Copyright Goodheart-Willcox Co., Inc.
Chapter 6 Cylinders 153
Summary
✓ Single-acting cylinders use fl uid pressure in
only one direction.
✓ A double-acting, single-rod cylinder
exhibits different forces when extending
and retracting under a given pressure
and different speeds when extending and
retracting using a given fl ow.
✓ Telescoping cylinders provide long strokes,
and compact lengths when retracted.
✓ A ram’s cylinder rod is the same diameter as
the cylinder’s piston.
✓ The gland guides the cylinder rod during
extension and retraction.
✓ Wear rings prevent metal-to-metal contact
during cylinder operation.
✓ Piston seals can be metal, Tefl on, lip design,
or O-ring.
✓ Rod seals retain the cylinder’s fl uid.
✓ Rod wipers prevent outside contaminants
from entering the cylinder.
✓ Cylinder shock loads can be dampened with
cushioned cylinders, orifi ces, accumulators,
or programmable kick-outs.
✓ Computing a cylinder’s speed requires
knowing the cylinder’s area and input fl ow.
✓ Potentiometers and magnetostrictive sensors
measure the position of a cylinder.
✓ When the cap end and rod end of a double-
acting cylinder are plumbed together, the
cylinder will regenerate.
✓ Cylinders can drift due to a bad pressure
control valve.
✓ A bad piston seal can cause cylinder drift
only if the rod points toward the ground.
✓ Manufacturers use master/slave series
designs to synchronize two cylinders.
✓ Rephasing orifi ces and rephasing relief
valves are used to place cylinders back into
synchronization.
✓ Compressed air and heat should never be
used to remove a seized cylinder piston or
gland.
✓ Do not mechanically restrict or stall an
operating actuator.
✓ Do not mechanically assist an actuator that is
under pressure.
Technical Terms
cap end
cushion
differential cylinder
double-acting cylinder
gland
head end
lip seal
magnetostrictive cylinder sensor
metering-in
metering-out
potentiometer
programmable kick-outs
ram
regeneration
rod seal
single-acting cylinder
spanner wrench
telescoping cylinder
tension load
thrust load
tie bolt cylinder
wear ring
wiper