Additionally there are other considerations when designing Loaded Lip U-Cups. Following are some cases.

In the back-to-back piston application as in a double acting piston, there is a need for the energizer to be removed to prevent pressure forming in between the seals. For these situations, it is recommended that the "B" style Loaded Lip U-Cup be used.

The energizer keeps the lips of the seal pressed against the sealing surfaces thus allowing the Loaded Lip U-Cup to seal under low pressure.

You will notice from the chart below that the groove axial length is a few thousandths of an inch more than the height of the Loaded Lip U-Cup. This allows the seal to float and helps it seal under slight side loads.

loaded Lip U-Cups give longer wear life because of a larger lip contact area than the live contact area of other conventional packings.

Finally loaded Lip U-Cups should be lubricated with suitable lubricant.

The chemical composition of all pressure mediums is of primary importance. Mediums used by many manufactures are by-products of the processes for which the hydraulic or pneumatic machinery is employed. Often, the result is that the chemically active liquids are the pressure media against which packings have to act. Use of a by-product is sound enough practice, provided that the chemical composition of the pressure medium is considered when packings are selected.

Depending on the specific application, Loaded Lip U-Cups are usually made of either Carboxylated Nitrite, Urethane, EPDM or Fluorestomer compounds. Again, the difference in material depends upon various application factors and operating environments.

Columbia offers three styles of the Loaded lip U-Cup: Standard, Deep Base, and "B" Styl. In addition, Columbia will supply Loaded Lip U-Cups in various types of elastomers to meet your specific requirements. Please refer to the figure on the right column of this page which shows these various styles.

The Standard deign is usually symmetrical in cross section in which the height of the U-Cups is the same as the cross section.

The Deep Base (DB) U-Cup is the same basic design as the standard style except the height is taller

The "B" Style has a back beveled lip and generally the same height as the deep base, but functions with more lip interference. This design helps to ensure optimum sealing function. This style is particularly useful in high pressure conditions. In addition, the design of the "B" style loaded Lip U-Cup combines ease of installation with rugged construction for highly effective seal in heavy duty applications.

This series of sealants can be designed into the original equipment for significantly longer life than some of the other types of seals.