Review an O-ring groove together with the seal cross-section, mating dimensions and operating conditions. Squeeze and gland fill describe different parts of that review: how much the cross-section is compressed and how much space the seal occupies. Neither number, on its own, establishes that an assembly will seal.
Begin with a drawing showing the assembled interface. Identify whether the seal is static or moving, how pressure acts, and which dimensions control the closed gap. A nominal O-ring size is only one input to that discussion.
Define the geometry before calculating squeeze
For a simple cross-section check, let d be the effective seal cross-section being evaluated and h the assembled gap in the direction of compression. The geometric calculation is:
Squeeze (%) = 100 × (d − h) / d
Use dimensions that describe the actual installation. Identify any installation stretch, the surfaces that establish the gap and the reference temperature. Keep this geometric check separate from the material response and the application's acceptance criteria.
Do not stop at nominal dimensions. Ask the design team to check the combinations of seal and mating-part tolerances that produce the smallest and largest compression. Record the drawing revisions used so later changes can be reviewed against the same basis.
Check available gland space separately
Gland fill compares the seal volume with the available gland volume:
Gland fill (%) = 100 × seal volume / available gland volume
The Parker O-Ring Handbook discusses squeeze and gland fill separately and identifies tolerances, swelling and thermal expansion as design considerations. Use the guidance applicable to the actual seal arrangement; a percentage taken from another application is not a finished design specification.
Prepare a drawing-review package
| Input | What to identify |
|---|---|
| Seal definition | Inside diameter, cross-section, units, tolerances and material designation |
| Mating geometry | Groove dimensions, closed gap, clearances, corners and surface requirements |
| Assembly | Installation route, mating materials, fastening or closure method and permitted lubricant |
| Service | Fluid or gas, pressure history, temperature cycle and movement |
| Acceptance | Leakage criterion, test conditions, sample quantity and approval responsibility |
Connect the calculation to sample evaluation
Agree how samples will be assembled and inspected before comparing candidate materials. Keep dimensional checks, installation observations and assembly-test results identifiable. Where the application includes movement, discuss the relevant operating cycle rather than relying only on a static closure check.
If a sample leaks, retain the seal and record the installation and test conditions before changing the groove or material. The investigation should distinguish an observed dimension or damage mark from a proposed cause. Changing several variables at once makes a comparison harder to interpret.
What should you send RubberQ?
Send the seal and mating-part drawings, current material specification, operating conditions and acceptance requirement. Include an existing sample or part reference where available and explain whether you are reviewing a new design or investigating an existing assembly.
Use the O-ring size guide to prepare dimensional information, review custom seal requirements, or send the groove and seal specification for a project discussion.