Everything You Need to Know About Seals and O-Rings

Seals are crucial for mechanical and hydraulic systems, with O-rings being the most common type, and their effectiveness depends on their substance.

What is an O-ring?

O-rings, doughnut-shaped rings made of NBR, fluoroelastomers, silicone, rubber compounds, and thermoplastics, prevent gas or liquid escape and keep extraneous parts out of equipment. They secure liquid and gas channels by crushing and squeezing.

What is an O-ring seal?

O-ring seals, consisting of a gland and O-ring, prevent fluid and gas leakage. They offer minimal friction, stability, insulation, high-temperature sterilisation resistance, biocompatibility, durability, and intrinsic purity.

The benefits of using O-rings

• O-rings seal under diverse pressure, temperature, and tolerance conditions. 
• No retightening is required. 
• Structural damage is rare due to no complicated torque produced during tightening.
• O-rings are compact and easy to carry.
• In contrast to non-elastic flat seals, O-rings are reusable.
• O-rings have a lifetime comparable to their material’s natural ageing term when appropriately used.
• O-ring breakdown is slow and apparent, informing the user. 
• O-rings are affordable from the best O-ring supplier.

Types of O-ring seals

• Nitrile O-rings

Excellent fluid, lubricant, and hydraulic liquid resistance make nitrile O-rings versatile seals. Ketones, brake fluid, halogenated hydrocarbons, and nitrohydrocarbons pose a threat.  

• Neoprene O-rings

Neoprene O-rings are good for refrigerant sealing in air conditioning and refrigeration systems owing to their moderate resistance to petroleum lubricants and weather.

• Silicone O-rings

Silicone O-rings, suitable for extreme temperatures ranging from -100°C to 220°C, are ideal for static applications due to their elasticity and compatibility with water, steam, and petroleum.

• Viton O-rings

Viton O-rings (FKM O-rings) are utilised in aviation, automotive, chemical processing, and mechanical engineering facilities because of its superior mechanical properties, low gas permeability, and temperature tolerance. 

• PTFE O-rings

PTFE machined components with O-rings offer good wear, abrasion and corrosion resistance, chemical inertness, non-permeability, and low absorption, making them suitable for automotive paint guns and steering devices.   

O-ring applications

These are just a few of the sectors that use O-rings:

• Transportation

O-rings decrease vibrations, chemical exposure, and high temperatures in heavy-duty vehicles, automobiles, aerospace, liquid rocket propellants, fuel systems, brake systems, and engines.

• Medical

O-rings are used in various medical devices, such as syringes, pumps, filters, and connections.

• Petroleum and natural gas

O-rings must tolerate harsh media, high pressures, various temperatures, chemicals, and additives in oil and gas applications.

Choosing an O-ring

When developing and choosing an O-ring, consider these aspects.

• Compatibility

The interaction between the O-ring and the fluid(s) to be sealed must be thoroughly checked, considering the potential harm caused by severe chemicals.

• Temperature

The gland design may require adjustments based on system temperature, increasing gland volume for high-temperature surgery and reducing depth for low-temperature operations.

• Pressure

Pressure impacts the O-ring seal design. Low pressures allow tight sealing and low durometer hardness, while higher pressures dictate safe maximum clearance.

• Extrusion

Backup or anti-extrusion devices can prevent O-ring extrusion, as small, durable rings placed between the gland’s seal and clearance gaps provide no clearance.

• Lubrication

O-ring lubrication is crucial for static and dynamic seal installation. It protects O-rings from cutting, pinching, and abrasion and improves seating, assembly speed, and automation.