Seals are key components of designs all around us. It is basically a matter of hermetically sealing two units with uneven surfaces or surfaces in motion, and a seal can have the form of a ring, a profile or a bearing.

"The choice of design and material used for seals depends on a number of factors that must be taken into consideration," explains Nils Levin, materials consultant. The choice of material takes into account such factors as working temperature, resistance, mechanical strain, environmental situation, abrasion and lifespan.

"Seals, which can be made from natural rubber, conventional elastomer compounds or perfluoroelastomers, offer excellent mechanical properties for a whole range of applications including aerospace, food and beverage processing, and in rotary and highpressure pneumatic and hydraulic applications, for example," says Levin.

"Polyurethane seals offer effective abrasion resistance and also provide an effective barrier against oil and fuel and are often used in high-pressure hydraulic systems," he adds. "PTFE is a high temperature-resistant thermoplastic material that can withstand temperatures exceeding 260°C, has exceptionally good resistance to chemical corrosion and offers very low friction."

Seals can be manufactured in a variety of ways, depending on their design and function.

Moulded seals include O-Rings, radial and shaft seals where an elastomer lip is bonded to a metal ring. V-shaped seals are often used in hydraulic systems where the rubber may be textile-reinforced to withstand high pressure.

Long extruded seals are used to seal doors and windows and are often made by a co-extrusion of two materials. Diaphragms are often punched from continuous cured rubber sheeting and are sometimes reinforced with textiles.

The oil and gas industry is another extremely challenging environment for sealing solutions.

Whether for use during exploration, offshore or onshore production, upstream, midstream or downstream, they must withstand highly destructive and aggressive chemicals and gases, abrasive media, intense temperatures and high pressure.

Trelleborg seals for the oil and gas industry aim to minimise maintenance and maximise ‘life of well’ sealing integrity, whether a seal is 1.2 millimetres or three meters in diameter. These seals must offer a range of stringent qualities including temperature resistance from cryogenic up to 850°C, almost universal chemical resistance, thermal stability, steam and explosive decompression resistance, and good mechanical strengths.

Providing indoor comfort

Using sealing profiles to seal the gaps around windows and doors improves indoor comfort and saves energy, which is good news not just for the household budget but for the environment too. In many major building projects globally, advanced thermal technology keeps interiors warmer in winter and cooler in summer, while keeping out dust and dirt.

Sealing profiles supplied by Trelleborg range from relatively simple products for the DIY market to individually engineered solutions for some of the most innovative buildings in the world.

Producing the tiny O-Ring seals used in precision industries like watch-making requires precision instruments right the way from production to assembly. The smallest of these miniature seals has a cross-section diameter of just 0.3mm with a 0.25 inside diameter, which means that 10 000 of them would represent just a small handful. Their inherent flexibility and the fact they can often be highly electrostatic makes assembly all the trickier, so all the tools on the production and assembly lines turning out the tiny rings are custom-made and highly specialised. Nevertheless, over the past 20 years, Trelleborg has turned out more than 700 million of these mini-rings that are worn on millions of wrists around the world.

Sealing is obtained by deforming the O-ring in a groove. Using higher pressure, the O-ring is pressed against one side of the groove.

For more information, visit www.trelleborg.com