Hydraulic Cylinder Selection Guide
Select a hydraulic cylinder based on load, pressure, stroke, speed, mounting, rod stability, and operating conditions.
01. Define the Application
Define the required load, stroke, speed, available cylinder pressure, duty cycle, installation space, operating environment, and control requirements.
| Parameter | Engineering Considerations |
|---|---|
| Operating Load | Required extension and retraction force, holding load, load direction |
| Available Cylinder Pressure | Operating pressure, maximum pressure, pressure spikes |
| Stroke Length | Required stroke, end clearance, installation limits |
| Cycle Speed | Extension and retraction speed, required flow |
| Environment | Ambient temperature, moisture, dust, chemicals, outdoor exposure |
| Control Requirements | Position sensing, end-of-stroke detection, feedback requirements |
02. Select Cylinder Construction
Select the cylinder construction and series according to machine design, duty cycle, mounting requirements, pressure rating, and installation envelope. Verify pressure capability against the applicable manufacturer data.
| Selection Parameter | Tie-Rod Cylinder | Welded Cylinder |
|---|---|---|
| Typical Application | Stationary industrial machinery, machine tools, automation, presses, and general industrial equipment | Mobile machinery, OEM equipment, compact installations, and application-specific machinery |
| Serviceability | Tie-rod construction generally supports straightforward disassembly and component service | Compact welded construction; service method depends on the specific design |
| Pressure Rating | Series-specific; verify manufacturer rated pressure and application limits | Series-specific; verify manufacturer rated pressure and application limits |
| Selection Basis | Mounting standard, load path, dimensions, duty, speed, environment, and required options | OEM geometry, load path, installation envelope, duty, environment, and service requirements |
03. Calculate Piston & Annular Areas
Use a candidate bore and piston rod size, then calculate the effective piston and annular areas for extension and retraction. Use mm, mm², MPa, kN, L/min, and mm/s throughout.
Piston Area — Cap End
Ap =
πD2
4
Ap: Piston Area (mm²)
D: Bore Diameter (mm)
Calculation Example: For an 80 mm Bore, Ap = (π × 80²) / 4 = 5,026.5 mm².
Annulus Area — Rod End
Aa =
π(D2 − d2)
4
Aa: Annulus Area (mm²)
D: Bore Diameter (mm)
d: Piston Rod Diameter (mm)
Calculation Example: For an 80 mm Bore / 45 mm Piston Rod, Aa = [π × (80² − 45²)] / 4 = 3,436.1 mm².
04. Theoretical Extension & Retraction Force
Calculate theoretical extension and retraction force from powered-chamber pressure and effective hydraulic area. Select a bore that meets the required force; opposing-chamber pressure is neglected for preliminary sizing.
Theoretical Extension Force
Fext,th =
=
P · Ap
1000
πD2P
4000
Fext,th: Extension Force (kN)
P: Pressure (MPa)
Ap: Piston Area (mm²)
D: Bore Diameter (mm)
Calculation Example: Bore = 80 mm, Pressure = 16 MPa (160 bar): Fext,th = (16 × 5,026.5) / 1000 = 80.4 kN.
Theoretical Retraction Force
Fret,th =
=
P · Aa
1000
π(D2 − d2)P
4000
Fret,th: Retraction Force (kN)
P: Pressure (MPa)
Aa: Annulus Area (mm²)
D: Bore Diameter (mm)
d: Piston Rod Diameter (mm)
Calculation Example: Bore = 80 mm, Rod = 45 mm, Pressure = 16 MPa (160 bar): Fret,th = (16 × 3,436.1) / 1000 = 55.0 kN.
05. Net Hydraulic Force with Significant Back Pressure
Include opposing-chamber pressure when back pressure is significant. Use actual or calculated cylinder-port pressures for detailed verification.
Net Hydraulic Force — Extension
Fext,hyd =
(PcapAp) − (Prod,backAa)
1000
Fext,hyd: Net Hydraulic Force (kN)
Pcap: Cap-End Pressure (MPa)
Prod,back: Rod-End Back Pressure (MPa)
Ap, Aa: Areas (mm²)
Calculation Example: Pcap = 16 MPa, Prod,back = 1.5 MPa: Fext,hyd = [(16 × 5,026.5) − (1.5 × 3,436.1)] / 1000 = 75.3 kN.
Net Hydraulic Force — Retraction
Fret,hyd =
(ProdAa) − (Pcap,backAp)
1000
Fret,hyd: Net Hydraulic Force (kN)
Prod: Rod-End Pressure (MPa)
Pcap,back: Cap-End Back Pressure (MPa)
Ap, Aa: Areas (mm²)
Calculation Example: Prod = 16 MPa, Pcap,back = 1.0 MPa: Fret,hyd = [(16 × 3,436.1) − (1.0 × 5,026.5)] / 1000 = 50.0 kN.
Actual rod force may be lower due to friction, pressure losses, misalignment, side loading, and dynamic effects.
06. Cylinder Speed and Hydraulic Flow
Determine cylinder velocity from inlet flow and the effective area of the active chamber.
Extension Velocity
vext =
16666.7 · Qcap
Ap
vext: Extension Velocity (mm/s)
Qcap: Cap-End Inlet Flow (L/min)
Ap: Piston Area (mm²)
Calculation Example: Flow = 30 L/min, Piston Area = 5,026.5 mm²: vext = (16666.7 × 30) / 5,026.5 = 99.5 mm/s.
Retraction Velocity
vret =
16666.7 · Qrod
Aa
vret: Retraction Velocity (mm/s)
Qrod: Rod-End Inlet Flow (L/min)
Aa: Annulus Area (mm²)
Calculation Example: Flow = 30 L/min, Annulus Area = 3,436.1 mm²: vret = (16666.7 × 30) / 3,436.1 = 145.5 mm/s.
Required Flow
Q =
A · v
16666.7
Q: Required Flow (L/min)
A: Effective Area (mm²)
v: Required Velocity (mm/s)
With equal inlet flow, a conventional single-rod cylinder normally retracts faster than it extends. Regenerative and other special circuits require separate analysis.
07. Typical Metric Bore / Rod Reference
Use the table as a preliminary metric reference only. Verify piston rod diameter against load, stroke, mounting, and the selected cylinder series before final selection.
| Bore Diameter D (mm) | Typical Piston Rod Diameter, d (mm) | Piston Area Ap (mm²) |
|---|---|---|
| 40 | 22, 28 | 1,256.6 |
| 50 | 28, 36 | 1,963.5 |
| 63 | 36, 45 | 3,117.2 |
| 80 | 45, 56 | 5,026.5 |
| 100 | 56, 70 | 7,854.0 |
08. Rod Stability / Buckling Verification
Check piston rod stability for long-stroke cylinders under compressive load. For an ideal slender member within the elastic range, the Euler buckling relation is:
Euler Elastic Critical Load
Fcr =
, Le = KL , I = πd4/64
π2 · E · I
Le2
Fcr: Critical Load (N)
E: Young's Modulus (N/mm²)
I: Second Moment of Area (mm⁴)
Le: Effective Length (mm)
K: Effective Length Factor
L: Unsupported Length (mm)
d: Piston Rod Diameter (mm)
Calculation Example: Rod Diameter = 45 mm, I = 201,289 mm⁴, Steel E = 210,000 N/mm², Effective Length = 1,200 mm: Fcr ≈ 289.7 kN.
Engineering Boundary: Euler buckling is a preliminary stability check, not a stand-alone piston rod sizing method. Final selection must consider actual compressive load, effective length, mounting, rod-end connection, alignment, load guidance, and cylinder-series limits. Engineering verification is required.
09. Cushioning & End-of-Stroke Energy
Check cushioning when significant moving mass must be decelerated near the end of stroke. Verify piston speed, moving mass, available deceleration distance, and cushion capability for the selected cylinder series.
10. Cylinder Mounting & Rod-End Connection
Select the mounting and rod-end connection according to the machine load path, alignment, and installation space. Keep the load as close to the cylinder centerline as practical and use external guidance for sustained side loads.
11. Cylinder Force & Speed Calculator
Preliminary Hydraulic Cylinder Calculator
Enter bore, piston rod diameter, operating pressure, and inlet flow for preliminary force and speed calculations. Final performance must be verified against the actual hydraulic circuit and cylinder-series limits.
mm
mm
MPa
L/min
Theoretical Extension Force
0.0 kN
Theoretical Retraction Force
0.0 kN
Extension Velocity
0.0 mm/s
Retraction Velocity
0.0 mm/s
Calculator Limitation: Results are theoretical preliminary values. Verify final performance against actual cylinder pressures, direction-specific flow, circuit losses, load conditions, and cylinder-series limits.
12. Port Type, Port Size & Flow Velocity
Select the connection standard and port size according to required flow, cylinder speed, pressure drop, line size, operating pressure, and installation space. Verify thread and sealing compatibility with the selected cylinder series.
13. Hydraulic Fluid, Seals & Environment
Select the seal system according to hydraulic fluid, pressure, temperature, sliding velocity, duty cycle, contamination, and operating environment. Verify compatibility with the selected cylinder series.
| Service Condition | Seal-System Guidance |
|---|---|
| Mineral-Oil Service | Standard seal package within series pressure, speed, and temperature limits. |
| Water-Glycol / Water-Based Fluid | Use a seal package approved for the fluid and operating conditions. |
| Elevated Temperature | Use a high-temperature seal system compatible with the fluid and temperature range. |
| Low Temperature | Use low-temperature seals and wipers suitable for start-up and operation. |
| Severe Contamination | Use heavy-duty wipers and contamination-resistant sealing. |
Replacement sealing components: Hydraulic Cylinder Seal Kits.
14. Selection Verification Checklist
Review the key sizing, mounting, hydraulic, sealing, and operating parameters before final cylinder selection. Complete engineering verification where required.
- Application and load case defined
- Required extension and retraction force established
- Available pressure at the cylinder confirmed
- Bore and piston rod diameter reviewed
- Stroke and installation envelope confirmed
- Rod stability reviewed where required
- Cylinder mounting and rod-end connection confirmed
- Extension and retraction velocity established
- Required hydraulic flow verified
- Port type, port size, and flow velocity reviewed
- Cushioning and end-of-stroke energy reviewed
- Hydraulic fluid, temperature, and seal system confirmed
- Duty cycle and environmental conditions reviewed
- Position sensing and control requirements confirmed
- Final engineering verification completed
15. Technical Application RFQ
Submit the available model, drawing, or application information for technical review and quotation.
