JB/T 5315-2019 Underslung Crane Standard Explained
JB/T 5319-2015 "Underslung Cranes" is the product standard for underslung crane systems. It defines the classification, technical requirements, test methods, and inspection rules for underslung cranes, and is applicable to electric-hoist-type single-girder underslung cranes and double-girder underslung cranes operating on I-beam rails.
JB/T 5319-2015 is the product standard governing underslung cranes, covering their classification, technical requirements, test methods, and inspection rules. Underslung cranes run on rails suspended from the factory building structure or on dedicated support tracks, offering a compact footprint and flexible operation. They are widely used for material handling along production lines and in warehouses.
Product Classification and Structural Features
JB/T 5319-2015 classifies underslung cranes into two main types: Single-girder underslung cranes — the electric hoist travels along a single I-beam rail, with a rated lifting capacity of 0.5–10 t and spans of 3–12 m. This is the most widely used underslung crane configuration. Double-girder underslung cranes — two rails each support a main girder, and the electric hoist travels on the girders. These offer rated capacities of 5–16 t and spans up to 15 m, making them suitable for applications requiring higher capacity or wider spans.
Core structural components of underslung cranes: Suspension device — connects the rail to the main girder via a wheel bogie or connecting plate, with the travel wheels running on the lower flange of the I-beam. Main girder — fabricated from I-beam or H-beam sections (box girder for larger spans). Electric hoist — travels along the lower flange of the main girder (CD1 or MD1 models). Operation mode — floor pendant control, radio remote control, or cabin operation.
Technical and Safety Requirements
Technical requirements specified in the standard: Main girder deflection — under rated load, the main girder deflection must not exceed span/600 (consistent with the general-purpose bridge crane standard). The contact between the suspension device's travel wheels and the lower flange of the I-beam must be uniform, and the clearance between the wheel flange and the I-beam web plate must not exceed 3 mm. The electric hoist must be securely mounted, with connection bolt torque to the main girder meeting design requirements.
Safety requirements: The crane must be equipped with a hoisting height limiter (automatically cutting hoisting power when the hook reaches the upper limit), travel limit switches (stopping the trolley at both ends of the rail), and an overload limiter (providing an alarm and cutting hoisting power under overload conditions). Underslung cranes must also be fitted with fall protection — safety chains or anti-drop wire ropes at both ends of the main girder to prevent accidental detachment.
Rail and Suspension System
Requirements for the suspension rail: The rail must be made of I-beam (selected based on span and wheel load), with a straightness deviation of no more than 2 mm per 2 m and a cumulative deviation of no more than 10 mm over the full length. The height difference at rail joints must not exceed 1 mm. End stops must be installed at both rail ends (with a height of at least 1.5 times the wheel radius). The travel wheel diameter of the suspension device is determined by load-bearing capacity, and wheels are typically made of cast steel or ductile cast iron.
Suspension system connections: Suspension bolts must be Grade 8.8 or 10.9 high-strength bolts, with tightening torque applied per bolt specification. The spacing between suspension attachment points to the factory building structure is typically 1.5–2.5 m. The load at each attachment point must not exceed the design load-bearing capacity of the building structure — a structural capacity verification of the factory building is mandatory before installation. Kelude can provide pre-installation building assessment services for underslung crane systems.
Testing and Inspection
Factory acceptance tests: No-load test (all mechanisms operate smoothly without jamming), static load test (1.25 times rated load applied for 10 minutes to check main girder deflection and permanent deformation), and dynamic load test (all mechanisms operate continuously under 1.1 times rated load). Type tests are conducted every 5 years and include additional fatigue life and durability testing.
In-service inspections: Daily checks for loose rail connection bolts, travel wheel wear, and proper brake operation. Monthly inspections of main girder deflection (measured under no-load conditions) and the function of all safety devices. An annual comprehensive inspection (including static load test) is required. Underslung cranes in service for more than 15 years must undergo a safety assessment.
Rated Lifting Capacity
0.5~16t
Span Range
3~15m
Work Duty
A3~A6
Travel Speed
10~30m/min
Lifting Speed
4~8m/min
Operation Mode
Pendant / Remote / Cabin
Kelude Heavy Industry: Overhead & Gantry Crane Solutions
Kelude Heavy Industry specializes in the design and manufacture of heavy-duty overhead cranes, gantry cranes, and electric hoists. Our equipment is engineered for reliable performance in demanding industrial environments, from steel processing and shipbuilding to general manufacturing and logistics.
Frequently Asked Questions
Q: What is the typical lead time for a standard overhead crane?
A: For single-girder cranes up to 20 tons, lead time is typically 6–8 weeks. Double-girder and custom-engineered cranes generally require 10–14 weeks, depending on configuration and optional features.
Q: Do you provide installation services in the US and Europe?
A: Yes, we have certified installation crews available for both overhead and gantry crane projects. We also offer full project management, including foundation drawings, electrical hookup, and load testing.
Q: Can your cranes be retrofitted with remote control or anti-sway systems?
A: Absolutely. Most of our cranes can be upgraded in the field with radio remote control, variable-frequency drives, and anti-sway modules. We provide detailed retrofit kits and technical support for your maintenance team.
Q: What safety standards do your cranes comply with?
A: Our cranes are designed to meet ISO 4301, ISO 12480, and IEC 60204-32 for electrical equipment. For explosive atmospheres, we offer ATEX and IECEx certified hoists and crane packages.
Q: Do you offer spare parts for older crane models?
A: Yes, we maintain a comprehensive inventory of spare parts for cranes manufactured in the last 20 years. If a part is not in stock, we can manufacture it to original drawings within a short turnaround.
Q: What is the warranty period on your cranes?
A: All new cranes come with a 24-month warranty covering workmanship and materials. Extended warranty and preventive maintenance plans are available upon request.
Q: Can you help with crane inspection and safety audits?
A: Yes, our service engineers can perform thorough inspections, load testing, and risk assessments to ensure your equipment meets current safety regulations and operational standards.
| Parameter | underslung crane | General purpose bridge crane |
|---|---|---|
| Crane Rail Support | Factory building Girder orsuspension rail | Floor-mounted Crane Railor Load-bearing Beam |
| Footprint | Compact(Space-saving) | Large(Requires Independentrail foundation) |
| Span | ≤15m | ≤35m(Standard) |
| Lifting Capacity | 0.5~16t | 5~500t |
| Operation Mode | Pendant Control Primary | Cab Operation/Remote Control |
| Application Scenarios | Workshopproduction line, Warehouse | Workshop, Storage Yard, Warehouse |
FAQ
Q: What is the main difference between an underslung crane and an overhead crane?
A: An underslung crane runs on rails mounted to the factory roof structure or on a dedicated suspension rail system, freeing up all floor space. It is typically used for lighter loads and shorter spans (≤16t/≤15m). An overhead crane, by contrast, operates on rails supported by load-bearing beams or a rail foundation and can handle much heavier loads—up to 500t. Because the wheel loads of an underslung crane are transferred directly to the building structure, the factory's load-bearing capacity must be verified before installation.
Q: What are the rail installation requirements for an underslung crane?
A: The suspension rail must be made of I-beam or H-beam sections (selected based on span and design loads). The rail straightness deviation must not exceed 2mm per 2m. At rail joints, the vertical misalignment must be kept within 1mm. Connection bolts securing the rail to the factory roof structure must be Grade 8.8 high-strength bolts. Both ends of the rail must be fitted with end stops and buffers.
Q: What safety devices are required on an underslung crane?
A: The following safety devices are mandatory: a hoisting height limit switch, a travel limit switch, an overload limiter, buffers, and anti-derailment devices (rail end stops). In addition, an underslung crane must be equipped with a secondary fall-protection system—safety chains or safety wire ropes installed between the main girder and the rail to prevent accidental derailment.
Q: What should be included in the daily inspection of an underslung crane?
A: Daily checks: inspect rail connection bolts for loosening, check travel wheels for abnormal wear, and verify that the hoisting mechanism brake operates correctly. Weekly checks: inspect runway rail straightness and joint condition, and check the connections between the suspension beam and the rail. Monthly checks: test the functionality of all limit switches, verify overload limiter sensitivity, and inspect the rail for wear and deformation.
