Gasket Material Selection Is More Than Just a Shop Visit

[MikePhua]

Why Gaskets Matter in Hydraulic Systems
In hydraulic equipment, gaskets play a critical role in sealing joints, preventing fluid leaks, and maintaining system pressure. Whether it’s a pump flange, valve housing, or cylinder end cap, the gasket must withstand high pressure, temperature fluctuations, and chemical exposure. A failed gasket can lead to downtime, contamination, and even catastrophic failure.
Terminology note:

• Gasket: A mechanical seal that fills the space between two mating surfaces to prevent leakage.
  
• Compression set: The permanent deformation of a gasket material after prolonged pressure, reducing its sealing ability.
  

The Myth of “Just Ask for Gasket Material”
It’s tempting to walk into a hydraulic shop and ask for “gasket material,” but this approach often leads to mismatches. Not all gasket materials are created equal, and using the wrong type can compromise safety and performance. Shops may offer generic sheets like rubber, cork, or fiber, but without knowing the application specifics, the recommendation may be inadequate.
Key factors to consider before selecting gasket material:

• Operating pressure and temperature
  
• Fluid type (hydraulic oil, water-glycol, synthetic blends)
  
• Surface finish and flange type
  
• Bolt load and torque specifications
  
• Exposure to UV, ozone, or abrasive particles
  

Common Gasket Materials and Their Properties
Here’s a breakdown of popular gasket materials used in hydraulic systems:

• Nitrile rubber (Buna-N)
  • Good resistance to petroleum-based fluids
    
  • Temperature range: -40°C to 120°C
    
  • Common in low-pressure hydraulic covers
    
• Viton (FKM)
  • Excellent chemical and heat resistance
    
  • Temperature range: -20°C to 200°C
    
  • Used in high-performance hydraulic seals
    
• Compressed non-asbestos fiber (CNAF)
  • Reinforced with aramid or cellulose fibers
    
  • Suitable for moderate pressure and temperature
    
  • Often used in pump flanges and valve covers
    
• PTFE (Teflon)
  • Chemically inert and low friction
    
  • Temperature range: -200°C to 260°C
    
  • Ideal for aggressive fluids and high-temp systems
    
• Graphite sheets
  

• Excellent thermal conductivity and pressure resistance
  
• Used in high-pressure hydraulic manifolds
  
• Can be laminated with stainless steel for durability
  

Terminology note:

• CNAF: A safer alternative to asbestos-based gaskets, widely used in industrial sealing.
  
• PTFE: Polytetrafluoroethylene, known for its non-stick and chemical-resistant properties.
  

Field Story and Practical Insight
A technician in Alberta once tried to seal a hydraulic valve cover using a generic rubber sheet from a local shop. Within two days, the gasket had softened and extruded under pressure, causing a leak that contaminated the entire hydraulic reservoir. After consulting the equipment manual, he switched to a CNAF sheet rated for 1,000 psi and 120°C, cut to spec using a punch set. The system ran leak-free for over a year.
Lesson: Always match material to application, and never assume “rubber” is good enough.
Cutting and Installing Gaskets Correctly
Even with the right material, improper cutting or installation can ruin a seal. Best practices include:

• Use a gasket punch set or CNC cutter for precision
  
• Avoid over-torquing bolts, which can crush the gasket
  
• Clean mating surfaces thoroughly before installation
  
• Apply a thin layer of compatible sealant only if specified
  
• Store gasket sheets flat and away from sunlight or moisture
  

Recommendations:

• Keep a catalog of gasket specs for each machine model
  
• Label leftover sheets with material type and rating
  
• Train technicians on torque patterns and flange prep
  

Alternatives to Sheet Gaskets
In some cases, pre-molded gaskets or O-rings may be better suited than cut sheets. Hydraulic cylinders, for example, often use O-rings with backup rings to handle dynamic sealing. Flanged connections may benefit from spiral-wound gaskets or metal-clad designs.
Terminology note:

• Backup ring: A rigid ring placed behind an O-ring to prevent extrusion under pressure.
  
• Spiral-wound gasket: A composite gasket made of metal and filler material, used in high-pressure flanges.
  

Conclusion
Choosing gasket material for hydraulic systems isn’t just about grabbing a sheet from the shop—it’s about understanding the demands of the system, the properties of the material, and the consequences of failure. With the right knowledge and preparation, technicians can ensure long-lasting seals and avoid costly downtime. Precision, not guesswork, is the key to sealing success.