ASTM D4057 standard practice for manual sampling of petroleum and petroleum products
8. Manual Sampling Concepts and Objective
8.1 Objective of Manual Sampling - The objective of manual sampling varies. In some instances, the intention is to obtain a small portion of product that is representative of the tank or container contents. In other instances, samples are specifically intended to represent product only at that one particular point in the tank, such as a top, dead bottom, or suction level sample. When a tank is determined to be homogenous, a series of spot samples may be combined to create a composite sample. Precautions should be taken to maintain the integrity of the sample by preventing it from being contaminated by the sample point, the sample apparatus and equipment, the cleanliness of the container, the weather, and sample transfer operations. Manual sampling may be applied under all conditions described in this practice. Alternative sampling procedures may be used as agreed upon by all interested parties.
8.2 Training - Personnel shall be trained for the sampling to be performed, including topics such as sample integrity, safety, and special handling related to specific tests.
8.3 Physical and Chemical Property Tests:
8.3.1 The sampling procedure, sample container, quantity required, and sample handling requirements will be based on the test(s) to be performed, sample instructions related to a custody transfer and sample retention requirements.
8.3.2 In many liquid manual sampling applications, the product to be sampled contains a heavy component (such as free water) that tends to separate from the main component. In these instances, it should be recognized that sampling will likely result in varying sample quality until such time as the heavy component completely settles out. This period could range from only a few minutes to several weeks based on, but not limited to, the product, temperature, agitation and the use of chemical additives.
