| Application and Load | Required pushing and pulling force, load direction, stroke, cycle frequency, and operating speed. | Calculate force using F = p × A. A 100 mm bore at 160 bar produces approximately 126 kN theoretical extension force before efficiency losses. | Incorrect force or speed calculations can cause stalled motion, overheating, structural damage, or unstable operation. | Define load, stroke, speed, duty cycle, mounting condition, and allowable side load before selecting the cylinder. |
| Cylinder Type | Suitability of welded, tie-rod, telescopic, mill-duty, servo, lock, or custom construction. | Welded cylinders are commonly used in mobile and compact equipment; tie-rod cylinders are common in industrial machinery; telescopic cylinders provide long stroke in limited installation space. | Each construction has different strength, serviceability, packaging, and sealing characteristics. | Choose the construction according to space, pressure, environment, maintenance access, and required service life. |
| Rated Pressure | Continuous working pressure, peak pressure, proof pressure, and relief-valve setting. | Many industrial systems operate around 140–210 bar. Some heavy-duty systems operate near 250–350 bar, subject to design approval. | Operating above the rated pressure can damage the tube, rod, seals, ports, or mounting components. | Confirm working and peak pressure ratings | Ensure the cylinder rating exceeds the system’s maximum pressure, including transient pressure spikes. |
| Safety Factor | Structural margin for the barrel, piston rod, welds, mounts, pins, and threads. | Safety factors are application-dependent; values around 2:1 or higher against yield are commonly considered for static structural checks, but dynamic and fatigue loads require engineering analysis. | Shock loads, eccentric loading, buckling, and repeated cycles may create stresses much higher than the nominal load. | Request calculations or test evidence for buckling, fatigue, pressure containment, and mounting loads. |
| Piston Rod Sizing | Rod diameter, unsupported length, compression load, side loading, and surface finish. | Long compression strokes may require a larger rod or a reduced working load to prevent buckling. Side load should generally be minimized. | Rod buckling and bending are major causes of premature seal wear and cylinder failure. | Use external guides for side loads | Check Euler buckling, rod slenderness, mounting alignment, and the need for rod guides or spherical bearings. |
| Stroke and Cushioning | Effective stroke, end-of-stroke speed, cushioning length, and stopping energy. | Adjustable cushions are useful where the moving load must decelerate near the end of the stroke. Cushion performance depends on load, speed, oil viscosity, and adjustment. | Insufficient cushioning can cause impact, noise, vibration, and damage to mounts or seals. | Specify end-of-stroke speed and moving mass; verify cushion adjustment range during commissioning. |
| Mounting Compatibility | Mount type, pin diameter, clevis width, flange dimensions, centerline height, and available space. | Common mounting options include clevis, trunnion, flange, foot, and threaded mounts. Pin and bore tolerances must match the machine structure. | Misalignment creates bending loads, uneven wear, and premature failure. | Verify complete dimensional drawing | Check mounting geometry, pin hardness, lubrication points, alignment, and clearance throughout the full stroke. |
| Hydraulic Port Compatibility | Port thread standard, port size, hose routing, flow capacity, and pressure rating. | Common port standards include metric, BSPP, BSPT, and UN/UNF. Port size must support the required flow without excessive pressure loss. | Wrong threads or undersized ports can cause leakage, restriction, heat generation, and connection failure. | Match the exact thread standard and sealing method; never force incompatible fittings together. |
| Seal and Fluid Compatibility | Hydraulic fluid type, temperature, pressure, speed, contamination level, and seal material. | Mineral-oil systems commonly use seal materials such as polyurethane, nitrile, or fluorocarbon, depending on temperature and chemical exposure. | Incompatible fluids or temperatures can swell, harden, soften, or rapidly wear seals. | Confirm fluid and temperature compatibility | Specify minimum and maximum fluid temperature, ambient temperature, fluid type, and expected contamination conditions. |
| Operating Temperature | Hydraulic-fluid temperature, ambient temperature, startup temperature, and heat dissipation. | A typical mineral-oil hydraulic system may operate around 0–80°C, while the allowable range depends on fluid, seals, coating, and cylinder design. | High temperature accelerates seal aging and fluid oxidation; low temperature increases viscosity and starting force. | Use application-specific temperature limits | Provide heating, cooling, insulation, or low-temperature seals where the operating environment requires it. |
| Environmental Protection | Water, dust, mud, salt spray, chemicals, UV exposure, and corrosive atmosphere. | Rod coatings, wipers, protective bellows, stainless components, and corrosion-resistant finishes may be required for harsh environments. | Contamination on the rod can damage the wiper and primary seal, allowing particles into the hydraulic system. | Specify ingress and corrosion requirements; add rod protection for abrasive or corrosive service. |
| Rod Surface and Coating | Rod material, hardness, surface roughness, plating or coating, and corrosion resistance. | Chrome-plated or corrosion-resistant rods are commonly used. The required surface finish depends on the seal design and environment. | A damaged or rough rod surface quickly wears seals and can create external leakage. | Inspect for pitting, scoring, peeling, and rust; protect the rod during transport and installation. |
| Guidance and Alignment | Parallelism, concentricity, lateral movement, and external machine guidance. | Hydraulic cylinders are primarily force-producing devices and should not normally be used as the sole guide for a moving load. | Side loading increases friction, seal wear, rod bending, and bearing stress. | Use independent mechanical guidance | Measure alignment through the entire stroke and provide guides, rollers, or linkages where necessary. |
| Load Holding and Locking | Need for load holding, hose-failure protection, drift control, and emergency stopping. | Options may include pilot-operated check valves, counterbalance valves, mechanical locks, or redundant support systems. | A standard cylinder alone may not safely hold a suspended or safety-critical load after a hose or valve failure. | Do not rely on hydraulic pressure alone for personnel safety | Use a properly rated mechanical support or locking device for suspended loads and maintenance access. |
| Leakage Control | Internal bypass, external leakage, seal arrangement, rod wiper, and port sealing. | Minor film formation may occur on some rod seals, but visible dripping or pressure loss indicates a condition requiring investigation. | Leakage can reduce performance, contaminate the environment, and create slip or fire hazards. | Establish acceptance limits and inspect seals, rod condition, fittings, hoses, and valve settings. |
| Cleanliness | Internal cleanliness, flushing procedure, filtration, hose cleanliness, and capped ports. | Hydraulic cleanliness is commonly specified using ISO 4406 codes; the required code depends on valves, pumps, and system sensitivity. | Particles can damage pumps, valves, seals, and cylinder surfaces. | Define a cleanliness target | Keep ports capped, flush hoses, use suitable filtration, and prevent dirt from entering during installation. |
| Maintenance Access | Seal replacement, wear-band access, lubrication points, inspection areas, and spare-part availability. | Replaceable seals and accessible wear components can reduce downtime compared with permanently sealed or difficult-to-disassemble designs. | Good serviceability lowers lifecycle cost and improves equipment availability. | Confirm overhaul procedure, required tools, seal-kit identification, and recommended inspection intervals. |
| Inspection Frequency | Visual checks, leakage checks, pin and bushing wear, mounting bolts, rod condition, and abnormal noise. | Inspection frequency should be based on duty cycle and risk; high-cycle or harsh-service equipment generally requires more frequent checks. | Early detection prevents secondary damage and unplanned shutdowns. | Record inspection findings and trend leakage, drift, cycle time, and operating temperature. |
| Testing and Documentation | Pressure test, dimensional inspection, material records, seal details, drawings, and traceability. | Acceptance tests commonly include pressure holding, leakage inspection, stroke verification, and functional cycling. | Documented testing confirms that the cylinder matches the design and installation requirements. | Require a test report and approved drawing | Review test pressure, duration, acceptance criteria, serial traceability, and revision-controlled documentation. |
| Service Support | Technical response time, troubleshooting, repair capability, spare seals, replacement parts, and field support. | A practical support plan should identify normal spare parts, emergency contacts, repair lead times, and warranty handling. | Fast technical support can reduce downtime when a custom cylinder fails or operating conditions change. | Agree on support terms before purchase | Confirm spare-part identification, repair instructions, service locations, warranty scope, and escalation process. |
| Lifecycle Cost | Purchase price, installation, energy use, seal replacement, downtime, inspection, and disposal. | A lower initial price may result in higher total cost if the cylinder has short seal life, difficult maintenance, or long replacement lead times. | Total cost of ownership gives a more reliable basis for comparing special-cylinder designs. | Compare expected service life, maintenance intervals, repair cost, availability, and downtime risk. |
