HYDRAULIC CYLINDER
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HYDRAULIC CYLINDER
How do hydraulic cylinders work in practice?
In hydraulic cylinders, the pressure energy of a medium is converted into mechanical energy. The resulting force is generated by the pressure exerted by the fluid on the piston surface. By changing the volume flow into the cylinder chamber, the speed of the piston rod can be adjusted while maintaining the same diameter. Alternatively, the speed of the piston rod can also be adjusted by changing the piston diameter while maintaining a constant volume flow. The force, in turn, can be influenced by the operating pressure and/or by changing the piston diameter.
HYDRAULIC CYLINDER
Your reliable development partner
We develop tailor-made solutions that are precisely tailored to our customers' individual applications. In doing so, we take into account special requirements such as temperature range, service life, corrosion resistance, maximum weight, environmental conditions and working pressure. Each cylinder is rigorously tested before use to ensure the highest quality. On request, we can also equip our cylinders with intelligent additional functions such as sensors for measuring travel, pressure, temperature, force and points.
1. Which hydraulic cylinder is suitable for which task?
Single-acting differential cylinders:
- Pressure can only be applied in one direction
- Only one direction of action and force
- Return by external force
- Different surface ratios between the piston and rod sides result in a smaller volume flow in the tank during extension.
Double-acting differential cylinder:
- Can be pressurised in both directions/on both piston sides
- Two directions of action and force
- Different surface ratios between the piston and rod sides result in differences in extension speed or force ‘fast travel’ when volume flow is on the side with the ring surface.
Plunger cylinders:
- Pressure can only be applied in one direction
- Only one direction of action and force
- Reset by external force Simple design, as only one side needs to be sealed
Double-acting equal speed cylinder:
- Can be pressurised in both directions / on both sides of the piston
- Two directions of action and force
- Equal surface areas, as both sides form a ring surface.
- This results in equal volume flows, forces and travel speeds.
Telescopic cylinder:
- Can be designed as single-acting or double-acting
- In the single-acting hydraulic cylinder shown on the right, the pistons extend one after the other (first the piston with the largest surface area) or retract one after the other (first the piston with the smallest surface area). With certain designs, it is also possible to achieve synchronous extension or retraction of all pistons.
There are different variants depending on the area of application. A single-acting hydraulic cylinder uses only one pressure side – it extends under pressure but returns under its own weight or spring force. These cylinders are well suited for lifting or clamping movements. In a double-acting design, both the extension and retraction are actively controlled by pressure. This allows loads to be guided precisely regardless of the installation position – for example, in mobile machines, presses or production lines.
1.1 Single-acting and double-acting hydraulic cylinders
Single-acting cylinders only operate in one direction with pressure – the return stroke is usually performed by their own weight or a spring. This makes them low-maintenance and particularly suitable for clear, repetitive movements. Many applications in agricultural engineering or for lifting stationary loads rely precisely on this design. A double-acting hydraulic cylinder is always required when controlled movements in both directions are necessary. Here, the pressure acts both during extension and retraction. This offers advantages in changing load conditions, in any installation position and wherever precision counts under real loads.
1.2 Hydraulic cylinders with integrated pump
Solutions with manual energy generation are suitable for applications without a central hydraulic supply. A hand pump for hydraulic cylinders allows cylinders to be operated mobile and independently – for example, in assembly fixtures or during maintenance work. Even more convenient are units in which hydraulic cylinders are combined with a pump in a compact system. This saves space, reduces connections and significantly simplifies handling.
2. What makes a durable hydraulic cylinder?
Material, workmanship and sealing technology all play a role here. Clean piston guidance prevents tilting movements, while high-quality seals for hydraulic cylinders protect against leaks and ensure that the full pressure can be utilised. Regular maintenance significantly extends the service life. If cylinders are used in dusty environments or under high loads, it is worth taking a look at the materials used and the sealing concept. In special applications, solutions are also available that prevent leakage even under the influence of high transverse forces. Furthermore, the coating of the piston rod is an important criterion for influencing both corrosion resistance and service life.
3. Special designs and specific applications
Hydraulic cylinders are available in many different designs. The design and connection type are adapted to suit the specific application – sometimes compact, sometimes designed for high force. For machines with limited installation space or clearly defined motion sequences, round cylinders are a frequently chosen solution. Thanks to their cylindrical geometry, they can be integrated in a space-saving manner without compromising on performance. These variants are frequently used, particularly in test benches, pressing equipment or machine tools.
QUESTIONS AND ANSWERS
Here you will find answers to the most frequently asked questions about our services, products and
processes – summarised quickly and clearly.
A hydraulic cylinder is a component that generates linear motion using fluid pressure. In practice, it moves loads, adjusts positions or transmits forces, depending on how it is designed. Such cylinders can be found almost everywhere in vehicles, machines and systems. They often work behind the scenes, but perform key functions without which many processes would come to a standstill.
That depends on the piston diameter and the system pressure. A cylinder with a diameter of 100 millimetres at 200 bar exerts a force of around 15 tonnes. The decisive factor is therefore the combination of surface area and pressure. For exact values, it is worth taking a look at the technical data sheet.
Air in the system impairs its function. To vent a cylinder, move it slowly through its entire stroke and hold it briefly under pressure at the end positions. If the system has vent screws, these may only be opened when the system is depressurised. In complex systems, it may be advisable to fill the cylinder under vacuum. If pre-treated, degassed hydraulic oil is used for this purpose, any residual air may dissolve back into the hydraulic fluid, thereby largely preventing the formation of air in the system.
That depends greatly on the application. With good design, regular maintenance and clean oil quality, many cylinders can achieve several thousand operating hours. Excessive lateral forces, contamination or unsuitable seals significantly shorten the service life.
The most common cause is a damaged or worn seal. Even fine scratches on the piston rod or dirt in the oil can cause the cylinder to lose pressure. In some cases, incorrect installation is enough to put uneven strain on the sealing elements. Temperature changes, contaminated operating media or overload further accelerate wear. Keeping the system clean and checking it regularly will help to prevent major damage at an early stage.
Yes, many cylinders can be repaired, depending on the design and the type of damage. Often, it is sufficient to replace the seals or guide rings. Damage to the piston rod or cylinder tube is more complicated to repair. The decisive factor is whether the repair makes economic sense.