TEFLON® U-CUP PACKINGS

U-cup packings have low frictional qualities and are completely automatic in action. Due to their design, they can be assembled satisfactorily in glands which havbe vvariations in cross sectional dimensions, thus permitting more liberal manufacturing tolerances. U-cups packings are also very successful in applicationsj where it is desirable to reduce excessive packing friction.

Design & Installation

The gland ring supporting the heel of the packing must be close fit to the rod, having ja maximum radial clearance of .003". It is recommended that the rod surface finish be 16 RMS (max.). Internal threads should be offset so that no damage will be done to the U-cup lips upon installation.

The installations shown in the drawing above are recommended. One illustrates a typical outside packed installation and the other an inside packed installation. The same general design rules apply for both of these types; however, provision should be made for support of the cup at the base of the groove to permit the lips to flex under varying pressurej loads. The metal support ring or adapter used for this purpose should not exert axial pressure at the base of the groove, since this would tend to retract the lips of the cup away from the sealed surfaces. It is suggested that the metal support ring be constructed so that it will be properly centered. U-cup packings can also be adapted for spring loading.

Operating Pressure

U-cup packings conforming to the drawing below are generally recommended for operating pressures up to 1500 psi. On installations where operating pressures exceed 300 psi, diametral clearances at the heel of the cup should be held to .004" - .006".