What is pressure intensification in hydraulic cylinders

Questions & Answers - Hydraulic Cylinders

Pressure Intensification Glossary Link Pressure intensification is an increase in pressure above the Glossary Link relief valve setting. When you use a hydraulic system, you think that the pressure is limited

by the relief Glossary Link valve; well? sometimes is not. If there are lines that are not connected to the relief valve in certain moments, they are not protected.


We are going to talk this time about the intensification of the pressure in hydraulic cylinders when the Glossary Link flow is controlled, meter-out.


Intensified pressure in hydraulic cylinders


The rod of the hydraulic Glossary Link cylinder is extending at a speed controlled by the meter-out flow Glossary Link control. In the graphic, the flow is coming from the Glossary Link pump to the back of the cylinder and the reading in the Glossary Link pressure gauge is the pressure relief valve setting. The flow Glossary Link control that is reducing the flow that exits the rod side of the cylinder creating a Glossary Link back pressure that is higher than the relief valve setting.


Looking at the forces acting in the cylinder Glossary Link piston, we can see that the Glossary Link force acting from the left side of the piston is equal to the force acting from the right side + the load. or:



A x Pin = Ar x Pout + Load



A= Area of the piston

Ar= Area annular (A - rod area)

Pin= Inlet pressure or relief valve pressure setting

Pout= Outlet pressure before the flow control.


The worst case scenario is when the load is insignificant or very low and the rod diameter is big compared to the piston diameter. Taking the load off the formula, we have that the force from the left is equal to the force from the right, or:


A x Pin = Ar x Pout    so, Pout = Pin x A/Ar


Knowing that Ar is always smaller than A, then Pout is always going to be higher than pin. Now, the question is how much higher?

It is inversely proportional to A/Ar or in other words, the bigger the rod against the piston, the higher the pressure intensification.


Let's put an example:


A cylinder has:  4" piston diameter, 3" rod.

Then, A = 12.56 sq inch. Ar = 12.56 - 7.06 = 5.5 sq inch

If Pin = 2,000 psi, then Pout = 2000 x 12.56/5.5 = 4,567 psi a lot higher than 2,000 psi.


In the following video, the relief valve pressure setting is 85 psi. The intensified pressure goes up to 125 psi.





If the load is not neglected, then it lowers the intensification effect.

Whenever you have meter-out flow meters and low loads, you can expect pressure intensification.

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