What is the sampling rule of thumb for insulating fluids with a specific gravity greater than 1?

The sampling rule of thumb for insulating fluids with a specific gravity greater than 1 indicates that sampling should be conducted from the top of the fluid. This recommendation is primarily based on the behavior of liquids with a higher specific gravity, where denser substances tend to settle towards the bottom of a container or system. As a result, the top layer is more likely to contain lighter, more volatile, and potentially more desirable components for analysis.

In practice, sampling from the top allows for the assessment of the condition of the insulating fluid in its uppermost layer, where degradation or contamination may be detected more readily. This helps in understanding the overall health of the fluid and the transformer system it serves, as the top layer typically influences the performance and insulation quality of the fluid in use.