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Hydraulic Design

Hydraulic design turns the flows and hydraulic profile into real pipework, pumps and valves — pipe sizing by Darcy–Weisbach, pump selection on the system curve, valve specification and a closed pressure-drop budget from inlet to outlet.

Hydraulic Design — in Detail

The work that turns the brief into defensible engineering

Pipe Sizing

Diameters set by Darcy–Weisbach friction loss and velocity limits — fast enough to self-scour, slow enough to control head loss and water hammer.

Pump Selection

Duty point found where the pump curve meets the system curve, with NPSH available checked against required to rule out cavitation.

Valve & Fittings

Control and isolation valves sized on flow coefficient (Cv) with minor losses from bends and fittings carried into the head budget.

Pressure-Drop Budget

A reconciled head budget across the whole route so the selected pump delivers the design flow at every operating point.

Darcy–Weisbach and the Duty Point

Friction head loss follows Darcy–Weisbach, hf = f·(L/D)·(v²/2g), where the friction factor f comes from the Reynolds number and relative roughness (Colebrook / Moody). Summing pipe friction and the minor losses from fittings builds the system curve; the pump runs where that curve crosses its characteristic. Two checks make or break the design: velocity must stay within band (typically ~0.9–2.4 m/s for these duties) to self-scour without hammer, and the NPSH available must exceed the pump’s NPSH required with margin, or the pump cavitates. Getting these right is the difference between a plant that delivers design flow quietly and one that throttles, surges or fails on its suction.

Built Into the Design

Surge & Hammer

Transient analysis where rapid valve or pump events could otherwise damage the pipework.

Turndown Hydraulics

Confirming the network still behaves at minimum flow, not just at peak.

Net Positive Suction

Suction layout and submergence designed so NPSH is satisfied across the operating envelope.

Related Design Steps

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