Specifics of rubber-metal seals in water and gas pipelines

Rubber-metal gaskets are an indispensable element in engineering practice for connecting piping systems made of different materials. They are a composite element, where a steel core (usually made of carbon or stainless steel) is completely encased in a vulcanized elastomer.

This construction addresses a fundamental problem: how to achieve high sealing performance at extremely low tightening torques required by thermoplastic flanges (PE, PP, PVC) or brittle cast iron.

Construction and function of the steel core

The steel insert inside the gasket serves as the "spine." It prevents uncontrolled radial deformation (extrusion) of the rubber from the joint, which would occur with a purely rubber gasket even with slight over-tightening of the bolts.

Thanks to this rigidity, rubber-metal gaskets can be safely used in vacuum systems, where regular rubber could be sucked into the piping.

Principle of achieving sealing

In terms of sealing, rubber-metal gaskets utilize concentric edges (lips) on their surface.

These edges:

• concentrate the clamping force into a very small area
• create high contact pressure
• allow for sealing even at minimal tightening torque

This principle enables reliable sealing even with material-sensitive flanges.

Material design for water and gas

The choice of elastomer is crucial for the proper function of the gasket in a specific application.

Water supply – EPDM

For drinking water distribution, the key material is EPDM with the appropriate certifications for contact with drinking water. This material:

• excels in aging resistance
• is resistant to ozone
• meets hygiene requirements

Gas and petrochemicals – NBR

In gas and petrochemical applications, NBR (nitrile-butadiene rubber) predominates, which:

• is resistant to swelling
• withstands hydrocarbon action
• retains its properties in the given environment

Importance of proper installation

When installing rubber-metal gaskets, it is critical to ensure the cleanliness of the flanges. While soft rubber can compensate for irregularities, abrasive particles could create a path for media leakage at the edges. A clean and prepared flange surface is therefore a fundamental prerequisite for the long-term sealing of the joint.

Summary

Rubber-metal gaskets represent an effective solution for connecting piping systems made of various materials, especially where high sealing demands are placed at low tightening torques.

Their main advantages lie in:

• the combination of a steel core and elastomer
• resistance to deformation
• ability to operate in vacuum
• high sealing performance due to concentric edges
• applicability in water and gas distribution

With proper design and installation, rubber-metal gaskets are a reliable and long-lasting component of piping systems.