General Principles of Gas Chemical Products Sampling GB 6681-86 “The General Principles for Gas Chemical Products Sampling” provides criteria for sampling variety of gas chemical products, as well as provisions and modeling diagrams of sampling device. This standard effectively protects the fair trading, market supervision and inspection of gas chemical products and is applicable to liquefied hydrocarbon gases, compressed gases, liquefied natural gas and their mixtures, and to other kinds of gas chemical products during transportation, storage and use by civil sector, or sales by gas production enterprises. 1.Scope 1.1 This Standard specifies the general principles of sampling of all kinds of liquefied hydrocarbon gases, compressed gases as well as liquefied natural gas and their mixtures (hereinafter referred to as gas chemical products); it is applicable to such circumstances as production, transportation and sale of the gas chemical products and for storage and use in the civil sector. 1.2 This standard does not apply to the sampling principles for tracergs, special gases and some combustible and explosive gas products, or the sampling principles for gas which results from chemical synthesis process . 2. Sampling plane. Sampling plane refers to the specified position on the equipment where the sample is taken. According to the container shape, the sampling plane can be divided into the three categories : horizontal type, vertical type and outlet type. 3. Sampling methods and principles 3.1 Sampling method. Depending on the influences to technical parameters of the equipment and the operating pressure, sampling for storage tanks and containers, sampling for fountain-head, pressure-reducing and metering station, and sampling for tracheal and conduit shall be done in such ways as withdrawing from the pipes, withdrawing from the stem valves and other ways. Withdrawal from stem valves is applicable to sampling of various types of tank and containers. 3.2 Sampling principles (1)The sampling time and sampling frequency shall be determined according to relevant laws and standards. (2)The sampling and sealing device shall be installed in accordance with relevant regulations in the country. (3)Samples withdrawn from the pipeline, container, fountain-head, pressure-reducing and metering station, etc., shall be taken at the same specified positions every time. (4) If the tank and container are of the same category, one sampling throat shall be provided each; if the tanks and containers are different in category, one sampling throat shall be provided for each. (5) In order to prevent sample volatility or leeching of material components , a large sample bag or tube and stuffing filler shall be provided to collect the sample and keep it intact. (6) Samples shall be retained and inspected according to relevant laws and regulations. (7) Samples shall be transported and stored in accordance with relevant regulations in the country. (8) Reasonable precautions shall be taken to prevent the sample from being polluted by foreign matters.
4. Sampling device There are three categories of sampling device depending on the type of sampling plane: horizontal, vertical and outlet. The data concerning the modeling and device provisions for these three categories are described in detail in Appendix A. 5. Report of results The inspection report of the sample shall include the following contents:(1) Sampling time, sampling location and sampling personnel; (2) Sampling device utilized; (3) Sampling laws and provisions; (4) The results of sampling and testing; (5) The conclusion. 6. Quality assurance measures In order to ensure the accuracy and safety of sampling results, the following quality assurance measures shall be taken:(1) Qualified personnel shall conduct the sampling; (2) The sampling and testing device and equipment shall comply with the relevant regulations and shall not be used if they are out-of-tolerance; (3) Due attention shall be paid to the protection of environment during sampling and testing; (4) Regular maintenance and calibration of the sampling and testing equipment shall be undertaken. 7. Notes 1, In this standard, liquefied hydrocarbon gases refer to liquefied petroleum gas and liquefied natural gas. 2, Compressed gases refer to such gases as hydrogen, oxygen, nitrogen, argon, krypton, xenon, and air,etc. 3, The range of gas chemical mixtures includes hydrocarbon mixtures, liquefied hydrocarbon gases and compressed gases mixtures and other sorts of gas chemical mixtures. 8. Reference Documents GB/T 82-1993 Sampling of apparent porosity GB/T 1169-1985 General principles for the evaluation of conformances of quality for storage tank and pressure container GB/T 1968-1993 Gas chromatographs test method GB/T 2191-1995 Gas chromatographs determination of hydrocarbons
GB 6681-86 is a standard that provides guidelines on sampling of gas chemical products. This standard is applicable to liquefied hydrocarbon gases, compressed gases, liquefied natural gas and their mixtures, and to other kinds of gas chemical products during transportation, storage and use by civil sector, or sales by gas production enterprises. The standard consists of 8 chapters covering the scope, sampling plane, sampling methods and principles, sampling device, report of results, quality assurance measures, notes, and reference documents.
This standard specifies the general principles of sampling of all kinds of liquefied hydrocarbon gases, compressed gases as well as liquefied natural gas and their mixtures, as well as production, transportation and sale of the gas chemical products and for storage and use in the civil sector. Furthermore, it does not apply to the sampling principles for tracergs, special gases and some combustible and explosive gas products, or the sampling principles for gas which results from chemical synthesis process.
The sampling plane is divided into the three categories : horizontal type, vertical type and outlet type, according to the container shape. The sampling method will usually depend on the influences to technical parameters of the equipment and the operating pressure, such as withdrawing from the pipes, withdrawing from the stem valves and other ways. Furthermore, it is important to also note that the samples withdrawn from the pipeline, container, fountain-head, pressure-reducing and metering station, etc., shall be taken at the same specified positions every time.
The sampling device consists of three categories of sampling device depending on the type of sampling plane: horizontal, vertical and outlet. The data concerning the modeling and device provisions for these devices are stated in Appendix A.
In order to ensure the accuracy and safety of sampling results, quality assurance measures should be taken, such as installation and maintenance of the sampling equipment, qualification of personnel, and regular maintenance and calibration of the sampling and testing equipment.
The report of results should include the sampling time, sampling location and sampling personnel; sampling device utilized; sampling laws and provisions; the results of sampling and testing; and the conclusion.
In conclusion, this standard effectively protects the fair trading, market supervision and inspection of gas chemical products, and provides guidelines on sampling of gas chemical products. Adhering to this standard also guarantees the accuracy and safety of sampling results.
