Frequently Asked Questions


Q. How do we figure out the open area of screen? 

A. Wedge screen open area ratio (OA) is calculated using the following formula (multiply by 100 for percent) 


Q. What are the standard tolerances for Federal Screen Products on screen? 

A. Specialty tolerance maybe requested, especially on custom machined items.

Tolerance of O.D: .005”
Tolerance of slot size: +/- .002”
Fabrication: +/- 1/16” (2 PL DEC = 0.020”, 3 PL DEC = 0.010”)
Angles: +/- 1 degree

Q. How much does it cost? 

A. Federal Screen’s screens are all custom manufactured and due to the fact that there is limitless of possible combinations of wire profile, slot size, material choices and length depending on the applications, the cost per unit varies and must be calculated on a per-job basis.

Q. What is the standard slot size and size?

A. There is no real standard size. Due to the large range of applications we deal with on a day to day basis, each requires very different slot sizes. Typically, the rule of thumb for most applications is to use a slot size that is half the size of the smallest media particle.

Having said that however, we have seen reoccurring slot sizes being used in such applications as Ion exchange applications (underdrain laterals, media traps) which commonly have ranged of from 0.15mm to 0.20mm. Intake screens for fish protection in Canada generally require 2.54mm slots; in USA 3.175mm. Otherwise, the exception being sieve bends where the slot is sized about twice the desired separation size.  Screens are available in slot sizes ranging from 0.001 in. (25μm) up to (1/2”) and  larger slots may be available constrained by wire profile and tooling.

Have a question that isn't listed? Please contact us directly with any questions you may have.