Hydraulic Hose Velocity Calculator
Calculate fluid flow velocities (ft/sec), determine proper dash size hoses, and prevent destructive pump inlet cavitation and excessive backpressure.
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How Hydraulic Hose Velocity & Dash Sizing Work
Hydraulic fluid velocity directly determines turbulence, frictional pressure drop, heat generation, and pump inlet cavitation:
Fluid Velocity (ft/sec) = (Flow GPM × 0.4085) / (Internal Diameter in Inches)²
Minimum Inside Diameter = √[ (GPM × 0.4085) / Max Target Velocity ]
Dash Sizes (-04 = 1/4", -06 = 3/8", -08 = 1/2", -12 = 3/4", -16 = 1", -20 = 1-1/4", -24 = 1-1/2", -32 = 2")
The Suction Line Cavitation Trap: Never undersize a pump suction line! Atmospheric pressure pushing oil into the pump inlet is only 14.7 PSI. If suction velocity exceeds 4 ft/sec, inlet vacuum drops below oil vapor pressure, causing vapor bubble implosions (cavitation) that pit gear teeth and destroy pumps in hours.
Frequently Asked Questions
What are standard recommended fluid velocities for hydraulic lines?
Standard fluid power guidelines mandate: Pump Suction Lines: 2 to 4 ft/sec; Tank Return Lines: 10 to 15 ft/sec; Medium Pressure Lines (<3,000 PSI): 15 to 20 ft/sec; High Pressure Lines (>3,000 PSI): 20 to 25 ft/sec.
What is a "Dash Size" in hydraulic fittings and hose?
A dash size indicates the internal diameter of the hose measured in sixteenths of an inch. For example, -08 is 8/16" (1/2" ID), -12 is 12/16" (3/4" ID), and -16 is 16/16" (1.0" ID).
What happens if a return line is undersized?
An undersized return line creates high fluid velocity that generates excessive backpressure on cylinder seals and motor case drains, blowing out shaft seals and creating fluid aeration (foaming) in the oil reservoir.