Product category:
Hydraulics and Pneumatics
News Release from: Parker Hannifin | Subject: Dead Sea potash plant
Edited by the Processingtalk Editorial
Team on 22 February 2006
High performance cylinders eliminate
dithering
A range of high performance hydraulic cylinders from the Hydraulic Cylinder Division of Parker Hannifin is being used in a potash plant based on the coast of the Dead Sea in Israel
A range of high performance hydraulic cylinders, developed and manufactured by the Hydraulic Cylinder Division of Parker Hannifin, is being used in a potash plant based on the coast of the Dead Sea in Israel The cylinders have been specially designed for this application and have to withstand extreme conditions of temperature, humidity and dust abrasion, while operating continuously 24 hours a day, seven days a week
This article was originally published on Processingtalk on 19 Jun 2008 at 8.00am (UK)
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The cylinders are used in 10 compacting systems, with each machine using a pair of cylinders, mounted high off the floor, in combination with a bladder accumulator to control the relative position of two 1.5 metre diameter rollers.
These large rollers are used to compress the potash into 'biscuits' that are subsequently broken up, dispatched and used as fertiliser all over the world.
The operating conditions are incredibly harsh, with high concentrations of dust, and caused the cylinders that were previously used to fail at least once a month, resulting in as much as two days of downtime for each machine during replacement.
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To complicate matters further the application required cylinders with a 340mm bore, a stroke of just 1mm and an operating frequency of 2.5Hz.
This complex set of parameters meant that in addition to withstanding the severe environmental conditions the cylinders had to be constructed to eliminate the problem of seal dithering.
Dithering occurs when the piston seal continuously covers the same area of the cylinder tube as the piston cycles rapidly backwards and forwards in a distance that is less than the seal's width.
Lack of lubrication then leads to heat build-up under the seal, leading, in turn, to rapid seal and bore wear.
To resolve this problem, Parker designed a unique piston which overcame the problem of lubrication while still preserving a short overall length and retaining stability in the bore.
The short stroke and mounting configuration made it difficult to use a conventional design of port located at the end of the piston stroke, as the mounting end had no provision for a port to pass through it.
As an alternative solution, Parker drilled a port through the piston, to align with the port in the cylinder tube.
In operation, pressurised hydraulic fluid passes through the wall of the piston to the hollowed out centre, where it exerts a force to extend the piston.
A second set of 'ports', adjacent to the first set, overcomes any dithering as pressurised fluid is allowed to pass back through the piston wall to provide lubrication for the wear rings and piston seals.
A bleed is provided to prevent the positive pressure from rupturing the seals and, to protect against any external contamination from entering the system; dust proof rubber covers are also used.
Following the success and unparalleled performance of the initial installation, further Parker cylinders have since been ordered. Request a free brochure from Parker Hannifin ...
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