Regenerative hydraulic circuits, in Hydraulic double acting cylinders.

Written by Camilo H Rueda Wednesday, 06 July 2011 00:00

Articles - Education

Regenerative circuits are widely-used to produce faster cylinder extension speeds by grabbing the oil from the rod end and redirecting it to the head end of the cylinder.

Because of this the effective area during extension is the rod area that will give a faster speed but additionally a reduced force. Which indicate that by using a cylinder with a 2:1 area ratio between piston and rod, equivalent speeds and forces can be found in both directions without using a double rod.

Hydraulic Cylinder Ratio:

The Cylinder Ratio is the relation between The complete area of the piston and the same area minus the area of the rod.

A=0.785 x D² where D= Piston diameter

A_R=0.785 x R² where R= Rod diameter

CR=Ratio=A/(A-A_R)

The assortment of hydraulic cylinder ratios will have a substantial effect on the performance of your system. Hydraulic Double Acting cylinders are designed in an almost countless combination of ratios. All of these ratios affect the velocity and force of extension and retraction of all the cylinders. With a 2:1 ratio cylinder, using a regenerative connection the extend speed and force will equal the retract speed and force.

Speed and Force in a regen cylinder.

S_out= Speed rod extending,

F_out= Force rod extending

S_in= Speed rod retracting,

F_in= Force rod retracting

Q_P= Pump Flow

As we can see in the drawing, having a regen. double acting-single rod cylinder circuit is equivalent to having a single acting cylinder with A_R rod when it is extending.

Using a 10 GPM pump and a relief valve setting of 2000 psi in a cylinder 4"  bore diameter and 2.5" rod dia. 20" stroke. CR=1.64

Without regeneration: Click to get the calculation

S_out=Q_p/A = 20"/6.52 sec= 3.06 in/sec

S_in= Q_p x CR/A=20"/3.97 sec=5.03 in/sec

F_out= 25,120 Lbs max.

With Regeneration:Click to get the calculation

S_out=Q_p/A_R = 20"/2.54 sec= 7.87 in/sec

S_in=5.03 in/sec because Regenerative circuit only works when the rod is going out.

F_out= 9,812 Lbs max.

As we can see, the regenerative circuit helps to increase the speed of the rod going out (from 3.06 in/sec to 7.87 in/sec) but with the reduction in capable force (from 25120 lbs to 9812 lbs).