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Content

            1. Diagrammes de taille de joints en 'u' comblé
            2. Description de joints en 'u' comblé
            3. Profils
            4. Numéros de la pièce
            5. Considérations de design
                        Finition de surface
                        Chamfer
                        Cross-Section Vs Diameter
                        Pressure Resistance
 


Loaded U-Cup Description

Loaded U-cups are excellent seals for low-pressure rod and piston applications. With loaded U-cups, as the system pressure increases, so does the force on the loading lips. This automatically compensates for the higher pressure, while still maintaining a positive seal. A variety of styles, materials and sizes are available to suit specific requirements.



Profiles

Square with a Straight Lip

The standard O-ring loaded U-cup profile is square in cross section and it is suitable for both rod and piston applications. The standard design can be used to replace existing hydraulic packing and O-Rings without changing gland design.

Deep with a Straight Lip

The deep O-ring loaded U-cup design is a modified version of the standard square U-cup shape. This design has approximately 1-1/2 times the axial depth of the square profile, which greatly adds to the stability of the design in higher-pressure applications. Generally, a gland would have to be modified for this seals when replacing O-rings. The deep O-ring loaded U-cup is an ideal design for replacing V or W packing, or braided rope packing.


Deep with a Beveled Lip

The type B O-ring loaded U-cup is similar in design to the deep U-cup with a straight lip, except it features a back beveled sealing lip. The beveled lip is designed to provide additional film breaking ability and increased squeeze on the sealing surface. The back bevel on the lip aligns the seal interface near the centerline of the O-Ring energizer. This provides an increased sealing force, which adds to the low pressure sealing capability while also increasing the high pressure sealing ability. The added length also provides stability to the seal.

Square with a Beveled Lip

The Square beveled design provides you with the additional sealing ability of the back bevel
lip design, while still being able to replace o-rings without changing the groove.



Part Numbers




Prefix
Base Material
Loader Material
LUC
Urethane
Nitrile
HSN
Highly Saturated Nitrile
Highly Saturated Nitrile
VUC
Viton®
Viton®
HTL
Hytrel®
Nitrile


Example: LUC 1250 1062 250 B - Urethane U-cup with a straight lip and Nitrile O-ring- 0.125” C/Sm 1.062” Nominal I.D., 0.250” Height (nominal depth)

Go to loaded U-cup size charts.



Design Considerations



Surface Finish

Surface finishes that are too high or low can reduce seal life. The chart below provides a general guideline on surface finish. However, RMS surface finish alone does not ensure good seal performance. With some applications contacting Hi-Tech Seals for additional recommendations is suggested.

 Static 100 RMS
 Dynamic 32 RMS

Chamfers

Chamfers are used as a guide to aid seal installation. The “A” dimension shown below will allow the O-ring loaded U-cup to enter a cylinder bore and should be the minimum width designed.

Nom. C/S
Straight Lip
Square
A
Straight Lip
Deep
A
Beveled Lip

A
1/8
0.031
0.036
0.046
3/16
0.046
0.050
0.062
1/4
0.050
0.062
0.078
5/16
0.062
0.071
0.078
3/8
0.062
0.078
0.083
1/2
0.094
0.100
0.109
9/16
0.100
0.125
0.125
5/8
0.100
0.125
0.125
3/4
0.109
0.125
0.143
7/8
0.120
0.156
0.156
1
0.133
0.163
0.172


Cross Section vs. Diameter

If the seal’s cross-section it too large in relation to the seal’s diameter installation can become increasingly difficult. The guidelines below are based on urethane.

Cross Section
Rod Seal
Min. U-Cup I.D.
Piston Seal
Min. U-Cup O.D.
1/8
0.750
1.250
3/16
1.000
1.750
1/4
1.750
3.000
3/8
3.000
6.000
1/2
6.000
10.000
3/4
8.000
15.000
1
10.000
25.000

Guideline is based on urethane


Pressure Resistance

Several variables affect a u-cups ability to resist pressure. These factors include material, heat, and extrusions gap.


Extrusion Gap

Radial Depth H
emax at 60°C
2300 PSI
3600 PSI
5800 PSI
0.125
0.008
0.004
-
0.156 to 0.187
0.014
0.008
-
0.218 to 0.250
0.018
0.010
0.004
0.281 to 0.437
0.020
0.012
0.006
0.500 to 0.562
0.024
0.012
0.008
0.625 to 0.750
0.024
0.012
0.008