Assembly-Hints; Chamfers; Traversing Of Cross Drilled Ports; Cleanliness And Cleaning Materials - Parker O-Ring Handbuch

10. Assembly-hints

10. Assembly-hints
Leak-free seals are achieved only when proper sealing material
is selected in the right sizes and sufficiently deformed. Correct
deformation depends on observance of machine element toler-
ances and surface finishes. In practical terms all factors influenc-
ing the seal must be considered. Care not taken on assembly
leads to high servicing costs and subsequent down-time.

10.1 Chamfers

To prevent damaging of seals during assembly, chamfers are
necessary on all leading edges. All edges must be free from
burrs and sharp edges bevelled.
Fig. 10.1 Assembly example of piston
Fig. 10.2 Assembly example of rod
15° to 20°
"Leading edge
chamfer" x > y
Fig. 10.3 The diagram shows the leading edge chamfer and an O-ring before defor-
mation. The dimension X should be greater than dimension Y to ensure a
trouble-free assembly operation
15° to 20°
15° to 20°

10.2 Traversing of cross drilled ports

An O-ring can be sheared when a spool or rod moves in a bore
broken by cross-drilled ports. The deformed O-ring returns to its
original round cross-section as it enters the port and is sheared
as it leaves the drilled area. To avoid this, connection holes
should be repositioned. If repositioning should not be possible,
an internal chamfer is recommended.
Fig. 10.4
Fig. 10.5 Internal chamfer
Fig. 10.6 Optimal solution is the relief of the bore on complete circumference which
allows the O-ring to return to a round cross-section before being com-
pressed again

10.3 Cleanliness and cleaning materials

Lack of cleanliness of O-ring glands leads to leakage. To ensure
protection from foreign particles of sealing faces during working
life it is necessary to use filters or to plan maintenance cycles.
Cleaning material must also be a medium which is compatible
with the elastomer. Also grease used to ease assembly must be
compatible.
177
O-Ring Handbook
Parker Hannifin GmbH
O-Ring Division Europe