Sizing a Cylinder

Sizing a Cylinder

These pressure, force and area relationships are sometimes illustrated as shown
below to aid in remembering the equations.

To determine the size cylinder that is needed for a particular system, certain
parameters must be known. First of all, a total evaluation of the load must be made.
This total load is not only the basic load that must be moved, but also includes any
friction and the force needed to accelerate the load. Also included must be the force
needed to exhaust the air from the other end of the cylinder through the attached
lines, control valves, etc. Any other force that must be overcome must also be
considered as part of the total load. Once the load and required force characteristics
are determined, a working pressure should be assumed. This working pressure that
is selected MUST be the pressure seen at the cylinder's piston when motion is taking
place. It is obvious that cylinder's working pressure is less than the actual system
pressure due to the flow losses in lines and valves.
With the total load (including friction) and working pressure determined, the
cylinder size may be calculated using Pascal's Law. Force is equal to pressure being
applied to a particular area. The formula describing this action is:
Force = Pressure * Area
Force is proportional to pressure and area. When a cylinder is used to clamp or
press, its output force can be computed as follows: F = P*A
P = pressure (PSI (Bar) (Pascal's))
F = force (pounds (Newtons))
A = area (square inches (square meters))