Crane Buffer Technical Requirements: JB/T 7017-2015 Guide
JB/T 7017-2015 "Buffers for Cranes" is the technical specification standard for crane buffers. It defines the classification, technical requirements, test methods, and inspection rules for buffers.
Buffer Types & Selection Guide
Kelude offers buffer selection services in accordance with the standard. The buffer types specified include polyurethane buffers (excellent elasticity and weather resistance, suitable for small to medium tonnage up to 50t, applicable speed ≤0.5m/s), spring buffers (simple and reliable construction, suitable for up to 100t, applicable speed ≤0.8m/s), and hydraulic buffers (high energy absorption, smooth deceleration, suitable for large tonnage up to 500t and high speeds up to 2m/s). Buffers are mounted at the ends of crane rails or on the trolley to absorb impact energy at the end of travel, protecting both the structure and equipment.
Buffer selection is determined by the crane's travel speed, mass, and work duty classification. The maximum energy absorption capacity of the buffer must exceed the maximum kinetic energy at impact, with a recommended safety factor of 1.5 to 2 times. All buffers on the same crane must be of the same model. Buffers must maintain proper shaft alignment when contacting the flange, with an offset of ≤±5mm.
The standard specifies the selection calculation for buffers — the maximum energy absorption E must satisfy: E ≥ 1/2 × m × v² × k, where m is the mass of the crane (or trolley) in kg, v is the impact speed in m/s, and k is the safety factor (typically 1.5–2.0). For bridge buffers, the impact speed is calculated at 70%–85% of the rated travel speed; for trolley buffers, it is calculated at 100% of the rated travel speed. The appropriate buffer type should also be selected based on work duty and ambient temperature — polyurethane buffers operate in −20°C to +60°C, spring buffers in −30°C to +80°C, and hydraulic buffers in −10°C to +70°C.
Installation requirements for buffers — buffers must be mounted on the buffer bracket at the end of the crane rail, properly aligned with the opposing buffer or flange, with an offset of ≤±5mm. Mounting bolts must be secured with anti-loosening nuts or spring washers. After installation, the oil level of hydraulic buffers must be checked to ensure it falls between the upper and lower marks on the sight glass. Polyurethane buffers must not come into contact with grease or oil-based substances after installation, as these can cause swelling and aging of the rubber. The contact surface between the buffer and the flange must be flat, with a contact area of no less than 80% of the design value.
Installation & Maintenance Best Practices
Buffers must be installed at the extreme travel limits of the crane bridge and trolley, mounted perpendicular to the guide rail surface. Mounting bolts must be tightened to the torque specified in the Operation Manual. A monthly inspection should be carried out to check for cracks, deformation, or delamination on the buffer exterior. Polyurethane buffers must be replaced when they harden due to aging or develop surface cracking. Spring buffers must be replaced if the spring is broken or has suffered permanent deformation. Hydraulic buffers must be replaced if oil leakage or abnormal reset behavior is detected.
Hydraulic
Hydraulic ≤500t
Hydraulic ≤2m/s
Impact Energy
Alignment ≤±5mm
Spring / Hydraulic
| Buffer Type | Energy Absorption(k J) | Maximumspeed | applicable tonnage | Features |
|---|---|---|---|---|
| polyurethane type | ≤10 | ≤0.5m/s | ≤50t | Elasticity Weather Resistance |
| Spring | ≤30 | ≤0.8m/s | ≤100t | Simple Structure |
| hydraulic type | ≤100 | ≤2.0m/s | ≤500t | High Energy Absorption |
Testing & Inspection Standards
Tests specified by the standard include visual inspection (dimensional accuracy, surface quality), compression testing (measuring buffer force at rated compression, which must fall within ±10% of the design value), and durability testing (no permanent deformation after 1,000 consecutive compression-release cycles). Hydraulic buffers must also undergo a leakage test, holding pressure at 1.25 times the rated pressure for 5 minutes without any leakage.
| inspection items | technical requirements | Cycle | Assessment |
|---|---|---|---|
| Visual inspection | No Cracking Deformation | Monthly | Conforming |
| Compression Test | Force at±10%Within | factory | Conforming |
| Durability | 1000Cycles Without Deformation | type test | Conforming |
| Sealing Durability(Hydraulic) | 1.25Times×5min | factory | No Leakage |
Standard maintenance requirements for hydraulic buffers — hydraulic buffers must reset automatically after each stroke, with a reset time of ≤30s. If the buffer fails to reset properly, inspect the hydraulic system's sealing integrity and the piston rod's freedom of movement. Hydraulic oil in the buffer must be replaced every 2 years. The buffer mounting base must have sufficient strength and stiffness to prevent visible deformation during impact.
Frequently Asked Questions
Q: What are the functions and types of crane buffers?
A: Buffers are mounted at the ends of crane rails or on the trolley to absorb impact energy generated when the crane reaches the end of its travel. Common types include polyurethane buffers (good elasticity and weather resistance, ideal for small to medium tonnage), spring buffers (simple and reliable construction), and hydraulic buffers (high energy absorption, smooth deceleration, suited for large tonnage and high-speed applications).
Q: How are buffers selected?
A: Selection is based on crane travel speed, mass, and work duty classification. The maximum energy absorption capacity must exceed the peak kinetic energy at impact, with a recommended safety factor of 1.5 to 2 times. Applicable speeds: polyurethane buffers ≤0.5 m/s, spring buffers ≤0.8 m/s, and hydraulic buffers ≤2 m/s.
Q: What are the installation requirements for buffers?
A: Install buffers at the extreme travel limits of the crane bridge and trolley, mounted perpendicular to the rail surface. All buffers on the same crane must be of the same model. Maintain shaft alignment with the contact flange within an offset of ≤±5 mm. Tighten mounting bolts to the specified torque.
Q: How should buffers be inspected and maintained?
A: Perform monthly inspections for visible cracks, deformation, or delamination. Replace polyurethane buffers that show signs of aging, hardening, or cracking. Replace spring buffers if the spring is broken or has permanent deformation. Replace hydraulic buffers if oil leakage or abnormal reset behavior is detected.
