What is the green range on the psi scale, and what does it mean?

• A. (0-10 PSI) and it means elements are clean
• B. (20-35 PSI) and means elements must be changed at the end of operation
• C. (0-20 PSI) and it means elements are not clean
• D. (0-20 PSI) and it means elements are clean

Answer: (D)

The main idea is that the green range on the psi scale shows the filter is operating with minimal resistance to flow. In a fuel filtration system, the pressure drop across the filter element tells you how loaded the element is with contaminants. A low differential, in the green band, means the element is clean and there’s no significant restriction to flow. That green range is 0-20 psi, which is why the correct statement is that the elements are clean when the differential is within 0-20 psi. As contaminants accumulate, the pressure drop rises; reaching the higher range like 20-35 psi signals it’s time to change the element, and higher levels indicate the element is clogged. So the green range being 0-20 psi and indicating cleanliness is the best answer.