Sealing seats - combination of metal and rubber

What is a tight fit?

A sealing seat is the part of a valve, tap or fitting that forms the actual sealing surface - often referred to as the sealing face. Metal composite part manufactured. It ensures that no medium flows through when the valve is closed and that a controlled flow remains possible when the valve is open. The sealing seat therefore forms the central functional surface of every shut-off or control element. The functional principle is based on the close contact between the sealing seat and the closing element (e.g. valve disc or ball).

The contact pressure creates an almost hermetic seal. The seat must be designed to permanently withstand the pressure and temperature loads of the medium without losing its shape or surface quality:

  • High dimensional accuracy and surface quality (often Ra < 0.4 µm)
  • Resistance to Abrasion, erosion and chemical influences
  • Optimum material pairing between seat and sealing element
  • Low wear and reproducible sealing effect over many switching cycles

Sealing seats are installed in almost all systems with flow or pressure control - from large industrial valves to the smallest valves in medical technology.

 

What functions & applications are there for sealing seats?

The main function of a sealing seat is to reliably separate or regulate the flow of a medium. The transition between the open and closed position is controlled by precise manufacturing and accurate mating with the closing element. This creates a tight, permanent dividing line that guarantees freedom from leakage even at high pressures and with aggressive media.

Functions at a glance:

  • Sealing: complete closure when the valve is closed
  • Control: controlled flow limitation at partial load or actuating mode
  • Fuse: Pressure limitation or non-return protection in safety-relevant systems
  • Media separation: Prevention of mixing of different fluids or gases

 

What are the components & materials of sealing seats?

Sealing seats are made of materials that have to withstand a combination of mechanical pressure, chemical stress and temperature stress. They are often an integral part of the valve body or designed as replaceable seat rings.

Metal sealing seats for high pressures and temperatures (e.g. steam, gas, oil) are manufactured by turning, grinding or lapping in order to achieve a defined contact geometry:

  • Stainless steelcorrosion & temperature resistant, forms the standard for many industrial valves
  • brassgood workability and thermal conductivity and is often used in water and heating systems
  • Hardened steels or carbides: high wear resistance with abrasive media or high pressures
  • Bronze: resistant to seawater and cavitation

Soft-sealing seats combine metal carriers with rubber. The material is often moulded directly into the valve body. vulcanised, to optimise form fit and adhesion:

  • NBR (nitrile rubber): oil and fuel resistant, ideal for hydraulic valves
  • EPDMResistant to water, vapour and ozone, suitable for air and drinking water applications
  • FKMchemically resistant, high temperature resistance up to 200 °C
  • Silicone (VMQ): excellent elasticity over a wide temperature range, often used in medical technology