Calculating Hydraulic Cylinder Force
A hydraulic system has many vital components all working together to function properly. Overall efficiency has increased through the engineered machinery’s lifespan with innovative designs and processes. Many engineers have worked to solve numerous functionality flaws within these machines. There is also a variety of resources that have been calculated and evaluated to create an easier, more streamlined process when using your hydraulic system. Because the cylinder within your system is what applies the linear motion and force, it’s imperative to correctly calculate the force the cylinder will exert. This way you can ensure you have not only the correct cylinder for your system but also the correct cylinder for your projects’ needs and specifications.
About the Hydraulic Cylinder
The cylinder(s)is a crucial part of the hydraulic system and is the backbone of a functioning machine. Anything that is pushed, pulled, lifted, dropped is due to a hydraulic cylinder within the truck, crane, dozer, tractor doing the work. The industrialized world as we know it would not exist if it wasn’t for the design and production of the hydraulic cylinder. Although these machines perform complex tasks they are quite simple in design.
The cylinder is made up of five main components:
As a fundamental piece of the hydraulic cylinder, the piston is the foundation of the operations within the cylinder. The main components of the cylinder rely on the proper function and integration of the correct piston and seal. Serving as the moving part contained by the hydraulic cylinder, the piston is a pivotal part of operations. This component is made fluid tight by piston seals which seal the gap between the piston and the cylinder. The piston’s purpose is to transfer fluid pressure force to the cylinder rod. Thus that force transfers into the work needed. Always think - the larger the cylinder the more it can lift. This is why integrating the correct piston and piston seal is critical in having control and sustained pressure from the hydraulic cylinder.
The rod, also known as the shaft, is what attaches the piston to the cylinder. As one of the most hardworking parts of the hydraulic cylinder, the rod is the combination of extreme durability and fluidity. This is so it can protect the cylinder and piston from bending, corrosion or pitting and prevents leaks of fluid or pressure due to its smooth makeup.
The component within the cylinder refers to how far the piston travels within the cylinder. The stroke controls and maintains the distance in which the cylinder can push or pull, which directly correlates with how far the cylinder can move or lift something.
Cylinder Gland aka Cylinder Head
In order to keep contamination out of the cylinder, a proper rod seal and wiper seal is key. These can be found within the gland of the cylinder which can be found at the head of the hydraulic component. This component is what the rod pushes or pulls through. It will extend and retract through the gland ensuring clean, fluid movement and proper functioning.
Cylinder Cap aka End Cap
On the other end of the hydraulic cylinder, you’ll find the cylinder cap. This is where you can find a variety of attachment points for the integration of your hydraulic machinery. All of these parts are critical for well-executed operation. These hydraulic cylinders role is two exert a pushing or pulling force and this is by utilizing a single acting or double acting cylinder.
Cylinder Push Force vs Pull Force
When looking for a hydraulic cylinder you need to consider whether you are looking your a pressing force or the ability for a pulling force. This is also a critical factor when calculating the overall hydraulic cylinder force output. If you need a cylinder that can extend and retract using hydraulic power, in other words, have the ability to push and pull, then a double acting cylinder is what you’re looking for. It is a common agreement that the double acting cylinder is a stronger option with the capability of using less energy to do the same job its counter, the single acting cylinder.
If the hydraulic cylinder you utilize only pushed the object in play, then you are working with a single acting cylinder. The piston in a single acting cylinder allows a one-way track for fluid to work its way through the hydraulic component. Within that, you’ll find a steel spring that helps retract the piston.
Calculating the Force Output
In order to properly calculate the exerted pressure being forced out from the hydraulic cylinder, it’s important to understand all the working parts. Each part factors into the extended calculations and can affect the outcome of the evaluated formula. To properly calculate the total force you take the total square inch surface area of the piston and multiply it by the pressure difference on the opposite sides of the piston. The same single acting formula can be applied to both varieties of a hydraulic cylinder because you are simply measuring the push through force which occurs in either cylinder.
Cylinder Push Force Formula
To calculate the force of a cylinder pushing on an object you need to evaluate two main components. First, you need to find out what the system pressure (PSI) is and also you’ll need to compute the piston’s (or bore’s) diameter. You can do that through establishing the cylinder’s working area. To do so follow the formula below:
Area = D^2 (diameter) x π/4
Now that you have formulated the working area of the system’s cylinder you can plug that data into the formula below and calculate the push force of your hydraulic cylinder.
Push force = PSI (system pressure) x D^2 (diameter) π/4
(Push force = PSI x Area)
Double Acting Cylinder Pull Formula
When working with a hydraulic cylinder that pushes and pulls the object at hand, there is a slight modification in the formula. The main factor that causes a slightly altered calculation is the loss of surface area. For example, in comparison to the single acting side, there is the full area of the piston. On the retract side of the cylinder, you now have the piston rod area taking away from the overall surface. Therefore this calculation factors in the surface area of the entire rod area. You find the cylinder road area by:
cylinder rod area = π x cylinder bore^2 - cylinder rod diameter^2 /4
Once you’ve established the cylinder rod area you can continue to calculate the cylinder force for double acting hydraulic cylinders.
The formula is the following:
Double acting cylinder force = PSI x Cylinder Rod Area
Air and Hydraulics Equipment Inc. in Middle Tennessee
Finding the right fluid equipment can sometimes be a task. Our expert team at AHE will help guide you to exactly what you need to get the job done. A key factor in proper operation is proper maintenance. If your rod seal is leaking or cylinder piston rod is bent, the hydraulic system will begin to operate poorly. To avoid that we suggest routine checkups, necessary repairs and possible replacement of your existing hydraulic equipment and it’s components. Give us a call today to speak with one of our hydraulic experts!