Cylinders allow hydraulic systems to use linear motion and power without mechanical gears or levers by transferring the pressure from fluid through a piston to the idea of operation.
Hydraulic cylinders are in 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 can be simpler, more long lasting, and offer greater power. For example, a hydraulic pump provides about ten times the energy density of an electric motor of comparable size. Hydraulic cylinders are also obtainable in an impressive array of scales to meet an array of application needs.
Choosing the right cylinder to get an application is critical to attaining maximum functionality and reliability. That means taking into consideration several parameters. Fortunately, a variety of cylinder types, mounting techniques and “guidelines” are available to help.
Cylinder types
The three many common cylinder configurations are tie-rod, welded and ram styles. Tie-rod cylinders use high-strength threaded metal tie-rods, typically externally of the cylinder casing, to provide additional stability. Welded cylinders include a heavy-duty welded cylinder housing with a barrel welded right to the end caps, and require no tie rods. Ram cylinders are just what they sound like-the cylinder pushes directly ahead using very high pressure. Ram cylinders are used 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 vary from less than an in . to several feet or more. Bore diameters can range from an in . up to a lot more than 24 in., and piston rod diameters range from 0.5 in. to more than 20 in. Used, however, the decision of stroke, bore and rod measurements may be limited by environmental or design circumstances. For example, space could be too limited for the ideal stroke duration. For tie-rod cylinders, raising the size of the bore does mean increasing the number of tie rods had a need to retain stability. Raising the diameter of the bore or piston rod is definitely 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 important role in cylinder overall performance. Generally, fixed 
mounts on the centerline of the cylinder are best for straight line power transfer and avoiding use. Common types of mounting include:
Flange mounts-Very strong and rigid, but possess little tolerance for misalignment. Specialists 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 install and service, but the mounts produce a turning moment as the cylinder applies force to lots, increasing wear and tear. To avoid this, specify a stroke at least so long as the bore size for side mount cylinders (weighty loading can make short stroke, huge 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 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 in combination with rod-end attachments that also pivot. Clevis mounts can be utilized in any orientation and tend to be recommended for short strokes and small- to medium-bore cylinders.
Key specifications
Operating conditions-Cylinders must match a specific application with regards to the amount of pressure (psi), force exerted, space requirements imposed by machine design, etc. But knowing the operating requirements is half the challenge. Cylinders must withstand high temperatures, humidity and even salt water for marine hydraulic systems. Wherever temperatures typically rise to a lot 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 durable than they appear at first glance.
Fluid type-Most hydraulics use a form of mineral oil, but applications involving synthetic liquids, such as phosphate esters, require Viton seals. Once again, Buna-N seals may not be adequate to take care of synthetic fluid hydraulics. Polyurethane can be incompatible with high water-based fluids such as water glycol.
Seals -This is just about the most vulnerable aspect of a hydraulic system. Proper seals can reduce friction and put on, lengthening service life, while the wrong type of seal can lead to downtime and maintenance nightmares.
Cylinder hydraulic cylinder materials -The type of steel 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 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 tough industrial tasks. The kind of piston rod material can be important in wet or high-humidity environments (electronic.g., marine hydraulics) where17-4PH stainless steel may be more durable than the regular case-hardened carbon steel with chrome plating utilized for some piston rods.