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Home//Municipal//Engineering Tools & Calculators//Weir and Orifice Calculator
Weir & Orifice Calculator
The Weir and Orifice Calculator is used to determine the inlet capacity in sag (ponding) conditions by use of the Weir and Orifice equations. Knowing this information will allow you to select the proper grate type and size for your specific job or project.
Weir Flow Calculations
Weir Equation: Q = 3.3P(h)1.5
- Q = Capacity in CFS
- P = Feet perimeter
- h = Head in feet
- Weir Information
Orifice Flow Calculations
Orifice Flow Equation: Q = 0.6A 
- Q = Capacity in CFS
- A = Free open area of grate in sq. ft.
- g = 32.2 (feet per sec/sec)
- h = Head in feet
- Orifice Information
Instructions:
- Select a catalog number (will automatically fill in Open Area and Perimeter) or enter your own values
- Enter head value
- Click "calculate"
The results will determine automatically if your situation falls into a Weir, Transitional or Orifice flow. Additionally, Neenah grates which fall within the parameters chosen will appear below the calculator.
| Catalog Number and Grate Type: | ||
|---|---|---|
| Feet perimeter (P): | Head in feet (h): | Free open area in sq. ft. (A): |
| Weir capacity in cfs: | Transitional flow in cfs: | Orifice capacity in cfs: |
For additional information regarding Neenah Inlet Grate Capacities, please contact Steven Akkala P.E., at (920) 729.3653 or email at sakkala@nfco.com.
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