12.01.2016

My physics teacher used to call it the “Law of Natural Cussidness” – the inconvenient tendency of every advantageous property we exploit in a material to be accompanied by a corresponding disadvantage. Take hydraulic fluid. Its principal virtue is its incompressibility, which allows it to multiply small forces many times and convey them over distance to where the work needs to be done. But the very incompressibility of hydraulic fluid means that while it’s great for transmitting kinetic energy, it’s incapable of storing it, and no good at all at absorbing shock.

Hydraulic accumulators go some way to overcoming this “Natural Cussidness”. A hydraulic accumulator works by compressing nitrogen in a flask, using energy drawn from the motor during periods of low demand or idleness. As illustrated, there are three kinds of accumulator design – bladder, piston and diaphragm. Particularly when teamed with Load Sense logic, accumulators provide smoother and more economical operation of hydraulic systems.

That’s particularly useful for certain kinds of hydraulically operated agricultural machinery, a case in point being the modern seeders which use hydraulics to achieve unprecedented depth control. The seeder’s tines must follow the terrain closely, and be able to rise abruptly when obstacles like stones, to avoid being damaged. The accumulator essentially behaves as a spring, the rising tine compressing the nitrogen in the accumulator. Once the tine has passed the obstacle and is free to descend, the nitrogen expands, propelling the tine downwards and returning it to its correct seeding height.

The accumulators in your machinery work hard, and even at rest contain compressed nitrogen that makes them hazardous if mishandled. They should be tested at least once a year using purpose- built equipment, and only serviced by qualified fitters.