Hydraulic Hose Sizing

Hydraulic Hose Sizing

The size of the suction hose for the power cube, it is calculated from the fluid velocity in the hose. The general values used are:

Pressure: 20 ft/sec

Return: 15 ft/sec

Suction: 5 ft/sec

The formula for calculating the hose size is as follows:

V = Q / (3.117 * pi/4 * D ^ 2)

or

D = (Q / (3.117 * pi/4 * V) ) ^ 1/2

Where:

V is fluid velocity in ft/sec

Q is fluid volume in gallons/min

D is hose inside diameter in inches

In the case of the Power Cube suction hose, V = 5 ft / sec and the Q is approximately 13 GPM, so:

D = (13 GPM / (3.117 * pi/4 * 5 ft/sec) ) ^ 1/2 = 1.03 in

The sizing guidelines say to always round up - meaning take the next size larger than 1.03 inches (probably 1 1/4").

While I thought the sizing for the pressure lines was OK, I double-checked and found the formula indicates that the supply and return hoses should be larger as well:

D = (13 GPM / (3.117 * pi/4 * 20 ft/sec) ) ^ 1/2 = 0.515 in

Also, the return lines appear to be undersized as well:

D = (13 / (3.117 * pi/4 * 15 ft/sec) ) ^ 1/2 = 0.595 in

Both Pressure and Return hose sizes should be increased to 3/4", as well as all couplers and fittings.

Horsepower to Flow

Horsepower = Pressure × Flow / 1714

  -or-

HP = PQ / 1714

For our 28 HP Power Cube delivering 3000 PSI, we calculate the flow as follows:

28 = (3000 * Q) / 1714

Therefore, Q = (28 * 1714) / 3000 = 15.997 GPM

For the upcoming 50 HP Power Cube delivering 3000 PSI, we calculate the flow as follows:

50 = (3000 * Q) / 1714

Therefore, Q = (50 * 1714) / 3000 = 28.5 GPM

Pump Displacement (Cubic Inch Per Revolution, or CIPR)

CIPR = Flow Rate (in GPM) × 231 x Pump Efficiency / Pump RPM

   -or-

CIPR = GPM × 231 * PE / RPM

The 28 hp Briggs & Stratton engine HP is rated at 3600 RPM. With 97% pump efficiency, the pump size is calculated as follows:

CIPR = 16 × 231 * 0.97 / 3600 = 0.996 CIPR

The 50 hp Briggs & Stratton engine HP is rated at 3000 RPM. With 97% pump efficiency, the pump size is calculated as follows:

CIPR = 28.5 × 231 * 0.97 / 3000 = 2.12 CIPR

Fluid Flow Rate (Q)

GPM = Flow (in Gallons) / Time (in Minutes) Q = V / T