API MPMS 8.6 2020 pdf download.Manual of Petroleum Measurement Standards Chapter 8.6.
3.8 gasify Term used to express “vaporization” related to a treatment during a process. 3.9 intermittent sampling Continuous collection of LNG from the main line during loading/unloading operations. NOTE However, the fully vaporized LNG from the vaporizer can be directed to an online analyzer and/or intermittently pumped into a constant pressure floating piston (CP/FP) sample container on a timed basis or proportional to flow basis. A CP/FP sample container maintains constant pressure during the sampling of gas from the process line into the gas cylinder. The gas sample collected in the CP/FP sample container is for offline analysis. 3.10 LNG Liquids composed predominantly of methane. 3.11 LNG sample vaporizer Apparatus to completely gasify the LNG sample collected from the LNG transfer line. 3.12 LNG transfer line Pipeline used for transferring LNG. 3.13 offline analysis Procedure of analysis implemented on the representative sample gas that is once charged into a gas sample container or a CP/FP sample container. 3.14 online analysis Procedure of analysis implemented using analytical equipment that is directly connected through pipelines or other means to the sampling device. 3.15 online gas chromatograph Gas chromatograph that is directly connected to the pipelines or sampling device to implement online analysis. 3.16 pressure regulator Pressure-regulating valve and pressure sensor provided to keep the gas pressure constant at the gas sample holder inlet. 3.17 sample filter Filter used to protect the sampling valve for the online gas chromatograph from scoring due to the presence of foreign contaminants, such as metal shavings, dirt, and so forth. 3.18 sample probe Device inserted into the LNG to sample from the LNG transfer line to collect an LNG sample. 3.19 seal water Water used in the water-seal-type gas sample holder to preclude contact of the gas sample with the atmosphere.
3.22 waterless-type gas sample holder Holder without seal water (typically using an expandable/contractible, transformable rubber membrane) and used for collecting gasified LNG. 3.23 water-seal-type gas sample holder Holder with seal water used for collecting gasified LNG. 4 Outline of Sampling System 4.1 General Regardless of whether the sampling method is continuous or intermittent, the LNG sample collected through the sample probe provided on the LNG transfer line is gasified in the LNG sample vaporizer. 4.2 Continuous Sampling Gasified LNG from the LNG sample vaporizer outlet is continuously fed into the gas sample holder by its inherent pressure when the pressure is sufficiently high or after its pressure has been boosted by the compressor for transferring gasified LNG when the pressure is insufficient. In this process, the gas pressure in the sampling line is controlled by a pressure regulator and the flow into the gas sample holder is maintained by the gas sample holder inlet valve. The gas sample collected in the gas sample holder is fed into the gas sample container. An outline flow process diagram of the sampling system is shown in Figure 1 for a water-seal-type gas sample holder and in Figure 2 for a waterless-type gas sample holder.
5 Precautions 5.1 Precautions to be Taken in Handling LNG Because LNG has a very low boiling point, contact of the skin with LNG can cause frostbite and, if the gas diffuses into the air, it will lower the oxygen content, which can result in suffocation or, if ignited, fire. Suitable precautions shall be taken against these risks. 5.2 Partial Evaporation of the LNG Sample LNG normally exists in a state close to its boiling point. Therefore, partial evaporation readily occurs in the LNG transfer line and sampling line with minute heat input or by pressure variation. For this reason, extreme precautions shall be taken so that the collected gas sample represents transferred LNG with best possible accuracy. 5.3 Supervision During Sampling Pressures, temperatures, and flow rates in the LNG transfer line and the sampling system shall be monitored continuously. Frequent inspection of the entire system shall be made, paying particular attention to any leak or failure of the thermal insulation. Defects identified by such inspections shall be remedied immediately. 6 Apparatus 6.1 Materials Used The materials of construction of the sampling system shall have sufficient strength and durability to withstand the pressure and temperature conditions to which they are exposed. The possibility of embrittlement of materials at low temperatures shall be taken into account. Materials shall neither be affected by exposure to the fluids handled nor have any effect on the composition of the fluids being sampled.