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Content

            1. Loaded U-Cup Size Charts
            2. Loaded U-Cup Description
            3. Profiles
            4. Part Numbers
            5. Design Considerations
                        Surface Finish
                        Chamfer
                        Cross-Section Vs Diameter
                        Pressure Resistance
 


Loaded U-Cup Description

The loaded U-cup is an excellent seal in low pressure rod and piston applications. As the system pressure increases, the loading lip force also increases, automatically compensating for the higher pressure while maintaining a positive seal. A variety of styles, materials and sizes are available to suite your 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 widely 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 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, you would have to make gland modifications for this seal when replacing O-Rings, but this design is ideal 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 but it features a back beveled sealing lip designed for additional film breaking ability and increased squeeze on the sealing surface. By adding the back bevel on the lips, it aligns the seal interface near the centerline of the O-Ring energizer to provide 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 B 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
* Height is only listed if the axial height is greater than the cross section

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

The chart below provides you with a general guideline on surface finish. However, RMS surface finish alone does not ensure good seal performance and in some applications you will need to contact Hi-Tech Seals for additional recommendations. Surface finishes that are too high or too low can reduce seal life.

 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 cross section of the seal is too large in relation to the seal diameter it can be increasingly difficult to install. Below are general guidelines:

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