What procedures apply when sampling transformer oil for laboratory testing?

Procedures include confirming safe access, using the correct sampling point, cleaning the valve, flushing a sufficient volume, and collecting in approved bottles for each test type. DGA samples require gas tight bottles, while moisture and acidity may use separate containers. Chain of custody documentation is completed. Samples are stored and shipped to minimize temperature swings and exposure to light. Field notes record load condition and any recent maintenance like filtration or oil top up, since those can affect lab interpretation and trending.