Papua New Guinea Back-up Rings

Back-up rings are manufactured from extrusion resistant material as protection and support elements, normally with a rectangular cross-section. For static applications they are used together with an elastomer seal – usually an O-ring – placed in the groove. Because there is a tight fit between back-up ring and bore hole or rod it prevents the O-ring from extruding into the sealing gap under pressure.

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Papua New GuineaProduct Category

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Product Description

BACK UP RING

Back-up rings are manufactured from extrusion resistant material as protection and support elements, normally with a rectangular cross-section.

For static applications they are used together with an elastomer seal – usually an O-ring – placed in the groove.

Because there is a tight fit between back-up ring and bore hole or rod it prevents the O-ring from extruding into the sealing gap under pressure.

Gap extrusion destroys the O-ring

Back-up ring supports the O-ring

Back-up Rings Can Be Used In Static Applications As Well As In Translational Movements Or Slow Rotations

If the pressure is one-sided, it is sufficient to install the seal on the side opposite the pressure.

With pressurization on alternate sides, two back-up rings should be used, one back-up ring on each side of the O-ring.

O-Ring Installation Clearance Details And Recommendations

Pressure direction <->

Pressure direction ->

Pressure direction <->

Back-up ring SU
– Rectangular profile
– For static and back and forth movements or slow rotations

Back-up ring SG
– Rectangular profile, split
– As alternative to unsplit back-up rings if these cannot be installed or in case a split groove is not possible
– For static and back and forth movements
– Oblique cut at 30°or 45°angles, the back-up ring is cut chipless so that there will be no gap when installed.

Back-up ring SKG
– Concave profile, split
– Mainly for static applications, possible use in back and forth movements
– Protects the O-ring against extreme deformations during pulsating pressures due to the larger contact surface.
– The form stability of the O-ring has a favorable influence on leak tightness and service life
– As alternative to the unsplit SKU back-up rings if these cannot be installed or in case a split groove is not possible

Back-up ring SP
– Back-up ring, spiral form
– As alternative to unsplit back-up rings if these cannot be installed or in case a split groove is not possible
– For static and back and forth movements
– Oblique cut at 30° or 45° angles
– Application under large temperature fluctuations
– Large tolerance variations are compensated through spiral contraction and expansion

Back-up ring SUQ
– Special designs made of PTFE (snap-back, quenched)
– Easy installation in enclosed groove areas due to the recovery property of the PTFE material
– Because the dimensions deviate from standard designs, these back-up rings are manufactured only on request based on drawings

O-Ring Installation Groove Dimensions For Static Applications

cord strength (mm)	droove depth (mm)	w/o back-up ring (mm)	1 back-ring (mm)	2 back-ring (mm)	recommended back-up ring width (mm)
ø d	t ± 0,05	b + 0,25	b1 + 0,25	b2 + 0,25
1,50	1,10	2,10	3,10	4,10	1,00
1,78	1,35	2,50	3,50	4,50	1,00
2,00	1,56	2,70	4,20	5,70	1,50
2,50	2,05	3,30	4,80	6,30	1,50
2,62	2,18	3,50	5,00	6,50	1,50
3,00	2,52	3,90	5,40	6,90	1,50
3,50	3,00	4,40	5,90	7,40	1,50
3,53	3,00	4,40	5,90	7,40	1,50
4,00	3,40	5,00	6,70	8,40	1,70
5,00	4,25	6,30	8,00	9,70	1,70
5,33	4,53	6,70	8,40	10,10	1,70
5,70	4,85	7,10	9,10	11,10	2,00
6,00	5,10	7,50	9,50	11,50	2,00
6,99	5,94	8,80	10,80	12,80	2,00
7,00	5,95	8,80	10,80	12,80	2,00
8,00	6,80	10,00	12,50	15,00	2,50
10,0	8,50	12,50	15,00	17,50	2,50