API MPMS 8.2:2020 pdf free download.Manual of Petroleum Measurement Standards Chapter 8.2 Standard Practice for Automatic Sampling of Petroleum and Petroleum Products
5. Representative Sampling Components
5.1 The potential for error exists in each step of the sampling process. The following describes how sampling system components or design will impact whether the sample is representative. Properly address the following considerations to ensure a representative sample is obtained from a flowing stream.
5.1.1 Location—Locate the sampling system close to or at a position where the custody transfer is deemed to have taken place. The quality and quantity of the linefill between the extractor and the sample container may be significant enough to impact the quality of the sample.
5.1.2 Conditioning of the Flowing Stream—Disperse and distribute (homogenize) the sample stream at the sample point so that the stream components (for example oil, water, and sediment) are representative at the point of the slip stream sample loop inlet (if used) or where the sample is to be extracted.
5.1.3 Sample Extraction—Take grabs in proportion to flow. However, ifthe flow rate during the total batch delivery (hours, days, week, month, and so forth) varies less than 610 % from an average flow rate, and if the sampling stops when the flow stops, a representative sample may be obtained by the time proportional control of the sampling process.
5.1.4 Sample Containers—The sample container shall be capable of maintaining the sample’s integrity, which includes not altering the sample composition. Minimize the venting of hydrocarbon vapors during filling and storage and protect the sample container from adverse ambient elements. The sample container should also be compatible with the fluid type to avoid degradation ofthe sample container and possible leakage ofthe sample.
5.1.5 Sample Handling and Mixing—Provide a means to allow the sample to be made homogenous before extraction of aliquots for analysis, retention, or transportation. For more information regarding the handling and mixing of samples, refer to Practice D5854 (API MPMS Chapter 8.3).
5.1.6 System Performance Verification—Perform test(s) to verify the system is performing in accordance with the criteria set forth within this practice or as otherwise agreed.
5.1.7 Performance Monitoring—Provide performance mea- surement and recording of the sampling system to validate that the system is operating within the original design criteria and compatible with the current operating condition.
6. Design Criteria 6.1 The following items shall be addressed when designing a sampling system:
6.1.1 Volume of sample required for analysis and retention;
6.1.2 Conditions (temperature, pressure, viscosity, density, minimum and maximum flow rates, sediment, water, and contaminants);
6.1.3 Type of fluid (crude oil, gasoline, diesel, kerosine, or aviation fuel);
6.1.4 Grabs per Batch—Ensure the sample extractor(s) samples at a high enough frequency to obtain the required number of grabs without exceeding the limits of the equipment or other sampling system constraints. Increasing the number of grabs taken per batch reduces sampling uncertainty as de- scribed in Annex A1. For large custody transfer batch quantities, to ensure representativeness of the total volume of extracted sample in the sample container, some operators have set an expectation that is equivalent to a margin oferror of0.01 with 95% confidence. Eq A1.6 calculates this to be 9604 grabs per batch. In practice, a rounded up recommended value of 10 000 grabs per batch is often used in industry. Small batch sizes, small capacity of the primary sample container and other sampling system constraints may result in designs with a different design criterion than 9604 grabs per batch. For additional information on refined product sampling, refer to Section 19.
6.1.5 Batch Size(s)/Duration—Ensure the sample extrac- tor(s) samples at a high enough frequency to obtain the required sample volume without exceeding the limits of the equipment; 6.1.6 Homogeneity of the Fluid/Stream Conditioning— Ensure the pipeline content is homogeneous at the point of extraction (sample point) over the entire flow range of all anticipated product types. Give special consideration to viscosity, density, and vapor pressure;
6.1.7 Consider the interface between batches; API MPMS 8.2 pdf download.API MPMS 8.2:2020 pdf free download
