מחשבון קוטר צינור לפי קצב זרימה

Use the formula d = √(4Q / (πv)), where Q is the flow rate in m³/s and v is the maximum allowable velocity in m/s.

Example: 60 L/min at max 4 m/s → d = √(4 × 0.001 / (π × 4)) = 17.8 mm → round up to DN20 (ID 20.9 mm).

Recommended maximum velocities:

• Hydraulic suction: 0.5 – 1.5 m/s (to avoid cavitation)
• Hydraulic pressure: 3 – 6 m/s (up to 7 for short runs)
• Hydraulic return: 2 – 4 m/s
• Water supply: 1 – 3 m/s (≤2.5 in buildings for noise)

These are economic velocities — balancing pipe cost vs pumping energy.

DN (Diamètre Nominal) sizes for Schedule 40 steel pipe:

• DN15 (½″): ID 15.8 mm
• DN25 (1″): ID 26.6 mm
• DN50 (2″): ID 52.5 mm
• DN100 (4″): ID 102.3 mm
• DN150 (6″): ID 154.1 mm
• DN200 (8″): ID 202.7 mm

Note: ID depends on the schedule (wall thickness). Schedule 40 is most common; Schedule 80 has thicker walls and smaller ID.

Economic velocity is the speed that minimizes the total lifecycle cost of a piping system — which includes both the capital cost of the pipe and the ongoing energy cost of pumping.

Larger pipes cost more to buy but have lower pressure drop → less pumping energy. Smaller pipes are cheaper but need more pumping power.

For systems running continuously (>4000 h/yr), use lower velocities. For intermittent systems, higher velocities are acceptable.

Rounding down would exceed your velocity limit, causing:

• Higher pressure drop (ΔP ∝ v²)
• Noise and vibration
• Potential cavitation on suction lines
• Increased erosion and fitting wear

Always round up. The actual velocity with the larger pipe will be lower than your limit — which is safe.