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Hydraulic Cylinder Dangers
Dangers Associated with Hydraulic Cylinders
Although hydraulic cylinders are a necessary and integral part of industry, there some very real dangers
associated with them that could become fatal. Not least of which is pressure intensification.
Pressure intensification in hydraulic cylinders
The force applied in a hydraulic cylinder is calculated with the equation (F = P * A). In
a double acting
cylinder(one that is powered both in and out) the area of the piston on the bottom or
cap end
side is much larger than the area of the piston on the rod side. This causes an
unequal
pressure difference on either side because, on the rod side, the smaller area has to
have
more pressure pushing on it to keep the piston from being moved by the pressure
pushing on the larger area of the piston on the other side.
If the effective surface area of the piston on the rod side of the cylinder has half
the area of that on the piston side, it will produce half the force on the piston side
for the same amount of pressure. Getting back to our equation, Force = Pressure
multiplied by effective piston surface Area using a 3” piston on a 2” rod and a
pressure of 2000psi we get a force of 14000lb on the piston side and only 8000lb on the rod side.
If, for any reason, the piston side of a double-acting cylinder is pressurized and at the same time fluid is
blocked on the rod side, pressure will increase (intensify) in the rod side of the cylinder until the forces
become balanced or the cylinder fails catastrophically. When we transpose the equation above to calculate the
pressure produced, we get P = F/A, Pressure = Force divided by piston surface Area.
Applying this to our 3” piston 2” rod and 2000psi pressure, on the piston side we get:- P = 14000 / 4 which
equals 3500 psi. Considerably more than the pressure on the other side. If we take the main relief pressure of
most systems of 2800psi, then our pressure goes to a staggering 4900psi which is definitely not good for your
system. Depending on where the hydraulic fluid is blocked, this could result in anything from a blown hose to
blowing the gland seals out or even catastrophic damage to the cylinder.
Remember, at Central Qld Hydraulics, we take any old cylinders that are preserved well, replace their
damaged parts to make them go on doing their outstanding work as new cylinders.
Call us today for more information
07 4952 5621
Surface area 7 inch²
Surface area 4 inch²
Cross sectional
surface area 3 inch²
2000psi
CENTRAL QUEENSLAND HYDRAULICS
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