Page 275 - The Tribology Handbook

B23 Lip seals

SEALS FOR RECIPROCATING SHAFTS

Packing types

Cups and hats Semi-automatic (flange clamping problems).
Rubber obsolescent but leather and
rubber/fabric still used

‘U’ packings Used for any piston or rod application up to
100 bar (1500 psi) (rubber) or 200 bar
(3000 psi) (rubber/fabric or
polyurethane)

N ylon-supported Enables all the advantages of nitrile ‘U’
packings to be obtained up to 250 bar
(4000 p.s.1.)

Composites I I Many proprietary designs-usually with
rubber sealing lips, rubber/fabric
supporting portions and nylon wearing
portions. Pressure range varies, but is
usually in the 150-250 bar
(250C-4000 psi) region

Materials

Rubber (nitrile) Highest sealing efliciency. Easily formed to shape. Low cost. Limited pressure capability, 100 bar
(1 500 p.s.i.). Excellent wear resistance. Poor extrusion resistance
Rubber-impregnated fabric Great toughness, resistance to cutting and extrusion. Wear resistance inferior to plain rubber

Polyurethane rubber Best toughness and wear resistance. Used for flexible packings at the highest pressures
~ ~~ ~ ~~~
Leather Good wear and extrusion resistance. Limited shaping capability Poor resistance to permanent set
Nylon Combines well with rubber to resist extrusion and to provide good bearing surfaces

823.4