designed because of the following advantages of such
Small space requirement
No adjustment required
No critical torque in clamping
Low distortion structure
Ease in maintenance
Ease of installation
Effectiveness over wide pressure and temperature
O-rings are used in both static (as gaskets) and
dynamic (as packing) applications. An O-ring has always
been the most satisfactory choice of seals in static
applications when the fluids, temperatures, pressure, and
Quad-Rings. The quad-ring is very similar to the
O-ring, the major difference being that the quad-ring has
a modified square type of cross section, as shown in
figure 3-45. Quad-rings are molded and trimmed to
extremely close tolerances in cross-sectional area, inside
diameter, and outside diameter. Quad-rings are ideally
suited for both low pressures and extremely high
U-CUPS.The U-cup (fig. 3-46) is a popular
packing due to its ease of installation and low friction.
U-cups are used primarily for pressures below 1,500 psi;
but, they can be used for higher pressures with the use of
backup rings. When more than one U-cup is installed,
they are installed back to back or heel to heel. This back-
to-back installation is necessary to prevent a pressure trap
(hydraulic lock) between two packings.
Figure 3-46.Typical U-cup seal.
HYDRAULIC SYSTEM MAINTENANCE
Maintenance of a hydraulic system that is properly
operated and cared for is a routine task. Maintenance
usually consists of changing or cleaning filters and
strainers, and occasionally adding or changing the fluid
in the system. However, overheating, excessive pressure,
and contamination can damage an improperly operated
Proper maintenance reduces your hydraulic troubles.
By caring for the system using a regular maintenance
program, you can eliminate common problems and
anticipate special ones. These problems can be corrected
before a breakdown occurs.