ISO 10715:2022 天然ガス — ガスサンプリング | ページ 6

3.1

absorption

extraction of one or more components from a mixture of gases when brought into contact with a liquid

Note 1 to entry: The assimilation or extraction process causes (or is accompanied by) a physical or chemical change, or both, in the sorbent material.

Note 2 to entry: The gaseous components are retained by capillary, osmotic, chemical, or solvent action.

[SOURCE:ISO 14532:2014, 2.2.2.6]

3.2

adsorption

retention, by physical or chemical forces of gas molecules, dissolved substances, or liquids by the surfaces of solids or liquids with which they are in contact

Note 1 to entry: For example, retention of methane by carbon.

[SOURCE:ISO 14532:2014, 2.2.2.7]

3.3

contaminant

constituent in very low levels, such as particulates, glycol, compressor oil, etc., that are assumed to be intrusive and not part of the gas to be sampled

Note 1 to entry: Such contaminants are generally harmful to the analytical equipment and if they enter the sampling process they need to be removed from the sample before it enters the analyser. However, once the contaminants enter the sampling process they continue to influence any following sample that come into contact with them. Over a period of time the accumulation of contamination in the sampling system can have a profound effect on the sample such that it is no longer representative of the mass.

Note 2 to entry: Contaminants are not to be confused with trace components that are inherent to the gas to be sampled.

3.4

desorption

removal of a sorbed substance by the reverse process of adsorption or absorption

Note 1 to entry: From solution in a liquid phase for example.

[SOURCE:ISO 14532:2014, 2.2.2.8, modified — Note 1 to entry added.]

3.5

direct sampling

sampling in situations where there is a direct connection between the natural gas to be sampled and the analytical unit

3.6

floating-piston cylinder

container which has a moving piston separating the sample from a buffer gas, where the pressures are in balance on both sides of the piston

3.7

gas sorption effect

physical process whereby some gases are adsorbed onto or desorbed from the surfaces of a solid without transformation of the molecules

Note 1 to entry: The force of attraction between some gases and solids is purely physical and depends on the nature of the participating material. Natural gas can contain several components that exhibit strong sorption effects. Special care should be taken when determining trace concentrations such as heavy hydrocarbons, water, sulfur compounds, mercury and hydrogen.

[SOURCE:ISO 14532:2014, 2.3.4.6]

3.8

high-pressure natural gas

natural gas with a pressure exceeding 0,2 MPa

3.9

hydrocarbon dew point

temperature, at a given pressure, at which hydrocarbon vapour condensation begins

3.10

incremental sampler

sampler which accumulates a series of spot samples into one composite sample

3.11

indirect sampling

sampling in situations where there is no direct connection between the natural gas to be sampled and the analytical unit

3.12

liquid separator

unit, in the sample line, used to collect liquid fall-out

3.13

purging time

period of time during which a sample purges a piece of equipment

3.14

representative sample

sample having the same composition as the natural gas it is attributed to, when the latter is considered as a homogeneous whole

[SOURCE:ISO 14532:2014, 2.3.4.2]

3.15

residence time

time it takes for a sample to flow through a piece of equipment

3.16

retrograde condensation

production of a liquid phase of heavy hydrocarbons at a particular pressure and temperature where, at that same temperature, the gas stays in a single phase at a higher pressure as well as at a lower pressure

Note 1 to entry: Retrograde behaviour describes the non-ideal phase properties of hydrocarbon gas mixtures, such as natural gas.

3.17

sample container

container for collecting the gas sample when indirect sampling is necessary

3.18

sample line

line provided to transfer a sample of the gas from the sampling point (3.21) to the sampling device or the analytical unit

Note 1 to entry: Devices necessary to prepare the sample for transportation and analysis (conditioning unit) can be part of it.

3.19

sample probe

device inserted into the gas source, used to extract a sample and to which a sample line (3.18) is connected

3.20

sampling place

whereabouts along the gas pipeline or on the process plant where the sample probe (3.19) is located

3.21

sampling point

exact point in space defined by the sampling place (3.20) , the sampling position (3.22) and by the location of the inlet on the sample probe (3.19)

3.22

sampling position

location within the cross-sectional area of the gas pipeline or process plant at the sampling place from where a sample is taken

3.23

spot sample

sample of specified volume taken at a specified place at a specified time from a stream of gas

3.24

trace component

component present at very low levels

Note 1 to entry: Trace components generally include hydrocarbons or groups of hydrocarbons above n-pentane and other components listed in ISO 14532.

3.26

wetted surface

surface of the material in contact with the sampled gas