Torque and horsepower relations: T = HP x 5252 ÷ RPM HP = T x RPM ÷ 5252 RPM = HP x 5252 ÷ T Torque values are in foot pounds.
Velocity of oil flow in pipe: Charles’ Law for behavior of gases: Boyle’s Law for behavior of gases: Circle Formulae: Heat equivalent of fluid power: Hydraulic cylinder piston travel speed: Thrust or force of any cylinder: Force for piercing or shearing sheet metal: Side load on pump or motor shaft: Effective force of a cylinder working at an angle to direction of the load travel: Heat radiating capacity of a steel reservoir: Burst pressure of pipe or tubing: Relationship between displacement and torque of a hydraulic motor:


English Units  Metric Units  
Torque, HP, Speed Relations inHydraulic Pumps and Motors 

T = HP x 5252 ÷ RPM HP = T x RPM ÷ 5252 RPM = HP x 5252 ÷ T T = Torque, footlbs. RPM = Speed, revs/min HP = Horsepower 
T = Kw x 9543 ÷ RPM Kw = T x RPM ÷ 9543 RPM = Kw x 9543 ÷ T T = Torque, Nm (Newtonmeters) RPM = Speed, revs/min Kw = Power in kilowatts 

Hydraulic Power Flowing Through the Pipes 

HP = PSI x GPM ÷ 1714 HP = Horsepower PSI = Gauge pressure, lbs/sq. inch GPM = Flow, gallons per minute 
Kw = Bars x dm^{3}/min ÷ 600 Kw = Powers in kilowatts Bars = System pressure dm^{3}/min = Flow, cu. dm/minute 

Force Developed by an Air or Hydraulic Cylinder 

T = A x PSI T = Force or thrust, in lbs. A = Piston area, square inches PSI = Gauge pressure, lbs/sq. inch 
N = A x Bars x 10N = Cylinder force in Newtons A = Piston area, sq. centimeters Bars = Gauge pressure 

Travel Speed of a Hydraulic Cylinder Piston 

S = V ÷ A S = Travel speed, inches/minute V = Vol. of oil to cyl., cu.in/min A = Piston area, square inches 
S = V ÷ 6A S = Travel speed, meter/sec V = Oil flow dm^{3}/minute A = Piston area, square centimeters 

Barlow’s Formula –Burst Pressure of Pipe & Tubing 

P = 2t x S ÷ O P = Burst pressure, PSI T = Pipe wall thickness, inches S = Tensile str., pipe material, PSI O = Outside diameter of pipe, inches 
P = 2t x S ÷ O P = Burst pressure, bars T = Pipe wall thickness, mm S = Tensile str., pipe material, bars O = Outside diameter of pipe, mm 

Velocity of Oil Flow in Hydraulic Lines 

V = GPM x 0.3208 ÷ A V = Velocity, feet per second GPM = Oil flow, gallons/minute Velocity of an oil flow in pipe“GPM is oil flow in gallons per minute”.= Inside area of pipe, sq. inches 
V = dm^{3}/min ÷ 6A V = Oil velocity, meters/second dm^{3}/min = Oil flow, cu.dm/minute A = Inside area of pipe, sq.cm. 

Recommended MaximumOil Velocity in Hydraulic Lines


fps = feet per second Pump suction lines – 2 to 4 fps Pres. lines to 500 PSI – 10 to 15 fps Pres. lines to 3000 PSI – 15 to 20 fps Pres. lines over 3000 PSI – 25 fps Oil lines in air/oil system – 4 fps 
mps = meters per second Pump suction lines – .6 to 1.2 mps Pres. lines to 35 bar – 3 to 4½ mps Pres. lines to 206.8 bar – 4½ to 6 mps Pres. lines over 200 bar – 7½ mps Oil lines in air/oil system – 1¼ mps 
At RAM, we’re 100% committed to our customers and to their satisfaction.
OUR PLEDGE IS SIMPLE:
“The job’s not done right until you say it’s done right.”
Rules of Thumb:
Horsepower for driving a pump:
For every 1 HP of drive, the equivalent of 1 GPM @ 1500 PSI can be produced.
Horsepower for idling a pump:
To idle a pump when it is unloaded will require about 5% of its full rated horsepower.
Compressibility of hydraulic oil:
Volume reduction is approximately 0.5% for every 1000 PSI pressure.
Compressibility of water:
Volume reduction is about 0.3% for every 1000 PSI pressure.
Wattage for heating hydraulic oil:
Each watt will raise the temperature of 1 gallon of oil by 1 °F per hour.
Flow velocity in hydraulic lines:
Pump suction lines 2 to 4 feet/second; pressure lines up to 500 PSI, 10 to 15 feet/second; pressure lines 500 to 3000 PSI, 15 to 20 feet/second; pressure lines over 3000 PSI, 25 feet/second; all oil lines in airoveroil system, 4 feet/second.