Valve sizing and pressure-control calculators

Valve sizing and pressure-control calculations

Tenselo provides valve sizing calculators for control-valve flow coefficients, pressure-sustaining duties and pressure-reducing valve selection. Start with the required flow and the pressure you need to control, then review the equipment against its manufacturer operating limits.

Control valve sizing calculator: Cv and Kv

VLV-001, Control Valve Cv / Kv Sizing, calculates a required flow coefficient from liquid flow, pressure drop and relative density, or estimates flow from a known Kv. Its cavitation and choked-flow check also uses vapour pressure and the valve's pressure-recovery factor. Follow the calculator's absolute-pressure input convention for that check.

Static arithmetic example: for water with relative density 1.0, a flow of 36 m³/h and a pressure drop of 1 bar, Kv = 36 / √(1 / 1) = 36. Using Cv = 1.156 × Kv gives Cv ≈ 41.6. This illustrates the liquid coefficient equation; selecting a control valve also requires its operating range, opening characteristic and cavitation limits.

Pressure sustaining valve sizing, including Bermad duties

VLV-002, Pressure Sustaining Valve, supports assessment of an upstream-pressure duty from flow, upstream pressure, the sustaining setpoint and downstream conditions. A sustaining valve maintains a minimum upstream pressure as downstream demand changes. A pressure-reducing valve controls the downstream pressure. See the verified worked example.

For Bermad equipment, confirm the exact model and pilot arrangement. The Bermad 730 manufacturer information describes inline pressure sustaining and a separate branch arrangement for pressure relief. Tenselo's calculator includes Bermad-family data, but the final selection must use the current product curve, pilot range and local supplier confirmation.

Pressure reducing valve sizing and selection

VLV-003, PRV Selector, uses design flow, upstream pressure, the required downstream pressure and the control type to assess PRV options. Review the pressure class, pilot setpoint range, flow velocity and available pressure difference together. Closing-time and pressure-reduction warnings are checks based on stated assumptions; complex transient behaviour needs a system-level assessment.

Connect the valve duty to the rest of the design

Check minimum, normal and peak operating cases. Use pipe hydraulics calculations to assess losses and filter sizing and backwash calculations to establish the filtration duty. A valve chosen for service flow may also need to operate during backwash or changing irrigation demand.

New accounts require approval. These public descriptions and the static example explain the methods; running project calculations requires authorised application access. See availability and registration. Have the complete pressure-control arrangement reviewed before specifying equipment.