Cylinders allow hydraulic systems to apply linear motion and force without mechanical gears or levers by transferring the pressure from fluid through a piston to the idea of operation.
Hydraulic cylinders are in work in both commercial applications (hydraulic presses, cranes, forges, packing machines), and mobile applications (agricultural machines, construction equipment, marine equipment). And, in comparison to pneumatic, mechanical or electrical systems, hydraulics could be simpler, more durable, and offer greater power. For instance, a hydraulic pump offers about ten times the energy density of a power motor of similar size. Hydraulic cylinders are also obtainable in an impressive selection of scales to fulfill a wide selection of application needs.

Selecting the right cylinder intended for an application is critical to attaining maximum functionality and reliability. That means considering several parameters. Fortunately, a variety of cylinder types, mounting techniques and “guidelines” are available to greatly help.
Cylinder types

The three most common cylinder configurations are tie-rod, welded and ram styles. Tie-rod cylinders make use of high-strength threaded steel tie-rods, typically externally of the cylinder casing, to provide additional stability. Welded cylinders include a heavy-duty welded cylinder housing with a barrel welded right to the end caps, and require no tie rods. Ram cylinders are simply what they sound like-the cylinder pushes directly ahead using very high pressure. Ram cylinders are used in heavy-duty applications and more often than not push loads instead of pull.

For all types of cylinders, the key measurements include stroke, bore diameter and rod diameter. Stroke lengths vary from less than an in . to several feet or more. Bore diameters can range between an in . up to a lot more than 24 in., and piston rod diameters range from 0.5 in. to a lot more than 20 in. Used, however, the decision of stroke, bore and rod sizes may be limited by environmental or design conditions. For example, space may be too limited for the ideal stroke duration. For tie-rod cylinders, increasing the size of the bore does mean increasing the number of tie rods needed to retain stability. Increasing the diameter of the bore or piston rod is definitely an ideal way to compensate for higher loads, but space factors may not allow this, in which particular case multiple cylinders could be required.
Cylinder mounting methods

Mounting methods also play an important role in cylinder efficiency. Generally, fixed mounts on the centerline of the cylinder are best for straight line push transfer and avoiding put on. Common types of mounting include:

Flange mounts-Very strong and rigid, but possess small tolerance for misalignment. Specialists recommend cap end mounts for thrust loads and rod end mounts where main loading places the piston rod in pressure.

Side-mounted cylinders-Easy to set up and service, but the mounts create a turning moment as the cylinder applies force to a load, increasing deterioration. To avoid this, specify a stroke at least so long as the bore size for side mount cylinders (weighty loading tends to make short stroke, huge bore cylinders unstable). Part mounts have to be well aligned and the strain supported and guided.

Centerline lug mounts -Absorb forces on the centerline, but require dowel pins to secure the lugs to avoid movement in higher pressures or under shock conditions.

Pivot mounts -Absorb force on the cylinder centerline and allow cylinder alter alignment in a single plane. Common types consist of clevises, trunnion mounts and spherical bearings. Because these mounts allow a cylinder to pivot, they should be used in combination with rod-end attachments that also pivot. Clevis mounts can be utilized in any orientation and are generally recommended for brief strokes and little- to medium-bore cylinders.
Key specifications

Operating conditions-Cylinders must match a specific application with regards to the quantity of pressure (psi), push exerted, space requirements imposed by machine design, and so forth. But knowing the operating requirements is half the challenge. Cylinders must also withstand high temps, humidity and also salt water for marine hydraulic systems. Wherever temperatures typically rise to a lot more than 300° F, standard Buna-N nitrile rubber seals may fail-choose cylinders with Viton synthetic rubber seals instead. When in question, assume operating hydraulic cylinder conditions will be more tough than they appear initially.

Fluid type-Most hydraulics use a type of mineral oil, but applications involving synthetic liquids, such as for example phosphate esters, require Viton seals. Once again, Buna-N seals might not be adequate to take care of synthetic liquid hydraulics. Polyurethane can be incompatible with high water-based fluids such as water glycol.

Seals -This is just about the most vulnerable facet of a hydraulic system. Proper seals can decrease friction and wear, lengthening service life, as the wrong type of seal can result in downtime and maintenance nightmares.

Cylinder materials -The kind of metallic used for cylinder head, base and bearing could make a big change. Most cylinders use SAE 660 bronze for rod bearings and medium-grade carbon metal for heads and bases, which is sufficient for most applications. But stronger materials, such as 65-45-12 ductile iron for rod bearings, can offer a big performance advantage for tough industrial tasks. The type of piston rod material can be essential in wet or high-humidity environments (e.g., marine hydraulics) where17-4PH stainless may be more durable than the regular case-hardened carbon metal with chrome plating used for most piston rods.