ASTM D4177 Standard Practice for Automatic Sampling of Petroleum and Petroleum Products
7. Sampling Frequency
7.1 Guidelines for sampling frequency can be given in terms of "grab per lineal distance of pipeline volume". For marine and pipeline service this minimum guideline can be related to barrels per grab using the following equation:
where:
D = nominal pipe diameter, mm and
d = nominal pipe diameter, in.
7.2 This formula equates to one grab for every 25 lineal metres (approximately 80 ft) of pipeline volume.
7.3 Sampling frequency should be based on maximizing grabs for the available receiver size. Typically, Lease Automatic Custody Transfer (LACT) or Automatic Custody Transfer (ACT) units are paced at one grab per one to ten barrels.
7.4 The optimum sampling frequency is the maximum number of grabs which may be obtained from any parcel operating within the grab frequency and grab volume limitations of the equipment. The completed sample should be of sufficient volume to mix and properly analyze while not over filling the sample receiver.