Spider cranes (also known as spider cranes), with their uniquely compact design, exceptional stability, and flexible outrigger system, have become essential equipment for lifting and hoisting in confined and crowded spaces, such as indoor renovations, historic districts, equipment-intensive factories, and courtyard operations. In industrial and mining environments, such as factory renovations, refrigeration equipment installation, and wind turbine foundation construction, limited space, narrow passageways, numerous equipment obstructions, and complex ground conditions are common challenges. Traditional large-scale lifting equipment often makes access and deployment difficult, potentially leading to construction delays and high costs.
The Spider Crane (Mini Crawler Crane), a "small size, big capacity" solution, is an ideal choice for lifting operations in confined spaces thanks to its crawler tracks, narrow width, retractable outriggers, and multi-directional deployment capabilities.
This article will systematically introduce the operating techniques and precautions for spider cranes in confined spaces from a professional perspective, covering four key aspects: pre-operation preparation, site positioning, lifting operations, and site clearance. This article aims to provide a reference for engineers, safety managers, and equipment operators.
1.1 Equipment Selection and Capacity Verification
First, select a model based on the operating environment (space width, aisle height, ground load, and obstacle distribution) and the load (mass, size, shape, center of gravity position, operating radius, and lifting height).
For example, some spider cranes can operate in aisles as narrow as 595 mm.
Verify the equipment's rated lifting capacity, maximum radius, maximum height, and rotation range. Consider the lifting plan and determine the remaining capacity within the specified working radius (i.e., the characteristic that lifting capacity decreases with increasing radius must be taken into account).
Review and familiarize yourself with the machine's operating manual, safety devices, outrigger layout diagram, outrigger pressure distribution, ground contact area, gradeability, luffing speed, slewing speed, and travel speed.
1.2 Technical and Safety Assessment
A site risk assessment should be conducted before operation: check whether the ground is flat and capable of supporting loads; whether there are steps, stairs, or ditches; and whether the floor is a finished surface (such as concrete, tile, or marble). Consider the pressure exerted by the crane on the ground.
Check for environmental obstacles: check for height differences, floor load limitations, and the presence of cables, pipelines, hanging objects, and areas for personnel movement above and around the lifting path.
Develop an operation plan: This should include the lifting sequence, equipment positioning, outrigger deployment method, operating path, personnel deployment, signaling system, and communication methods. If conditions are complex, a virtual simulation or a "trial run" low-height test lift is recommended.
Operator Qualification Verification: Operators must be trained and familiar with the operating procedures for the crane model and safety devices (such as overload alarms, outrigger position sensors, and tilt alarms).
1.3 Equipment Inspection
Before operation, a thorough inspection of the spider crane should be conducted: crawler and drive system, hydraulic system, outrigger (or support leg) assembly, slewing mechanism, boom, wire rope, hook, safety devices, communications equipment, controller, etc.
Inspect the floor condition: for signs of water accumulation, oil stains, cracks, soft soil, or settlement. For finished floors, such as tile or stone, consider installing outrigger pads or outrigger plates to reduce pressure.
Inspect the contact surface between the outrigger pads and the outriggers for integrity and deformation. The configuration should be in accordance with the manufacturer's specifications.
2.1 Equipment Location Selection
When entering a confined space, the optimal access route should be selected based on the aisle width, ceiling or floor height, and load size. The spider crane's narrow width allows for indoor access through doorways, stairs, or elevators.
When in position, ensure that the boom is as unobstructed as possible during operation. There should be ample operating space to the rear and sides, and the crane should avoid contact with walls or obstacles. This ensures unobstructed vision for the operator and safe operation for the signalman.
Ground contact pressure: Because the ground may be weak in confined spaces, the ground's bearing capacity should be analyzed. Spider cranes experience significant variations in ground pressure depending on the outrigger position, so the outriggers should be deployed in areas with good bearing capacity whenever possible.
2.2 Outrigger/Support System Arrangement
Deploying the outriggers is critical to ensuring stability. Spider cranes can deploy their outriggers at various angles and positions to accommodate complex terrain, such as slopes, stairs, and platform edges.
Ensure that all outriggers are grounded and that the pads/outrigger plates are properly positioned. If the outriggers are placed on soft ground or hollow floors, consider adding steel pads or support structures to prevent them from sinking or deforming.
Use a level or onboard tilt alarm system to confirm that the equipment is within a safe tilt range. Modern spider cranes are typically equipped with tilt alarms and operating range limiting systems.
When arranging the outriggers, the most adverse lifting conditions (such as maximum radius, maximum load, camber angle, wind load, etc.) must be fully considered and a safety margin should be provided.
2.3 Isolation of Aisles and Work Areas
When working in confined spaces, it is even more important to isolate the lifting area to prevent personnel from accidentally entering the lifting danger zone. This includes the installation of warning tape, warning signs, lighting, and signal personnel.
Ensure clear visibility and communication between operators and signal personnel. Especially in indoor areas or areas with numerous obstacles, clear operating signals, human-machine separation principles, and prohibiting personnel from approaching the underside of the load should be implemented.
3.1 Attaching and Controlling the Center of Gravity
In confined spaces, loads often include large panels, mechanical equipment, air conditioning units, glass curtain walls, etc., which pose a high risk of center of gravity shift and small margin failure. The center of gravity of the load, the location of the attachment point, the specifications of the lifting straps/chains, and the condition of the lifting rings must be confirmed.
Use appropriate lifting accessories, such as vacuum cups (for glass panels), grippers, and lifting beams, to improve lifting stability and safety.
Before lifting, perform a test lift by slowly lifting the load from a low height to a small distance off the ground to confirm that the load is in good condition, the attachment point is secure, and there is no noticeable sway.
3.2 Lifting, Moving, and Positioning Techniques
Lifting should be performed smoothly, avoiding sudden stops and starts, or sudden speed changes, to reduce load swing and adverse impacts on the equipment's outriggers.
When operating a crane in a confined space, slewing, luffing, telescoping, and horizontal movements should be controlled slowly and precisely to minimize collisions between the load and surrounding structures.
When moving the load, maintain a safe distance from ground obstacles to prevent the load from getting stuck or scratched when passing through confined spaces such as passages, doorways, and stairways.
During the positioning phase, use the micro-speed mode (if available) or remote control to achieve high-precision alignment, which is particularly important indoors or in finished product environments.
When working in confined spaces, the crane's own movement should be minimized. All movements should be completed after the load is positioned as closely as possible to reduce the need for the equipment to move within the confined space.
3.3 Monitoring Loads and Safety Margins
The crane's operating range and the compatibility of the load weight with the crane's capacity must be monitored in real time. Modern spider cranes are equipped with load monitoring systems and tilt alarm systems.
If any abnormal conditions, such as overload, outrigger imbalance, slippage, or tilt, occur, operations must be stopped immediately. The margin for error in confined spaces is extremely low.
Also, environmental conditions, such as wind speed, ventilation (for indoor operations), surface conditions (wet, oily, and contaminated), and personnel evacuation must be monitored.
4.1 Operational Risks and Control Measures
The main risks are load unhooking, swing impact, collision with obstacles, equipment overturning, and personnel accidentally entering the danger zone.
When working in confined spaces and passageways, the crane's swing and rotation must be carefully controlled to avoid contact with structures, glass curtain walls, and personnel passages.
If the ground load is insufficient, the outriggers may sink or slip, leading to overturning. This can be controlled by laying support plates, performing preload tests, and using tilt alarms.
During operations, no unauthorized personnel are allowed to enter the hazardous lifting area, and a safety cordon must be established.
For indoor operations, ventilation, lighting, noise, and emissions (if using a diesel engine) should also be considered. Cables and power supply layouts should be protected from damage by the load.
4.2 Special Environmental Considerations
When operating within existing buildings (such as hospitals, office buildings, and shopping malls), considerations should be given to vibration, noise, floor protection (e.g., stone and tile), and the path of the load through elevators or staircases. Electric models of Spider cranes are suitable for zero-emission, low-noise environments.
When operating outdoors in confined spaces (such as gaps between two buildings or on rooftops), attention should be paid to wind speed, tilt angle, surrounding falling object risks, and nighttime lighting.
4.3 Operator and Teamwork
Operators should be qualified to operate cranes and be familiar with the equipment model, controls, and safety devices.
Signalmen, supervisors, and safety officers must be deployed, and a clear command and signal system must be established to ensure good coordination within the lifting route and surrounding personnel.
A safety briefing should be held before any operation to clarify operating procedures, personnel responsibilities, and emergency measures. If any unsafe conditions are discovered, operations should be suspended.
After the lifting is completed, the outriggers must be removed in reverse order, the boom must be slowly retracted, and the vehicle must be moved at a controlled speed to the evacuation location.
Clean the work area, inspecting the ground for damage, equipment leaks, and any obstructions along the lifting route.
Record equipment usage, abnormality records, and repair and maintenance requirements to ensure proper equipment maintenance.
If the equipment is to be moved to the next work area, the survey, layout, and risk assessment process must be repeated.
The Spider Crane demonstrates Spider-Man-like agility in confined spaces. Its compact structure, flexible maneuverability, versatile outrigger adaptability, and rapid deployment make it an efficient and safe solution for complex operating environments. Every successful hoisting operation is built on a deep understanding of equipment performance, a meticulous assessment of the operating environment, strict adherence to safety regulations, and a reverent awareness of potential risks. To achieve optimal results, a systematic and rigorous operational process must be established, encompassing model selection, safety assessment, outrigger placement, hoisting techniques, personnel coordination, risk prevention and control, and even removal and maintenance.
Operators must continuously refine their skills and internalize safety procedures as second nature, enabling them to navigate confined spaces with ease. Only by ensuring precise technical expertise, rigorous management, and standardized operations at every stage can the advantages of spider cranes be fully realized and the risks of hoisting in confined spaces be minimized.
