Water flow in plant piping: what is the typical “normal” range of average velocity selected for design?

Introduction / Context:
When designing plant water lines (cooling water, service water), engineers balance pressure drop, pipe size, erosion potential, and noise. A widely used rule-of-thumb velocity range provides a good compromise between capital and operating costs while avoiding cavitation and excessive vibration.

Given Data / Assumptions:

• Clean water service in carbon-steel or similar piping.
• Economic pipe sizing based on standard friction criteria.
• Aim to avoid erosion and keep pump head reasonable.

Concept / Approach:
Average velocities of roughly 1–2 m/s are commonly selected for water distribution in plants. Below this, pipe diameters become large and capital cost rises; above this, friction losses escalate and risk of erosion, noise, and water hammer increases. Local velocities can be higher at fittings, but the line sizing target remains in this band for most services.

Step-by-Step Solution:

Verification / Alternative check:
Pipe-sizing charts used in utilities engineering consistently map economically optimal diameters for water to velocities near 1–2 m/s for a wide variety of flows.

Why Other Options Are Wrong:

• 0.1–0.5 m/s oversizes lines and is uneconomical except in special cases.
• 10–50 m/s and 15–30 m/s are far above practical levels, causing severe head loss and erosion risk.

Common Pitfalls:
Ignoring water quality (solids can lower allowable velocity); not checking noise limits in building services; neglecting transients that can spike velocities.

Final Answer:
1–2 m/s