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Low pressure hydraulic systems? No problem ben lee

Humans are creatures of habit, we like routine and familiarity as it makes us feel safe.  Change is a hard pill to swallow; although some people deal with it better than others it can take a lot for someone to proactively look at a different way of doing things.  Change is usually something that is imposed upon a person out of necessity, so if there is no perceived reason to change a situation then we generally carry on as normal.



This thought pattern may be one reason why hydraulic systems designers tend to opt for high pressure systems and the familiar components that can cope with being under extreme pressure.  It is far easier to take an existing basic idea and tailor it for a new application without even considering alternative approaches, which is why low pressure hydraulic systems are something of a rarity in the world of fluid power. 


The basic equation of force = pressure x area, lends itself to working with a smaller area and a higher pressure to exact the same amount of force that a large area under lower pressure would exert.  This is attractive to designers as it means systems can have sleek, narrow cylinders and in many cases, this is needed to ensure the assembly fits in the space available.  That is not always the case, however, so hydraulic designers should consider low pressure systems as a possibility for some applications.



Low pressure hydraulic systems can be a lot more cost effective than high pressure ones, as there is a reduce possibility of leaks, and if they do occur they will take less time to clean up and fix.  The materials used to build the components can also be a lot cheaper, as they will not have to withstand the high pressures normally associated with hydraulic systems.  Plastic components, flexible nylon tubing and even thin extruded aluminium cylinders all work perfectly well at pressures under 50 or 60 bar, and are a lot more economical than the high pressure alternatives.



Sometimes a low-pressure system is really the only possible solution to a problem, especially when designing complex systems with many lengths of tubing, serving several small cylinders off a central motor.  This is when the materials that need to be used dictate the operating pressure of the system, rather than the operating pressure dictating the materials.  If the pipes need to fit through pre-defined holes in the machinery casing, or need to wind around parts of the machinery then flexible nylon is the best option.  This low-pressure approach allows designers to consider every angle from which to solve the design problem, and can result in some great innovations that otherwise might have gone undiscovered.



The only drawback to low pressure hydraulic systems is the need for a larger reservoir to hold the extra fluid that is needed to fill the system when it is in operation.  Size and space can be a stumbling block for low pressure systems, as the larger cylinder diameter means more space is needed.  Sometimes this can be cleverly engineered in, by placing the reservoir further away from the operational components of the hydraulic system and making good use of the cheap nylon tubing to run the fluid up to the moving parts.



There will always be cases where high pressure systems are a must, due to the application, the forces needed and the space available to house the hydraulic system, but at the same time there will always be systems where low pressure is more effective in terms of performance and cost, so considering both angles before diving in to a design is a worthwhile task that could lead to the next big thing in hydraulics.

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