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TM 9-2320-356-BD
14-7.
BOOM ELEVATING OR CROWD CYLINDERS INOPERATIVE
General Information:
Most hydraulic cylinder failure is caused by faulty seals
A hydraulic cylinder consists of a cylinder body, a movable piston, and a piston
rod attached to the piston.
End caps are attached to the cylinder body barrel by
threads, keeper rings, tie rods, or a weld.
(Industrial cylinders use tie rods.)
As the cylinder rod moves in and out,
it is guided and supported by a removable
bushing called a rod gland.
The side through which the rod protrudes is called the head. The opposite side
without the rod is termed the cap.
Inlet and outlet ports are located in the head
and cap.
For proper operation,
a positive seal must exist across a cylinder’s piston as well
as at the rod gland.
Cylinder pistons are sealed by using lipseals or cast iron
piston rings.
Rod gland seals come in several varieties.
Some cylinders are equipped with a
V-shaped or cup-shaped primary seal made of leather, polyurethane, nitrile, or
viton, and a wiper seal which prevents foreign materials from being drawn into the
cylinder.
One popular type of rod gland seal consists of a primary seal with serrated edges
along its inside surface.
The edges contact the rod continuously and scrape it
clean of fluid.
A second wiper seal catches fluid which may get by the primary
seal and also wipes the rod of foreign material when the rod retracts.
Limitations:
o Degraded load capacity
Personnel/Time Requirement:
o 1 soldier
o 1 to 2 hours
Materials/Tools:
o Pump packing
o S t r i n g
o Rope
o Candles or paraffin-base wax
o Lip protection balm
14-6
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