Cup packings are recommended wherever hydraulic packings are subjected to destructive action of corrosive or solvent fluids. Cup packings are also used to seal against chemical solutions, aromatics, corrosive gases, and other aggressive fluids.
There are four standard cup packings designs, all of which are available in 100% virgin PTFE or filled PTFE.
A-Cups: Recommended for use on inside packed pistons. The lip of this cup forms a tight seal under discharge pressure but relaxes on the reverse stroke to reduce wear and friction.
A base thin enough to minimize cold flow yet thick enough to give the cup rigidity.
A tapered lip which increases the sealing effectiveness of the cup while yielding to the bore to prevent lip damage.
A thick heel to provide increased material for longer cup life.
Flared lips so the lip diameter has sufficient interference with the cylinder bore.
(See figure 1)
U-Cups: Recommended for applications on pistons where low operational friction is necessary.
Tapered lips which increase the sealing effectiveness of the cup and which yielded sufficiently during installation to eliminate lip damage.
A thick heel which provides increased material for longer cup life and stability.
Flared lips for sufficient initial interference.
(See figure 2)
Hat cups: Recommended for rod applications with material for longer cup life and stability.
A base of sufficient thickness which adequately supports the sealing lip and which allows sufficient compression of the base to prevent leakage at that location.
A tapered lip which increases the sealing effectiveness of the cup and which yields sufficiently during installation to prevent lip damage.
A thick heel which provides increased material for longer cup life.
Flared lips which give the lip diameter sufficient interference with the shaft.
(See figure 3)
Rof wipers: Recommended for rod applications which require less surface contact with the shaft than hat cups provide.
Design features: Same as those of hat cups, except for the greater lip angle and less surface contact with the shaft.
Note: Cup packings will be furnished to the standard design unless otherwise specified. Cup packings with other nominal dimensions are available upon request. Please include all nominal dimensions and tolerances with request for quotation or purchase order.