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PTFE Back-up Rings, Spiral Backing Rings and deformed parts

2018-12-25T07:46:12+00:000000001231201812


Description
Back-up Rings have no intended sealing function.
They are protective and supporting elements made from extrusion-resistant materials which generally have a rectangular cross section. They are installed in a groove together with an elastomeric sealing element preferably with a corresponding O-Ring in static applications.Due to the tight fit of the Back-up Ring in the housing, they prevent extrusion of the pressurised elastomeric sealing element into the sealing gap.

Advantages
– Use of O-Rings in high pressure applications
– Use of O-Ring materials with a low hardness
– Compensation of radial sealing gaps
– Use for internal and external sealing applications
– Reciprocating and rotating movements possible
– Compensation for large temperature fluctuations
– Static and dynamic applications

External sealing (Bore)
Back-up Ring types, uncut
Type BM
– Rectangular cross section
– Material: PTFE
– Static and dynamic use
– Reciprocating and rotating movements possible
Type BCM
– Concave cross section
– Materials: NBR, FKM
– The large contact surface protects the O-Ring against
deformation in case of high pulsating pressure
– Dimensional stability of the O-Ring improves the sealing force and increases the service life
– Preferably for static use
– Reciprocating movements possible

Back-up Ring types, cut
Type BG
– Rectangular cross section
– Material PTFE
– Cut angle of 30° or 45° or 20°
– Static and dynamic use
– Reciprocating and rotating movements possible
– Preferred for installations in a closed groove where uncut Back-up Rings are not suitable
Type BCC
– Concave cross-section
– Material: PTFE
– Cut angle of 30° or 45°
– The large contact surface protects the O-Ring against
deformation in case of high pulsating pressure
– Dimensional stability of the O-Ring improves the sealing force and increases the service life
– Static and dynamic use
– Reciprocating movements possible
– Preferred for installations in a closed groove where uncut Back-up Rings are not suitable
Back-up Ring types, spiral
Type SP
– Rectangular cross section
– Material: PTFE
– Cut angle of 30° or 45°
– Consists as standard two spiral windings which are cut at the ends at an angle
– Static and dynamic use
– For reciprocating movements only
– Preferred for installations in a closed groove where uncut Back-up Ring are not suitable
– Compensation of large temperature changes and tolerances without difficulties by a
screw-like elongation and contraction. Easy Installation in closed grooves for external sealing
applications
– The dimensions are different compared to standard Back-up Rings
Internal sealing (Rod)
Back-up Ring types, uncut
Type BM
– Rectangular cross section

– Material: PTFE
– Static and dynamic use
– Reciprocating and rotating movements possible
Type BCM
– Concave cross-section
– Materials: PTFE, NBR, FKM
– The large contact surface protects the O-Ring against deformation in case of high pulsating
pressure
– Dimensional stability of the O-Ring improves the sealing force and increases the service life
– Static and dynamic use
– Reciprocating movements possible
Back-up Ring types, cut
Type BG
– Rectangular cross section
– Material: PTFE
– Cut angle of 30° or 45°
– Static and dynamic use
– Reciprocating and rotating movement possible
– Preferred for installations in closed grooves where uncut Back-up Ring are not suitable
Type BCC
– Concave cross-section
– Material: PTFE
– Cut angle of 30° or 45°
– The large contact surface protects the O-Ring against deformation in case of high pulsating
pressure
– Dimensional stability of the O-Ring improves the sealing force and increases the service life
– Static and dynamic use
– Reciprocating movements possible
– Preferred for installations in a closed groove where uncut Back-up Rings are not suitable
Back-up Ring type, spiral
Type SP
– Rectangular cross section
– Material: PTFE
– Cut angle of 30° or 45°
– Consists as standard two spiral windings which are cut at the ends at an angle
– Static and dynamic use

– For reciprocating movements only
– Preferred for installations in a closed groove where
uncut Back-up Ring are not suitable
– Compensation of large temperature changes and tolerances without difficulties by a
screw-like elongation and contraction
Figure Back-up Ring types

External sealing (Bore)
Type BM
– Rectangular, uncut, PTFE
– Standard: AS568 MS27595,JIS B2407
Type BCM
– Concave, uncut, PTFE+NBR + FKM
Type BG
– Rectangular, cut, PTFE
– Standard:AS568 MS28774,MS28773,JIS B2407,AS8791/1,AS4716,AS5860
Type BCC
– Concave, cut, PTFE
– Standard:AS568
Type SP
– Spiral, PTFE
-Standard: AS568 TF171,MS28782,MS28783,JIS B2407
Internal sealing (Rod)

H Type BM
– Rectangular, uncut, PTFE
– Standard: AS568 MS27595,JIS B2407
H Type BCM
– Concave, uncut, NBR + FKM + PTFE
– Standard:AS568
H Type BG
– Rectangular, cut, PTFE
– Standard:AS568 MS28774,MS28773,JIS B2407,AS8791/1,AS4716,AS5860
H Type BCC
– Concave, cut, PTFE
– Standard:AS568
H Type SP
– Spiral, PTFE
-Standard: AS568 TF171,MS28782,MS28783,JIS B2407
Materials
Back-up Rings are as standard manufactured from virgin PTFE. In view of the unfavourable
cold flow behaviour of virgin PTFE, these Back-up Rings are used only for low to medium loads. For higher load requirements, filled PTFE materials (with glassfibre, bronze, carbon, etc.) have to be used. For sealing against high pressures, Back-up Rings made from specially modified thermoplastic materials are used.For the series production of larger quantities, injection moulded Back-up Rings can be manufactured, e.g. NBR 90 Shore A, FKM90 Shore A, or thermoplastic elastomers (TPE) on request.

Applications
Application examples
– Injection moulding machines
– Machine tools
– Presses
– Excavators

– Agricultural machines
– Valves for hydraulic circuits
Technical data
Operating pressure
Static applications: Up to approx. 250 MPa depending on the Back-up Ring material and sealing gap
Dynamic applications: Reciprocating up to approx. 40 MPa Oscillating/slowly rotating up to approx. 15 MPa
Speed: Reciprocating or rotating up to approx. 2 m/s depending on the material
Operating temperature: – 200 °C to + 260 °C depending on the material

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