Cylinders allow hydraulic systems to apply hydraulic cylinder linear motion and drive without mechanical gears or levers by transferring the pressure from liquid through a piston to the idea of operation.
Hydraulic cylinders are in work in both industrial applications (hydraulic presses, cranes, forges, packing machines), and cellular applications (agricultural machines, construction equipment, marine equipment). And, when compared with pneumatic, mechanical or electric systems, hydraulics can be simpler, more durable, and provide greater power. For example, a hydraulic pump provides about ten times the power density of an electric motor of similar size. Hydraulic cylinders are also available in an impressive array of scales to meet an array of application needs.

Choosing the right cylinder intended for an application is critical to attaining maximum performance and reliability. Which means taking into consideration several parameters. Fortunately, a variety of cylinder types, installation techniques and “rules of thumb” 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 housing, to provide additional stability. Welded cylinders feature a heavy-duty welded cylinder housing with a barrel welded directly to the finish caps, and require no tie rods. Ram cylinders are simply what they audio like-the cylinder pushes directly ahead using high pressure. Ram cylinders are used in heavy-duty applications and almost always push loads instead of pull.

For all sorts of cylinders, the key measurements include stroke, bore diameter and rod diameter. Stroke lengths vary from less than an inch to several feet or even more. Bore diameters can range between an inch 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 choice of stroke, bore and rod sizes may be tied to environmental or design conditions. For example, space could be too limited for the ideal stroke length. For tie-rod cylinders, raising the size of the bore also means increasing the number of tie rods needed to retain balance. Increasing the diameter of the bore or piston rod is certainly an ideal way to compensate for higher loads, but space considerations may not enable this, in which case multiple cylinders may be required.
Cylinder mounting methods

Mounting strategies also play an essential role in cylinder overall performance. Generally, set mounts on the centerline of the cylinder are greatest for straight line pressure transfer and avoiding put on. Common types of mounting include:

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

Side-mounted cylinders-Easy to install 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 provided that the bore size for aspect mount cylinders (heavy loading can make short stroke, large bore cylinders unstable). Aspect mounts have to be well aligned and the load 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 allow cylinder change alignment in one plane. Common types include clevises, trunnion mounts and spherical bearings. Because these mounts enable a cylinder to pivot, they must be used in combination with rod-end attachments that also pivot. Clevis mounts can be utilized in any orientation and are generally recommended for short strokes and small- to medium-bore cylinders.
Key specifications

Operating conditions-Cylinders must match a particular application with regards to the quantity of pressure (psi), drive exerted, space requirements imposed by machine design, etc. But knowing the operating requirements is only half the task. Cylinders must also withstand high temps, humidity and actually salt drinking water for marine hydraulic systems. Wherever temperature ranges typically rise to a lot more than 300° F, regular Buna-N nitrile rubber seals may fail-choose cylinders with Viton synthetic rubber seals instead. When in doubt, assume operating conditions will be more tough than they appear initially.

Fluid type-Most hydraulics use a form of mineral essential oil, but applications involving synthetic liquids, such as phosphate esters, require Viton seals. Once more, Buna-N seals might not be adequate to take care of synthetic fluid hydraulics. Polyurethane is also incompatible with high water-based liquids such as water glycol.

Seals -This is probably 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 metal used for cylinder mind, base and bearing can make a big change. Most cylinders use SAE 660 bronze for rod bearings and medium-grade carbon steel for heads and bases, which is adequate for most applications. But more powerful materials, such as for example 65-45-12 ductile iron for rod bearings, can provide a sizable performance advantage for difficult industrial tasks. The kind of piston rod materials can be important in wet or high-humidity environments (e.g., marine hydraulics) where17-4PH stainless may be more durable than the standard case-hardened carbon metal with chrome plating used for some piston rods.