Crane Hydraulic Cylinders RFQ Checklist: What OEM Buyers Should Specify

An accurate crane hydraulic cylinder quotation starts with the machine function, operating loads and installation geometry—not with bore and stroke alone. OEM buyers should identify where the cylinder works, provide the complete interface dimensions, define the hydraulic and environmental conditions, and state the required inspection and documentation. This prevents a supplier from quoting a cylinder that fits the nominal dimensions but cannot safely reproduce the machine’s motion, holding performance or service life.

Гидравлика Чжэнцян’s verified product data covers crane cylinders for lifting machinery from 1 to 4,000 tons. The published portfolio spans 40–620 mm bore, 25–535 mm rod diameter, 30–15,875 mm stroke and 10–42 MPa working pressure, with listed output limits up to 9,656 kN thrust and 3,674 kN tension. These figures describe the available product envelope; they are not a single recommended configuration. The final design must be checked against the specific crane and cylinder function.

1. Identify the crane and cylinder function

State the crane type, manufacturer, model, rated lifting capacity and serial or equipment revision when available. Then identify the cylinder position. The product application records include truck cranes, crawler cranes, rough-terrain cranes, gantry and overhead cranes, tower cranes, truck-mounted or folding-boom cranes, and aerial ladder fire-truck booms.

• Outrigger cylinder: supports and levels the machine and must resist compressive and eccentric loads.
• Luffing cylinder: changes the main-boom angle and works repeatedly under load.
• Telescopic boom cylinder: extends multi-section booms and may require an unusually long stroke.
• Slewing cylinder: drives rotational positioning on applicable designs.
• Counterweight or hook-control cylinder: supports load-management functions on heavy cranes.
• Jib or fly-jib auxiliary cylinder: folds, unfolds or locks auxiliary boom sections.

Do not describe the unit only as a “crane cylinder.” Two cylinders on the same machine can have different load directions, holding requirements, speeds, interfaces and failure consequences.

2. Provide drawings and interface dimensions

The preferred RFQ attachment is a controlled drawing with units, tolerances and revision number. For a replacement cylinder, include the retracted pin-to-pin or datum-to-datum length, extended length, effective stroke, barrel and rod diameters, mounting style at both ends, pin diameters, lug widths, clevis gaps, spherical-bearing details and available installation envelope. Mark the port positions and orientation relative to the mounts.

If the original drawing is unavailable, supply dimensioned photographs and a measurement sheet. Also explain whether the old cylinder is original, previously repaired or already modified. A sample unit can help confirm geometry, but the quotation should still record which dimensions are measured and which remain subject to approval.

3. Define hydraulic performance

• Normal and maximum working pressure, including any short pressure peaks known to the OEM.
• Required push and pull force at the relevant pressure.
• Target extension and retraction speed or cycle time.
• Pump flow and control-valve arrangement where speed or synchronization matters.
• Load-holding, counterbalance or integrated-valve requirements.
• Port thread, port size, port orientation and any manifold interface.
• Acceptable internal leakage, external leakage and drift criteria.
• Whether multiple cylinders must move in sequence or remain synchronized.

Pressure and force should be submitted together. Pressure defines the hydraulic loading, while the required force and mounting geometry determine whether the selected bore and rod are appropriate. The verified Zhenqiang crane-cylinder range is 10–42 MPa, but the RFQ must identify the actual machine requirement rather than selecting the top of the range by default.

4. Describe the mechanical load case

Include the maximum operating load, load direction, lever-arm geometry, dynamic impact, side-load risk, buckling length and whether the cylinder holds a suspended load. Outrigger cylinders require particular attention to eccentric loading and stability. Long telescopic-boom cylinders require alignment, support and deflection information. If the cylinder can reach a hard stop, explain how the system controls deceleration and pressure spikes.

5. State the operating environment and duty cycle

Record the ambient and oil temperature range, working hours per day, cycles per hour, expected service life, outdoor exposure, dust, mud, rain, salt spray, chemicals and storage conditions. The published operating-temperature envelope is −40 to 100 °C. A buyer should not assume that every seal, coating and oil combination covers that entire range; the final material system must be confirmed for the actual environment.

Also state whether the crane works at ports, mines, offshore or marine sites, construction sites, high-altitude locations or emergency-service duty. These details influence rod protection, corrosion control, wiper selection, sealing and inspection requirements.

6. Specify materials and protection without guessing

The RFQ should request the required tube, rod, piston, gland and mounting materials or ask the supplier to propose them against the stated load case. Define rod-surface treatment, coating expectations, corrosion category, paint color and paint system if the machine standard controls them. If a named seal brand or material is mandatory, state it. Otherwise, specify the temperature, fluid, pressure, speed and contamination conditions so the supplier can propose a compatible sealing system.

7. Define inspection, testing and documents

The product record states that the cylinders pass pressure testing before delivery. Convert that general requirement into an RFQ acceptance plan: test pressure, hold time, leakage limit, functional cycling, dimensional inspection, coating inspection and required reports. State whether material certificates, welding records, non-destructive testing, traceability, inspection photos, packing photos or a third-party witness are required. Do not leave certification requirements until after production.

8. Add commercial and logistics information

• Prototype and annual quantity, including expected call-off batches.
• Destination country and delivery location.
• Required delivery date and whether a sample approval stage is needed.
• Incoterm, packing method and export-marking requirements.
• Spare seal kits, service parts and documentation language.
• Warranty and nonconformance process requested by the buyer.
• Drawing ownership, confidentiality and change-control expectations.

Copy-and-paste RFQ template

• Crane manufacturer/model and equipment capacity:
• Cylinder position and function:
• OEM part number or drawing number/revision:
• Длина в сложенном состоянии, длина в выдвинутом состоянии и ход:
• Bore and rod diameter:
• Mounting details and pin dimensions:
• Working pressure and peak pressure:
• Required push/pull force:
• Extension/retraction speed and duty cycle:
• Hydraulic fluid and temperature range:
• Port size, thread, orientation and valve/manifold details:
• Load-holding, drift and synchronization requirements:
• Side load, impact and buckling conditions:
• Environment and corrosion protection:
• Inspection, test and document requirements:
• Quantity, destination, Incoterm and target date:

Before sending the inquiry

Check that every dimension has a unit, every drawing has a revision, and every performance value states whether it is normal, maximum or acceptance-limit data. Separate mandatory requirements from supplier-proposed items. If a field is unknown, write “supplier to propose” or “to be confirmed” instead of copying a value from another crane.