X-Ring Groove Dimensions & Selection Guide | AS568A-Compliant Star Seals

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Overview

The X-Ring (also known as a Quad Seal) is a four-lip sealing element with an X-shaped cross-section. Developed as an enhanced alternative to O-rings, it fully complies with the AS 568A standard for O-ring dimensions and can replace O-rings in most applications.

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Advantages

• Reduced Friction: Lubricant reservoirs between sealing lips minimise startup resistance.

• Optimised Flash Trim: Trimming at recessed cross-sectional areas ensures superior sealing performance.

• Non-Rolling Design: Non-circular cross-section prevents rotation during reciprocating motion.

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Technical Data

X-Rings are suitable for diverse applications. Material selection depends on:

• Temperature range (static vs. dynamic)

• Pressure conditions

• Media compatibility

Critical Considerations:

• Peak vs. continuous operating temperatures

• Duty cycle requirements

• Frictional heat generation in rotary applications

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Sealing Mechanism

As a self-energising dual-action seal, the X-Ring generates radial and axial sealing forces proportional to system pressure. Increased pressure enhances compression deformation, improving total sealing force for reliable performance.

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Selection Guidelines

1. Static Seals & Linear Motion

• Bore Seals:

  • Inner diameter (ID) ≈ groove outer diameter (OD) -2%

  • Pre-compression prevents twisting

• Shaft Seals:

  • ID ≈ shaft OD +0.2–0.3mm (or +1%)

  • Facilitates installation and extends service life

2. Rotary Seals

• ID ≈ shaft OD +2–5%

  • Compensates for thermal shrinkage (Joule effect)

  • Smaller cross-sections for static use; larger for dynamic

3. High-Pressure/Extrusion Risks

• Use harder compounds (e.g., N70 NBR, Shore A70)

• Always pair with PTFE backup rings for gaps >0.1mm

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Material Compatibility

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Installation Dimensions

Cross-Section Diameter (mm)	Radial Initial Compression (mm)		Groove Dimensions (mm)					Radius r₁	Extrusion Gap Sₙₐₓ
	Dynamic Seal (Max/Min)	Static Seal (Max/Min)	Groove Depth		Groove Width
			Dynamic t₁⁺⁰‧⁰⁵	Static t₂⁺⁰‧⁰⁵	b₄⁺⁰‧²	b₂⁺⁰‧²	b₃⁺⁰‧²
1.02	0.300 / 0.115	0.350 / 0.165	0.08	0.75	1.2	—	—	0.1	0.03
1.27	0.330 / 0.145	0.430 / 0.245	1	0.9	1.4	—	—	0.1	0.03
1.52	0.350 / 0.165	0.450 / 0.265	1.25	1.15	1.7	—	—	0.22	0.04
1.78	0.360 / 0.175	0.460 / 0.275	1.5	1.4	2	3.4	4.8	0.22	0.05
2.62	0.400 / 0.215	0.450 / 0.265	2.3	2.25	3	4.4	5.8	0.3	0.08
3.53	0.430 / 0.205	0.530 / 0.305	3.2	3.1	4	5.4	6.8	0.4	0.08
5.33	0.560 / 0.250	0.710 / 0.400	4.9	4.75	6	7.7	9.4	0.4	0.1
7	0.700 / 0.250	0.950 / 0.600	6.4	6.2	8	10.5	13	0.6	0.1

Notes:

1. All dimensions in millimetres (mm).

2. Tolerance notations:

   • t₁⁺⁰‧⁰⁵: Groove depth tolerance for dynamic seals: +0.05 mm

   • b₄⁺⁰‧², b₂⁺⁰‧², b₃⁺⁰‧²: Groove width tolerances: +0.2 mm

3. Not applicable for the specified cross-section.

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Model and Specifications Table for X-Rings

*Compliant with ISO 3601-1 and AS568 standards*

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