Each tank to be used in the transfer should be sampled in sufficient quantity to meet any analysis, retain, and distribution requirements. Sample containers must be clean and, in the case of petroleum products, should be flushed with product prior to drawing the sample. Sample containers must meet certain requirements (see API MPMS Chapter 8.1, 8.3, & 8.4). Containers that are used for transport and storage of samples must meet appropriate regulatory requirements. When non-homogeneous products are sampled, upper, middle and lower spot samples are usually obtained. If stratification is suspected, or upper, middle, and lower spot samples confirm significant stratification, samples at additional levels must be taken to ascertain an accurate profile of the tank contents. If only part of the product in a tank will be used for the transfer, zone (spot) samples may be taken from that part of the tank, in order to draw samples that will represent what is to be transferred out of the tank. All concerned parties should be notified if the material is deemed to be stratified (i.e., nonhomogeneous), and each party should agree on further actions before proceeding. Note whether the tank is equipped with mixers, a circulating system, or aerators, and the extent of mixing that was performed on the tank.
2.4.4 Automatic Temperature Systems Automatic temperature systems with accuracy and/or measurement tolerances consistent with “API MPMS Chapter 7.3” may be used for custody transfer by mutual agreement among the parties involved. If an automatic temperature system is used and the readings are not verified by manual measurements, record the last two times that the automatic system and the manual measurements were compared, and if any differences were noted. Record on the inspection report that automatic temperatures were used. 2.5 Sampling All samples should be promptly labelled after drawing the sample with the appropriate tank number and other pertinent data. 2.5.1 Manual Tank Sampling The objective of manual sampling is to obtain a small portion (spot sample) of material from a selected area within a container that is representative of the material in the area, or in the case of running or all-levels samples, a sample whose composition is representative of the total material in the tank. A series of spot samples may be combined to create a representative sample.
2.5.2 Automatic Sampling
Automatic sampling is the preferred method of sampling a cargo transfer. If an automatic sampling system is installed, it should meet the requirements and be operated in conformance with “API MPMS Chapter 8.2”. When instructed to confirm automatic sampler system performance that SGS do not own or operate, we are reliant on the terminal providing the required data. However, in these instances the SGS Inspector should observe and record the following: • Confirm that the automatic sampler receiver, via visual inspection, is both empty and clean prior to the commencement of the transfer. • On at least three occasions during the transfer, observe by non-intrusive means whether the automatic sampling system is operating. • Note the starting time of the automatic sampling system and the amount of oil in the sample receiver (weight or volume) when periodically observing the sampler in operation. • Record the actual weight of the sample from the scale (which can then be converted into volume) or volume of sample in the sample receiver (via a graduated sight glass) at the end of the sampling operation.
Any deficiencies should be noted and reported.
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