How Do Hydraulic Cylinders Work?


Hydraulic cylinders haven’t really changed a lot over the years. The manufacturing processes are much more streamlined and the tolerances are much tighter, but for the most part cylinders are still the hard working push/pull tools they have always been. These things have literally shaped the world around us. Anything that gets lifted, pushed, hauled, dumped, dug, crushed, drilled or graded has gotten that way by some truck, crane, dozer or tractor using a hydraulic cylinder. But how do hydraulic cylinders work?

The amazing amount of force a cylinder exerts is due to the simple mechanical principle of pressure exerted on the surface area of the piston. Simply put, the larger the diameter of the cylinder, the more it will lift. The formula for this is Area X PSI (Pounds per square inch) = Force.

Simple hydraulic cylinder diagram

The PISTON is inside the cylinder, the diameter of which is known as the BORE. OK, Technically, the the bore is the inside diameter of the tubing but this difference is of minor significance. The piston needs a piston seal to keep the pressure from bypassing to the other side, which allows it to build the required pressure (If a cylinder isn’t lifting the force it should, the piston seal is probably worn).

The piston is attached to the ROD (or shaft) of the cylinder, usually with the rod passing through the piston and attached with a large nut on the opposite end. To correctly calculate the pulling force of a cylinder, the surface area of the rod must be subtracted from the formula. The rod is probably the hardest worked component in the whole system. The rod is the largest single chunk of steel in the cylinder, unpainted and exposed to all the elements. It has to be extremely strong (to resist bending), exceptionally hard (to resist corrosion and pitting), and smooth as silk (to keep the rod seals intact to prevent leakage of fluid and pressure). The STROKE of the cylinder is the total travel possible from the fully retracted length and the fully extended length of the rod.

The GLAND or “head” of the cylinder is the part that the cylinder rod extends and retracts through. It contains the rod seals & the wiper seal which keeps contamination out of the cylinder.

The BUTT is the base or “cap” end. This end usually can use a variety of attachment points. Speaking of attachments, how do cylinders attach to their implement? Usually by using a CLEVIS, CROSS TUBE, PIN-EYE or TANG.

Most commercially available cylinders are double-acting which means they have ports on each end and they are used to push AND pull. These are easy to convert to single-acting (push or pull only) by using a simple breather device to allow the air on the unused side to be expelled.

So that’s pretty much all there is to hydraulic cylinders and how they work! They really are simple devices, capable of doing tremendous amounts of work. If you have anything to add, questions or corrections, feel free to contact me or leave a comment!

Top 10 Tips for Hydraulic Pump Maintainenance

The hydraulic pump are a major part of many industrial machinery. They are of supreme importance in almost every mechanical application and cannot be neglected. Hydraulic pumps are used worldwide because they have made impossible tasks possible. But everything comes with a price. The price of this mechanical marvel is proper maintenance and regular check-ups.

Machines aren’t unlike the human body when it comes to care and maintenance. The human body cannot function well if it is not taken care of properly. If a machine is not checked at required regular intervals, then not only will it give poor performance but it also becomes non-functional after a while.

Hydraulic pumps power the moving parts of most large machines. Drive systems employ hydraulic pumps as a source converting mechanical power into hydraulic power. Hydraulic pumps come in various shapes and sizes. All of them, despite their complexity, require proper maintenance.

Here are 10 top tips that can help in maintaining your hydraulic pumps:

  1. Maintain cleanliness:

Keeping the hydraulic pumps clean is the first and the fundamental step in maintaining them in proper shape and performance. Follow a regular schedule to clean the pumps.

  1. Check the hydraulic fluid:

Hydraulic fluid is the lifeline for a hydraulic system. Check at proper intervals and replace when needed. Also keep in consideration the grade of hydraulic fluid. Compatibility of the hydraulic fluid increases the performance of the hydraulic pump.

  1. Control Temperatures:

Temperature of the hydraulic pump is crucial and needs important consideration. Fluid passing through the hydraulic pump generates heat. Constantly maintain temperature at the optimum operating level as specified by the manufacturer.

  1. Check Vacuum:

The vacuum on the suction side of the hydraulic pump is responsible for the fluid intake. Maintain proper suction vacuum or the efficiency of the pump will be affected, leading to heat build-up, cavitation or worse.

  1. Check the voltage supply:

Monitor the voltage supply to the hydraulic pump’s motor regularly. A constant and optimum voltage supply leads to the better performance of the machine. Check the other electrical components like wires, switches, etc. at intervals for wear.

  1. Maintain pressures:

The pressures are equally important in hydraulic pumps as the temperatures. Always maintain proper pressure in the hydraulic pumps throughout its operation.

  1. Assembly inspection:

Regularly inspect of all the connections, pipes, hoses etc. visually at regular intervals. Any fault in the assembly can lead to a serious issue. Assembly inspection helps in increasing the efficiency of the overall pump.

  1. Check for Leakages:

Any leakage can be disastrous to the operation of a hydraulic pump. It can also render nearby machinery susceptible to danger.

  1. Check for aeration:

Aeration of the fluid in hydraulic pumps can also affect the working of pumps. Eliminate aeration as early as possible.

  1. Use clean hydraulic fluids:

Always use clean hydraulic fluids to prolong hydraulic pump life.

Hydraulic pumps need special attention since they perform under critical conditions of pressures and temperatures. Proper care is the best ingredient for the maintenance of a hydraulic pump. Make sure to use the right tools for their maintenance. All this, ultimately, contributes towards a better life and better performance of the machinery.

7 Top Tips for Buying Hydraulic Valves

Hydraulic valves are important components of machinery that can make a major difference in overall efficiency of the system. Here are top 7 tips for buying best hydraulic valves:

    1. Know and understand the function of hydraulic valve. It is important to understand that hydraulic valves are meant to control the pressure and flow of fluids (hydraulic) within your mechanical system. Hydraulic valves are employed in a system to direct, stop and start the flow of fluid. Hydraulic valves are usually made of spools or poppets and can function hydraulically, pneumatically, manually, electrically or mechanically. They are vital for precisely controlling the function and safety of the equipment. Having a good theoretical knowledge of hydraulic valves is vital for buying best hydraulic valves.
    2. Have an understanding of the components. Like a good driver knows the basic components of a car, knowing the components of a hydraulic valve would help you in buying the best hydraulic pumps. Generally speaking, a hydraulic valve comprises of a bonnet, seat and a disc (to prevent ay leakages).
    3. Be specific about what you are looking for. Hydraulic valves come in numerous types depending upon their application and operating principle. Look for the type that fits your system as per specifications and nomenclature exactly. A slight difference in size or specs can mean a malfunction.
    4. Always pick the right size. Be wary of the valve sizes while buying them. DO NOT rely on the manufacturer’s valve flow rating (other than OEM) as it may not be the best size guide for selecting the size of the valve. This is because each manufacturer bases its own flow rating on a certain “standard” drop of pressure (which may be variable for different manufacturers). The smartest way to pick the right size is to opt for the Original Equipment Manufacturer (though it may be a bit expensive). But, this can prove cheaper in the long run owing to longer operating periods and less maintenance time.
    5. Opt for three-position directional valves (four-way), where the operational cycle of your system allows that. This arrangement of valves is knows to bring in better efficiency. However, pressure drops through series components are additive. Look for mobile stack type valves made by quality manufacturers ( as they offer multiple combinations of parallel and series circuits for better system efficiency. However, consult a system engineer to ensure compatibility where in doubt.
    6. Improvise by bringing in smaller valves, especially when a specific actuator or machine is used less frequently. They can be a good choice to bring down valve costs without any adverse effects on the machine efficiency. However, DO NOT implement such improvisations without consulting the OEM.
    7. Opt for a brand name or OEM when the machinery is critical where the valve is required to be installed or replaced. Certain operating conditions warrant use of extreme caution in sizing, quality of material and adherence to specifications (especially when the hydraulic valves involve operation of CNC applications and units).

How Do Hydraulic Systems Work? An Intro to Hydraulic Components

Almost anywhere there’s work to be done, you’ll find hydraulic equipment at the center of it. A hydraulic system provides lots of power, precise control, and great reliability. With just a bit of know-how to keep it in good running condition, nothing can accomplish what a hydraulic system can.

The Parts of a Hydraulic System

The three main parts of a hydraulic system are the reservoir, a hydraulic cylinder, a valve, and a pump. Pumping hydraulic fluid from the reservoir from the pump and through the valve into the bottom cavity of the cylinder causes the piston rod to bе рuѕhеd out. This pushes the fluid in the other cavity bасk into the reservoir, pressurizing the chamber and extending the piston to its full length. Pumping hydraulic fluid into the upper port of the cylinder рuѕhеѕ the piston rod down, which finally рuѕhes the oil in the other chamber bасk into the reservoir.

Hydraulic systems come in many diffеrеnt forms depending on its purpose of operation. These are some basic hydraulic components with their operations, раrtѕ and their application areas.

Hydraulic Cylinders

Also known as a linear hydraulic motor or linear actuator, hydraulic cylinders do the job of giving unidirectional force via its stroke. The hydraulic cylinder is made of mainly a cylinder base, cylinder head, cylinder tube, piston rod, ѕеаl glаnd, piston and ѕеаlѕ. The hydraulic cylinder has a piston сonnесtеd with a piston rod and рlасеd inside the cylinder barrel. This piston rod moves bасk and forth. The base of the cylinder is сlоѕеd and the head of the cylinder has an opening whеrе the piston rod gоеѕ оut of the cylinder. The piston creates a partition, dividing it into two distinct chambers; the head end and the base end. The power to the hydraulic cylinders iѕ provided by the pressurized fluid or oil.

Tуреѕ of Hydraulic Cylinders

Therе are mainly two types of basic hydraulic cylinders; the wеldеd body cylinder and tie-rod cylinder. The tie-rod cylinder uses high strength, threaded steel rods to hold the cylinder barrel to the end caps. In the саѕе of welded body cylinders, tiе-rodѕ are not present. The ports are welded to the barrel and the barrel to the еnd caps directly. The front rod gland is either bоltеd оr threaded into the cylinder barrel in оrdеr to remove it for servicing.

Application of Hydraulic Cylinders

Hydraulic cylinders find their application in various areas like manufacturing machinery, civil engineering and most importantly in construction & agricultural equipment.


Hydraulic Motors

Hydraulic motors are similar to hydraulic cylinders in that they are hydraulic actuators that except motors are radial actuators. The fluid passing into the motor turns the shaft, and then exits the motor through the opposite port to re-enter the system. Motors are placed in series or in parallel circuit, depending on the usage.

Hydraulic motors power the drive wheels on heavy equipment or turn belts or pulleys on conveyor systems, as well as many other tasks.


Hydraulic Pumрѕ – Fluid in Motion

Hydraulic pumps сonvеrt mechanical energy and motion into hydraulic fluid power. The basic idea is very ѕimрlе: force is applied at onе position and trаnѕmittеd to another position using а fluid, such as оil, which cannot bе compressed but rather iѕ displaced when pressure is applied.  The pump does not actually generate pressure, however. The hydraulic pump generates flow by moving the fluid through the system. As a result, this creates pressure, which is more of a by-product, regulated by a relief valve.

Gear pumps, piston pumps and vane pumps are the most common types of pumps. Either fixed or variable displacement, most pump systems have one of these.


Hydraulic Valves

Hydraulic valves are essntial to any system, since theу control the flоw of оil in the system. Choosing the most suitable valve is crucial to any hydraulic system. Valves come in different sizes, types and configurations. In addition, valves should be specified according to the pressure of the system and the flow rаtе

3 Main Types of Hydraulic Valves

There are 3 main types of hydraulic valves: directional, pressure and flow control. Directional valves control the fluid’s direction of flow, such as extending or retracting a cylinder or actuate a motor. Pressure control valves do exactly that: they regulate the pressure in a system. By diverting fluid back to the reservoir when a pressure threshold is reached, the system and components are protected. Flow controls control the flow rate of the fluid in the system, usually expressed in GPM or LPM. Most valves are either manually, electronic, or in some cases, air actuated.

 Other Types

There are many other special hydraulic valves used in various applications, configured in any way you could imagine. Some examples might be multi-block directional, mоdulаr, саrtridgе, еlесtrо-hydraulic servo, еlесtrо-hydraulic proportional/digital, micro-hydraulic and water pressure control.

Multi-blосk directional valves are larger banks with several valves such as a directional, a pressure and a сhесk vаlvе that iѕ used to centralize control of the machine.


In Conclusion

Hydraulic equipment plays a significant role in engineering. In conclusion, we hope the above discussion can help readers in selecting the right hydraulic equipment and therfore to make smart decisions when the need arises.


Hydraulic Pumps – The Heart of a Hydraulic System

Hydraulic Pumps

In humans, the heart occupies a role of great importance. Its main function is to circulate blood throughout the body through arteries and veins, which is essential to the proper functioning of all body parts. In a hydraulic system, the pump plays an equally important role, which is similar to that played by the heart in humans. The pump used to circulate, through pipes, a hydraulic fluid that move charges through cylinders or hydraulic motors. In view of the hydraulic components, the hydraulic pumps are designed to convert the mechanical energy supplied by the heat engine into hydraulic energy. The pump is the basic of a hydraulic circuit. In mobile machinery, agricultural, public works, handling…

Many manufacturers provides two technologies:

Hydraulic gear pump

The gear pump is the most prevalent in mobile machines as it is the most economical. It generally has two gears animated by an external axis. The volume between the gears is compressed and discharged according to the internal geometry of the pump. This volume discharged per revolution (360 °) is called the capacity of the pump, generally between 1 and 250 cm3. The flow rate is equal to the engine multiplied by the speed of rotation of the drive shaft. The hydraulic pressure depends on the hydraulic receiver: cylinders or motors; the maximum pressure depends on the game and the seal between the gears, generally 210 bar. The gear pump is lubricated with a small amount of oil taken low side. In recent years, pump manufacturers have made very significant progress on reliability, noise and pressure, thanks to helical gears, profiles more accurate teeth, better quality steels and machined more precisely. The wear of a gear pump mark is the progressive drop in pressure due to wear of the gears ends. A drop in activity of the pump, by pressure or by volume causes usually a default filter of the hydraulic circuit

Hydraulic piston pump

More complex and costly than the first design, the piston pump provides higher pressure, 350 bar on big machines and several thousand bars in the industry; mainly used in large public works equipment, are use is spreading in agricultural machinery. Pistons slide in a sealed chamber and pushes the admin fluid by a valve and a valve; both technologies are prevalent:

1-Axial piston pump, piston parallel to the transmission axis,

2-Biases axes or radial piston pump, piston driven by a cam shaft.

Unlike the gear pump, it allows a variable displacement, a higher pressure and a more easy renovation. SOCOMHY Look for a complete renovation, change segments, axes, shirts, pistons. Even more than the first, it is sensitive to contamination of the hydraulic circuit.

Application of hydraulic pumps

Very wide range of hydraulic pump to a pressure of 180 to 350 bar:

*Replacement of the hydraulic pump of the tractor Original interchangeable on all tractor,

*Hand hydraulic pump,

*On the PTO of the tractor, or on a gimbal, choose a standard agricultural pump that mounts with a multiplier,

*On a trailer, to ensure an independent hydraulic supply 60 to 80 liters / minute of the trailer from a gimbal: compressor trailer

*On a truck or fixed installation, to create a hydraulic power from the electric current 12,24,220 or 380V: hydraulic power.

What is a JIC Fitting?

What are JIC fittings and why should you use them? JIC stands for “Joint Industry Council”, which the fittings are named for as defined by the SAE. JIC fittings are flared fittings with a 37-degree chamfer seating surface and straight threads. They are most commonly made of carbon steel, stainless, brass or nickel alloys. So what makes it useful?

According to the Wikipedia page: JIC fittings are “widely used in fuel delivery and fluid power applications, especially where high pressure (up to 10,000 psi) is involved.” The JIC fitting uses its flared seating surface to seal, instead of an o-ring that could corrode or the old-tapered threads of NPTF fittings. This means that they can be re-used, and disconnected & reconnected repeatedly with little or no deformation and hold a high pressure seal. This is very useful in hydraulic applications where equipment is frequently being changed out or on testing equipment. The sizes run the same as other SAE fittings (IE: SAE #4, #6, #12, etc) so they are very easy to size.

I like JIC fittings quite a lot. They make installation and maintenance a breeze. Whenever possible, I put a male JIC fitting on cylinders, motors pumps and power units, so that we can then use a female JIC swivel on our hose ends. This makes it super fast to change out hoses, as well as replace the components when needed. This way you don’t have to worry with hose orientation so much, you don’t’ really need to worry about leaks, and you just have a nice little nipple on all of your equipment for attachment.