Cylinders allow hydraulic systems to apply linear motion and power 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 industrial applications (hydraulic presses, cranes, forges, packing machines), and mobile applications (agricultural machines, construction equipment, marine equipment). And, in comparison to pneumatic, mechanical or electric systems, hydraulics can be simpler, more long lasting, and provide greater power. For example, a hydraulic pump offers about ten times the power density of an electric motor of comparable size. Hydraulic cylinders are also obtainable in an impressive array of scales to fulfill a wide range of application needs.
Choosing the right cylinder for an application is critical to attaining maximum efficiency and reliability. That means taking into consideration several parameters. Fortunately, an assortment of cylinder types, installation techniques and “guidelines” are available to greatly help.
Cylinder types
The three many common cylinder configurations are tie-rod, welded and ram styles. Tie-rod cylinders make use of high-strength threaded metal tie-rods, typically externally of the cylinder housing, to provide additional stability. Welded cylinders feature a heavy-duty welded cylinder casing with a barrel welded right to the end caps, and need no tie rods. Ram cylinders are just what they audio like-the cylinder pushes straight ahead using high pressure. Ram cylinders are found in heavy-duty applications and almost always push loads rather than pull.
For all types of cylinders, the key measurements include stroke, bore diameter and rod diameter. Stroke lengths change from less than an ” to several feet or even more. Bore diameters can range between an in . up to more than 24 in., and piston rod diameters range from 0.5 in. to more than 20 in. Used, however, the choice of stroke, bore and rod sizes may be tied to environmental or design circumstances. For example, space could be too limited for the perfect stroke length. For tie-rod cylinders, raising how big is the bore does mean increasing the amount of tie rods had a need to retain balance. Raising the diameter of the bore or piston rod is an ideal way to pay for higher loads, but space factors may not allow this, in which case multiple cylinders could be required.
Cylinder mounting methods
Mounting hydraulic cylinder methods also play an essential role in cylinder efficiency. Generally, fixed mounts on the centerline of the cylinder are greatest for straight line pressure transfer and avoiding put on. 
Common types of installation include:
Flange mounts-Very solid and rigid, but possess small tolerance for misalignment. Professionals recommend cap end mounts for thrust loads and rod end mounts where main loading puts the piston rod in stress.
Side-mounted cylinders-Easy to install and service, but the mounts produce a turning moment as the cylinder applies force to a load, increasing deterioration. In order to avoid this, specify a stroke at least as long as the bore size for side mount cylinders (weighty loading can make short stroke, huge bore cylinders unstable). Side mounts need 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 prevent movement in higher pressures or under shock conditions.
Pivot mounts -Absorb force on the cylinder centerline and let the cylinder alter alignment in a single plane. Common types consist of clevises, trunnion mounts and spherical bearings. Because these mounts enable 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 tend to be recommended for short strokes and little- to medium-bore cylinders.
Key specifications
Operating conditions-Cylinders must match a particular application in conditions of the quantity of pressure (psi), force exerted, space requirements imposed by machine design, etc. But knowing the operating requirements is half the challenge. Cylinders must also withstand high temperature ranges, humidity and also salt water for marine hydraulic systems. Wherever temperature ranges typically rise to a lot more than 300° F, standard Buna-N nitrile rubber seals may fail-choose cylinders with Viton synthetic rubber seals rather. When in doubt, assume operating conditions could be more durable than they appear at first glance.
Fluid type-Most hydraulics use a type of mineral oil, but applications involving synthetic fluids, such as for example phosphate esters, require Viton seals. Once more, Buna-N seals might not be adequate to take care of synthetic fluid hydraulics. Polyurethane can be incompatible with high water-based fluids such as for example water glycol.
Seals -This is probably the most vulnerable aspect of a hydraulic program. Proper seals can reduce friction and put on, lengthening service life, while the wrong type of seal can result in downtime and maintenance nightmares.
Cylinder materials -The type of metallic used for cylinder head, base and bearing can make a big change. Most cylinders make use of SAE 660 bronze for rod bearings and medium-grade carbon steel for heads and bases, which is adequate for most applications. But stronger materials, such as for example 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 important in wet or high-humidity environments (e.g., marine hydraulics) where17-4PH stainless may be stronger than the standard case-hardened carbon metal with chrome plating utilized for some piston rods.