This historical boiler-feedwater filter carries water upward through felt supported by wire gauze and perforated plates. The animation follows the service-flow path in Hiscox’s item 406. A separate calculator uses entered loss coefficient, liquid density, reference velocity and resistance multiplier to compare ideal pressure loss and equivalent liquid head.
Boiler Feedwater Filter Interactive Calculator
Compare dynamic pressure, pressure drop at the entered loss coefficient, and the effect of a chosen resistance multiplier.
Equation Used
- Entered velocity is a representative velocity for the entered loss coefficient's definition.
- Density is constant and the calculation is incompressible.
- The entered multiplier scales clean resistance but is not a fouling prediction.
- The calculation does not determine strainer size, screen mesh, pressure rating, cleaning limits or suitability for a boiler system. Flashing, two-phase flow and pressure transients are omitted.
The multiplier is a scenario input, not a predicted fouling curve. Real selection must use the chosen manufacturer's Kv/Cv data or pressure-loss chart and maximum allowable differential pressure.
Historical upward-flow filter
Water enters at the lower left and rises through the filter layers before leaving at the upper right. Hiscox describes felt held between wire gauze and perforated plates, with space for sponge or coarse sawdust between the layers. The cutaway shows the upper flushing inlet and lower drain closed during normal upward flow. This is an illustration of the historical arrangement, not a specification for modern boiler service.
Compare pressure-loss inputs
The calculator can check units and show how an entered K, velocity, density and resistance multiplier affect ideal incompressible pressure loss. It cannot select, rate or approve a strainer.
Pressure-loss identity
Dynamic pressure is q=rho v²/2. Clean entered-K loss is Kq. The displayed multiplied loss is mKq, where m is explicitly entered rather than predicted. Equivalent liquid head is deltaP/(rho g).
Example calculation
For K=3.5, rho=965 kg/m³, v=2.18 m/s and multiplier 2.75, dynamic pressure is about 0.0229 bar, clean entered-K drop is 0.0803 bar, multiplied drop is 0.2209 bar, and equivalent liquid head is about 2.33 m. Compare the result with the selected strainer’s data and allowable differential pressure.
Selecting a strainer
Select an actual strainer using its flow data, screen mesh and free area, allowable differential pressure, and body and screen ratings. Check the liquid conditions, piping and manufacturer instructions as part of that selection. The multiplier here is not a cleaning interval or a prediction of debris accumulation.
Questions
Is the multiplied drop a cleaning limit?
No. The multiplier scales the entered clean resistance; the selected strainer’s instructions determine cleaning requirements.
Can K replace a manufacturer curve?
No. Use selected-product data for design.
Does this model steam?
No. The equation is an incompressible constant-density simplification.
Historical filter and modern pressure-loss references
Gardner D. Hiscox, Mechanical Movements, Powers, Devices and Appliances (1901), page 111, item 406: upward-flow filter for boiler feedwater. The modern strainer references below concern equipment selection and pressure-loss data, not the construction of this historical filter.
Spirax Sarco's strainer guidance describes basket strainers as vertically oriented chambers with large free straining area and directs users to Kv values or pressure-loss diagrams. TLV strainer documentation describes screens removing dirt and scale and lists model-specific mesh and pressure/temperature ratings. Consult those product-specific values when selecting or assessing a strainer.
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