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Regenerative Assemblies

Supplier: Custom Fluidpower
12 February, 2008

Sun Hydraulics, in addition to their superior cartridge valve range also has a significant range of standard valve packages fully assembled for immediate installation. This article deals with valve packages that focus on regenerative assemblies. These assemblies allow fast extension speeds without the need for large or supplementary pump systems.

In short summary the regenerative principle provides for the return of rod end oil (annulus area) to the cap end of the hydraulic cylinder. This volume effectively makes up the full piston area minus the rod area and allows our flow condition to act directly on the rod area only with regard to speed and force. The trade off is for high speed extension of the cylinder however cylinder force during this mode is greatly reduced.

Design of regenerative principles into new systems where controls are in place is generally not a problem. This is mainly due to cylinders being deliberately sized to maximize the benefit that this principle can offer. This is particularly so concerning the piston to rod ratio.

The large majority of applications involving regeneration are press circuits and systems so as to allow a high speed approach to the job. As the system pressure increases the valve will switch allowing normal operation of the cylinder with system pressure now available to the full piston area. (Maximum Force)

The biggest problem we have seen over the years is when regeneration is applied to existing cylinder installations. The results range from amusing to disaster.  Part of the problem is a lack of understanding of the principles and also applying undersized valve assemblies.

Some applications (existing) will not suit regeneration as a solution to increased extension speed. Generally you should get more concerned and cautious as the ratio between rod and piston area increases. Ideally the reference point is normally considered as a 2:1 ratio.  Eg. 4 inch Bore with a 2.75 inch rod or a 5 inch bore with a 3.5 inch rod.

This does not mean you cannot use differing ratios but, it is important to do the calculations and understand what will happen. As we have mentioned previously always discuss ideas and circuit issues with colleagues especially when working in new areas or modifying an existing system.

As far as the range of options are concerned Sun produce both line mounted and sandwich (cetop) assemblies. They are available in both permanent regenerative mode and pressure sensitive.

The Sun catalogue is available online at and there is a detailed and lengthy powerpoint presentation on Regeneration which was produced by Sun. If anyone would like a copy please contact us.