Fresh ideas in the hydraulics and pneumatics sectors
Hydraulics and pneumatics are often viewed as fairly mature industrial components with application, rather than technology, standing out. Nonetheless, some recent innovations are worthy of note.
The first comes from the US-based Technetics Group, which has introduced a weight-saving composite overwrap accumulator designed specifically for reliable, lightweight and maintenance-free applications.
Accumulators ensure there is sufficient hydraulic pressure when it is required. In turn this allows pumps to be smaller, which is a key factor in the modern drive for weight saving, particularly in aerospace applications.
Typical applications for Technetics accumulators come from the aerospace industry and could include flight control actuation systems, propeller pitch control, braking, and control surfaces. Similarly, they could be used by the oil and gas industry for applications such as blowout preventers (BOPs), where instant hydraulic actuation is critical to safety.
Weighing in at approximately 1.5kg, the Technetics Composite Overwrap Accumulator is 66% lighter than an equivalent high-strength steel accumulator. The weight reduction is achieved by applying a carbon fibre overwrap to the outside of the accumulator's metal liner. The carbon fibres can stand the same internal pressures and loadings compared to a metallic vessel, but at a fraction of its weight.
The accumulator uses Technetics' proven Belfab edge-welded metal bellows, which are available as either titanium, for specific critical applications, or stainless steel. Belfab bellows are long-lasting, and are tested to withstand 10 million full stroke cycles.
Unlike accumulators that use bladders, or pistons and 'O' ring seals, the Belfab bellows are hermetically sealed, meaning that periodic services such as replacing charge gas are not required. This makes the accumulator ideal for difficult-to-access airframe locations and long-term space applications.
Another innovation comes from JBJ Techniques in the form of its low-noise, low-pulsation gear pump. The teeth profile of the gear within its Elika pump eliminates air encapsulation, which can be a significant cause of noise and vibration. This reduces noise by an average 15dBA compared to conventional equivalents.
The pump's configuration minimises internal leakage, making it suitable for work operations at low speeds and high pressures. Also, due to its wide rotational speed range, large working pressure, and viscosity bands the new pump is suitable for a wide range of applications.
Dubbed the ELI2, it has a displacement range between 7 and 35cm3/rev, a maximum operating pressure of up to 300bar, and is easily interchangeable with the standard group of two gear pumps. Its helical gear ensures its continuity of movement and the low number of teeth and shape of the profile significantly reduces pressure oscillations and vibrations during operation, reducing the noise of the hydraulic system. Axial forces induced by the helical teeth are balanced in all conditions by the axial compensation system in the pump cover.
Specific compensation areas in its flange and cover are insulated by special gaskets and reinforced with an anti-extrusion allowing free axial and radial movement of the bushings. In this way, internal leakage is reduced, ensuring good volumetric and mechanical pump performance as well as proper lubrication of the moving parts.
