Cylinders allow hydraulic systems to apply linear motion and push without mechanical gears or levers by transferring the pressure from fluid through a hydraulic cylinder 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, when compared with pneumatic, mechanical or electric systems, hydraulics can be simpler, more durable, and provide greater power. For example, a hydraulic pump has about ten times the power density of an electric motor of comparable size. Hydraulic cylinders are also obtainable in an impressive selection of scales to fulfill a wide selection of application needs.
Selecting the right cylinder designed for an application is critical to attaining maximum overall performance and reliability. That means taking into consideration 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 externally of the cylinder casing, to provide additional stability. Welded cylinders feature a heavy-duty welded cylinder casing with a barrel welded right to the finish caps, and require no tie rods. Ram cylinders are just what they audio like-the cylinder pushes directly ahead using high pressure. Ram cylinders are found in heavy-duty applications and almost always push loads rather than pull.
For all sorts of cylinders, the key measurements include stroke, bore diameter and rod diameter. Stroke lengths change from less than an in . to several feet or more. Bore diameters can range between an inch up to more than 24 in., and piston rod diameters range from 0.5 in. to a lot more than 20 in. In practice, however, the choice of stroke, bore and rod sizes may be limited by environmental or design circumstances. For example, space may be as well limited for the ideal stroke length. For tie-rod cylinders, raising how big is the bore also means increasing the amount of tie rods had a need to retain stability. Raising the diameter of the bore or piston rod is certainly 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 methods also play an important role in cylinder efficiency. Generally, fixed mounts on the centerline of the cylinder are greatest for straight line pressure transfer and avoiding wear. Common types of installation include:
Flange mounts-Very solid 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 produce a turning moment as the cylinder applies force to a load, increasing wear and tear. In order to avoid this, specify a stroke at least as long as the bore size for side mount cylinders (heavy loading tends to make short stroke, large bore cylinders unstable). Aspect 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 avoid movement at higher pressures or under shock conditions.
Pivot mounts -Absorb force on the cylinder centerline and let the cylinder modify alignment in a single plane. Common types consist of 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 used in any orientation and tend to be recommended for short strokes and small- to medium-bore cylinders.
Operating conditions-Cylinders must match a specific application in conditions of the quantity of pressure (psi), drive exerted, space requirements imposed by machine design, etc. But knowing the operating requirements is only half the challenge. Cylinders must also withstand high temperature ranges, humidity and also salt water for marine hydraulic systems. Wherever temps 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 question, assume operating conditions could be more durable than they appear initially.
Fluid type-Most hydraulics use a form of mineral 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 can be incompatible with high water-based liquids such as for example water glycol.
Seals -This is probably the most vulnerable aspect of a hydraulic system. Proper seals can decrease friction and put on, lengthening service life, while the wrong type of seal can lead to downtime and maintenance nightmares.
Cylinder materials -The kind 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 some applications. But stronger materials, such as 65-45-12 ductile iron for rod bearings, can offer a sizable performance advantage for challenging 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 regular case-hardened carbon metal with chrome plating utilized for some piston rods.