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LNG SAMPLE TAKE-OFF PROBE

LNG SAMPLE TAKE-OFF PROBE. PURPOSE LNG custody transfer requires WI , composition and density measurements with better repeatability than 0.01 mj/m 3 (ISO 6976) and reproducibility between lab and in line GC better than 0.15% (ASTM D 1945). Precise sampling is periquite for both analysis.

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LNG SAMPLE TAKE-OFF PROBE

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  1. LNG SAMPLE TAKE-OFF PROBE

  2. PURPOSE LNG custody transfer requires WI , composition and density measurements with better repeatability than 0.01 mj/m 3 (ISO 6976) and reproducibility between lab and in line GC better than 0.15% (ASTM D 1945). Precise sampling is periquite for both analysis. SAMPLING MODES Contiuous sampling: continuous collection of LNG which is subsenquently vaporized and stored in gas holder . Discontinuous sampling: continuous collection of LNG which is subsenquently vaporized and analyse or sampled in bombs at regular intervals

  3. APPLICABLE STANDARDS ISO 8943-1991: LNG continuous sampling method ISO 8943-2004 : draft of sampling with piston cylinder EN 12838: test to assess the LNG sampling suitablility SAMPLING SUITABILITY KEYS Enthalpy rise of LNG < subcooling degree ( boiling boling point at given temperature) – Thermal insulation LNG transformation in supercritical state to eliminate fractionated vaporization which generates fluctuations in gas composition

  4. CALCULATION OF SUBCOOLING DEGREE

  5. Fractionation 4460J/Kg

  6. KEY PARAMETERS 1-Pressure drop to decreases subcooling degree: reducing pressure regulator vaporizer cannot be applied. 2- With conventional probe insulation material, process pressure must be above of 2 bar-g : the fractionation point is near of 1.5 bar-g, during loading on unloading process the pumps pressure is frequently dropping below 2 bar-g . 3- Insulation thermal conductivity is the only factor to be upgraded for low process pressure compensation 4- Sample flow vaporized is reverse proportional to enthalpy rise; with conventional probe insulation material this flow rate has to be above of 10 000 SL/H gas.

  7. KEY FEATURES OF PROBE .Super thermal insulation by high vacuum below.10-4 torr minimizing heat link by conduction and refraction with radiation shield material. Apparent thermal conductivity k value is below 0.4 milliwatt per meter- kelvin versus 18 mw/m-k for conventional probe insulation system. Sample Sample probe is supplied with certification of enthalpy rise to be < to subcooling degree. THUS FRACTIONATED DISTILATION effect will not occur upstream of vaporizer even for low pressure in line

  8. SYSTEM DESCRIPTIVE .Flange item 2 tied with vacuum jacket and assembled with high vacuum technology. .Sample isolation core valve item 3 encapsulated in vacuum jacket to isolate system from pipe-line without process service disturbance for any maintenance work. . Capillary item 4 for breaking equilibrium between pipe- line and sample take-off pressures. . Operated isolation valve item 5 with extended bonnet and pneumatic actuator item 9 – auto-switch off is provided from pneumatic logic item 8 if the temperature at outlet of vaporizer is dropping below the application set point. . Check valve item 7 is operating as pressure barrier between process line and sample volume expansion at nozzle of vaporizer. . Two thermocouple type K item 11 at inlet and outlet of vaporizer for system temperature monitoring . . High purity bellows valve item 6 with vacuum pressure gauge and generator provide facility for re-establishing vacuum if required.

  9. PROBE OTHER TESTS • Resonant frequency calculations: • As the probe tip, is recommended to be located at the centre of pipe-line , the vortex induced vibration is to be considered, mainly above of 7 m/s LNG velocity in line. • The standard BS IEC 61831 calculation with constant OD probe is applied up structural frequency at 7 m/s above this value a dedicated test program has been undertook to determine the vortex shedding (wake frequency) with varying OD probe according to the ASM PTC 19-3 standard.

  10. Constant and varying OD probes

  11. TECHNICAL SPECIFICATIONS . Pipe-line pressure: 1 to 15 bar-g . Pipe-line temperature: from –180 °C . Volume of gas vaporized: approx. 1200 l/h . Lag time through probe and vaporizer: 30 sec. approx . Thermal conductivity of probe: 0.4 milliwatt per meter- kelvin . Heating capacity of vaporizer: 0.5 Kw. . Protecting electrical code: ATEX II 2 G – group 2B- class T4 . Enclosure rating: IP 65

  12. PROBE & VAPORIZER STANDARDS COMPLIANCE - Sample probe resonant frequency calculation: -BS IEC 61831:1999 for on line velocity <7 m/s -API RP 551 for on line velocity > 7 m/s -Main welding test: APAVE certified under CODAP 2000- Rev 04-04-IA4--ASME V- APIRP 551 - Probe subcooling degree calculation: ISO 8943-1991- Annex A -Vaporizer :- capacity calculation: ISO 8943-1991- Para 6.5.2 & 6.6 - Ex-proof ATEX II 2G EExde II C T4 - Probe & vaporizer pressure test: PED 97 23 EC - calcualtions approved Bureau Veritas - Suitability testing of discontinuous sampling with lab and process GC by supplier: EN 12838- Class A of accuracy with 54 kJ/kg Gross Calorific Value and 18*10 -4 kg/m3 Density maximal random error.  - Suitability testing of continuous sampling with ISOSAMPLE 8100 piston cylinder holder and process GC by supplier: EN 12838- Class A of accuracy with 9.0 kJ/kg Gross Calorific Value and 3.0*10 -4 kg/m3 Density maximal random error.

  13. VAPORIZER & CONTROL UNIT

  14. THERMODYNAMIC + 50°C process pressure LNG transformation in supercritical state to eliminate fractionated vaporization which generates fluctuations in gas composition + 65°C -80°C P> 80 bar Critical point -150 °C Process pressure vapor liquid Liquid +vapor Vaporizerinlet 2 phases max pressure highest dew point temp Liquid state ceases

  15. SYTEM DESCRIPTIVE . Vaporizerintegrated at extremity of sample probe. . Vacuum insulation is continuous from sample take-off in pipe-line to vaporizer coil exchanger . Coil exchanger is a 2 m * 3 mm OD tubing sealed in calorific block temperature controlled. . Critical point is located at check valve and vaporization occurs in the 0.5 CC tubing volume at vaporizer coil exchanger inlet : FRACTIONATED DISTILATION effect does not occur . . Coil exchanger designed for not remaining heavier fractions . Temperature points monitored: TS1 at coil inlet - TS2 controlled at the exchanger calorific block – TS5 at vaporiser outlet – TS6 trip alarm calibrated at 135 ° (T4) .

  16. Probe / Vaporizer processing . The TS1 temperature at vaporizer coil inlet is monitored in the range of –160 to + 40°C ; the expected value is –80°C . . The vaporizer calorific block TS2 temperature is controlled at 65 °. . If TS1 rises over -50°C the TS2 controller set point is decreased from 65 to 15°C. . The TS3 temperature at vaporizer outlet is 65°C , if this temperature drops below –20°C the sample probe actuated valve is shut-off. . Processing is controlled by PLC in autosampling system or by instruments for manual sampling.

  17. LNG • AUTOMATIC • SAMPLING SYSTEM

  18. SAMPLE LINE COMPONENTS . Back Pressure Regulator item 10: to stabilise the pressure at outlet of vaporizer under 1000 SL/H in order to comply with subcooling degree requirement . The microflow regulator item 14 is provided for controlling the flow of charge holder. The charge holder cylinder is interfacing the vaporizer and the portable containers (bombs) train

  19. SPOT and CHARGE AUTOSAMPLING PID

  20. SPOT AUTOSAMPLING PID

  21. Charge Holder Piston Cylinder

  22. Charge Holder filling procedure Theholder piston cylinder features PTFEseals double piston barrier with a piston scrapper to auto-clean the cylinder electropolished wall between two samplings. Original purging is compliant with the ISO 8943-91 section 6 6 2 and 7 2 a : this purging is made through the piston shaft bore On the "ISOSAMPLE 8100" this procedure is fully automated: the buffer gas chamber been pre charged by compressed air with piston in down position, the sample chamber is reduced to the nominal zero volume before of sampling. Then the sample purge valve is actuated to open for purging the tiny dead volume between piston/end plate through the piston shaft venting to atmosphere. For a sampling line from vaporizer of 5 m with 3 mm ID tubing electropolished a purging cycle of 1min (programmable) is operated, then the purge valve is closed. Direct mounted position indicator and level switch (high and low) are provided. Stirrer is not supplied for this application.

  23. Charge bombs train

  24. Charge bombs filling procedure Charge aggregate bombs are provided with automatically/manual interchange sequential control system as well as time programmed automatically purging and filling for complete unloading sampling (about 14 hr. & programmable). The accumulated average sample gas of charge unloading is transferred to the bombs and the gas will be controlled in constant pressure of 7 bar-g at final charging.. -Procedure for purging will be as per the fill and empty method referto Annex D of ISO 10715 and Appendix C of ISO 8943-91defined according to the final pressure in cylinder : i.e: 5 cycles (programmable) at 7 bar-g.

  25. Spot holder filling procedure -The spot  holder is made and operated within the same technologie than charge holder but the volume is usually 6 time lower. The system microflow is controlling a time proportional charging of the holder piston cylinder during a period of 1 to 3 H (programmable) . At the end of this period , the holder piston cylinder supposed to store 13.5 to 40.5 L of gas is automatically isolated and connected to the spot containers train for loading a new bumb. -The six spot bumbs are loaded during the batch transfer of 10 to 12 H , then the system is stopped waiting for operator new cycle validation once the six spot bombs have been collected and replaced in the rack . The loading pressure of floating piston holder is controlled at 4 bar-g for charging and purging and at 4 bar-g as well for the bombs end charging.

  26. Spot bombs train

  27. System processing Application processed via a solenoid valve actuator BUS manifold with profibus data-link. Sampling sequence and alarm history reported on screen with data acquisition by keyboard. Communication with user via RS-232 slave MODBUS over multi-mode fiber . As addition to sampling sequence following data's are provided to / from DCS. - High / low level alarm of gas sample holder - Sample take-off valve closing - Pressure alarm at vaporizer outlet - Temperature measurement at vaporizer inlet & outlet - Temperature at vaporizer core - Sampling suspended from customer DCS

  28. Processing System

  29. System PLC

  30. AUTOMATIC SAMPLING SYSTEM STANDARD COMPLIANCES -Constant pressure piston cylinder holder : - ISO 8943 - Sept 04- draft- para 6.9 - holder residual gas purging to ISO 8943-91 sect. 6 6 2 and 7 2 a - pressure test: PED 97 23 EC - holder capacity calculation to ISO 8943 para 6.6.1 - Holder to portable container transfer: fill and empty method Annex D of ISO 10 715 or ISO 8943 para 7.3-b - Suitability testing of continuous sampling with ISOSAMPLE 8100 piston cylinder holder and process GC by supplier: EN 12838- Class A of accuracy with 9.0 kJ/kg Gross Calorific Value and 3.0*10 -4 kg/m3 Density maximal random error.

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