ASTM D923 standard practices for sampling electrical insulating liquids
SAMPLE CONTAINERS
9. Construction
9.1 Use amber colored glass (Note 1) or high-density polyethylene bottles (do not use for long term storage when water content is to be determined), aluminum or TFE-flurocarbon lined or welded seam metal cans as containers for the samples. The glass bottles may be either glass-stoppered or fitted with screw caps having a pulp-board liner faced with tin or aluminum foil, or with a suitable oil-resistant plastic such as polyvinylidene chloride or polytetrafluoroethylene. Do not use any incompatible natural or synthetic rubber materials.
NOTE 1 - While amber-colored glass bottles are used for storing samples as protection against light, clear glass bottles afford better visual inspection of the samples or test specimens for impurities such as water and foreign particles. Take samples that are to be subjected to referee tests in new amber-colored containers that have been cleaned as described in 10.2. Refer to Test Method D3613 for the proper techniques and materials used to retrieve test specimens for dissolved gas analysis.
9.2 If glass-stoppered bottles are used, take precautions to ensure that the stoppers provide a perfect fit. If tin-plated steel cans are used, use only those having welded seams and provided with screw caps lined as described in 9.1. Cans with soldered seams should not be used because the sample may become contaminated.
10. Cleaning and Preparation
10.1 Because of the inherent susceptibility of most insulating liquids to contaminating influences of the most minute nature, the cleanliness of the sample container is of paramount importance for ensuring that the sample obtained is representative of the bulk from which it was taken. For these reasons, it is essential that the procedures outlined in the following paragraphs are strictly observed.
10.2 If containers have been previously used for sampling liquids that are to be subjected to referee tests, thoroughly rinse the container with Stoddard solvent, precipitation naphtha, or other suitable cleaning agent that completely dissolves the liquid residue, and then subject to a soap and water cleaning and water rinse. If a water-soluble cleaning agent such as trisodium phosphate is used, rinse thoroughly with tap water. Invert the containers and drain for 10 min; then immerse in a 10 % solution of non-chro-mate acid-based cleaner for not less than 1 h. At the end of this period rinse with tap water, then with distilled water, and dry in an upright position in a forced-draft oven at 110°C for not less than 1 h. In the case of containers that have not been previously used, the initial cleaning may be omitted and the containers placed immediately in the non-chromate solution followed by the rinsing and drying outlined above.
10.3 Clean and dry containers for samples or test specimens to be subjected to routine tests as described in 10.2 except that after the initial tap-water rinse, rinse with distilled water.
10.4 Clean and dry glass stoppers in a manner similar to that of the container in which they are to be used. Do not reuse covers having vinyl liners. Dry new covers with vinyl liners in an oven at 110°C for not less than 30 min immediately prior to being placed on the bottles.
10.5 When the drying periods for the bottles and covers or stoppers have expired, tightly stopper each bottle immediately as it is removed from the oven, taking care not to touch the lip of the container or that portion of the stopper or cover likely to come in contact with the sample.
11. Storage and Handling
11.1 Keep containers that are to be stored for future use in a warm, dry storage cabinet. Store all sample containers with or without samples or test specimens in them in such manner that the possibility of their being contaminated is eliminated. Keep containers sealed until immediately before sampling, and seal again as soon as the sample or test specimen is taken to prevent contamination by dirt or moisture. As soon as samples are taken, properly identify them. To prevent breakage, handle the sample container after filling with care during transportation and storage. Store samples in the dark when clear glass bottles are used. Amber-colored glass bottles provide good protection against degradation of the sample by sunlight.
