Hydraulics meet exacting demands
In many instances, hydraulics are more reliable than mechanical systems in extreme environments.
Their relative simplicity and consequent reliability means that, if nothing else, there is less to go wrong in hydraulic systems than in their mechanical counterparts and, while there may be a consequent trade off in terms of efficiency, this reliable and predictable performance from hydraulic components and systems under adverse conditions gives them a distinct advantage.
One example can be seen in Parker Hannifin's 160 bar and 250 bar hydraulic 'mill' cylinders, which are an established global favourite in hostile environments and arduous applications. As their name suggests, they were originally designed for use in steel mills and are of heavy duty, all-steel construction and are fatigue-free at their maximum rated pressure.
The latest generation of these cylinders extends the standard fitment of induction hardened piston rods, offering the ultimate resistance to damage in tough applications. A new, wider range of mounting accessories offers greater versatility for the designer, while web-based CAD models and an on-line configurator speed and simplify the selection process.
Mill cylinders can be used at operating temperatures of between -20ºC and +150ºC and generate up to a massive 2000kN, making them the ideal choice for high force applications in the toughest conditions.
Another example of hydraulic components being well-suited to harsh operating conditions can be found instances where liquids need to be pumped at high temperatures. This can cause problems for pumps designed to operate at ambient temperatures and reliant on close tolerances for operational efficiency. Differential thermal expansion can also cause fit problems with bearings, bushes and dynamic seals.
Hydra-Cell pumps from Wanner are designed not to suffer from such problems and to handle liquid temperatures as high as 120°C with ease. This is possible because their multi-diaphragm design has no dynamic seals and incorporates neither tight fits nor close tolerances.
The increased corrosivity of hot liquids is a further problem encountered (water at 90°C is 64 times as corrosive as water at 20°C.) Corrosion of pump internals, including gears, screws, rotors, stators, impellors, bearings, bushes, pins and seals impairs operation, causes leaks and can lead to catastrophic failure. However, in a Hydra-Cell pump there are no dynamic seals and no bearings or bushes, operating within the pumped liquid, to be affected by thermal expansion or corrosion. The liquid is always isolated from the drive end of the pump and the selection of appropriate pump head material ensures that corrosion is not a problem.
High pressure, of course, places strain on all aspects of a hydraulic system, including hoses. And, with today's hydraulic systems requiring ever-higher flow rates, increased working pressures and performance, the hose needs to be able to keep up. Eaton's new Dynamax EC850 hose and fitting series is designed for working pressures up to 500 bar (7,250 psi).
With a bend radius 10% better than the SAE100R15 industry standard, the hose is also extremely flexible which enables the end user to easily install the hose assembly in tight areas. The Dynamax EC850 was also designed with a new generation of inner tube material that enables it to achieve significantly increased service life while meeting the REACH regulation.
