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Capacity Chart Instructions

Determining the right double flap airlock valve for your application

Plattco Double Flap Airlock® Valves are volumetric feeders.  To choose a suitable valve for an application, we first need to know the desired flow rate or tonnage.  One must calculate the volume of material flow.

Step 1: Determine the material bulk density.

Bulk density must be in units of pounds per cubic feet (lbs/ft^3) for this calculation.  It is important to choose a bulk density that corresponds to the aerated condition of the material being handled and that corresponds to real operating bulk density.  For example, a fluidizable powder in the non-fluidized state may weigh 80 lbs/ft^3, but in the fluidized condition it could weigh as little as 35 lbs/ft^3.  This makes a very big difference to the size of the Plattco valve suitable for this application.

Step 2:  Determine the target mass flow rate for the valve.

Mass flow rate must be in units of pounds per hour (lbs/hr).  Perform any necessary conversions to arrive at the mass flow rate of (lbs/hr).

Step 3:  Calculate the required volumetric flow rate for the application.

Divide the mass flow rate by the bulk density to arrive at the required volumetric flow rate for the application.  (lbs/hr) ÷ (lbs/ft^3) = (ft^3/hr)

Step 4:  Reference the Capacity Chart

Using the capacity chart, one can then find the range of valves suitable to handle the application flow rate requirements.  Note, the flow rates included in the chart already include a fill rate safety factor.

A practical example:

  • Material being handled is Fly Ash
  • Process conditions constitute the use of 50 lbs/ft^3 bulk density
  • Process mass flow rate is expected to be 25000 lbs/hr
  • Calculated volumetric flow rate equals: 25000 lbs/hr ÷ 50 lbs/ft^3 = 500 ft^3/hr

Suitable valves to handle the required flow rate for the example application are shown in the following capacity chart in green.  

  • Choose the suitable valve size in the left most column.  
  • Then choose the corresponding Dutchman, or spool piece, from the matrix that meets the desired flow rate.  
  • For this example, one may choose an H-series valve: 12” size with a 6” tall Dutchman.  This valve is capable of 524 ft^3/hr.