A Brief Guide to Metal Sealing Solutions

Metal-to-metal seals can offer much higher performance and resilience than conventional elastomeric seals such as rubber O-rings and gaskets. Ideally suited to applications involving high temperatures and pressures – and capable of withstanding extreme chemical and physical conditions – metal sealing solutions are used in applications such as cryogenic systems, nuclear power plants, aircraft, chemical plants, and UHV systems. This technical article takes a look at the development of metal-to-metal seals, and how metal sealing solutions such as metal boss seals provide effective and resilient metal-to-metal sealing in demanding applications.

The Development of Metal Sealing Solutions

Prior to around 50 years ago, minimizing leak rate was not the primary goal of sealing. Instead, sealing devices – typically elastomeric gaskets and O-rings – mainly just provided a way for systems to reach specific operable conditions of pressure and temperature. Elastomeric seals perform this function well, ensuring mechanical integrity and easy installation without necessarily providing a high degree of leak-tightness.

However, over the following years, the development of high-tech systems – nuclear power, ultra-high vacuum (UHV) and a range of other systems with high pressure and temperature requirements – created a new demand for high-performance seals that eliminated leakage and provided increased resilience.

Intensive research determined that metal sealing solutions can overcome many of the limitations of conventional elastomeric seals. Metal-to-metal seals are typically “positive seals”, meaning that they do not allow any leakage whatsoever.

Over the last few decades, metal sealing solutions have been refined to comply with the most extreme requirements and are now produced in a variety of materials and configurations to suit virtually any requirements. Metal sealing solutions are now the standard for critical applications such as power generation, cryogenics and UHV systems.

Advantages of Metal Sealing Solutions

Metal sealing solutions are the go-to choice for the most demanding and critical applications, offering superior performance to elastomeric seals in a range of environments. As well as providing excellent sealing characteristics for high-pressure and high-temperature applications, metal sealing solutions are also resistant to aggressive chemicals and radioactive environments. In contrast to elastomeric seals, metal sealing solutions are also inherently non-permeable and boast an unlimited shelf-life.

Metal Boss Seals

Metal boss seals are a type of pressure-loaded positive sealing device, specifically designed for use in AN port-to-tube fittings.

This type of metal sealing solution consists of a metal crush ring housed within a metal jacket. When the seal is installed with the recommended torque, the crush ring mates the coating of the seal to the surfaces of the port and tube fitting, providing a high-quality metal-to-metal seal. Once installation is complete, the metal boss seal is spring-loaded and pressure-sensitive to ensure seal integrity is maintained over very wide temperature and pressure ranges.

Metal boss seals from Saint-Gobain Seals maintain superior sealing capabilities within a temperature range of -269°C (-452°F) to +815°C (+1,499°F). The completely non-permeable assembly fits standard AN, MS and MC hardware; providing a seal pressure limit beyond the proof pressure of the hardware.

Saint-Gobain Seals produces metal boss seals in a range of sizes and configurations to suit high-specification uses. Made from either stainless steel or Inconel® alloy 718, their metal boss seals can be provided with Teflon, silver, gold, nickel or copper coatings (as well as uncoated). To find out more about Saint-Gobain Seals’ metal sealing solutions, get in touch with one of their experts today.