Cylinders allow hydraulic systems to use linear motion and force without mechanical gears or levers by transferring the pressure from liquid through a piston to the point of operation.
Hydraulic cylinders are at work in both commercial applications (hydraulic presses, cranes, forges, packing machines), and cellular applications (agricultural machines, construction equipment, marine equipment). And, in comparison to pneumatic, mechanical or electrical systems, hydraulics could be simpler, more long lasting, and offer greater power. For instance, 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 satisfy an array of application needs.
Choosing the right cylinder to get an application is crucial to attaining maximum functionality and reliability. Which means considering several parameters. Fortunately, a variety of cylinder types, installation techniques and “guidelines” are available to help.
The three many common cylinder configurations are tie-rod, welded and ram styles. Tie-rod cylinders use high-strength threaded steel hydraulic cylinder tie-rods, typically on the outside of the cylinder housing, to provide additional balance. Welded cylinders include a heavy-duty welded cylinder housing with a barrel welded directly to the end caps, and need no tie rods. Ram cylinders are simply what they sound like-the cylinder pushes straight 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 crucial 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 from an ” up to a lot more than 24 in., and piston rod diameters range between 0.5 in. to more than 20 in. Used, however, the decision of stroke, bore and rod measurements may be tied to environmental or design conditions. For example, space could be too limited for the perfect stroke size. For tie-rod cylinders, increasing the size of the bore does mean increasing the number of tie rods needed to retain balance. Increasing the diameter of the bore or piston rod is usually an ideal way to compensate for higher loads, but space considerations may not enable this, in which particular case multiple cylinders may be required.
Cylinder mounting methods
Mounting methods also play a significant role in cylinder functionality. Generally, set mounts on the centerline of the cylinder are greatest for straight line power transfer and avoiding use. Common types of mounting include:
Flange mounts-Very strong and rigid, but have small tolerance for misalignment. Experts recommend cap end mounts for thrust loads and rod end mounts where major loading places the piston rod in tension.
Side-mounted cylinders-Easy to set up and service, however the mounts create a turning moment as the cylinder applies force to lots, increasing deterioration. To avoid this, specify a stroke at least so long as the bore size for part mount cylinders (large loading can make short stroke, huge bore cylinders unstable). Part 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 circumstances.
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 allow a cylinder to pivot, they should be used 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.
Operating conditions-Cylinders must match a particular application when it comes to the amount of pressure (psi), pressure exerted, space requirements imposed by machine design, and so forth. But knowing the working requirements is half the task. Cylinders must also withstand high temperatures, humidity and even salt drinking water for marine hydraulic systems. Wherever temperatures typically rise to more than 300° F, standard Buna-N nitrile rubber seals may fail-select cylinders with Viton synthetic rubber seals instead. When in doubt, assume operating conditions will be more tough than they appear at first glance.
Fluid type-Most hydraulics use a kind of mineral essential oil, but applications involving synthetic fluids, such as for example phosphate esters, require Viton seals. Once again, Buna-N seals may not be adequate to handle synthetic liquid hydraulics. Polyurethane is also incompatible with high water-based fluids such as water glycol.
Seals -This is just about the most vulnerable aspect of a hydraulic program. Proper seals can reduce friction and use, lengthening service life, as the wrong kind of seal can result in downtime and maintenance headaches.
Cylinder materials -The type of steel used for cylinder mind, base and bearing could make a significant difference. 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 more powerful materials, such as for example 65-45-12 ductile iron for rod bearings, can provide a big performance advantage for difficult industrial tasks. The kind of piston rod materials can be essential in wet or high-humidity environments (electronic.g., marine hydraulics) where17-4PH stainless steel may be more durable than the standard case-hardened carbon metal with chrome plating used for most piston rods.