Rethinking the existing design of an oil tank, led to the idea of a completely new, moulded seal that simplifies the task of construction and enhances the quality of the whole entire hydraulic system.
This case involved an oil tank for a hydraulic steering system in windmills. A rectangular welded steel tank with a lid, to which are installed hydraulic pumps etc. This is normally a well-working construction that works well, but the manufacturing process is too cumbersome. A steel gutters has to be welded to the tank to collect waste oil, a solution which is both costly and impractical. Leaks and deformation of the relatively large gasket occur because correct lid tightness is difficult to achieve. Therefore, PMC wants to optimise the design in two areas: Establishing a stable connection between oil tank and lid, that does not leak. Coming up with a solution for the collection of the inevitable waste oil that is efficient in terms of manufacture.
The first part of the task WAS was solved by moulding flat metal washers into the seal that are 20 percent thinner than the rubber. This ensures precisely the optimal amount of compression for the application. The second part of the task is achieved by integrating oil collection into the form of the rubber gasket: Because of its position under the lid, it is an obvious solution to allow the gasket to do the “guttering” and safely divert the oil to a collection container or recycling. The choice of sealing material is in itself a challenge and a contributing factor to the leaks. On the inside, the application is exposed to an oil mist. On the outside, a mixture of atmospheric oxygen and ozone from a generator is broken down. Common rubber types have difficulty by having resistance to both these media. The solution is to switch to an AEM compound; a rubber mix which excellently combines the properties of NBR rubber (optimal in relation to the oil vapour) and EPDM (especially suited to withstand outdoor climate and atmospheric impact).
The in-moulded washers now control compression and releases the installation technician from the task of manually measuring and checking torque on the lid bolts: an improvement that eliminates the risk of leakage. As a bonus, the task of installation become faster.
As PMC has get rid of the difficult welding of a steel gutter around all of the four sides, construction of the tank is significantly simplified. PMC increases the value of the product considerably, with no additional total unit costs whatsoever.
"The gasket has really shown its strengths with its built-in compression control, easy installation and long-term durability. However, it is more than just a good gasket. The solution also has an integrated feature that diverts waste oil into a sealed plastic container. A specially-designed solution may sound costly, but for PMC this solution has a zero-figure financial impact: Total manufacturing cost per system unit is unchanged, but the quality has been distinctly improved."
— Brian Krøll, Product Manager at Betech A/S