Is an 8-Ton Spider Crane Enough for a 21 m Lift? 5 Checks Before Upsizing
A high-level installation does not automatically require a larger crane. For steelwork, rooftop equipment, curtain-wall installation or industrial maintenance, the right choice depends on the load and lift geometry—not height alone.
The Onchtech 8-ton spider crane specifies an 8-ton rated lifting capacity, a maximum above-ground lifting height of 21 m and a maximum working radius of 18 m. Its compact tracked chassis can support access to areas where larger lifting equipment may be difficult to position.
A 21 m lift is a suitability question, not a capacity guarantee. The published maximums do not establish that the crane can lift 8 tons at 21 m, or at an 18 m radius. Confirm the complete lift against the applicable manufacturer load chart, equipment configuration and site-specific lift plan.
What the published specifications tell you
These specifications provide an initial screening reference. They describe separate equipment limits and dimensions, not a combined operating point.
| Parameter | Published specification | Assessment relevance |
|---|---|---|
| Rated lifting capacity | 8 t | Not the capacity at every radius or boom configuration. |
| Maximum above-ground lifting height | 21 m | Check usable hook height and installation clearance. |
| Maximum working radius | 18 m | Does not establish simultaneous maximum height and reach. |
| Machine weight | 8.7 t | Relevant to access routes, transport and supporting surfaces. |
| Overall dimensions | 6.15 m long × 1.6 m wide × 2.25 m high | Check entrances, turning space and overhead obstructions. |
| Travel system | High/low-speed hydraulic drive; 350 mm rubber tracks | Assess route suitability separately from lifting setup. |
| Outrigger system | Two-section legs; manual swing-out and hydraulic support; maximum extension dimension of 7,000 mm | The deployed lifting footprint is substantially larger than the chassis width. |
Five checks before selecting a larger crane
1. Establish the total suspended load
Start with the verified weight of the item being lifted. Include slings, shackles, lifting beams and other below-hook equipment. Apply hook-block and accessory deductions as required by the applicable load chart.
Decision point: Use the complete load calculation, not the component’s nominal weight. Confirm the centre of gravity and lifting points so that the rigging arrangement is suitable.
2. Measure the required working radius
Working radius is the horizontal distance from the crane’s centre of rotation to the vertical load line. Measure it at pickup, along the planned movement and at final placement. The most demanding position may occur between the start and finish.
Decision point: Assess the full load path against the chart. A closer setup position may improve suitability, but only where access, ground support and outrigger deployment permit it.
3. Check lifting height and clearance together
A component’s installation elevation is not necessarily the required hook height. Allow for the component’s dimensions, rigging height and clearance above parapets, steelwork or other obstacles. Check boom clearance throughout the movement as well.
Decision point: If the installation point is 21 m above the setup surface, the required hook position may be higher than 21 m. Do not assume the published maximum height makes that installation feasible.
4. Verify capacity in the applicable load chart
Use the manufacturer load chart for the actual machine and planned configuration. Check the relevant radius, boom length, operating sector, outrigger arrangement and any accessory-specific requirements or deductions.
Wireless remote control, a load-moment controller and a hydraulic fly jib are listed as optional equipment. Their availability does not establish additional lifting capacity; a fly-jib configuration requires its own applicable capacity information.
Decision point: The supplied product specifications do not include a load chart. A permissible load at 21 m cannot therefore be calculated from these specifications alone.
5. Confirm access, setup space and ground support
The 1.6 m machine width helps with access screening, but it does not define the space needed for lifting. Verify the complete travel route, deployed outrigger footprint, overhead clearance and separation from other site activities.
Ground or structural support must be assessed for the applicable travel loads and outrigger reactions. For floors, roofs, slopes or locations near underground services, obtain a site-specific assessment rather than relying on machine weight alone.
Decision point: Rubber tracks and adjustable supports do not make every surface suitable. Confirm permitted setup conditions, support arrangements and operating limits before lifting.
When should you consider another crane?
Consider a larger crane or a different lifting arrangement when the verified load exceeds chart capacity at the required radius, the required hook height or clearance is unavailable, or the site cannot support the approved setup.
A larger capacity rating alone may not resolve the problem. Compare candidate equipment using the same load, lift path, geometry and site constraints. Where practical, review positioning or rigging changes with the lift planner before changing equipment.
Common questions about a 21 m lift
Can this spider crane lift 8 tons to 21 m?
That is not established by the published specifications. The 8-ton rating and 21 m maximum height are separate limits. Capacity must be confirmed for the actual lift geometry and configuration.
Can maximum height and maximum radius be used together?
Do not assume so. Confirm the achievable height-and-radius combination using the applicable working-range information, then verify the load against the load chart.
Is it suitable for rooftop or indoor equipment installation?
Rooftop lifting and workshop equipment relocation are listed applications. Suitability for a particular project still depends on access, structural capacity, lifting geometry, ventilation where relevant, and the approved lift plan.
Request a configuration-specific assessment
Onchtech, the equipment brand of Hunan Hongchang Machinery Co., Ltd., offers engineering machinery manufacturing and customized OEM/ODM/OBM cooperation. For this 8-ton spider crane, share the following information to support product selection and a configuration-specific quotation:
- Verified load weight, dimensions, lifting points and rigging details.
- Pickup and placement elevations, working radii and proposed load path.
- Access dimensions, obstacles, setup-space measurements and site photographs.
- Available ground or structural assessment and project location.
- Required engine specification, local compliance requirements and optional equipment.
Ask for the applicable load chart and working-range information before confirming selection. Final lifting suitability should be established by qualified personnel using the machine documentation and a site-specific lift plan.
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