21 August, 2018

More safety for hydraulic sealing systems for wind power plants (Mar 09)

20 May, 2009

Hydraulic systems in wind power plants, such as pitch cylinders or hydraulic brake systems, demand the highest possible level of operating reliability. Sealing systems for the piston rod and piston have proven most reliable when it comes to combining high pressure in hydraulic cylinders for high actuating forces with absolute protection against leaks. Hydraulic systems in wind power plants sometimes have to work under very high system pressures. High-performance sealing systems comprising the following standard components have proven extremely capable of providing the required reliable seal:
 
  • an Omegat primary seal with pressure relief,
  • a secondary seal as a U-packing,
  • a double wiper,
  • an Omegat seal set as a piston seal,
  • Guivex guide tapes for the rod and piston, and
  • Coverseal and Stricomatic seals as a static seal for withstanding high pressures.
 
These sealing systems reliably ensure zero leakages over a period of years. This is achieved by adapting all of the individual components in the sealing system until they complement each other perfectly, each sealing element assuming a specific function.
The primary rod and pistons seals, which are exposed to the full pressure of the system, are said to ensure reliable pressure build-up in the hydraulic system. For this reason, the Omegat primary seals are made of a special PTFE compound. This sealing material is highly resistant to wear and boasts low friction, outstanding dimensional stability, and extrusion stability. The PTFE seal does, however, leave behind a thin film of oil. This minimal film of drag oil is, however, almost completely kept back by the U-packing, which acts as the secondary seal. The oil that collects in the space between the primary and secondary seals is pumped under the primary seal back into the main hydraulic chamber on the instroke.
Varying parameters can, however, mean that despite the outstanding pump-back capability of the primary seal, the returned volume of oil is smaller than the volume of oil that is dragged out. In this case, the pressure that builds up in the area between the two seals can quickly lead to an increased activation of the secondary seal and therefore to higher wear and even the extrusion of the primary seal in the direction of the main chamber. A patented pressure relief bore hole in the Omegat primary seal solves all these problems.
 
Wiper and guides adapted to suit the application
This sealing system comprising a primary and secondary seal is protected against the penetration of dust, water, or dirt from the outside by a special wiper. The wiper also facilitates the highly effective return of the extremely thin residual oil film on the rod into the system. To ensure optimum pre-stress for both the sealing and wiper edges, the wipers feature the double O-ring system that has proven such a resounding success for over 15 years. The special wiper structure is said to ensure that the contact pressure is ideally suited to the sealing edge featured in this application. This in turn reportedly ensures that the wiper functions perfectly over a long period of time.
 
www.simrit.co.uk
 
 
 





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