Obtaining Natural Gas Sample
Posted on | September 12, 2008 | 2 Comments
In the analysis of natural gas quality, early stage to consider is taking a sample (sampling). Contaminants are carried at the time of sampling will certainly affect the results of the analysis. The main purpose of the sampling process is to obtain a representative sample that represents the product of the source / point-making, which is required for the purposes of physical and chemical analysis of these products in the laboratory, with the parameters and test methods specified.
Standard Methods:
1. ASTM D 1145: Test Method for Sampling Natural Gas
The procedure was differentiated based on the content of the gas to be analyzed,
Needs some differential sampling methods, namely:
- Natural gas to the main content of hydrocarbons and nitrogen,
- Natural gas that containing hydrogen sulfide and organic sulfur or other sulfur contaminants,
- Natural gas that containing CO2,
- Natural gas that containing gasoline and condensate,
2. GPA 2166: Obtaining Natural Gas Samples for Analysis by Gas Chromatography
Sampling methods based on the conditions of temperature, pressure source of gas samples and equipment available. With standard sampling procedures performed to obtain GPA spot representative sample container for analysis in laboratory. Some of the existing sampling procedures, suitable for wet gas sampling (wet / rich Natural Gas) at a pressure of 1100 psig, while for the (dry / lean Natural Gas) there is no specific limit to the pressure.
Main tools used:
- Sample container / cylinder (usually called: sample bomb)
- Transfer pipe (flexible hose)
- Separator
- Sampling Probe
1. Sample container / cylinder
- Type of sample tube made of metal with the maximum safety levels and resistance to corrosion.
- Recommended materials: from stainless steel.
- The size of the tube depending on the number of samples required for analysis in the laboratory.
- At the end of the tube, the hole output pressure gauge should be installed to ensure the tube was filled with the sample.
- To analyze the sulfur compounds, using tubes of Sulfinert Materials, to avoid sample decomposition.
2. Transfer Pipe (Flexible Hose)
- Transfer pipe made of stainless steel materials, steel, copper or other metals that are not flexible reactive with sample products.
- Stainless steel material better because of resistance to pressure or 1000 psig gas containing H2S.
- Pipe flow is best equipped with the container 2 valve cover
- Resistant to react with sample produck.
3. Separator
- Needs to obtain the representative sample.
- The existence of a liquid during wet gas sampling, resulting in a less representative sample.
- The presence of natural gas liquids, can be eliminated by installation of the correct sample probe or the use of sampling separator.
- Separator should be adjusted to the pressure vessel.
- Sampling separator can be installed permanently at the sampling point or points may be transferred from one sample to another point.
- Portable separator should be cleaned with a sample gas, and should not be any left over in the separator at the time of sampling.
4. Sampling Probe
- Needs to obtain the representative sample.
- The sample probe must be placed at the top pipe or vessel, to eliminate fluid shipped during the sampling.
- Sampling probe installed vertically in a horizontal position above the pipe sections and placed in the position of laminar flow.
- Sample probe materials have to be made from materials that do not react with the gas flow or to use materials with a diameter of 316 SS ¼ “, the probe must installed well so not easily bent or damaged when the gas flow pass.
- Do not put the probe on the location of the sample meter manifolds, blow down stacks, headers, dead end lines, downstream of turbulence generators, vertical lines (up or down).
Sampling Point Determination
- Determination of the location of sampling points should be appropriate to obtain a representative sample.
- Sampling points should be located in pipe sections with no gas flow disruption caused by network element pipes, elbows, tees, reducers, piping headers, manifolds, meter tubes, valves, orifice plates and so on.
- Movement flow in a pipe that passes through elbow or tee will cause the rotation of the flow or it can cause effects that cause the centrifugal movement of contaminants and heavy fraction components from natural gas to the pipe wall.
- Location of sampling point is usually not done by the pump, strainers, meters, manifolds or velocity. Regional acceleration or change in flow direction from horizontal to vertical can not be used to obtain a representative sample.
Sampling Cyliner Preparation
- Sample tube must be cleaned before sampling. This is done, especially if the sample cylinder was previously used for the sampling of hydrocarbons.
- Layer of oil, grease or sludge should be cleaned by Purging by washing with hot detergent solution or with an organic solvent.
- Drain and vacuum using a vacuum pump.
- Store the cylinder in a closed meeting (closed with a plug or the like).
- The cylinder is ready for use.
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Comments
2 Responses to “Obtaining Natural Gas Sample”
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December 11th, 2009 @ 17:41
I want to know how can I obtain natural gas sample.
December 15th, 2009 @ 23:43
Just make a tap into your pipe with a probe, then connect it to the sampling system as i described above.