Patent ID: 8142668

Claim:
A method for filtering a fluid with unequal concentrations of different types of particles having known size ranges, comprising the steps of: using a first surface filtration medium to capture a first type of said particles having a first size range exclusively on first respective surfaces of a first plurality of discrete layers of a first mesh material arranged in a first stack; using in combination a pore size of said first mesh material and a first number of said discrete layers in said first stack to provide a first absolute micron filter rating; using a second surface filtration medium downstream of said first surface filtration medium to capture a second type of said particles having a second size range different from said first size range exclusively on second respective surfaces of a second plurality of discrete layers of a second mesh material arranged in a second stack; using in combination a pore size of said second mesh material and a second number of said discrete layers in said second stack to provide a second absolute micron filter rating different from said first absolute micron filter rating; selecting a first number of said first plurality of discrete layers to provide a first capacity of said first surface filtration medium for collecting said first type of particles, and a second number of said second plurality of discrete layers to provide a second capacity of said second surface filtration medium for collecting said second type of particles; selecting said first number and said second number to provide a ratio of said first capacity and said second capacity which is approximately equal to a ratio of a relative concentration of said first type of particle to a relative concentration of said second type of particle; and selecting said first pore size larger than said first size range of particles, and said second pore size larger than said second size range of particles.