The Force Multipliers: Understanding 5 Key Types of Hydraulic Cylinders

Hydraulic cylinders play a vital role in an extensive range of industries, from construction and manufacturing to agriculture. They take the power from pressurized fluid, and create linear (straight-line) mechanical motion, allowing small forces to lift, push or pull large loads.

While all cylinders operate on the same essential principle—Pascal's Law—their designs, construction, and operation can be different and suited to different situations. Understanding these differences is key to finding the right "muscle" for the job.  Along with how they are constructed, cylinders may be defined by whether they are a single-acting or double-acting cylinder: 

Here is a breakdown of the 5 key types of hydraulic cylinders and where they are best put to use: 

1. Single-Acting Cylinders (The Simple Pusher) 

This is the simplest and least expensive of the cylinder designs; pressure operation and retraction rely on external force, such as gravity. Single-acting are best for applications that do no need a high amount of action, and are accomplished in good time with simple external actions. 

• How it Works: It operates on only one port for hydraulic fluid. When a volume of pressurized fluid enters, the force pushes the piston rod out to perform work (the "push" or "extend" portion). 
• Retracting: There is no action of fluid power to retract, instead relying on external force, such as gravity (or the weight of the load attached) or an internal return spring.
• Best Really For: These cylinders are best for simple lift, such as hydraulic jacks because they can change a very small amount of force into a very, extremely large one. Other applications like basic material handling, and equipment where gravity can assist the retracting stroke, such as a lift arm on a small front-loading tractor. 

2. Dual-Action Cylinders (The Controlled Driver)

The most common and adaptable type of cylinder

• Operation: It is designed with two ports, one at the rod side and the other at the head side of the cylinder. The pressurized fluid can flow to either side of the piston.
• Bidirectional control: Bi-directional control allows the cylinder to be powered both outward (extend) and inward (retract), giving the operator full control over the motion of the piston in both directions.
• Best suited for: Dual-action cylinders are used for applications requiring controlled and accurate movement and controlled push and pull of a load as in excavator booms, steering systems and industrial presses.

3. Telescopic Cylinders (The Long-Reach Specialist)

These cylinders took their name because they look similar to a telescope, as they are designed for maximum extension, while maintaining a compact size when fully retracted.

• How it Works: Telescopic cylinders contain several stages or sleeves that are nested, so they gradually get smaller in diameter as they are arranged towards the back of the cylinder. When fluid enters the cylinder the stages must extend one after the other to achieve such a long stroke.
• Space Saving: The retracted length is usually less than 20% of the all-extended length, making them ideal for equipment with tight space constraints.
• Best Applications: Equipment that must lift the load to a high position like the hoist of a dump truck, aerial work platforms (cherry pickers), and large mobile cranes.

4. Tie-Rod Cylinders (The Industrial Standard)

These cylinders are defined by their construction methods rather than their operation (meaning that they can be single or double-acting cylinders).

• How it Works: The components of the cylinder - barrel, head, and base cap are held together by four (or more) external tie rods which run the length of the cylinder and are secured by nuts. 
• Maintenance Advantage: In addition, the fact that the cylinder is bolted together makes it easy to disassemble, repair, and replace components, as each component can be easily swapped out as needed. Lastly, tie-rod cylinders are typically made to industry standards for interchangeability and built-in cost.
• Ideal Usage: Non-mobile industrial and factory machinery such as automation equipment, clamping systems, and production presses where ease of repair is important.

5. Welded Cylinders (The Tough Mobile Warrior)

Similar to tie-rod cylinders, with a focus on durability in construction.

• Operation: The end caps are permanently welded to the cylinder barrel, resulting in a tough, compact, and highly robust cylinder.
• Durability Advantage: Welded cylinders eliminate the failure of tie rods as points of failure, providing superior performance in high-stress and high-pressure and often dirty mobile environments. Welded cylinders are shorter in overall length for the same stroke than tie-rod type cylinders.
• Ideal Usage: Heavy-duty mobile equipment when space is an issue and conditions are rugged i.e., bulldozers, graders, agricultural equipment and most modern construction vehicles.