Pistons and hydraulics systems lay at the heart of ceramic tile equipment in a process that has undergone huge changes from original operations a thousands years ago in the city of Foshan in Guangdong Province, China.

Today, Trelleborg Sealing Solutions provides the seals for a large proportion of the ceramic presses built in China and supplies all of China’s main ceramic press manufacturers. The largest of these is Foshan Henglitai Machinery (HLT), which was established in 1957 and produced China’s first hydraulic ceramic press in 1988. The company currently has the largest market share and exports to numerous countries.

Advanced technology, according to Trelleborg, ensure smooth, efficient operation for hours on end, all year round in machines that can measure up to 10 metres (or 33 feet) high and four metres (or 13 feet) wide, exerting a force of thousands of tons, as the tiles are mass produced. A powder consisting mainly of clay and feldspar is pressed into a mold using a piston. Then another piston pushes the tiles out of the mold and away for drying, glazing and firing in a kiln.

"Our seals are critical components for these machines," says Elton He, application engineer with Trelleborg in southern China. "We supply all the seals used in the cylinders, and since these provide the power used to press the tiles, they are of crucial importance to the functioning of these machines. Most of the cylinders move at a rate of about ten or 15 cycles per minute and the machines normally operate about 20 hours a day.

"They might only be shut down at the end of the year to perform maintenance, so these are very tough operating conditions."

High-tech materials are crucial for the demanding conditions under which they must perform, an example would be HLT’s biggest ceramic press which exerts a maximum pressing force of 72,000 kN and contains between 100 and 150 Trelleborg Sealing Solutions seals, ranging in size from just 50 mm (or two inches) to 1.6 metres (or five feet, three inches). These include many high-performance Turcon-based PTFE seals – engineered thermoplastic compounds that offer low friction to reduce power loss and minimize wear over a long life. Orkot wear rings are also used, which are composite bearing materials that incorporate advanced polymer technologies.

Trelleborg offers 100-plus seals can be divided into four basic types:
• Piston seals, such as those installed on the groove of the pistons that press the actual tiles
• Turcon seals, such as patented Glyd Ring T, Stepseal 2K and Excluder
• Orkot and Turcite wear rings
• Large-diameter O-Rings, which function as static seals on all the cylinders and flanges in the ceramic press

The seals have to be durable to seal in the mineral oil-based hydraulic oil as well as strong, wear-resistant and capable of handling pressures up to 35 MPa / 5,075 psi and withstanding temperatures in the range of 60°C to 80°C.