Fluid-Power Sealing, Parker / AS568 Elastomer O-Ring Glands, Squeeze & Extrusion
Elastomer O-Ring Squeeze % & Gland Fill Swell Formula
Calculate Linear Diametral Interference Squeeze (mm), Percentage Cross-Sectional Squeeze (%), Swollen-Elastomer Rectangular Gland Fill (%), and Parker Static Gland Compliance.
Rubber is incompressible (`nu ≈ 0.499`)—machining an O-ring groove to 100% fill hydraulic-locks the flange or shears the O-ring on hot oil swell!
Novice CAD designers machine an O-ring groove JUST wide enough to fit the compressed circle (`Area = (PI()/4) * CS^2`)—forgetting two laws of elastomer physics: (1) Vulcanized FKM / NBR rubber is **nearly as incompressible as hydraulic oil** (`Poisson’s ratio ≈ 0.4995`), AND (2) rubber has **10x the thermal expansion coefficient of steel** plus `5%–15%` volumetric swell in hot hydrocarbon fluids! Under the **Parker O-Ring Handbook / ISO 3601-2** static radial/face gland rules, Gland Depth `h` (mm) compresses Cord Cross-Section `CS` (mm, e.g. `3.53` mm for AS568 `-2xx` series) by **Linear Squeeze `CS - h`** to hit **`15% <= Squeeze% <= 30%`** (`((CS - h) / CS) * 100`), WHILE Rectangular Groove Width `w` (mm) MUST keep **Swollen Gland Fill `Fill% = (((PI()/4) * CS^2 * (1 + Swell%/100)) / (h * w)) * 100 <= 85%`** (`75%` ideal) so the expanding elastomer has void breathing room without extruding into the clearance gap!
Verify on an AS568-224 (`CS = 3.53` mm) FKM Static Hydraulic Flange Gland—O-Ring_Cord_Cross-Section `CS` = 3.53 mm (B2), Machined_Groove_Depth `h` = 2.75 mm (B3 -> Linear Squeeze = `0.78` mm in E2 & Squeeze = `22.10%` in E3), Machined_Groove_Width `w` = 4.80 mm (B4), and Hot-Oil_Plus_Thermal_Volume_Swell = 12.0% (B5): Swollen Gland Fill equals `83.04% <= 85%` (E4), passing `"PARKER STATIC GLAND PASS"` (E5)!
| ISO 3601 / Parker O-Ring Gland KPI (CS=3.53 mm, Depth h=2.75 mm, Width w=4.80 mm, 12% Swell) | Formula | Verified Output |
|---|---|---|
| Diametral Compression Squeeze (mm) | Cord_CS_mm - Gland_Depth_h_mm | 0.78 mm |
| Cross-Sectional Squeeze (%) | ((CS_mm - h_mm) / CS_mm) * 100 | 22.10% (inside 15%–30% static window) |
| Swollen Gland Fill (%) | (((PI()/4)*CS^2*(1+Swell/100)) / (h*w))*100 | 83.04% (110.72% > 100% LOCK @ w=3.60 mm!) |
| Parker Static Gland Design Gate | 15% <= Squeeze <= 30% AND Fill <= 85% | PARKER STATIC GLAND PASS |
ISO 3601-2 O-Ring Cross-Section Squeeze & Swollen Gland-Fill Formula
Validate `0 < Gland_Depth h < Cord_CS`, `Gland_Width w >= Cord_CS`, and `Volume_Swell` in `[0%, 50%]` right on `E2` (checking `ISTEXT(E2)` on `E3..E4`)!
=LET(cs_m, B2, gh_m, B3, gw_m, B4, sw_p, B5, sq_p, ((cs_m - gh_m) / cs_m) * 100, ao_m, (PI() / 4) * (cs_m ^ 2) * (1 + sw_p / 100), fl_p, (ao_m / (gh_m * gw_m)) * 100, IF(OR(gh_m <= 0, cs_m <= gh_m, gw_m < cs_m, sw_p < 0, sw_p > 50), "Invalid O-Ring Gland", IF(AND(sq_p >= 15, sq_p <= 30, fl_p <= 85), "PARKER STATIC GLAND PASS", "EXTRUSION OR UNDER-SQUEEZE")))Cramped 3.60 mm Groove Width Hydraulic-Lock & Nibbling Extrusion Check (Set Groove Width B4 = 3.60 mm)
Narrow the machined groove width from `4.80` down to `3.60` mm (`B4 = 3.6`): Squeeze E3 stays `22.10%`, yet Swollen Gland Fill E4 jumps to `110.72%` (`> 100%` incompressible overflow!), triggering `"EXTRUSION OR UNDER-SQUEEZE"` in E5 as expanding rubber shears into the mating gap!
=IF(ISTEXT(E2), E2, ROUND((((PI() / 4) * (B2 ^ 2) * (1 + B5 / 100)) / (B3 * B4)) * 100, 2))Try the example
Use the original values or change them to test your understanding.