What is the rule of thumb for ensuring dirty oil is clean after passing through filters?

The rule of thumb that recommends that oil must pass through the filter seven times emphasizes the importance of thorough filtration to achieve effective oil cleanliness. This approach stems from the understanding that contaminants in oil can significantly impair equipment performance and reliability.

When dirty oil is circulated through a filtration system, multiple passes allow for a gradual reduction in particulate size and enumeration of contaminants. Each pass through the filter enhances the likelihood of trapping smaller particles, thus improving the cleanliness of the oil.

Using this guideline helps in establishing a practical framework for maintenance personnel to follow, allowing them to gauge the effectiveness of their filtration processes. By adhering to this rule, engineers and maintenance teams ensure a higher standard of oil cleanliness, which ultimately contributes to extended equipment life, lower risks of failure, and enhanced overall reliability.

The other options suggest varying numbers of passes, but seven has been determined to be the optimal number based on experience and practical application in the field.