KEVOS® MAKEOS · Engineering
O-Ring Groove Design (Depth, Width, Bore and Extrusion Gap)
What groove depth and width give my target squeeze and fill for this O-ring, what mating diameter does that set, and is the extrusion gap small enough?
Design of a radial O-ring gland (piston or rod): stretch of the ring on the groove diameter and the reduced cross-section, groove depth for your target squeeze, groove width for your target fill, the mating bore or rod diameter that results, and a check of the depth and width you actually choose for squeeze, fill and stretch against your limits (as the O-ring gland tool), with the extrusion gap against your allowable for the pressure.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Gland | choice | Whether the groove is on the moving inner part (piston) or in the housing (rod). |
| O-ring inside diameter | mm | Inside diameter of the O-ring. |
| O-ring cross-section | mm | Cross-section diameter of the O-ring. |
| Groove diameter (bottom for piston, outer for rod) | mm | For a piston, the diameter at the bottom of the groove; for a rod, the outer diameter of the groove. |
| Target squeeze | % | Squeeze you design to. |
| Target fill | % | Share of the groove area the ring fills, designed to. |
| Groove depth chosen (0 = use the design value) | mm | Groove depth on the drawing (0 to use the design value). |
| Groove width chosen (0 = use the design value) | mm | Groove width on the drawing (0 to use the design value). |
| Your limits | ||
| Smallest squeeze | % | Smallest squeeze you accept (for the duty; from the seal maker). |
| Largest squeeze | % | Largest squeeze you accept. |
| Largest fill | % | Largest fill you accept (room for swell and heat). |
| Largest stretch (piston) or compression (rod) | % | Largest stretch of the ring on a piston groove, or diametral compression in a rod groove. |
| Radial extrusion gap | mm | Radial clearance between the parts at the seal. |
| Largest gap for the pressure and hardness | mm | Largest clearance for the pressure and ring hardness (from the seal maker). |
Method and formulas
- Piston stretch = (groove diameter − ring ID) ÷ ring ID; rod compression from the ring OD; stretched cross-section = cs ÷ √(1 + stretch) (as the O-ring gland tool).
- Depth = cs′ (1 − squeeze); width = π cs′² ÷ 4 ÷ (depth × fill).
- Mating bore (piston) = groove diameter + 2 × depth; mating rod (rod) = groove diameter − 2 × depth.
- At the chosen groove: squeeze = (cs′ − depth) ÷ cs′; fill = π cs′² ÷ 4 ÷ (depth × width).
- Example: the ring stretches 1.6518%; 2.0789 × 3.4016 mm gives the target, and the chosen groove gives 19.188% squeeze and 70.154% fill.
Limitations
- Nominal dimensions; check squeeze and fill at the tolerance extremes too.
- Static or slow dynamic seals; high-speed and rotary seals need different glands.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Design a gland for a standard O-ring
- Check a drawn gland before machining
- Find the clearance a pressure allows
Who it is for
- Design engineers
- Hydraulic engineers
- Sealing engineers
What you get
- Stretch and stretched cross-section
- Design depth, width and mating diameter
- Squeeze, fill, stretch and gap checks at the chosen groove
Interpreting the result
- If the extrusion gap is too large for the pressure, fit a back-up ring rather than tightening the fit.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2591–2610. Topic reference; no source tables or recommended settings are reproduced.
- ISO 3601-2 Fluid power systems — O-rings — Housing dimensions for general applications
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Open the O-Ring Groove Design (Depth, Width, Bore and Extrusion Gap) calculator
