Cylinders allow hydraulic systems to apply linear motion and pressure without mechanical gears or levers by transferring the pressure from liquid through a piston to the idea of operation.
Hydraulic cylinders are at 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 electrical systems, hydraulics can be simpler, more durable, and provide greater power. For example, a hydraulic pump offers about ten times the energy density of an electric motor of comparable size. Hydraulic cylinders are also available in an impressive array of scales to meet an array of application needs.
hydraulic cylinder Choosing the right cylinder meant for an application is crucial to attaining maximum overall performance and reliability. Which means considering several parameters. Fortunately, an assortment of cylinder types, mounting techniques and “rules of thumb” are available to greatly help.
The three the majority of common cylinder configurations are tie-rod, welded and ram styles. Tie-rod cylinders make use of high-strength threaded metal tie-rods, typically on the outside of the cylinder casing, to provide additional stability. Welded cylinders feature a heavy-duty welded cylinder casing with a barrel welded directly to the end caps, and require no tie rods. Ram cylinders are simply what they sound 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 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 even more. Bore diameters can range from an " up to more than 24 in., and piston rod diameters range from 0.5 in. to more than 20 in. In practice, however, the choice of stroke, bore and rod dimensions may be limited by environmental or design conditions. For example, space may be as well limited for the perfect stroke length. For tie-rod cylinders, increasing the size of the bore does mean increasing the number of tie rods had a need to retain balance. Raising the diameter of the bore or piston rod is usually an ideal way to compensate for higher loads, but space factors may not enable this, in which particular case multiple cylinders may be required.
Cylinder mounting methods
Mounting methods also play an important role in cylinder performance. Generally, fixed mounts on the centerline of the cylinder are greatest for straight line force transfer and avoiding wear. Common types of installation include:
Flange mounts-Very strong and rigid, but have little tolerance for misalignment. Experts recommend cap end mounts for thrust loads and rod end mounts where major loading puts the piston rod in pressure.
Side-mounted cylinders-Easy to install and service, however the mounts create a turning moment as the cylinder applies force to a load, increasing wear and tear. To avoid this, specify a stroke at least as long as the bore size for side mount cylinders (weighty loading can make short stroke, large bore cylinders unstable). Side 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 circumstances.
Pivot mounts -Absorb force on the cylinder centerline and let the cylinder alter alignment in one plane. Common types consist of 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 used in any orientation and are generally recommended for short strokes and small- to medium-bore cylinders.
Operating conditions-Cylinders must match a particular application in terms of the quantity of pressure (psi), drive exerted, space requirements imposed by machine design, etc. But knowing the working requirements is only half the challenge. Cylinders must withstand high temperature ranges, humidity and also salt water for marine hydraulic systems. Wherever temperatures typically rise to a lot more than 300° F, regular Buna-N nitrile rubber seals may fail-select cylinders with Viton synthetic rubber seals rather. When in doubt, assume operating conditions will be more tough than they appear initially.
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 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 probably the most vulnerable facet of a hydraulic system. Proper seals can decrease friction and put on, lengthening service life, as the wrong kind of seal can result in downtime and maintenance headaches.
Cylinder materials -The kind of metallic used for cylinder head, base and bearing could make a big change. Most cylinders make use of SAE 660 bronze for rod bearings and medium-grade carbon metal 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 big performance advantage for tough industrial tasks. The type of piston rod material can be important in wet or high-humidity environments (electronic.g., marine hydraulics) where17-4PH stainless may be stronger than the standard case-hardened carbon metal with chrome plating utilized for most piston rods.