Displacement Cylinders

How It Works

Whilst a single acting cylinder is a type of displacement cylinder, what Delta describes as a "Displacement Cylinder" is that unlike single acting cylinders there is no piston seal in a displacement cylinder. Sometimes called a plunger cylinder, because there is no piston seal, displacement cylinders, in general, have a high OD piston rod relative to the ID of the bore.

Displacement hydraulic cylinders are single acting extension only cylinders that are retracted using the load lifted and gravity. The cylinder is initially filled with hydraulic fluid in the area surrounding the piston rod when in its fully retracted state, when more fluid is then pumped into the cylinder it will displace the volume of the piston rod therefore forcing the piston rod to extend from the tube.

This means the force generated by a displacement cylinder is less than the force generated by a single acting cylinder of the same size as the force is calculated based on the area of the piston rod and not on the tube bore as it is for single acting cylinders.

In a displacement cylinder there is no air in the annulus when retracted.

Applications

Displacement cylinders are used in applications where smooth operation in application is required and there is minimal weight/load to retract the rod.

Also, because in a Displacement Cylinder there is no air in the annulus of the retracted rod, a bleed port is not required which can reduce corrosion and contamination issues of a single-acting hydraulic cylinder.