Cylinders allow hydraulic systems to apply linear motion and pressure without mechanical gears or levers by transferring the pressure from fluid through a piston to the point of operation.
Hydraulic cylinders are at 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 offer greater power. For example, a hydraulic pump provides about ten times the power density of a power motor of comparable size. Hydraulic cylinders are also available in an impressive array of scales to satisfy an array of application needs.
Selecting the right cylinder pertaining to an application is crucial to attaining maximum performance and reliability. That means taking into consideration several parameters. Fortunately, a variety of cylinder types, mounting techniques and “guidelines” are available to greatly help.
Cylinder types
The three the majority of common cylinder configurations are tie-rod, welded and ram styles. Tie-rod cylinders use high-strength threaded steel tie-rods, typically on the outside of the cylinder housing, to provide additional balance. Welded cylinders feature a heavy-duty welded cylinder housing with a barrel welded directly to the finish caps, and need no tie rods. Ram cylinders are just what they sound like-the cylinder pushes directly ahead using high pressure. Ram cylinders are found in heavy-duty applications and more often than not 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 ” to several feet or 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 a lot more than 20 in. Used, however, the choice of stroke, bore and rod measurements may be tied to environmental or design circumstances. For example, space could be as well limited for the perfect stroke length. For tie-rod cylinders, increasing how big is the bore also means increasing the number of tie rods hydraulic cylinder needed to retain balance. Raising the diameter of the bore or piston rod can be an ideal way to pay for higher loads, but space considerations may not allow this, in which case multiple cylinders could be required.
Cylinder mounting methods
Mounting strategies also play an essential role in cylinder performance. Generally, set mounts on the centerline of the cylinder are greatest for straight line drive transfer and avoiding use. Common types of installation include:
Flange mounts-Very solid and rigid, but have little 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, however the mounts produce a turning moment as the cylinder applies force to lots, increasing wear and tear. In order to avoid this, specify a stroke at least provided that the bore size for part mount cylinders (heavy loading can make short stroke, large bore cylinders unstable). Aspect mounts need 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 at 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 enable a cylinder to pivot, they must be used with rod-end attachments that also pivot. Clevis mounts can be used in any orientation and tend to be recommended for brief strokes and small- to medium-bore cylinders.
Key specifications
Operating conditions-Cylinders must match a specific application in terms of the quantity of pressure (psi), power exerted, space requirements imposed by machine design, etc. But knowing the working requirements is half the task. Cylinders must withstand high temperature ranges, humidity and even salt drinking water for marine hydraulic systems. Wherever temps 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 could be more rugged 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 more, Buna-N 
seals might not be adequate to handle synthetic liquid 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 program. Proper seals can reduce friction and put on, lengthening service life, while the wrong kind of seal can result in downtime and maintenance headaches.
Cylinder materials -The kind of steel 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 stronger materials, such as for example 65-45-12 ductile iron for rod bearings, can offer a big performance advantage for difficult industrial tasks. The type of piston rod materials can be important in wet or high-humidity environments (electronic.g., marine hydraulics) where17-4PH stainless steel may be stronger than the standard case-hardened carbon steel with chrome plating utilized for some piston rods.