A hydraulic cylinder is a mechanical device which is used to create force in a straight line. It uses fluid (hydrostatic energy) to magnify linear force. A small force exerted over a small surface area is transferred and amplified into a large force over a large surface area.
Hydraulic cylinders are used in virtually all applications that need linear force magnification. In fact, the hydraulic cylinder market is expected to be worth over $16 billion by 2025.
A few applications include presses, clamps, and sheers for lifting, pulling, pushing, holding and bending. They are useful in many sectors including aerospace, industry, defense, and material handling, among others.
Enerpac has a vast selection of hydraulic cylinders, with a worldwide distribution network. If you’re looking to buy, choosing the right machine can be tough. There are hundreds of options and customizations, depending on your needs. This article discusses in detail.
1. SIZING/CAPACITY
The force exerted by a hydraulic cylinder depends on the internal pressure and surface area. To get the right size, therefore, you must work backward to determine the force/strength, speed, and capability you need. Subjecting it to a load bigger than its capacity can break the eye bearing and cause equipment malfunction.
Majority of industry applications use medium-duty cylinders, which exert about 1000PSI of force/pressure. Hydraulic presses and the automotive industry need heavy-duty cylinders that can exert up to 3000PSI.
2. SPEED
How much speed you get from your system determines the speed your machine moves at. However, your definition of speed will be different depending on your application.
Standard cylinder seals can usually handle up to 1 meters/second (3.28 feet/second). In reality, standard loads can only move at ⅔ meters/second (2.19 feet/second). If you need a higher speed, your hydraulic cylinder must have low-friction seals.
Bear in mind, however, that what you gain in performance you may lose another area. For instance, higher speed means greater fluid velocity and hence higher temperatures. You must account for this increased temperature on the entire hydraulic system to prevent overheating and malfunction.
In some hydraulic systems, increasing port size can deal with the increased temperature problem.
3. TEMPERATURE
Hydraulic systems without any customizations can operate at temperatures between 65°F (-54°C) and 500°F (260°C).
Consider that system temperature affects both ‘hard’ and ‘soft’ components of hydraulic cylinders over time. Therefore, applications requiring extreme temperatures should consider these effects and the right balance to have sustainable performance. For instance, around the poles, expect that extreme cold will cause seals and metal parts to contract.
4. MOUNTINGS AND CUSTOMIZATION
Proper functioning of a hydraulic system depends on the interplay between various components. By always thinking about the effect of each component on the whole system, you can avoid malfunctions. Such issues usually result from ordering components separately instead of the entire system at once.
For proper function, ensure the cylinder is fitted with the recommended/appropriate:
- micro/pivoting feet,
- flanged, trunnion or foot mountings,
- swivel or fixed clevis ends, and
- displacement
Mistakes when ordering/assembling system components can lead to poor performance and inefficiency at best and product failure at worst. Also, certain choices/actions can void your warranty when you need replacement parts or repair.
To ensure you get it right, work with a knowledgeable supplier and the manufacturer’s manual. Based on your needs, you can customize components for better performance without adversely affecting the entire system.
5. TYPES OF CYLINDERS
Hydraulic cylinders may be single or double acting. This describes the action of the fluid on the piston.
Single acting cylinders exert force on one side of the piston, i.e., they force the piston rod out in only one direction. You must use another cylinder, external springs or flywheels to get it back to the starting position. They are widely applied for internal combustion engines.
Double-acting cylinders can exert pressure alternately on both sides of the piston as needed, e.g. operating a crankshaft. They were commonly used in large-scale internal combustion engines like ship motors, and steam engines. Today, however, they are used in specialist applications, and sometimes in blast furnaces.
6. CYLINDER DESIGNS
Like with all other factors, the kind of design you need depends on your application. There are three main designs available today:
TIE ROD DESIGN
You have a cylinder barrel surrounded by strong steel rods attached to two caps on either end. Larger cylinders withstanding higher pressure must have more steel rods. Small units can have as few as four rods, while larger units can have as many as twenty.
They are mostly used for industrial applications. The tie rods are easy to remove, which makes maintenance easier compared with welded cylinders.
WELDED CYLINDERS
These have no tie rods; rather, caps are welded directly onto the cylinder barrel. As a result, they are stronger and narrower than tie rod cylinders. They can be easily miniaturized for use in smaller machinery and engines.
Welded cylinders are commonly used in vehicles like excavators, bulldozers and cranes.
TELESCOPIC CYLINDERS
Telescopic cylinders are made of several concentric, retractable welded barrels. They are made this way to facilitate long reach.
They include heavy-duty cylinders which have hydraulic oil – oil can withstand much higher pressures of up to 2,000-3,000 PSI.
7. PRICE
The price comes last as a factor deliberately, because you must choose according to your needs before checking the price tag.
Single-acting cylinders are cheaper than double-acting cylinders. Larger cylinders will be more expensive than smaller cylinders. There is an additional cost for installation and design or integration with other components.
Customizations will also cost extra, depending on the extent of customization. Specialist or robust/reinforced cylinders, such as those designed to work in extreme environments, will come with a handsome price tag.
You can also expect to pay more if you need customizations delivered faster. Larger batch orders cost less because input costs are reduced per unit when building more units.
Choose a reputable company that caters for small batch orders as well as large ones. You can get discounts for repeat orders too.
HYDRAULIC CYLINDERS – FINAL THOUGHTS
The most important tip if you’re getting hydraulic cylinders is to work with experienced and reputable manufacturers. Knowledgeable sales technicians will also help you choose the right cylinder and suggest customizations to improve efficiency and performance.
Do not be afraid to spend more on the outset for a cylinder if it’s designed to suit your needs. Higher quality, bespoke machinery will serve you better and offer returns in efficiency and longer lifespan.
Finally, be sure to keep up with the required repairs and maintenance. Working with a small malfunction can damage the entire system over time.
Do you have any questions? Feel free to contact us today.