Developing a hydraulic cylinder sealing arrangement with consistent performance over a wide range of applications has been a long-term engineering challenge. Trelleborg Sealing Solutions (formerly Busak+Shamban) claims what it calls "the first breakthrough" in the 1970s when it introduced Turcon Stepseal for fluid sealing in cylinder applications. Through ongoing research and development, Stepseal has been further refined and improved and has evolved into Stepseal 2K.
In hydraulic cylinders, used everywhere from earth moving machinery to lifting platforms, the requirements for sealing are varied and difficult. The seals must keep lubricants within the cylinder chamber and, at the same time, keep abrasive media out. The applications often operate at high speeds and significant pressures. A single seal is rarely a good enough solution, and in most cases a configuration of seals is required. Typically, a cylinder configuration is comprised of between three and five different dynamic seal and scraper types.
With Stepseal's introduction in 1972, Trelleborg claims it became the first choice for engineers designing rod and single-acting cylinder sealing.
Stepseal made it possible for the first time to arrange several seals, one behind the other, to create a static and dynamic sealing arrangement. This double-acting tandem seal configuration eliminated the buildup of disruptive intermediate pressures between seals, which was a long-standing problem for engineers and caused loss of operating efficiency, destruction of seals, and leakage.
The new seal was developed from a proprietary PTFE-based material, Turcon, which offers a low coefficient of friction and performs over a wide range of operating temperatures. This resulted in improved wear resistance compared with previously used materials.
In the 1980s, Trelleborg introduced Turcon Stepseal K, which had improved long-term sealing performance. Significant research and development resources were invested in continuing to develop its efficiency and application capability, partly driven by cylinder manufacturers changing the tolerance requirements between the rod and cylinder walls, along with the use of alternative hydraulic fluids and increasing temperatures and pressures.
Out of that R&D came Stepseal 2K with enhanced sealing efficiency. Better extrusion resistance gives improved leakage control and allows larger hardware tolerances, making cylinder production more economic. It also has more uniform, low-friction characteristics throughout an extended life and even during the run-in period, when friction forces can have the greatest effect on hydraulic seals.
Stepseal 2K is available in nine different compounds. They can be used with all lubricating and non-lubricating hydraulic fluids, including zinc-free oils and water-based hydraulic fluids. They can also be matched to specific mating surfaces and media. They are suitable for gas applications, and seals can be specified to meet the precise degree of extrusion and abrasion tolerance required for an application.
They are available for rod diameters up to 2600 mm (102 in) and bore diameters up to 2700 mm (106 in). They operate at pressures up to 800 bar (11,600 psi), temperatures from -45 to 200°C (-49 to 392°F), and speeds up to 15 m/s (49 ft/s) with reciprocating movements.