When drawing a liquid sample from a transformer, how much waste should be flushed through the sample valve before collecting the sample?

Flushing a sample valve before collecting a liquid sample from a transformer is a critical procedure to ensure the sample is representative of the fluid used in the transformer rather than contaminants or residues that may be present in the valve. Flushing helps in clearing out any stagnant fluid or particles that could skew the analysis of the sample.

The recommended practice is to flush through an adequate amount of fluid to ensure that what is collected afterwards reflects the actual condition of the transformer fluid. Flushing with two quarts is generally recognized as sufficient because it clears the line and reduces the risk of contamination. This amount is often enough to ensure that any residual liquid from the sampling apparatus is eliminated and the sample collected is fresh and of the highest quality for analysis.

Using less than two quarts may not be sufficient to ensure thorough flushing, leading to potential inaccuracies in the sampling process. Conversely, flushing with significantly more than two quarts may waste fluid unnecessarily, which is generally not desirable in a practical and operational sense. Thus, the practice of flushing with two quarts prior to sampling strikes a balance between thoroughness and efficiency.