Hydraulic Cylinders
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While the modern world certainly wouldn’t be the same without them, hydraulic systems are one of the most overlooked parts of our lives. They’re on the buses, trains, and aeroplanes we use to get around. And they’re also in the heavy (and light!) machinery used to create many of the products we enjoy.

However, choosing the right hydraulic cylinders involves more than just choosing the cheapest one available. It’s also not as easy as looking for an off-the-shelf replacement. Whether you’re getting hydraulic cylinders for a new build or as replacements for an existing system, here are some guidelines you should consider:

Think about the operating and environmental conditions.

  • Hydraulic cylinders are used in countless applications. If there is a need for an actuator that multiplies force, hydraulics could be a good fit for that use case.
  • In practice, this means that a hydraulic system that works for one set of conditions may not necessarily work in another—even if they’re meant for the same application.
  • For instance, the ideal hydraulic cylinders meant for a controlled indoor environment will likely be different from one designed for use outdoors, typically in dusty or humid conditions.
  • Ideally, hydraulic cylinders for a humid environment (such as along coasts, in tropical latitudes, or food processing facilities) will need to be made from corrosion-resistant materials. Cylinders meant to work in dusty environments, such as those used for heavy mining equipment, are usually designed with better abrasion resistance and dust-proofing.
  • The specifications for gaskets and protective boots will also have to be considered as well. Additionally, you will need to select the types of seals and cylinders needed based on the fluids intended for use in the system. In any case, it’s not enough to merely consider the bore size and length when choosing cylinders, as there are a wide variety of environmental and operating factors that come into play.

Choose between pivoted or straight-line types.

While there are some very specific applications where one may conceivably use either, cylinders are usually designed specifically for pivoted or linear (straight line) mounting. Be sure to carefully consider the type of movement your loads and forces will need to travel before choosing a cylinder for your project.

Know the operating pressures.

Cylinders typically operate with forces between 35 kg/cm² (500 psi) to 700 kg/cm² (10,000 psi). Knowing these forces will allow you to select a cylinder bore diameter as well as choose a type with the appropriate specifications.

A quick way of finding the needed bore diameter is to use the following formula: D = F / (Pi/4* P), where F is forces needed (kg), P is normal operating pressure (kg/cm²) and D is bore diameter (cm).

In any case, you may want to consider using the commercially available bore diameter closest to the requirement for your application. To introduce a safety margin, it’s often recommended to get a cylinder that’s a size up.

Consider the seals or O-rings.

O-rings and seals cannot be ignored when you’re choosing a hydraulic cylinder. As with all of a cylinder’s other components, these are likewise designed to operate within specific parameters. Seals can be the most vulnerable part of a hydraulic system, so it’s important to choose the appropriate recommended seals with any hydraulic cylinder.

Find a balance between bore size, rod length, and diameter.

When an appropriate bore size for a hydraulic piston is chosen, you’ll need to consider the rod length and diameter. Rods that lack sufficient structural strength may bend or buckle under stress, which can seize up the system or result in loss of transmitted power. If the rod is too long, there may be excessive leverage in the system that may also cause the same issues.

Using thicker rods to increase strength is not necessarily the answer in all instances, as this can add weight. And excess weight could cause other sets of problems—such as buckling—depending on the forces present.

To figure out the recommended rod length and diameter, there are programs available that you or your cylinder supplier could use. Depending on the application, you may also need to have custom rods built if no off-the-shelf rods are available.

Conclusion

There’s a lot that goes into choosing the right hydraulic cylinders for your system. Check out Hydraulic Solutions & Sales to find out which possible hydraulics solutions are right for your needs.

What issues have you encountered when sourcing hydraulics cylinders? Tell us!