There are many different types of hydraulic cylinders with varying features to suit the intended application. Depending on where you are in the world, you may know them as &#;hydraulic rams&#; or &#;hydraulic jacks&#;. But regardless of the name, all use the same working principle according to Pascal&#;s law &#; which states that Force = Pressure x Area.
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Pressure is applied to hydraulic fluid using a pump, and the area is the size (diameter) of the plunger/piston that extends and retracts. An important Unlike pneumatic cylinders, hydraulic fluid will not compress. This is why hydraulic cylinders are the choice for lifting heavy loads.
In this article, we cover the main types of high-pressure hydraulic cylinders. (Mostly the portable kind used for maintenance and tensioning jobs which can be used up to psi / 700 bar). We&#;ve listed them by category type based on their primary characteristics or features, but the reality is that hundreds of configurations are available using different combinations of the various features
&#; Single-Acting
&#; Double-Acting
&#; Pull Cylinders
&#; High-Tonnage
&#; Locknut
&#; Production
&#; Climbing Jacks
&#; Hollow
&#; Telescopic
&#; Lightweight
&#; Tie-Rod
A single-acting cylinder is the simplest type. Hydraulic force can only be applied to the cylinder through its single port &#; typically to extend the plunger. This is returned to its starting position through the weight of the load, or by a return spring within the cylinder.
Above: Single-acting double-acting and pull types of hydraulic cylindersA double-acting hydraulic cylinder uses hydraulic flow to both advance and retract the plunger. It includes two connection ports and a compatible pump is needed to provide hydraulic flow in both directions. The benefits of a double-acting cylinder are that they provide a faster and also more controlled retraction. This is especially useful for applications that demand both push and pull forces and those needing repeatable accuracy.
Pulling applications using hydraulic cylinders include cable and bar tensioning. Typically, these are single-acting with spring return. The typical maximum pulling force of a pulling cylinder is up to 60 tons. Pulling force can also be applied by using a hollow cylinder.
General-purpose hydraulic cylinders offer tonnage capacities from just a few tons up to several hundred, whereas high-tonnage models can handle applications up to tons. There is of course some overlap between the two, but high tonnage cylinders often include additional features. These extras can include low-wear high pressure seals, replaceable composite plunger support bearings, and tougher nitrocarburized finishes. They&#;re also available in single-acting, double-acting, lock nut, configurations and are often used with tilt saddles.
Above: High tonnage, locknut, and production hydraulic cylindersA locknut cylinder is ideal when the application requires load holding for extended periods. This feature is available on different cylinder types, such as low height, lightweight or high-tonnage models.
Hydraulic cylinders for manufacturing are designed with high-cycle performance in mind and they need to satisfy different mounting configurations for fixing to machinery. They do this using collar threads, base threaded holes, plunger end threads, and attachments such as foot mounts, flange mounts, retainer nuts and clevis eyes.
A climbing jack incrementally lifts or lowers a load and is used with cribbing blocks to overcome the height limitations of a cylinder&#;s stroke length. They are constructed using a large base with an anti-rotation rod that provides stability and safety. They also include double-acting hydraulic cylinders with tilting saddles up to 5°. A built-in safety valve prevents accidental over-pressurization
Hollow plunger hydraulic cylinders (sometimes called center-hole cylinders) provide both, pull and push forces. The hollow plunger features an internal thread allowing fixing to the item to be pulled and tensioned. Hollow plunger hydraulic cylinders can be specified as single-acting or double-acting, steel or aluminum, and with removable saddles, and steel base plates.
Above: Climbing jack, hollow plunger, and telescopic types of hydraulic cylindersTelescopic hydraulic cylinders provide extended stroke where space is limited. The telescopic action allows the operator to lift a load a greater distance without the need for temporary cribbing. When choosing a telescopic cylinder, make sure you check the maximum load capacity which decreases the further it is extended.
For many applications, aluminum hydraulic cylinders offer the capacity and strength to get the job done, but with the added advantage of being lighter and therefore easier to transport or move into position. Aluminum is inherently less non-corrosive than steel &#; which makes it a great material for use in many caustic environments. Like their steel equivalents, they&#;re available in all of the usual configurations and include a hardened steel saddle and base plate.
Tie-rod cylinders are so-called because of the way they&#;re constructed. They include a head, a base, and a cylinder barrel connected by four or more tie-rods. This differs from the more robust high-pressure cylinders mentioned previously, which are manufactured from a solid piece of high-alloy steel.
For this reason, tie-rod cylinders are not suitable for high-pressure lifting and pulling applications. They are better suited to manufacturing applications up to psi 210 bar &#; typically within machinery, transfer lines, and other equipment.
For more information to help you make the right choice see our other article &#;How to Choose the Right Hydraulic Cylinder&#;. Alternatively, browse hydraulic cylinders from Enerpac.
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Access Now!Hydra-pneumatic cylinders&#;commonly referred to in the industry as hydro-pneumatic cylinders, air-over-oil cylinders, or intensifier cylinders&#;are pneumatically controlled cylinders engineered to generate higher hydraulic pressures to achieve a greater stroke force than can be attained by solely pneumatic cylinders of the same bore size. For example, a 5-inch bore pneumatic cylinder can output less than 1 ton of force at 100 psi, while a 5-inch bore hydra-pneumatic cylinder can produce up to 10, 15, or 20 tons of force, depending on the design.
The following blog post provides an overview of hydra-pneumatic cylinders, including how they work, key features, typical applications, and solutions at HyperCyl.
In contrast to strictly pneumatic or strictly hydraulic cylinders, these hybrid cylinders rely on the surface area differential of an internal pneumatic piston-rod assembly to significantly increase the pressure of trapped oil above the work piston, to provide an intensified hydraulic cylinder output force. Initially, they function similarly to pneumatic, double-acting cylinders, extending and retracting to the workpiece with output forces typical of pneumatic cylinders. However, once in contact with the workpiece, a second pneumatically controlled cylinder section drives a rod into the oil section, sealing it off, and intensifying the internal pressure. The intensified oil pressure pushes against the work piston, producing an increased output thrust, typical of hydraulic cylinders.
Similar to other double-acting pneumatic cylinders, hydra-pneumatic cylinders utilize valves to control their motion. They have one four-way valve to control approach and retract motion, and one four-way valve to control oil pressure intensification. This design combines the advantages of pneumatic and hydraulic cylinders without any of the disadvantages (e.g., excess heat and noise, space limits, or risk of leaks). Compared to strictly pneumatic cylinders with a multi-stage design, these cylinders consume only about 1/4 to 1/3 of the air.
While hydra-pneumatic cylinders come in a variety of designs to suit different applications, some of their key features include:
The full line (six series) of HyperCyl® hydra-pneumatic cylinders are designed for machine builders and OEMs to use in their own presses and automation, as well as for use in HyperCyl supplied presses. HyperCyl presses are available with &#;C&#; frames or &#;H&#; frames, unguided, two-column guided, or four-column guided upper bolsters, and bench-mounted, pedestal, or machine base configurations. Due to their modular design, machine designers can choose a simple frame and drive unit design that facilitates integration into a larger assembly process, or a turnkey design that incorporates automation technology, controls, and more.
HyperCyl presses find use in a wide range of production applications, such as:
HyperCyl by Aries Engineering Company (AEC) is a privately owned company based in Dundee, Michigan. We specialize in the manufacture of hydra-pneumatic cylinders and presses for assembly, piercing, and forming applications. By utilizing our cylinders, our customers benefit from the following:
All of these qualities translate to lower investment, operational, and/or maintenance costs.
Since , we&#;ve helped our customers determine the force and stroke requirements for their applications to help them design and purchase the right equipment for their needs. By evaluating their parts with our in-house equipment, we help identify the forces needed, and which actuator is best suited for their assembly, piercing, or forming application. All supplied materials are accompanied by complete evaluation documentation and reporting. We also offer access to an extensive database of hundreds of previous assembly and forming applications for examples of our capabilities.
To learn more about our product solutions and how they can benefit your assembly or forming application, contact us today. To discuss your application requirements with one of our experts, request a quote.
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