When you need the power of a hydraulic cylinder, but you don’t have space for a traditional rod cylinder, the best solution is a telescopic hydraulic cylinder. Able to lift just as much as a standard cylinder, telescopic models can fit the same amount of power while only taking up 20% to 40% of its extended length while collapsed.

For more information, please visit EOOE.

There are several applications where a telescopic hydraulic cylinder is useful and the only way to perform certain functions.

This article will look at some of the different types of telescopic hydraulic cylinders and how they function. We’ll also look at some of the most common applications of these telescopic hydraulic cylinders and how you can make sure you choose the right cylinder for your needs.

How Telescopic Hydraulic Cylinders Work

While there are several varieties of telescopic hydraulic cylinders, they all work on the same principle. These cylinders are constructed from a series of steel tubes, which are nested in descending size.

The largest pipe, known as the barrel, is visible when the cylinder is retracted. The smallest pipe, or plunger, contains the end that attaches to the working load. The other sections, which extend to make up the rest of the stroke, are known as stages.

For stability reasons, the maximum number of cylinders in a telescopic hydraulic cylinder tops out at six. Any more than that, and the system tends to become unstable, presenting multiple problems at both the design and execution stages.

Hydraulic oil pumps into the system to extend the device. The oil pushes the stages out from biggest to smallest. Each stage extends to its full length before the next stage starts to extend until, finally, the plunger is extended all the way. As the cylinder retracts, the process repeats itself in reverse — the plunger retracts before the following stage retreats, and so on.

Bearings and Seals

Every stage in a telescopic hydraulic cylinder is supported by guide bearings, which keep the cylinders adequately aligned. These bearings define how far the inner stage projects from the previous stage and how much the two stages overlap.

There are a wide variety of options available when it comes to seals, each with a slightly different design and utility purpose. For example, two standard designs — multi-lip seals and hinged-V seals — are installed using stop rings and packing nuts, and these fit inside each telescoping section. The seal is formed between the outer diameter of the smaller stage and the inner diameter of the stage housing it. These seals create the pressure that allows the telescopic hydraulic cylinder to extend.

The Types of Telescopic Hydraulic Cylinders

The two primary types of telescopic hydraulic cylinders are single-acting and double-acting — most variations arise from combining these two styles.

Single-Acting Telescopic Hydraulic Cylinders

A single-acting cylinder requires pressure to extend. However, rather than retracting under pressure, the device relies on external forces to retract. This is most commonly the case when a constant load, such as gravity, is working against the cylinder, which allows the cylinder to retract. 

While a single-acting cylinder requires hydraulic oil to force each stage out of the cylinder, the retraction process occurs when that pressure is removed and the weight working against the cylinder gradually overcomes the hydraulic pressure. This forces the hydraulic oil back into the reservoir.

Double-Acting Telescoping Hydraulic Cylinders

As you might expect, a double-acting cylinder uses pressurized hydraulic fluid to extend and retract its stages, making them ideal for situations where gravity or another external force can’t be relied on to retract the cylinder.

In general, extending these cylinders works exactly the same as in a single-acting cylinder. That being said, to use pressure to retract these cylinders, each stage that moves has oil transfer holes built into it. As each stage retracts, it exposes the oil transfer hole in the next stage until the entire cylinder has retracted into the barrel.

This design creates complications that must be considered. Most double-acting telescopic hydraulic cylinders have both extension and retraction ports located in the plunger. But to protect the hoses and ports and limit the amount of hosing required to run the cylinder, the plunger remains anchored to the base, with the barrel located at the working end of the load.

Typical Applications for Telescopic Hydraulic Cylinders

There are several situations in which a telescopic hydraulic cylinder is the right tool for the job. For instance, single-acting cylinders are extremely common on dump trucks, and for a good reason. 

The container must be tilted to somewhere between 45 and 60 degrees to empty a dump truck. Regardless of the length of the container, the required stroke length to pivot the container on its hinge would be nearly the length of the truck bed. There would be no way to retract the rod all the way, making it impossible to load the truck or even drive it.

With telescopic hydraulic cylinders, on the other hand, the retracted cylinder takes up far less space. And with the weight of the container, it doesn’t require a double-acting cylinder to retract and bring the bed back to a horizontal position.

On the other hand, you’re more likely to see a double-acting cylinder when the hydraulic force is being used horizontally, meaning it can’t rely on gravity. Consider sanitation vehicles, where refuse is compacted throughout the route. The compactor is operated by a double-acting telescopic hydraulic cylinder, allowing the platen to press against the trash, then retract to allow more refuse to be added. Because the platen is operated from above, it requires a double-acting cylinder to pull the platen back to the top of the truck.

Other situations require telescopic cylinders, as well. For example, constant thrust and constant speed cylinders are used for deep drilling in which every stage is extended simultaneously under constant pressure. However, while you may find specialized telescopic hydraulic cylinders like this, it’s far more common to encounter single- and double-acting cylinders.

How to Choose the Right Telescoping Hydraulic Cylinder

Finding the right telescoping hydraulic cylinder is a matter of knowing how long the stroke needs to be and how much pressure you’ll need to handle the maximum load of your equipment. That requires understanding a few pieces of information about your specific needs and performing the proper calculations.

Let’s use a dump truck cylinder as an example. There are two measurements we need right off the bat. First, you need to identify where the container is hinged to the truck frame. Then, you need to measure the distance (in inches) between that hinge and the center of the load being lifted. This will be the middle of the dump body most of the time, but that may not always be the case.

The second measurement (also in inches) starts at the hinge again, but this time measures to where the cylinder connects to the dump body. This number will typically be much longer than the first.

Force and Stroke Calculations

The next step is to determine the initial amount of force you need to lift the load. The most difficult part of the lift is right at the start, with less force required as the angle of the dump body increases.

To figure out the force needed to lift the load, multiply the anticipated load in pounds (including the weight of the dump body) by the first measurement you took. Then, divide that number by the second measurement, which will give you the proper force you need to lift.

For example, let’s say you want to lift 14,000 pounds, with a length of 80” to the center of the load and a distance of 160” between the hinge and the cylinder base point.

14,000 x 80 = 1,120,000 / 140 = 8,000

That means that you need to be able to produce 8,000 pounds of force to start lifting your load of 14,000 pounds.

To determine your stroke length, you simply multiply the distance between the hinge and the cylinder base by a multiplier based on the dump angle. The dump angle is the angle created between the truck frame and the dump body as the cylinder extends. The angle you need is simply the angle at which the dump body can be emptied completely.

If you’re lifting your bed to 49˚, you would simply multiply the distance between hinge and cylinder base (140”) by the multiplier (.830) to get a stroke length of 116.2”.

See the MAC Hydraulics Difference

When embarking on any project requiring hydraulic cylinders, choosing the ideal type can be key to its success and efficiency. Hydraulic cylinders play an integral part in many industrial applications and selecting one can have major ramifications on performance, safety and cost-effectiveness of your operations - here is our comprehensive guide that can assist with selecting an adequate one:

Load Capacity 

A hydraulic cylinder's load capacity refers to its maximum force-bearing capability. To ensure optimal results from any application that uses this cylinder, it's vitally important that its capacity meet your demands without overloading. Overloading can lead to premature wear, damage and catastrophic failure - an overloaded cylinder may fail sooner rather than later! For additional tips regarding load capacity visit this post here -

Calculate the maximum load and take into account any potential overload conditions.

Select a cylinder that exceeds its maximum load capacity in order to ensure safety and longevity.

Stroke Length

Stroke length refers to the distance a piston travels from its fully retracted to fully extended position, and this measurement is essential for making sure cylinder can move load a set distance. Tip: Measure your application's exact stroke length requirement before making this measurement.

Think carefully about any extra stroke length needed for safety or to accommodate slight misalignments in alignment.

Mounting Options

A cylinder's mounting configuration determines how it connects with machinery and how it moves. Different mounting styles like flange, clevis, trunnion or side-mounted offer various advantages depending on its application.

Tips:

It is best to determine which mounting style best meets your setup.

Make sure the mounting points can handle the loads and stresses associated with operation.

Operating Environment

The operating environment for a hydraulic cylinder can have an immense effect on its performance and lifespan, from extreme temperatures, exposure to water, dust, chemicals or contaminants that might contaminate its contents to temperature extremes and exposure. When making decisions pertaining to this aspect of operation it's essential that all possible variables be considered including factors like temperature extremes, exposure to dust or chemicals along with any tips provided for improving longevity in operation such as temperatures extremes versus dust exposure etc.

Select materials and coatings designed to withstand corrosion and wear in challenging environments, and install seals and wipers designed for the conditions in which your cylinder will operate.

Additional Considerations

Speed and Frequency of Operation

Knowing the speed and frequency requirements for your cylinder's cycles can assist with selecting one that fulfills performance specifications without overheating or experiencing undue wear and tear. Tip: mes Check the specifications of your chosen model's cycle speed/frequency requirements.

Make sure that the cylinder has adequate cooling or heat dissipation if it will operate frequently or at high speeds.

Fluid Type and Compatibility

For optimal cylinder performance, your choice of hydraulic fluid must match up well with its seals and materials. Different fluids have differing viscosities and lubricities which could alter its performance, including viscosity or lubricity levels that could hinder its use. As an additional resource to this article:

Assure your cylinder is compatible with your hydraulic fluid of choice and use products which offer superior performance or longevity in your specific application.

Precision and Control

Some applications call for precise control over cylinder movements, such as in positioning systems and robotics. When such applications require precise regulation of movement, such as when positioning systems are involved or robotics are utilized, consider purchasing cylinders equipped with position feedback systems or those which can be combined with control valves and sensors for more effective precision and control. In such instances, consider purchasing cylinders equipped with position feedback systems as these will give greater accuracy than non-feedback systems or those that come equipped with position feedback sensors as these will give more accurate results. Tip: For optimal precision when controlling movements involving several moving cylinders mounted together using control valves paired with sensors

Always look for cylinders with integrated position sensors and ensure your control system can interact with their feedback mechanisms.

Types of Hydraulic Cylinders

Selecting the ideal hydraulic cylinder is key to the efficiency and success of any project, so here we will outline various types of hydraulic cylinders along with their specific applications to assist you in making an informed decision.

Single-Acting Cylinders

Single-acting cylinders exert force only in one direction--typically the extension phase. Hydraulic pressure extends their piston, while retraction may be accomplished via external force such as springs or gravity. For applications including:

Lifting Devices: Most often seen in jacks and hoists to lift loads before they descend under their own weight, clamping operations are ideal when only one-sided clamping force is required. They offer several advantages over conventional designs: simple construction with less moving parts means lower maintenance costs; less wear-and-tear; as well as simpler design with simplified maintenance needs for less cost overall. But there may also be limitations.

Limitations include applications requiring force in one direction only and slower retraction rates than double-acting cylinders.

Double-Acting Cylinders Double-acting cylinders provide force in both extension and retraction by using hydraulic pressure on both sides of the piston, making them highly versatile and efficient solutions for applications requiring movement in two directions. Their multidirectional performance also makes them suitable for many different industries including those dealing with materials handling. Applications:

Construction Equipment: Excavators and loaders that require bidirectional movement require construction automation systems for precise control over both movement directions. Industrial Automation: Used in machinery that needs precise control of movements in both directions requires precise movement control to operate optimally.

Contact us to discuss your requirements of Multi Stage Hydraulic Cylinder. Our experienced sales team can help you identify the options that best suit your needs.

Advantages: Increased control and versatility are offered.

Rapid operation as hydraulic pressure is used for both extending and retracting. Suited for many different applications. Limitations: Overly complex design.

Telescopic Cylinders Telescopic cylinders, commonly known as multi-stage cylinders, offer an extremely long stroke with minimal initial cost compared to single-acting cylinders. Their design includes multiple stages that extend sequentially for long stroke applications. Their primary application area includes aerospace.

Dump Trucks: Used when lifting beds to a high angle requires long strokes of lifting action, such as those seen on dump trucks.

Material Handling: Wide reach capabilities are needed from short starting positions. Advantages: When collapsed they save space when stored away while providing long extension range. Limitations: These models require complex construction process which may restrict usage in certain applications.

Applications: Commonly found on mobile equipment such as agricultural and construction vehicles, these sensors are often found within mobile equipment like agricultural tractors or construction vehicles. Their main advantage lies in their resistance to high pressures as well as compact design that fits tight spaces.

Their main drawback, however, would be their limited capabilities due to high pressures. Ultimately these limitations must also be considered.

Tie-Rod Cylinders: With their welded construction, these cylinders can be more challenging to service and repair.

Tie-Rod Cylinders differ by being held together using tie rods connecting end caps; often found in industrial machinery and manufacturing equipment. Among their many benefits are easier disassembly for maintenance and repair work and generally cost-efficient manufacturing costs; although their limitation includes being larger.

Mill-Type Cylinders Mill-Type Cylinders are heavy-duty cylinders designed for high pressure applications. Their robust construction with thicker walls makes them suitable for harsh environments and applications in steel mills are commonly found where this type of cylinder would be most appropriate. - Steel Mills: Heavy duty applications within this industry.

Mining: Mining equipment employing this material must withstand heavy loads and harsh conditions, and offers advantages such as extreme durability and designed for high pressures and long lifespan with minimum maintenance requirements. But it also comes with drawbacks like being heavier and bulkier compared to other options.

Due to their robust construction, initial costs may be higher.

Pressure Ratings

A deep understanding of hydraulic cylinder pressure ratings is vital to ensure the safety, reliability, and efficiency of any hydraulic system. Pressure ratings determine the maximum operating pressure a cylinder can withstand without failing. Here's an in-depth examination of why pressure ratings matter and how to select one with appropriate ratings for your project.

Why Pressure Ratings Matter

Safety: Exceeding a hydraulic cylinder's rated pressure can result in catastrophic failure, leading to equipment damage, injury to personnel and costly downtime.

Performance: Selecting an inappropriate pressure rating can lead to subpar performance, including slower operation and inability to withstand required loads.

Durability: Exceeding pressure ratings may result in premature wear and tear, shortening the lifespan of the cylinder and increasing maintenance costs.

Key Considerations for Pressure Ratings

Operating Pressure Vs Maximum Pressure

When selecting an operating pressure for normal conditions, ensure the cylinder can handle it without experiencing excessive strain or difficulty.

Maximum Pressure: Maximum pressure refers to the highest allowable operating pressure for each cylinder in an assembly and should be sufficient in terms of protecting against sudden pressure spikes or surges within your system.

System Pressure Requirements (SP Rqs).

Determine the operating pressure of your hydraulic system, taking note of any variations or spikes that might arise while operating.

Choose cylinders with maximum pressure ratings greater than peak pressure in order to maximize safety and reliability in your system.

Pressure Ratings of Different Cylinder Types

Low-Pressure Cylinders: Used in applications up to 1,000 PSI for light duty uses such as agricultural equipment or light industrial machinery.

Medium-Pressure Cylinders: Medium-pressure cylinders usually range between - PSI. Common applications include construction equipment, manufacturing machinery, and general industrial uses.

High-Pressure Cylinders (HPCs): With ratings exceeding 3,000 PSI, these high-pressure cylinders are essential for heavy-duty applications like mining, steel mills and high-performance industrial equipment.

Pressure Rating Standards mes Adherence to industry standards such as ISO, DIN and NFPA ensures the cylinder meets specified safety and performance criteria. Check whether it complies with these standards before purchasing a cylinder.

Manufacturers conduct regular pressure tests on their cylinders to verify they meet or surpass their rated pressures, providing additional assurance of safety and reliability.

Material and Design Affect Pressure Ratings As material of cylinder barrel and components can greatly influence their pressure rating, for instance steel can often handle higher pressure than aluminum cylinders.

Design: The design and construction methods, such as welding or tie-rod assembly, also play an important role in the pressure rating of a cylinder. Welded construction often handles higher pressure levels more effectively. Pressure Relief Mechanisms

Consider installing pressure relief valves into your hydraulic system to safeguard its cylinder from sudden pressure surges that exceed its rated capacity. Regular inspection and maintenance of these devices ensure they function correctly and protect the system.

Application-Specific Requirements

Different applications have different pressure requirements due to environmental conditions, operational cycles or load characteristics; it's important that cylinder selection matches these particular needs.

Speed Requirements

Speed requirements play an essential part in selecting a hydraulic cylinder suitable for your application, impacting performance, efficiency and precision of hydraulic systems. Here is an in-depth exploration of why speed requirements matter when making your selection decision for any project. Here is why speed requirements matter so much

Efficiency: A hydraulic cylinder's speed has an effect on your equipment or machinery's cycle time, impacting overall productivity and efficiency.

Precision: For certain applications such as robotics and automated systems, precise control over the speed of cylinders is required to guarantee accurate positioning and movement.

Safety: Operating a cylinder at speeds beyond its designed limits can create unsafe conditions, including overheating, excessive wear, and potential failure. Key Considerations for Speed Requirements

Desired Speed of Operation

Establish the required speed of extension and retraction. This may depend on your application. With that in mind, consider both average operating speeds as well as any peak speeds the cylinder may need to reach during specific operations.

Cylinder Design and Speed Capabilities | Piston Area and Flow Rate (Area and Rate of Hydraulic Fluid Flow). The speed of a hydraulic cylinder depends heavily upon both fluid flow rate and piston area - for instance, large piston areas require more liquid in order to achieve similar speeds as smaller pistons.

Port Size: Larger ports allow more fluid to enter and leave the cylinder quickly, speeding up operation. Make sure your port size meets your speed requirements for optimal results.

Cushioning: Cylinders equipped with inbuilt cushioning are an invaluable way of managing high-speed operations by decelerating piston at stroke's end, thus reducing impact and wear on moving parts.

Hydraulic System Flow Rate

The rate at which hydraulic fluid from pumps and control valves flows determines how quickly cylinders can operate; higher flow rates permit quicker speeds.

Be certain your hydraulic pump and system components can deliver enough flow rate to achieve the desired cylinder speed.

Speed Control Methods

Utilise flow control valves to precisely regulate the rate at which hydraulic fluid enters and exits cylinders for precise speed adjustments.

Proportional Valves: Proportional valves offer precise control of fluid flow for applications requiring variable speeds, providing smooth acceleration and deceleration with their fluid control properties.

Servo Valves: When applied in high precision applications, servo valves offer unrivaled control of cylinder speed; making them suitable for synchronized or dynamic movements.

Load and Speed Relationship

The speed of a cylinder may depend upon its load. Heavier loads may necessitate slower speeds to maintain control and avoid damage to either itself or to its surroundings.

Calculate the appropriate force and speed for your cylinder so it can support its load without compromising performance.

Cycle Time and Duty Cycle Cycle Time: Determining an adequate cylinder speed relies heavily upon knowing how long a full operation cycle requires - from extension, retraction, dwell times, to extension back out again and then retract.

Duty Cycle: When selecting the proper cylinder for continuous or intermittent use, its frequency of usage must also be taken into consideration. Heavy-duty cycles at higher speeds may necessitate special models designed to withstand increased wear.

Temperature Variations Environmental Factors Varying temperatures can alter the viscosity of hydraulic fluid, altering how quickly its cylinder operates. It's essential that systems be designed so as to deliver consistent performance regardless of any variations in temperatures.

Customization Options

Standard hydraulic cylinders may not meet all your project's requirements; therefore, consider looking for manufacturers that offer customizable options, including different sizes, mounting configurations and features such as position sensors or special coatings.

Budget Considerations

While selecting a hydraulic cylinder that fulfills all your technical specifications is key, it is also vitally important to keep budget in mind when making this purchase. Balancing quality with cost effectiveness will lead to smart investing.

Manufacturer Reputation and Support

Choose a reliable manufacturer who produces high-quality hydraulic cylinders. Consider factors like warranty, customer support and the availability of replacement parts when making this selection.

Conclusion

Selecting the ideal hydraulic cylinder for your project requires careful consideration of various factors, including application requirements, cylinder types, material and construction details, pressure ratings, speed requirements, customization options, budget considerations and manufacturer reputation. By taking time to evaluate these aspects carefully, you can ensure you select a hydraulic cylinder that will perform reliably and efficiently, helping ensure its overall success and contributing towards its ultimate success.

Want more information on dual hydraulic cylinder? Feel free to contact us.