Engineering Design Guidelines

Engineering Design Guidelines

Installation Spaces for O-Rings (1)

Installation Spaces for O-Rings (2)

Installation Spaces for Lip Seals (1)
Recommendations for Seal Selection

Installation Spaces for Lip Seals (2) 

Rod Seal: Use asymmetric profiles with good statical tight  fit (outer diameter) and shorter dynamic  sealing lip. Guide ring inside pressure space is better, due  to higher lubrication.

Installation Spaces for Chevron Packings

HN   =      Axial nom. inst. space dim.          =      HD + x • HM + HSt HV    =       Re-loading dimension* BN    =       Radial nom. inst. space dim. HS    =      Set height (slack measure-               ment)             HN BS     =      Set profile width                    (slack measurement)          >      BN

Installation Spaces for Rubber-Activated Glide Seals
Recommendations for Seal Selection

Adhere to axial gap „x“ to activate  pressure. Rectangular elastomer expander ring (1)  beneficial for uniform distribution of  contact force. O-ring-expander (2) results in less favourable contact force  distribution. Calibrate sealing rings (3) after installation.

Installation Spaces for Compact Seals 
Recommendations for Seal Selection

Angle guide ring without pressure relief/load  grooves (1) Seal body may rotate(2) Determination redundancy of radial angle guide rings (3)  Axial installation space too small (4)

Installation Spaces for Guiding Tapes
Recommendations for Seal Selection

If possible, position heavy-duty guide tapes  for piston rods in the pressure space (before  the seal) (1) for better lubrication and heat  dissipation. Softer PTFE-tapes positioned after the seal have better micro-contamination absorption  capabilities (2). Ensure that dimensions (axial) are sufficient for  lateral load.

Typical Design Errors Involving Seals
Example: Hydraulic Cylinder (1)

A       Chamfered spanner flat has sharp edges. Reduce diameter.

B       45°-chamfer too steep and sharp-edged. Chamfer and polish.

C       Thread unsuitable for centering. Unilateral gap formation.

D      O-ring too close to lead-in chamfer.

E       Guide bush constricts inlet cross-section (flow restrictor/throttle effect).  Air release.

F       Long guidance increases drag pressure. Plan for spiral groove.

G      Avoid sealing of cylinder tube at the front side, danger of O-ring being squeezed.

Example: Hydraulic Cylinder (2)

H      Lead-in chamfer at cylinder tube  for easy piston assembly missing.

I        Spacer ring must be fastened axially. Load-bearing lip ring must not rest on the second lip ring.

K       Avoid triangular installation space for O-ring. Lack of press-fit definition/reliability.

L       Thread length too short. Consider effects of mass and pressure peaks.

M     Guide tapes missing. Retainer shackle on outer diameter too large.

N      No provision for anti-rotation.

Favourable Design Features for Seal Assembly
Example: Hydraulic Cylinder (1)

A       Flat angle at lead-in chamfer; chamfered edges for protecting wiper and rod seal.

B       Burr-free spanner flat at piston rod.

C       Spanner flat on reset diameter.

D      Double wiper/scraper to reduce residual lubricating film on dynamic piston rod.

E       Thread in retainer plate has no centering function.

F       Multi-lip rod seal. Progressive sealing surface contact.

G      Concentrical O-ring-configuration (lead-in chamfer at sealing diameter).

Example: Hydraulic Cylinder (2)

H      Centered one-part seal and guide bush. Made of special, low-friction compounds (e.g. bronze) for low maintenance requirements.

I        Unrestricted power connection for optimised flow turbulences.

K       Proper O-ring-configuration. Simple groove creation.

L       Lateral- force-resistant guide tapes.

M     Highly mechanically and thermally resistant sealing set with elastomer rectangular expander.

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