The filter protects regulators, valves, and instruments from particles carried by natural gas.
Clean filter
Exhibits a relatively low pressure drop at normal flow.
Clogged filter
As contaminants accumulate, the differential pressure increases and the available flow is restricted.
Why visual inspection is not enough
The filter may appear clean on the outside but still create significant resistance to flow.
Proper assessment
Differential pressure must be compared at equivalent flow rates and against the manufacturer's limits.
