Single-acting hydraulic cylinders (piston or plunger) and double-acting hydraulic cylinders (piston) are used in the hydraulic systems of cranes, hoists, construction machinery, farm machinery, etc. The single-acting cylinders come with an air vent (piston cylinders) or without an air vent (plunger cylinders). The complete cylinder includes mounting elements. The most common mounting element is an eye fitted with a grease nipple:
- eye with spherical plain bearing (standard)
- eye with bushing (option).
- Eyes are welded directly to the cylinder and to the piston rod. A threaded eye can be screwed on a threaded piston rod as well.
Construction (with the example of HPA1 double-acting piston cylinder)
|1. eyes (carbon steel)||a) piston seals (NBR + TPE + POM)|
|2. ports (carbon steel)||b) o-ring NBR (static seal)|
|3. end cap (carbon steel)||c) wiper seal PU|
|4. body (carbon steel)||d) gland seal (NBR + fabric)|
|5. piston (carbon steel)||e) seal PU (static seal)|
|6. piston rod (NiCr coated alloy steel)|
|7. gland (cast iron)|
|8. spherical plain bearings (bearing steel)|
Plunger cylinders are bigger than piston cylinders. During operation the entire plunger is immersed in oil so the cylinder is more resistant to corrosion.
Piston cylinders are smaller than plunger cylinders. They are additionally equipped with an air vent to allow the piston/piston rod to move during cylinder operation.
Standard marking system for cylinders (with the example of Tubes code)
During selection consider the following criteria:
- cylinder type (single-acting or double-acting)
- maximum working pressure
- cylinder size (piston/piston rod)
- cylinder stroke
- cylinder mounting options (e.g. eyes with spherical bearings)
Available types of hydraulic cylinders
|Type||Operation||Construction||Mounting 1 (cylinder side)||Mounting 2 (piston rod/plunger side)|
|HPA1||double-acting||piston||eye with spherical bearing*||eye with spherical bearing*|
|HPE1||single-acting||piston||eye with spherical bearing*||eye with spherical bearing*|
|HPA2||double-acting||piston||eye with spherical bearing*||metric male thread**|
|HPE2||single-acting||piston||eye with spherical bearing*||metric male thread**|
|SE||single-acting||plunger||mounting hole||mounting hole|
|DE||double-acting||piston||mounting hole||mounting hole|
* – eye fitted with a grease nipple (requiring lubrication)
** – a threaded eye (Tubes code: HS-HP-KT…) can be screwed on this rod