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Rod and buffer seals

Rod sealing systems

Rod and buffer seals maintain sealing contact in sliding motion between the cylinder head and the piston rod. Depending on the application, a rod sealing system can consist of a rod seal and a buffer seal (fig. 1) or a rod seal only (fig. 2). Rod sealing systems for heavy duty applications typically consist of a combination of both seal types, whereas the buffer seal is arranged between the rod seal and the piston in the cylinder head. Rod seals determine the tolerance for the rod diameter d.

In addition to the sealing function, rod seals also provide a thin lubrication film on the piston rod that lubricates themselves and the wiper seals. The lubricant also inhibits corrosion of the piston rod surface. However, the lubrication film must be thin enough so that it returns to the cylinder during the return stroke.

Selecting profiles and materials for a rod sealing system is a complex task, considering all possible cylinder designs and application criteria. SKF supplies rod and buffer seals in many different profiles and in a wide range of materials, series and sizes, which make them appropriate for a wide variety of operating conditions and applications.

Rod seals

ProfileDescription
S1S

Single-lip U-cup profile made of polyurethane; suitable for medium to heavy duty applications
Additional information
Profile data
Size list metric [pdf]
ZBR

Double-lip U-cup profile made of polyurethane; suitable for medium to heavy duty applications
Additional information
Profile data
Size list metric [pdf]
Size list inch [pdf]
SIL

Double-lip U-cup profile made of polyurethane; suitable for low temperatures and light to medium duty applications
Additional information
Profile data
Size list metric [pdf]
PTB

Polyurethane U-cup profile with incorporated nitrile rubber X-ring, which provides good performance even at low pressure and temperature; suitable for medium duty applications
Additional information
Profile data
Size list metric [pdf]
Size list inch [pdf]
STD

Polyurethane U-cup profile with incorporated nitrile rubber X-ring, which provides good performance even at low pressure and temperature; fits narrow housings; suitable for medium duty applications
Additional information
Profile data
Size list inch [pdf]
DZ

Nitrile rubber primary sealing ring, polyurethane secondary sealing ring; low friction; suitable for medium to heavy duty applications
Additional information
Profile data
Size list metric [pdf]
Size list inch [pdf]
DZR

Nitrile rubber primary sealing ring, polyurethane secondary sealing ring, integrated triangular polyamide anti-extrusion ring; improved gap extrusion resistance; suitable for heavy duty applications and extreme pressures
Additional information
Profile data
Size list metric [pdf]
Size list inch [pdf]

Buffer seals

ProfileDescription
RBB

Buffer seal with polyurethane sealing ring, integrated polyacetal or polyamide anti-extrusion ring; designed to vent pressure back to system side; improved gap extrusion resistance at abrupt pressure peaks; fits narrow housings; suitable for heavy duty applications
Additional information
Profile data
Size list metric [pdf]
Size list inch [pdf]
S9B

Buffer seal with nitrile rubber O-ring energizer, PTFE slide ring; also available with polyurethane slide ring to improve wear resistance and ease installation; suitable for medium to heavy duty applications
Additional information
Profile data
Size list metric [pdf]
Size list inch [pdf]
RSB

Buffer seal with PTFE slide ring, nitrile rubber energizer; patented and improved design to reduce pressure peaks acting on the rod seal and vent pressure back to system side; improved gap extrusion resistance at abrupt pressure peaks; suitable for medium to heavy duty applications
Additional information
Profile data
Size list inch [pdf]
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