ASTM D4177 Automatic Sampling of Petroleum and Petroleum Products
ASTM D4177 Standard Practice for Automatic Sampling of Petroleum and Petroleum Products
10. Probes
10.1 Probe Location and Installation:
10.1.1 The recommended sampling area is approximately the center one-third of the pipeline cross-section area as shown in Fig. 3.
10.1.2 The probe opening must face upstream and the external body of the probe should be marked with the direction of flow to verify that the probe is installed correctly.
10.1.3 The probe must be located in a zone where sufficient mixing results in adequate stream conditioning. This zone is generally from 3 to 10 diameters downstream of piping elements, .5 to 4 diameters from static mixers, and 3 to 10 diameters from power mixers. When static or power mixers are used, the manufacturer of the device should be consulted for the probe's optimum location.
10.1.4 The line from the outlet of the extractor to the sample receiver must continuously slope downward from the extractor to the receiver and contain no dead space.
10.1.5 The preferred installation of a combined probe-extractor is in the horizontal plane.
10.1.6 If a vertical piping loop is used for stream conditioning, locate the probe in the downflow section of the loop to obtain the benefit of the additional stream conditioning provided by the three 90° elbows. Locate the probe a minimum of three pipe diameters downstream of the top 90° elbow and not closer than one-half pipe diameter upstream of the final exiting elbow (see Fig. 4).
10.1.7 According to tests sponsored by the American Petroleum Institute (API), locating a sample probe downstream of a single 90° bend is not recommended because of inadequate stream conditioning.
10.2 Probe Design:
10.2.1 The mechanical design of the probe should be compatible with the operating conditions of the pipeline and the fluid being sampled. There are three basic designs shown in Fig. 5. Probe openings should be in the center third of the cross sectional area of the pipe.
10.2.2 Probe designs commonly used are described as follows:
10.2.2.1 A closed end probe equipped with an open orifice (see Fig. 5A).
10.2.2.2 A short-radius elbow or pipe bend facing upstream. The end of the probe should be chamfered on the inside diameter to give a sharp entrance (see Fig. 5B).
10.2.2.3 A tube cut at a 45° angle with the angle facing upstream (see Fig. 5C).
