What is the difference between a gasket and a sealing ring?

Core Differences Between Gaskets and Sealing Rings

1. Fundamental Structural Differences

Gasket:

Sheet or plate-shaped material (metal/non-metal)
Fills the gap between two rigid flange surfaces (e.g., pipe flanges, engine cylinder heads)
Lacks elastic deformation capability; relies on bolt pressure to crush the material for sealing.

Sealing Ring:

Annular elastomer (rubber/polyurethane, etc.)
Installed in grooves (e.g., shaft seal grooves, piston grooves)
Achieves sealing through its own elasticity + system pressure expansion

2. Comparison of Sealing Mechanisms

Characteristics: Gasket | Sealing Ring
Source of Sealing Force: Bolt preload crushes the material; Material elasticity + medium pressure expansion
Contact Form: Full-plane static contact; Line contact/lip contact (dynamic)
Pressure Response: Relies on external pressure to maintain sealing; Higher system pressure results in a tighter seal.

3. Adaptability to Motion Scenarios

Gaskets:

Only suitable for completely stationary mating surfaces
No relative movement after flange bolts are tightened (e.g., heat exchanger end caps)
Vibration can cause seal failure (bolt loosening → leakage)

Ring Seals:

Designed specifically for moving parts
Can be used on rotating shafts (oil seals) and reciprocating piston rods (U-rings)
Elastomers compensate for micron-level vibration offsets

4. Failure Mode Differences

Typical Gasket Failures:

Bolt stress relaxation → Insufficient sealing pressure → Interface leakage
High-temperature creep → Permanent material flattening → Seal failure
Corrosion perforation → Media penetration (e.g., acid erosion through asbestos gaskets)

Typical Ring Failures:

Lip wear → Dynamic seal leakage (e.g., grooves worn into rotating shafts)
Loss of elasticity → Reduced compensation capacity (e.g., rubber aging and cracking)
Installation edge cutting → High-pressure fluid cutting the seal body

5. Typical Application Scenarios

Scenario Gasket Applicable Parts Ring Seal Applicable Parts
Engine Cylinder head-cylinder block mating surface Crankshaft oil seal, piston rings
Hydraulic System Valve block piping interface Hydraulic cylinder piston rod seal Magnetic encoder Housing fixing flange, shaft dustproof seal ring
Food machinery, tank flange connection, agitator shaft sanitary seal

6. Key installation differences

Gasket installation:

* Requires precise control of bolt torque (overtightening causes crushing/undertightening causes leakage)
* Low surface roughness requirement (Ra≤6.3μm)
* Cannot be reused (irreversible compression deformation)

Seal ring installation:

* Strict groove dimensional tolerance (±0.1mm)
* Contact surface must be polished (Ra≤0.8μm)
* Must be lubricated to prevent edge cutting (silicone grease applied to the lip)