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

Hydraulic Hose Sizing