How to choose a hydraulic cylinder? - HPS International

1Type of cylinders

First element to take into account is the type of cylinder. HPS International manufactures and sells 6 types of cylinders for various applications :

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• Block cylinders (compact) for plastic injections, molding, cosmetics and packaging.
• Tie rods for plastic injection, molding and aluminum injection applications.
• Round cylinders (ISO, DIN, CNOMO) for plastic injection and molding.
• Special cylinders (made to measure, double bore) for plastic injection, molding and die casting.
• Auto-locking cylinders for plastic injections, molding, cosmetics and packaging.
• Cylinders for foundries for aluminum injection.

• Example : Block cylinder
• High Speed : Go for the RCVN
• Compact : VBL, VBLS, VCR, VXP
• With mechanical sensor : VCE
• With inductive sensor : VDI
• With magnetic sensor : VBM
• Cooling : VRE

2Bore

The first essential information to take into account when choosing the size of the bore is the operating pressure.

Knowing the operating pressure you want to use will help you choose the size of the cylinder bore.

The second key information needed to choose the size of the bore is the amount of force required for the application. Here is a quick formula to find the approximate size of the bore in the direction of cylinder extension :

• F = required force (N)
• P = operating pressure (bar)
• A = Surface of the bore (mm²)
• D = bore diameter (mm)
• D = √4.F / √π.√p

As a general rule, the resulting bore diameter is rounded to the next standard bore size.

3Rod

Now that you know the minimum size of the hydraulic cylinder bore, you must now choose the ideal rod size. Most HPS cylinders come with several rod options.

The correct rod is chosen based on the necessary stroke length, which has an effect on the buckling resistance of the rod.

When selecting the rods, the smallest rod in the bore should only be used for reduced stroke thrust loads or in reduced pressure applications. The largest rod should be used in cases that depend on its reliability and maximum strength.

If the desired rod diameter is greater than the largest diameter in the bore size of the selected cylinder, it is time to re-examine the cylinder design parameters. It is usually in these situations that the application requires a custom hydraulic cylinder.

4Mounting

The hydraulic cylinders are divided into two types, depending on their mounting style, either a pivot mounting or a straight line mounting. Pivot mounted cylinders are used when a load is to be moved in an arc and includes supports such as a clevis and a trunnion.

Cylinders mounted in a straight line are used when the load is to be moved in a linear direction. It includes a flange support and a back or front foot.

5Seals

A hydraulic cylinder must have the right seals, as they play a vital role in preventing any oil leaks. This, in turn, guarantees a continuous and flawless use of the cylinder. The seal should be selected based on the cylinder's applications, operating environment and the maximum operating pressure it can withstand.
HPS International offers 4 types of seals :

• Standard N Nitrile seals, for temperatures from -20 ° to + 80 ° C, an operating speed of 0.5 m / s. Fluids: mineral oil, filtration ISO 19/17/14.
• Viton V FPM seals, for temperatures from -20 ° to + 200 ° C, an operating speed of 0.5 m / s. Non-combustible fluids based on Ester Phosphate (HFD-R), ISO filtration 19/17/14.
• Glycol G nitrile seals, for temperatures from -20 ° to + 90 ° C, an operating speed of 0.5 m / s. Fluids: Water-Glycol (HFC), ISO filtration 19/17/14.
• PTFE P seals in viton / PTFE, for temperatures from -20 ° ... + 240 ° C, an operating speed of 0.5 m / s. Non-combustible fluid based on Ester Phosphate (HFD-R), ISO filtration 19/17/14.

Other elements to consider when choosing a cylinder such as power, operating mode and switches.

6Sensors

HPS International offers 4 types of hydraulic cylinder sensors. The choice depends on the needs and demands of the clients.

• Mechanical : Adjustable, reliable, easy and fast assembly, compact (HPS).
• Inductive : Non-adjustable, reliable, easy and compact.
• Magnetic : Adjustable, popular, compact.
• Linear : Precise, compact (inside the stem).

7Hydraulic concepts:
Pressure, force, flow

• Pressure (bar) : Power creation
  P = F/S
• Forces developed by pushing (daN) :
  F = P x S1
• Forces developed by pulling (daN) :
  F = P x S2
• Flow (l / min) : Speed Creation
  V = Q / S

• With unit :
• P : bar Q flow: cm3/min
• F: daN S: π x r² cm² Vspeed: cm/min
• N = 100 daN = 1KN = 0.1 Ton

Do you need help knowing which hydraulic cylinder will fit your machine? Could you use some guidance on choosing the right cylinder for your specific application? In this article, we will provide you with all the identifying information you will need and each step to take to measure before choosing which hydraulic cylinder to buy. Avoid returns, and get it right the first time!

Hydraulic cylinders are utilized in various applications and can be found on many machines, from scissor lifts to skid steers, tractors, and log splitters. As such, finding the cylinder you need can be a challenge. Whether this is your first time buying a replacement cylinder or you're DIYing a new log splitter, we're here to help you choose the right hydraulic cylinder for your project.

Hydraulic Cylinder Components

Before we discuss your options, let's quickly review the basic hydraulic cylinder components so that we can all understand the terminology in our buying guide.

• Barrel: The barrel is the tube inside which the piston and rod travel. The bore, or the fit of the barrel, is the measurement of the barrel's inner diameter (ID).
• Rod: The rod is the solid steel column that extends and retracts, displacing part of the hydraulic fluid's volume. Rods are often chrome-plated to reduce friction. The rod measurement is the OD (outer diameter), which is easy to measure with a caliper.
• Piston: The piston is the disk that separates the two chambers within the barrel. Fluid acts on at least one side and pushes the piston. You probably don't need to worry about the piston measurements when buying a cylinder.
• Guide rings: Guide rings, wear rings, and support rings are different names for the same thing. They should be made from a material tough enough to support the piston and soft enough not to damage the inside of the barrel.
• Internal wear rings: Internal wear rings support the rod's movement.
• Piston seal: A piston seal prevents fluid from escaping. A worn-out seal is one reason the cylinder may only need to be overhauled rather than completely replaced.
• Base: The base, or cap, seals the end of the cylinder barrel, allowing pressure to build up to push the rod.
• Gland: The gland plays a vital role in maintaining the rod's position. RuggedMade welded cylinders feature threaded glands to handle higher pressures.
• Wiper seal: The wiper/dust seal can be seen from the outside, preventing dust and debris from getting inside.
• Mounts: A cylinder needs to be mounted with at least two points of contact. You can find several types of mounts, including ball/swivel, pin-eye, clevis (fixed at one end or thread-on or welded at the other), and cross-tube. Most cylinders have mounts at the base, but trunnion and flange mounts do not. Usually, cylinders are mounted using two pins, but some use bolts, like the flange mount. If the pins are discovered to be worn out when replacing a cylinder, replace them, too.
• Ports: The port is the hole in the cylinder that allows fluid to flow into and out of the barrel. Two types of ports are typically used in America. The first is NPT (national pipe tapered), which plumbers have used for decades. The second is ORB (O-Ring boss).

Watch our Parts of a Hydraulic Cylinder video for a visual guide to these hydraulic cylinder components.

How to Choose a Hydraulic Cylinder for Your Project

Our video guide, How to Measure a Hydraulic Cylinder, demonstrates the step-by-step process of measuring a hydraulic cylinder.

Questions to Consider

Many factors must be considered when buying a new hydraulic cylinder, like the type of mounts required. The mounting type affects the cylinder's alignment, operation, and ability to handle loads. Common types include flange, clevis, or trunnion mounts.

The cylinder's speed and force requirements will dictate the size and type of the cylinder and the hydraulic system's power needs.

If you're replacing a worn-out cylinder, what are the specifications of the old one? Bore size, rod diameter, stroke length, and pressure rating are key to finding an exact match or an upgrade.

Do you need a single-acting or double-acting cylinder? The choice depends on the application and whether it needs to exert force in one direction (single-acting) or both directions (double-acting).

Types of Hydraulic Cylinders

Identify the type of cylinder you need. RuggedMade offers the two most common types of cylinders used on various machines and across many applications: tie-rod and welded.

Goto Langnuo Mining Equipment to know more.

On RuggedMade's welded cylinders, the base is welded to the end of the barrel and is not meant to be removed. The cap at the gland end (where the cylinder rod moves in and out of the barrel) is threaded and can be removed.

On tie-rod cylinders, both the base and gland end can be removed. The gland and the base end cap are held together against the barrel using four threaded tie bolts or rods. These long bolts run the entire cylinder length and act like a vice holding the barrel caps together.

How to Measure a Hydraulic Cylinder

Several measurements describe a hydraulic cylinder. When replacing a hydraulic cylinder, accurately measuring the old one's dimensions will help ensure you buy the right one. One thing to keep in mind is that most manufacturers standardize measurements to the nearest whole or half inch. Four important measurements are used when sizing a cylinder.

We'll start with the hydraulic cylinder stroke length calculation because the question we hear most about sizing cylinders is, "What is the stroke length of a hydraulic cylinder?".

Stroke is the distance the rod and piston travel from the fully retracted to the fully extended positions. The simplest way to determine the stroke length is to measure the distance between the rod end pin center and base end pin center when the rod is fully extended and then when the rod is fully retracted. The difference between these two measurements is the cylinder stroke length.

For example, if the extended length is 18.25" and the retracted length is 14.25", then the cylinder has a 4" stroke (18.25 minus 14.25 equals 4).

If measuring from the pin center is too difficult, use the outer edge of each pin, but make sure you're looking at the same side for both (right to right or left to left, but not right to left).

If you plan on disassembling a cylinder, remember to measure the stroke first.

The next measurement is the cylinder port size.

As we said above, there are two commonly used types of ports: NPT (and NPTF) and ORB. The NPT type has tapered threads, while the ORB type has parallel threads. You can use a thread gauge and a thread gauge chart to help identify the thread standard. Measuring the size is tricky because the physical dimensions don't exactly match the nominal dimensions specified by the manufacturer.

If replacing a cylinder, you want the new cylinder to have the same size ports and, ideally, the same thread type. If you cannot find an exact match to the original port thread, you can use an adapter.

Another important measurement is the cylinder bore ID or the inner diameter of the barrel. The bore ID determines how much force the cylinder can generate. There are two ways to measure the bore ID.

The first method is to measure the outside width of the cylinder barrel and then subtract the width of the cylinder wall. For example, if the outside barrel width is 3.5" and the cylinder wall is 0.25", the bore ID is 3".

A more precise method involves disassembling the cylinder. This can be a messy process, but it allows you to use a caliper to measure the barrel's ID.

The final measurement is the cylinder rod OD. This is a straightforward measurement: Use a caliper to measure the outer diameter of the rod OD. Note that some cylinders have a tapered rod end.

Other Factors to Consider When Choosing a Hydraulic Cylinder

When a clevis mount is threaded onto the end of the rod, the mounting dimensions may be changed, but the stroke doesn't change. It's the stroke measurement that matters most. When you can't find an exact match, a close match may work fine, but the stroke measurements must match.

Some mounts are designed to be greased, so make sure the new one is greased, too.

If you're curious about how changing the rod's size can change a log splitter's cycle time, check out our experiment in this video.

Are you interested in learning more about hydraulic cylinder piston seal? Contact us today to secure an expert consultation!