sample probes shall be bi-directional if used in operations it may be required to lower temperature of the mixture the reverse flow direction. This enable correct sampling. Gas displaced composition due to flashing inside the : critical temperature of the pure component Differing designs of terminals and carriers cargo tanks. More details on how to i, see Table A of Appendix Loading and unloading of small scale vessels take this into account can be found in These factors should be considered when output flows of the ship, as shown in figures 12 section For small scale Once mass or flow meters are installed in both LNG and BOG lines, the determination of the vessels, the individual cargo tank uncertainty, the accuracy of the level measurement, and a energy transferred can be performed by using these measurements taken in the input and where reduced number of cargo tanks, may all contribute to an additional overall uncertainty.
Reloading operations in regasification terminals Reloadi ng operations in rega sification terminal s transferred and hence may have a negative An alternative way of taking into account this Regasification terminals are designed to receive impact on the energy balance of the terminal.
Some of could be to apply a correction factor to the total them have recently been adapted to diversify This error could be avoided by calculating the energy transferred based on the total quantity their activities such as for re loading operations. For safety and there will only be minor flashing and ageing of could be the application of a mass balance to efficiency reasons, carriers may require to the LNG, hence the total gas return quantity will the ship, for which a proper measurement of the decrease the final LNG temperature, which is be close to the volume of gas displaced.
In this gas return flow and quality would be required, in generally achieved by keeping the pressure low case the correction factor remains 1 and the addition to the devices already used in the LNG in their cargo tanks by sending a significant total energy transferred can be calculated by Custody Transfer Handbook.
Due to this LNG 2. However, the more gas is returned from the iterative calculation method for determining the transfer operation with negative pressure ship to the terminal e.
As example based on the LNG quality obtained from the sampling gas return flow. As the BOG volume error has a a number of performed reloading operations at system of the terminal. This phenomenon is negligible impact on the overall uncertainty in different regasification terminals , the correction similar to the natural ageing of LNG during a the molar balance, a meter for process factor may vary from 1 up to 1. Reloading operations in regasification terminals The application of the appendix 17 to calculate the LNG quality reloaded or even the LNG volume reloaded in accordance with the simplified method , will affect the loading documents, so all parties involved regasification terminal operator as well as terminal user which has a contractual relationship with the terminal operator shall agree in advance of the reloading operation about the information to be included in the loading documents i.
LNG sales contract custody transfer checklist LNG sales contract custody transfer che cklist The following is a tabulation of custody transfer - Composition limits mercury issues to consider for inclusion in an agreement methane oil for purchase and sale of LNG. LNG sales contract custody transfer checklist - Condition of ship, shore at gauging prior to Method of analysis gas and at completion of LNG transfer e. Annexes Section It is however recommended to consistently and coherently use either ISO or GPA references or other consistent contractual requirements.
These methods are regularly updated and readers are strongly advised to check that they are in possession of the latest issues. Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method.
Part 2: Single-phase properties gas, liquid, and dense fluid for extended ranges of application. Basic and general concepts and associated terms VIM 1.
JCGM , Evaluation of measurement data ship-shore interface. HM 21, Calculation procedures for static and practices CBP in the European natural gas dynamic measurement of light hydrocarbon industry, e.
Annexes value, harmonized units for calorific value and Wobbe number. Annexes Continuous sampling system with compressor Figure A6. Dewerdt et B. Corgier - Janvier Kaiser Optical Systems, Inc. Dewerdt — Mars Dewerdt — Applications Vol. Shen, T. Gao, W. Gu — Journal of Chemical Engineering Data vol. Tietz, M. Richter, R. Gao, T. Shen, W. Lin, A. Kunz, W. Wagner — - Journal of Chemical and Engineering Data vol. Kleinrahm, R. Span — The Journal of Chemical Thermodynamics vol. Grubbs and Glenn Beck.
Technometrics Vol. Coordinator: VSL. An accepted practice for ship cargo transfer is conventionally measured liquid meters, although they do not specifically LNG proving to a traceable standard does not by volumetric gauging for custody transfer.
Technology exist at the time of this publication. While in-line However, the question is often asked, can in-line selection can be evaluated based on the meters offer custody transfer quality LNG flow measurement be used for custody pressure loss available and flow rates required.
Without a prover, a meter could have address that topic. LNG proving has several Performance Ultrasonic meters require a density calculation hurdles that must be overcome: compensation e. Klosek-McKinley or Costald , but have no for temperature changes, capacity, elimination It has been demonstrated that both ultrasonic size or pressure drop limitations. From a flow measurement noted that one major joint venture is using in- seem practical, and a feasible concept has yet to perspective, this application presents few line measurement for allocation not custody be developed.
These challenges would flashing 2-phase flow occurs. Testing at a facilities have installed in-line meters as check impact the design of an LNG prover regardless of working LNG loading facility has shown that a meters in order to verify tanker loading the physical principles to be employed, e. Coriolis mass meter will agree with an ultrasonic measurements. Custody published uncertainties of both devices.
Annexes proving is developed and established in commercial use. Once it has, in-line measurement will be an acceptable alternative or a backup to ship measurement. The principle of laser type level gauge is based on a dual transmitter optical head composed of an emitter and a receiver, mounted on the top of the cargo tank. The emitter sends a laser beam down towards the surface of the liquid; the signal is reflected from the surface, detected by the receiver cell and send back to the unit control.
The system is calibrated at several target levels of the tank. Annexes involved. In the last decade we have seen a worldwide development of short term and spot cargo LNG tanks. It should be noted that at the time of writing trade, involving two new operating trends in there is still limited knowledge, reporting and With regard to safe operating practices, both LNG shipping: field experience regarding stratification and GIIGNL and SIGTTO published some rules of good practice in this respect: rollover issues in cargo tanks of LNG carriers.
LNG carriers. Annexes tank height , and then to reload it with a fresh minimum heel level, typically only 0. Here are a few proposed items for such a vapor pressure between the LNG parcels procedure. Filling an LNG cargo tank with a heel demonstrate in full detail and in writing be calculated with the same method. Therefore, before board the LNG carrier.
Annexes tank, as a guidance the following criteria for these LNG shore tanks are recommended: Max. Annexes Notes: 1 For measurement of temperature in the gaseous phase, see Section 4. The correction shrink is generally referred to as tape correction. On Moss ships, there is also a correction called shrinkage factor.
In this case the position of the gauge is at the starboard side of the ship's centre line. In this case the position of the gauge is on the stern-side of the sideline of the tank. These tables are established for heights varying mm by mm, see example in Table A Appendix 4 on the basis of certified tables indicating volumes for heights varying cm by cm. An example is given in Table A Appendix 4 for the empty tank No. Heights and corrections are in meters. The heights and the corrections are in meters.
Annexes compound see Figure A7. New technology, for information only, see illuminated as well as their relative abundance. This also avoids the need for the phase change or molecular control room. An initial calibration of the Raman spectroscopy is a form of vibration separation common with other analytical equipment is performed at the factory prior to spectroscopy where a material of interest is methods.
Due to the fact that the Raman effect shipment. Once installed on site, a simple illuminated by a highly monochromatic light calibration of the fibre transmission intensity is source, typically a laser, and the resulting is a relatively weak process, with the currently available technology it is typically not suitable all the calibration that is needed.
Analyser scattered light is analyzed. The scattered photons have the same components in LNG. Laboratory and LNG field testing allowed for the energy frequency and, therefore wavelength development of a mathematical model to The adaptation to LNG colour as the incident photons.
However, a convert the Raman spectrum to a composition small fraction of light approximately 1 in For LNG analysis a cryogenic optical probe and and energy content. This model will be photons is scattered at optical frequencies an internal calibration process were developed. The process diagnostics automatically. The actual molecular excitation takes The energy of a molecular vibration mode Data was collected on several LNG carrier place approximately to microns off the depends on the molecular structure of the window.
The results of the material. The probe repeatability is better than 0. Annexes is better than 0. After analysis, the bulk of the 0. This may be further improved through the use of a more sophisticated model that incorporates more extensive field and laboratory analysis.
If it is shown to be an outlier, observation, compute the test statistic G1: and exclude it, and repeat the test at the other extreme e. Table A shows the data from the GC. Note that if one component is detected as outlier, the whole analysis must be eliminated. Next, the test is repeated to the 10 analyses remaining, computing the G1 statistic. Ethane C2H6 0. Two interpolations must be carried out: 1 on the temperature, 2 on the molecular weight.
Methane CH4 0. The numerical value of the property Next, there is an example calculation of the GCV shall be rounded to the least significant figure in Gross Calorific Value: uncertainty for the composition of a typical LNG the rounded value of the expanded uncertainty. Kenbaar, NEL. Sakariassen, MetroPartner a. Doc no. Annexes Additional the molecular volume temperature For calculating the uncertainty of the LNG density the contributors with their uncertainty references are: uncertainty is included according below formula: Symbol Description Uncertainty Reference Individual component Amount based acc.
The possible error in these values is calculation method acc. The combined uncertainty composition Nitrogen 0. Typical reported values are: Note 1 Note 2 3 Volume m3 New economic impact GCV: 0. DEP Annexes Sequence of events compressor could be stopped, and the at an intentionally reduced rate, e.
At this meeting and act very prudently especially at the pumped out on unloading, immediate ship and shore should agree how to take beginning of the unloading operation. As a extensive flashing in the shore tanks appropriate precautions in concert. Make sure that for the increases by approx. If you detect any unloading. As a guide it is come through, the shore tank pressure appropriate unloading strategy in concert proposed that LNG density differences be decreased and the large unloading with the ship.
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