Natural Gas sampling has been performed for years with techniques handed down from generation to generation. Most of the methods are not sufficient to meet today’s requirements of accuracy and repeatability; however, standards have been developed to reach toward these demands. The most widely known standards are GPA-2166-05 and ISO-10715. API has produced a revised API 14.1, which was published in June, 2001. It has been updated and revised in 2006. This new standard has already generated significant interest in proper sampling techniques, due to a large volume of data produced during the revision work.
Proper maintenance of all sampling equipment is vital to the operations of all sampling methods. A review of relative sampling standards and the manufacturer’s operation, installation and maintenance manuals, is an important step the total accurate sampling process. Dirty or poorly maintained sampling apparatus will adversely affect the final results and profitability of the gas company’s operation.
By means of a mechanical device (or sampler), small sample grabs are taken from the flowing stream. These sample grabs are collected and distributed into a vessel to be taken to a laboratory for further analysis. By taking these sample grabs over a batch flow or a time-based period, we can get an accurate representative sample of what flowed inside the pipeline over that set period of time.
Spot sampling is meant to be a representation of the product at a single point in the pipeline or container, at a single moment in time.
Continuous online sampling gets its name from the use of online analyzer systems. These systems are meant to take real time samples of the flowing batch or stream based on flow rates. In most cases, these analyzers require a conditioned gas stream to provide an accurate result. This method provides users an accurate means of collecting a sample on a real time basis.