After considering the factors that generally affect all O-ring seals, you must also think about your specific type of application. O-ring seals fall into two main application categories: static and dynamic. Static seals exist where there is no relative motion between the mating surfaces being sealed. Both static and dynamic seals engender their own unique concerns. Relatively-speaking, however, static seals are easier to design because they can handle wider tolerances, rougher surface finishes, and higher pressure limits. There are four major types of static seals:
STATIC
RADIAL SEALS
Static radial seals are formed when squeeze (compression) is applied
to the inside diameter (I.D.) and outside diameter (O.D.) of the O-ring.
Cap and plug type configurations commonly utilize radial seals. An example
of a static radial O-ring seal for a male gland is shown in Figure
93. A static radial O-ring seal for a female gland is shown
in Figure 94. Gland design measurements for
static radial O-ring seals can be found in Table 41.
Gland dimensions can be found in Table 42.
STATIC
AXIAL (FACE) SEALS
Static axial seals (also known as face seals) are formed when squeeze
is applied to the top and bottom surfaces of the O-ring. Axial seals
are most often used in face (flange) type designs where an O-ring seats
against the groove’s low-pressure side. A static axial O-ring seal
(internal pressure) is shown in Figure 95.
A static axial O-ring seal (external pressure) is shown in Figure
96. Gland design measurements for static axial O-ring seals
can be found in Table 43. Gland dimensions
can be found in Table 44.
STATIC
SEALS WITH “DOVETAIL” GROOVES
Dovetails are face type designs that have been customized to form static
seals by structurally immobilizing the O-ring within the gland. Dovetails
are more expensive and difficult to design and install than the other
types of static seals. A dovetail seal is shown in Figure
97. Gland design measurements for dovetail grooves can
be found in Table 45.
STATIC
CRUSH SEALS
Static crush seals use a male cover with a machined 45° angle to “crush” an
O-ring into the corner of a triangular gland. Because the resulting distortion
to the O-ring is permanent, it cannot be reused later. An example of
a static crush seal is shown in Figure 98.
Gland design measurements for crush seals can be found in Table
46.
STRAIGHT
THREAD TUBE FITTING SEALS
Another
static seal application is the straight thread tube fitting seal. We
will not go into the subject in detail here because this particular type
is not as common a configuration as the above mentioned seals. Boss dimensions
for industrial straight thread tube fitting seals can be found in Table
47.
The gland dimensions for the above seals (with the exception of the tube fitting seal) can be calculated with our online O-Ring Calculator.
“Static seals exist where there is no relative motion between the mating surfaces being sealed.”
Figures
93-94
Table 41
Table 42
Figures 95-96
Table 43
Table 44
Figure 97
Table 45
Figure 98
Table 46
Table 47