zi hydraulic pump free sample

In the ceramics industry, hydraulic presses are among the big energy consumers because hydraulic pumps usually run here at constant speed, even though the power of the hydraulic system is only required at specific points. The energy requirements of a hydraulic press can be reduced by more than 50 %, depending on the requirement profile, by converting the hydraulics to a servo pump system, a combination of pump, motor and frequency converter. The reason is that the motor only runs when hydraulic power is actually needed. In this way, the plant can also be made more flexible, throughput can be...

This example models a triplex pump with a predictive maintenance algorithm that can detect which parts of the pump are failing simply by monitoring the pump output pressure.

The Simscape model of the pump can be configured to model degraded behavior due to seal leakage, blocked inlets, bearing wear, and broken motor windings. MATLAB code shows how to accelerate testing by reusing results from previous simulations. The model can be used to generate training data for the machine learning algorithm and can be used to test the deployed algorithm. MATLAB Live Scripts show you how to develop the algorithm.

Mechanical, hydraulic, and electrical parameters are all defined in MATLAB which lets you easily resize the pump. The pump housing is imported from CAD.

EPANET is a software application used throughout the world to model water distribution systems. It was developed as a tool for understanding the movement and fate of drinking water constituents within distribution systems, and can be used for many different types of applications in distribution systems analysis. Today, engineers and consultants use EPANET to design and size new water infrastructure, retrofit existing aging infrastructure, optimize operations of tanks and pumps, reduce energy usage, investigate water quality problems, and prepare for emergencies. It can also be used to model contamination threats and evaluate resilience to security threats or natural disasters.

With EPANET, users can perform extended-period simulation of the hydraulic and water quality behavior within pressurized pipe networks, which consist of pipes, nodes (junctions), pumps, valves, storage tanks, and reservoirs. It can be used to track the flow of water in each pipe, the pressure at each node, the height of the water in each tank, a chemical concentration, the age of the water, and source tracing throughout the network during a simulation period.

Full-featured and accurate hydraulic modeling is a prerequisite for doing effective water quality modeling. EPANET contains a state-of-the-art hydraulic analysis engine that includes the following capabilities:

EPANET-RTX (Real–Time eXtension) provides the methods and software tools by which operational data can be connected with a network infrastructure model, and the resulting network simulation model can be calibrated, verified, and continually tested for accuracy using operational data. EPANET-RTX is software for building real-time hydraulic and water quality models. EPANET-RTX brings real-time analytics to water distribution system modeling, planning, and operations. Analytics refer to the discovery and interpretation of patterns in data. EPANET-RTX software works by providing access accessing available utility data and effectively using it to run a hydraulic and water quality model.

In waterworks and wastewater systems, pumps are commonly installed at the source to raise the water level and at intermediate points to boost the water pressure. The components and design of a pumping station are vital to its effectiveness. Centrifugal pumps are most often used in water and wastewater systems, making it important to learn how they work and how to design them. Centrifugal pumps have several advantages over other types of pumps, including:

A centrifugal pump consists of a rotating shaft that is connected to an impeller, which is usually comprised of curved blades. The impeller rotates within its casing and sucks the fluid through the eye of the casing (point 1 in Figure 10.1). The fluid’s kinetic energy increases due to the energy added by the impeller and enters the discharge end of the casing that has an expanding area (point 2 in Figure 10.1). The pressure within the fluid increases accordingly.

The characteristic curves of commercial pumps are provided by manufacturers. Otherwise, a pump should be tested in the laboratory, under various discharge and head conditions, to produce such curves. If a single pump is incapable of delivering the design flow rate and pressure, additional pumps, in series or parallel with the original pump, can be considered. The characteristic curves of pumps in series or parallel should be constructed since this information helps engineers select the types of pumps needed and how they should be configured.

Many pumps are in use around the world to handle liquids, gases, or liquid-solid mixtures. There are pumps in cars, swimming pools, boats, water treatment facilities, water wells, etc.  Centrifugal pumps are commonly used in water, sewage, petroleum, and petrochemical pumping. It is important to select the pump that will best serve the project’s needs.

The objective of this experiment is to determine the operational characteristics of two centrifugal pumps when they are configured as a single pump, two pumps in series, and two pumps in parallel.

Each configuration (single pump, two pumps in series, and two pumps in parallel) will be tested at pump speeds of 60, 70, and 80 rev/sec.  For each speed, the bench regulating valve will be set to fully closed, 25%, 50%, 75%, and 100% open.  Timed water collections will be performed to determine flow rates for each test, and the head, hydraulic power, and overall efficiency ratings will be obtained.

The hydraulics bench is fitted with a single centrifugal pump that is driven by a single-phase A.C. motor and controlled by a speed control unit. An auxiliary pump and the speed control unit are supplied to enhance the output of the bench so that experiments can be conducted with the pumps connected either in series or in parallel. Pressure gauges are installed at the inlet and outlet of the pumps to measure the pressure head before and after each pump. A watt-meter unit is used to measure the pumps’ input electrical power [10].

Consider the pump shown in Figure 10.3. The work done by the pump, per unit mass of fluid, will result in increases in the pressure head, velocity head, and potential head of the fluid between points 1 and 2. Therefore:

While pumping fluid, the pump has to overcome the pressure loss that is caused by friction in any valves, pipes, and fittings in the pipe system. This frictional head loss is approximately proportional to the square of the flow rate. The total system head that the pump has to overcome is the sum of the total static head and the frictional head. The total static head is the sum of the static suction lift and the static discharge head, which is equal to the difference between the water levels of the discharge and the source tank (Figure 10.4). A plot of the total head-discharge for a pipe system is called asystem curve; it is superimposed onto a pump characteristic curve in Figure 10.5. The operating point for the pump-pipe system combination occurs where the two graphs intercept [10].

Pumps are used in series in a system where substantial head changes take place without any appreciable difference in discharge. When two or more pumps are configured in series, the flow rate throughout the pumps remains the same; however, each pump contributes to the increase in the head so that the overall head is equal to the sum of the contributions of each pump [10]. For n pumps in series:

The composite characteristic curve of pumps in series can be prepared by adding the ordinates (heads) of all of the pumps for the same values of discharge. The intersection point of the composite head characteristic curve and the system curve provides the operating conditions (performance point) of the pumps (Figure 10.6).

Parallel pumps are useful for systems with considerable discharge variations and with no appreciable head change. In parallel, each pump has the same head. However, each pump contributes to the discharge so that the total discharge is equal to the sum of the contributions of each pump [10]. Thus for  pumps:

The composite head characteristic curve is obtained by summing up the discharge of all pumps for the same values of head.  A typical pipe system curve and performance point of the pumps are shown in Figure 10.7.

d) Record the pump 1 inlet pressure (P1) and outlet pressure (P2). Record the input power from the watt-meter (Wi).  (With the regulating valve fully closed, discharge will be zero.)

d) Record the pump 1 and 2 inlet pressure (P1) and outlet pressure (P2). Record the input power for pump 1 from the wattmeter (Wi). (With the regulating valve fully closed, discharge will be zero.)

Correct the pressure rise measurement (outlet pressure) across the pump by adding a 0.07 bar to allow for the difference of 0.714 m in height between the measurement point for the pump outlet pressure and the actual pump outlet connection.

In each of above graphs, show the results for single pump, two pumps in series, and two pumps in parallel – a total of three graphs. Do not connect the experimental data points, and use best fit to plot the graphs

The term “total head” (H) is used to describe the energy in pumping systems and is how manufacturers represent the performance of their pumps as a function of flow rate. Total head is also commonly referred to as total dynamic head (TDH); however, the Hydraulic Institute (HI) uses the term total head and it will be used throughout this article.

It is important to understand the nuances of what makes up the total head of the system as a function of flow rate and varying system conditions so that if a user is designing or operating a pump system, the pump can be selected and operated properly. Additionally, if the goal is to measure the pump performance after installation, it is important to understand how to do that in the same way that the pump manufacturer will.

Elevation head, which is the difference in elevation that liquid will travel. For example, if a user was pumping from one tank to another and the level in the tanks were the same, there would be zero elevation head. But if pumping from a tank at ground level to the roof of a 100-foot building, there would be 100 feet of elevation head.

Pressure head is the difference in pressure between source and destination. For example, if taking liquid from a lake at atmospheric pressure and delivering it to a tank that had 10 pounds per square inch (psi) above atmospheric pressure, the pressure head would be 10 psi expressed as feet of the liquid being pumped. The conversion between pressure and head is described in the pump total head measurement section.

A free resource that provides additional tutorial information on this topic and includes a friction loss calculator is the Hydraulic Institute’s Engineering Data Library, which can be accessed at edl.pumps.org. For complex systems with many pieces of equipment and branches, it may be difficult to calculate the total head for the system by hand and hydraulic modeling software should be used. Some noncommercial versions of hydraulic modeling software are available as a free resource at pumps.org/freetools. A simplified equation for total head (system) is expressed in Equation 1 (page 100).

Image 1 shows a pump system where liquid is delivered from a supply tank to three closed product tanks. Considering the equation for total head (system), the supply tank would be point 1 and the product tanks would be point 2. The elevation head would be the difference in elevation between the level in the product tank and the supply tank. The pressure head would be the pressure difference between the product tank and the supply tank expressed as feet of the liquid pumped. Friction head would include all of the losses from the supply tank, piping, fittings, heat exchanger, control valves, etc.

The total head (pump) will match the total head (system) at a specific flow rate. This means, when plotted on the same graph, where the pump curve and system curve intersect will be the pump’s operating point. Image 3 shows how these curves are combined and that the resulting intersection is the operating point.

The pump curve or total head of the pump as a function of flow rate is measured much like the total head of the system but points 1 and 2 will be on the inlet and outlet of the pump, respectively. Image 4 shows pump pressure instruments referenced to a common datum and the direction of flow is indicated by arrows. The total head of the pump is the difference between the total discharge head (point 2) and the total suction head (point 1). The term “total” indicates that it includes the static pressure head (h), the velocity head (hv), and the elevation head (Z).

To measure the total head of the pump, pressure will be measured at points 1 and 2, the elevation from the pressure gauge to datum will be measured, and the velocity at the pressure measurement location will be calculated based on the volumetric flow rate and the pipe inside diameter. The pressure measured will need to be converted to feet of liquid based on Equation 3.

Total head is a fundamental that is beneficial to understand when working with pumping systems. It provides an understanding of the system requirements, valuable information for pump selection, and a key consideration of energy consumption. This article covers the basics but does not discuss in-depth review, calculation examples or scenarios that pump professionals will come across. For more information on this topic, including standards and training, visit www.pumps.org.

Hydraulic systems have the advantages of small size, light weight, high power, smooth transmission, and fast response. Hydraulic systems have been widely used in the aerospace, shipbuilding, metallurgical, machine tool, agricultural machinery, and engineering machinery industries, among other fields. The wide application of hydraulic systems has greatly promoted the development of industrial production [5]. Since entering the 21st century, hydraulic systems and hydraulic equipment have become more complicated and large-scale. Once a failure occurs, it not only can damage the equipment, but may even cause casualties [6]. Hydraulic pumps have the characteristics of complex structure, high speed, high pressure, and continuous operations, and are the most prone to failure. Therefore, fault diagnosis technology for hydraulic systems has become a research hotspot in recent years.

In fault diagnosis, the first step is to extract fault features from the acquired data [7,8]. Feature extraction is the process of obtaining fault features through signal processing [9,10]. Considering that the vibration signal of a hydraulic pump has non-linear and non-stationary characteristics, it is difficult to extract the fault features accurately by using traditional time- and frequency-domain analyses. The key information of the hydraulic pump vibration signal can be extracted more accurately by using time-frequency characteristic analysis methods. Time-frequency analysis methods include non-adaptive analysis and adaptive analysis. Adaptive analysis refers to the modal decomposition and reconstruction of the signal, according to the characteristics of the signal, in the process of signal processing, in order to achieve good analysis results.

Considering the mode mixing phenomenon of the empirical mode decomposition (EMD) method [11,12], Wu et al. proposed the ensemble empirical mode decomposition (EEMD) method, which effectively suppresses modal mixing by adding Gaussian white noise to the original signal [13]. In view of the shortcomings of the EEMD method, scholars have carried out a lot of research. Finally, Zheng et al. proposed the modified ensemble empirical mode decomposition (MEEMD) method [14], which adds a pair of Gaussian white noises with the same amplitude and opposite signs, such that they cancel each other and the influence of the noise on the signal is reduced. Compared with the EEMD method, this method has a better decomposition effect. Jiang et al. applied the MEEMD method to the fault diagnosis of the main shaft bearing of a wind turbine [15]. Their method showed good results, in terms of training accuracy and training speed, which verifies the feasibility of this method. Zheng proposed a method combining MEEMD and generalized adaptive S transform (AGST), which was successfully applied to the vibration signal analysis of an internal combustion engine [16]. Shi et al. applied the MEEMD method to fault feature extraction of rolling bearings, which not only effectively suppressed the phenomenon of modal mixing but also greatly reduced the number of pseudo-components and accurately extracted the weak fault information of rolling bearings [17]. Although the MEEMD method has been widely used in the field of fault diagnosis, it has seldom been reported in hydraulic system fault diagnosis. Therefore, in this paper, we applied it to the vibration signal feature extraction of an axial piston pump, in order to improve the accuracy of fault identification.

In this paper, a fault diagnosis method for a hydraulic pump based on the integration of the MEEMD, autoregressive (AR) spectrum energy, and WKELM methods is proposed and studied. First, the vibration signals of an axial piston pump under different working states were acquisited from a hydraulic pump fault simulation test bed. Secondly, signal decomposition and feature extraction were carried out for the acquired original vibration signals, using the fault feature extraction method based on MEEMD and AR spectrum. Finally, the fault diagnosis method based on WKELM was used to diagnose the working states of the hydraulic pump. The results show that the diagnosis accuracy rate can reach 100%. Compared with BP, SVM, and ELM, the feasibility and superiority of the method proposed in this paper are demonstrated.

A gear pump is a type of positive displacement (PD) pump. Gear pumps use the actions of rotating cogs or gears to transfer fluids. The rotating gears develop a liquid seal with the pump casing and create a vacuum at the pump inlet. Fluid, drawn into the pump, is enclosed within the cavities of the rotating gears and transferred to the discharge. A gear pump delivers a smooth pulse-free flow proportional to the rotational speed of its gears.

There are two basic designs of gear pump: internal and external (Figure 1). An internal gear pump has two interlocking gears of different sizes with one rotating inside the other. An external gear pump consists of two identical, interlocking gears supported by separate shafts. Generally, one gear is driven by a motor and this drives the other gear (the idler). In some cases, both shafts may be driven by motors. The shafts are supported by bearings on each side of the casing.

As the gears come out of mesh on the inlet side of the pump, they create an expanded volume. Liquid flows into the cavities and is trapped by the gear teeth as the gears continue to rotate against the pump casing.

No fluid is transferred back through the centre, between the gears, because they are interlocked. Close tolerances between the gears and the casing allow the pump to develop suction at the inlet and prevent fluid from leaking back from the discharge side (although leakage is more likely with low viscosity liquids).

External gear pump designs can utilise spur, helical or herringbone gears (Figure 3). A helical gear design can reduce pump noise and vibration because the teeth engage and disengage gradually throughout the rotation. However, it is important to balance axial forces resulting from the helical gear teeth and this can be achieved by mounting two sets of ‘mirrored’ helical gears together or by using a v-shaped, herringbone pattern. With this design, the axial forces produced by each half of the gear cancel out. Spur gears have the advantage that they can be run at very high speed and are easier to manufacture.

Gear pumps are compact and simple with a limited number of moving parts. They are unable to match the pressure generated by reciprocating pumps or the flow rates of centrifugal pumps but offer higher pressures and throughputs than vane or lobe pumps. External gear pumps are particularly suited for pumping water, polymers, fuels and chemical additives. Small external gear pumps usually operate at up to 3500 rpm and larger models, with helical or herringbone gears, can operate at speeds up to 700 rpm. External gear pumps have close tolerances and shaft support on both sides of the gears. This allows them to run at up to 7250 psi (500 bar), making them well suited for use in hydraulic power applications.

Since output is directly proportional to speed and is a smooth pulse-free flow, external gear pumps are commonly used for metering and blending operations as the metering is continuous and the output is easy to monitor. The low internal volume provides for a reliable measure of liquid passing through a pump and hence accurate flow control. They are also used extensively in engines and gearboxes to circulate lubrication oil. External gear pumps can also be used in hydraulic power applications, typically in vehicles, lifting machinery and mobile plant equipment. Driving a gear pump in reverse, using oil pumped from elsewhere in a system (normally by a tandem pump in the engine), creates a motor. This is particularly useful to provide power in areas where electrical equipment is bulky, costly or inconvenient. Tractors, for example, rely on engine-driven external gear pumps to power their services.

External gear pumps can be engineered to handle aggressive liquids. While they are commonly made from cast iron or stainless steel, new alloys and composites allow the pumps to handle corrosive liquids such as sulphuric acid, sodium hypochlorite, ferric chloride and sodium hydroxide.

External gear pumps are self-priming and can dry-lift although their priming characteristics improve if the gears are wetted. The gears need to be lubricated by the pumped fluid and should not be run dry for prolonged periods. Some gear pump designs can be run in either direction so the same pump can be used to load and unload a vessel, for example.

The close tolerances between the gears and casing mean that these types of pump are susceptible to wear particularly when used with abrasive fluids or feeds containing entrained solids. External gear pumps have four bearings in the pumped medium, and tight tolerances, so are less suited to handling abrasive fluids. For these applications, internal gear pumps are more robust having only one bearing (sometimes two) running in the fluid. A gear pump should always have a strainer installed on the suction side to protect it from large, potentially damaging, solids.

Generally, if the pump is expected to handle abrasive solids it is advisable to select a pump with a higher capacity so it can be operated at lower speeds to reduce wear. However, it should be borne in mind that the volumetric efficiency of a gear pump is reduced at lower speeds and flow rates. A gear pump should not be operated too far from its recommended speed.

For high temperature applications, it is important to ensure that the operating temperature range is compatible with the pump specification. Thermal expansion of the casing and gears reduces clearances within a pump and this can also lead to increased wear, and in extreme cases, pump failure.

Despite the best precautions, gear pumps generally succumb to wear of the gears, casing and bearings over time. As clearances increase, there is a gradual reduction in efficiency and increase in flow slip: leakage of the pumped fluid from the discharge back to the suction side. Flow slip is proportional to the cube of the clearances between the cog teeth and casing so, in practice, wear has a small effect until a critical point is reached, from which performance degrades rapidly.

Gear pumps continue to pump against a back pressure and, if subjected to a downstream blockage will continue to pressurise the system until the pump, pipework or other equipment fails. Although most gear pumps are equipped with relief valves for this reason, it is always advisable to fit relief valves elsewhere in the system to protect downstream equipment.

The high speeds and tight clearances of external gear pumps make them unsuitable for shear-sensitive liquids such as foodstuffs, paint and soaps. Internal gear pumps, operating at lower speed, are generally preferred for these applications.

External gear pumps are commonly used for pumping water, light oils, chemical additives, resins or solvents. They are preferred in any application where accurate dosing is required such as fuels, polymers or chemical additives. The output of a gear pump is not greatly affected by pressure so they also tend to be preferred in any situation where the supply is irregular.

An external gear pump moves a fluid by repeatedly enclosing a fixed volume within interlocking gears, transferring it mechanically to deliver a smooth pulse-free flow proportional to the rotational speed of its gears.

External gear pumps are commonly used for pumping water, light oils, chemical additives, resins or solvents. They are preferred in applications where accurate dosing or high pressure output is required. External gear pumps are capable of sustaining high pressures. The tight tolerances, multiple bearings and high speed operation make them less suited to high viscosity fluids or any abrasive medium or feed with entrained solids.

Our circuit builder simulation package and virtual hydraulic test rigs are not the same as AmeSim, FluidSim, or similar simulation packages. They cost and perform quite differently. Users must select the one that best fits their needs and almost certainly start with our program before moving on to the dynamic simulation packages as they progress. It"s likely that switch will only happen at advanced maintenance technician to experienced design engineer stage.

With dynamic simulations it"s far too easy to use incorrect parameters, such as valve leakage, which leads to incorrect results. These programs are best used by experienced design engineers who understand the complex component detail and have the time to build competent circuits that will avoid potential performance errors. Students new to hydraulics are likely to spend more time learning the program than the hydraulics and very few people use these programs in industry.

A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke.engineering vehicles), manufacturing machinery, elevators, and civil engineering.

Hydraulic cylinders get their power from pressurized hydraulic fluid, which is incompressible.oil is used as hydraulic fluid. The hydraulic cylinder consists of a cylinder barrel, in which a piston connected to a piston rod moves back and forth. The barrel is closed on one end by the cylinder bottom (also called the cap) and the other end by the cylinder head (also called the gland) where the piston rod comes out of the cylinder. The piston has sliding rings and seals. The piston divides the inside of the cylinder into two chambers, the bottom chamber (cap end) and the piston rod side chamber (rod end/head-end).

A hydraulic cylinder is the actuator or "motor" side of this system. The "generator" side of the hydraulic system is the hydraulic pump which delivers a fixed or regulated flow of oil to the hydraulic cylinder, to move the piston. There are three types of pump widely used: hydraulic hand pump, hydraulic air pump, and hydraulic electric pump.F on the piston rod equals the pressure P in the cylinder times the piston area A:

During the retraction stroke, if the oil is pumped into the head (or gland) at the rod end and the oil from the cap end flows back to the reservoir without pressure, the fluid pressure in the rod end is (Pull Force) / (piston area - piston rod area):

Hydraulic cylinders are used in earth-moving equipment such as excavators, back hoes and tractors to lift or lower the boom, arm, or bucket.hydraulic bending machines, metal sheet shearing machines, particle board or plywood making hot press.

The piston rod is typically a hard chrome-plated piece of cold-rolled steel that attaches to the piston and extends from the cylinder through the rod-end head. In double rod-end cylinders, the actuator has a rod extending from both sides of the piston and out both ends of the barrel. The piston rod connects the hydraulic actuator to the machine component doing the work. This connection can be in the form of a machine thread or a mounting attachment. The piston rod is highly ground and polished so as to provide a reliable seal and prevent leakage.

The cylinder head is fitted with seals to prevent the pressurized oil from leaking past the interface between the rod and the head. This area is called the seal gland. The advantage of a seal gland is easy removal and seal replacement. The seal gland contains a primary seal, a secondary seal/buffer seal, bearing elements, a wiper/scraper, and a static seal. In some cases, especially in small hydraulic cylinders, the rod gland and the bearing elements are made from a single integral machined part.

There are many component parts that make up the internal portion of a hydraulic cylinder. All of these pieces combine to create a fully functioning component.

Single-acting cylinders are economical and the simplest design. Hydraulic fluid enters through a port at one end of the cylinder, which extends the rod by means of area difference. An external force, internal retraction spring or gravity returns the piston rod.

Tie rod style hydraulic cylinders use high strength threaded steel rods to hold the two end caps to the cylinder barrel. They are most often seen in industrial factory applications. Small-bore cylinders usually have 4 tie rods, and large bore cylinders may require as many as 16 or 20 tie rods in order to retain the end caps under the tremendous forces produced. Tie rod style cylinders can be completely disassembled for service and repair, and they are not always customizable.

The National Fluid Power Association (NFPA) has standardized the dimensions of hydraulic tie-rod cylinders. This enables cylinders from different manufacturers to interchange within the same mountings.

Welded body hydraulic cylinders dominate the mobile hydraulic equipment market such as construction equipment (excavators, bulldozers, and road graders) and material handling equipment (forklift trucks, telehandlers, and lift-gates). They are also used by heavy industry in cranes, oil rigs, and large off-road vehicles for above-ground mining operations.

The piston rod of a hydraulic cylinder operates both inside and outside the barrel, and consequently both in and out of the hydraulic fluid and surrounding atmosphere.

Wear and corrosion-resistant surfaces are desirable on the outer diameter of the piston rod. The surfaces are often applied using coating techniques such as Chrome (Nickel) Plating, Lunac 2+ duplex, Laser Cladding, PTA welding and Thermal Spraying. These coatings can be finished to the desirable surface roughness (Ra, Rz) where the seals give optimum performance. All these coating methods have their specific advantages and disadvantages. It is for this reason that coating experts play a crucial role in selecting the optimum surface treatment procedure for protecting Hydraulic Cylinders.

The length of a hydraulic cylinder is the total of the stroke, the thickness of the piston, the thickness of bottom and head and the length of the connections. Often this length does not fit in the machine. In that case the piston rod is also used as a piston barrel and a second piston rod is used. These kinds of cylinders are called telescopic cylinders. If we call a normal rod cylinder single stage, telescopic cylinders are multi-stage units of two, three, four, five, or more stages. In general telescopic cylinders are much more expensive than normal cylinders. Most telescopic cylinders are single acting (push). Double acting telescopic cylinders must be specially designed and manufactured.

A hydraulic cylinder without a piston or with a piston without seals is called a plunger cylinder. A plunger cylinder can only be used as a pushing cylinder; the maximum force is piston rod area multiplied by pressure. This means that a plunger cylinder in general has a relatively thick piston rod.

The above differential cylinder is also called a regenerative cylinder control circuit. This term means that the cylinder is a single rod, double-acting hydraulic cylinder. The control circuit includes a valve and piping which during the extension of the piston, conducts the oil from the rod side of the piston to the other side of the piston instead of to the pump’s reservoir. The oil which is conducted to the other side of the piston is referred to as the regenerative oil.

Position sensing hydraulic cylinders eliminate the need for a hollow cylinder rod. Instead, an external sensing "bar" using Hall Effect technology senses the position of the cylinder’s piston. This is accomplished by the placement of a permanent magnet within the piston. The magnet propagates a magnetic field through the steel wall of the cylinder, providing a locating signal to the sensor.

Maximizing Cylinder Performance: A checklist of design guidelines ensures the best pneumatic cylinder for an application, Aug 20, 1998, Kenneth Korane, Machine Design magazine