The object of crude oil sampling is to determine the quality of the oil at the custody transfer point. The amount of basic sediment and water in the oil, a chemical analysis of the oil and shrinkage, and the API gravity should be determined. The process of accomplishing this task is not something to be left to convenience or ease of operations. The process must be accurate.
The purpose of a crude oil sampling system is to withdraw from a pipeline a small representative portion of the product that contains the water, oil, and contaminants in the same proportion as is flowing in the stream.
There are three well known sampling standards that are used worldwide for automatic sampling of crude oil. Two of the standards are considered as identical and parallel – those are API Chapter 8.2 and ASTM D 4177. The third standard is ISO 3171. Also, there are well known alternate standards like EI Section 2 Part VI.