Memorandum hydraulic jack

 

To determine a hydraulic jack, you must know:

 

• The thrust and retraction force to be exerted which depends on the pressure available to determine the cylinder diameter.

• Stroke length (standard lengths: 25, 40, 50, 80, 100, 125, 160, 200, 250, 320).

• The method of attachment: on the body (flange, lug, bracket, etc.); on the stem (ball joint, screw-nut, etc.)

 

Determining the diameter of a cylinder:

 

The theoretical pushing force (out stroke) of a cylinder is calculated by multiplying the effective area of ​​the piston by the operating pressure.

The effective area in thrust is equal to the complete area of ​​the cylinder bore

The thrust force of a jack is greater when the rod extends than when it retracts.

In order to avoid chattering and internal friction problems, a safety factor (generally 2) is applied to the calculated diameter.

Use of abacus

The charts make it possible to determine without calculation, the diameter of a cylinder because if the stroke is important, a steel rod subjected to a compressive force can be deformed suddenly, we then speak of buckling.

 

 

 

Reminder of concept of calculation of a cylinder :

 

D = piston diameter (Ø) in mm

d = diameter of the piston rod (Ø) in mm

A = piston area in cm²

p = pressure in bar

F = power dN

h = stroke in mm ηhm = degree of hydro-mechanical efficiency 0.85 – 0.95

Basic formula :

F = p x S = dN                             p = F / A = bar                         A = F / p = cm²

 

Calculation of pressure power (Fp):