A pulley block is a simple yet highly effective lifting and pulling system that, across many application areas at Darda GmbH, serves as a practical complement to hydraulic tools. Wherever, in concrete demolition, strip-out, rock excavation and tunnel construction, natural stone extraction, or special operations, loads must be moved, held, or finely adjusted in a controlled manner, the pulley block enables precise load guidance—such as securing concrete sections, pulling rock blocks after splitting, or positioning handheld tools and hydraulic power units.
Definition: What is meant by pulley block
A pulley block is understood to be an arrangement of at least two sheaves (upper block and lower block) and a rope or chain that yields a mechanical advantage. The greater the number of load-bearing rope parts, the lower the hand force required, allowing high loads to be moved in a controlled way. In practice, one distinguishes between rope tackles (taljes) with wire or fiber rope and chain hoists. Characteristic features include a suitable attachment at a fixed point, a movable block with a hook at the load, as well as lifting accessories such as shackles or lifting slings. The load capacity is governed by the weakest component in the system and is stated as the permissible working load.
Design and operating principle of a pulley block
A pulley block uses deflection sheaves to create multiple load-bearing parts. The more parts that carry the load, the lower the pulling force at the free end—minus the friction in sheaves and rope. Typical components include the upper block (at the fixed point), lower block (at the load), rope or chain, hooks, swivels, pins, as well as lifting accessories and edge protectors. Rope routing starts at the fixed point, runs alternately over upper and lower block, and ends at the free pulling end with a backstop or holding clamp. An adequate sheave-to-rope diameter ratio is important to limit bending cycles and increase rope service life.
Use in concrete demolition, strip-out, and rock excavation
In controlled deconstruction, the pulley block supports load guidance when tower cranes are not available or when components need only be repositioned over short paths. During strip-out, it can hold small to medium-sized components before they are separated with concrete demolition shears or notched with multi cutters. In rock excavation and tunnel construction, it helps pull split blocks out of the rock mass or lay them down in a controlled manner. In natural stone extraction, it serves as a gentle pulling means for raw blocks that were previously loosened with rock and concrete splitters. In special operations, a manual pulley block enables low-noise and spark-free load movement, which can be advantageous in sensitive environments.
Working with concrete demolition shears
When separating slabs, beams, or wall sections, a pre-rigged pulley block can take the load and limit unwanted tilting or rotation. By lightly pre-tensioning before the cut, the risk of the concrete demolition shear jamming is reduced. After separation, the component can be swung or lowered along a planned path. Robust anchorage points are essential; reinforcing steel alone is often not a suitable load pickup point.
Use with rock and concrete splitters
Splitting creates loosened blocks that may still be stuck. A pulley block acts here as a holding and pulling device: it pulls the block out of the mass in a controlled manner, prevents sudden release, and holds the load until it is safely placed down. Sliding surfaces or skid boards are recommended for the pull path to minimize friction and edge loads on the rope.
Mechanical advantage, friction, and efficiency
Theoretical advantage equals the number of load-bearing parts. Friction in sheaves and the rope reduces efficiency. As a rule of thumb, 5 to 10 percent loss can occur per sheave. Example: A 4-part pulley block with about 10 percent loss per sheave effectively delivers an advantage in the range of roughly 2.7 to 3.2 instead of 4. For planning, conservative values are always used.
- Mechanical advantage increases with the number of parts, but the pull rope must be moved farther.
- Large sheave diameters and high-quality bearings reduce friction.
- Clean, dry ropes with correct lubrication increase efficiency.
Selection: load capacity, rope, and components
Selection is based on load weight, pull distance, environmental conditions, and the intended application. In dusty environments (concrete demolition, tunnel construction), robust ropes and protected bearings are advisable. In wet or chemically aggressive areas, corrosion-resistant materials are recommended. The load capacity of the entire system is decisive; it is determined by the weakest link.
- Design load capacity and safety factor for the highest expected load, including dynamic components.
- Match rope type to sheave: wire rope requires larger sheave diameters than fiber rope.
- Use compatible hooks, shackles, lifting slings, and edge protectors.
- Consider weight and pack size, especially for strip-out with tight access.
- Documented markings and a visual inspection before each use.
Planning and safe application
Careful planning is the basis for safe use—especially when pulley blocks are combined with Darda GmbH tools that introduce forces into the component during cutting or splitting. Shock loads must be avoided; communication and exclusion zones must be defined before starting.
- Estimate the load: consider volume and density (e.g., concrete about 2.4 t per cubic meter) as well as reinforcement content.
- Select fixed points: use only load-bearing, certified anchors or structural points; plan the load path.
- Set up rope routing: protect edges, ensure correct sequencing of the parts, perform a no-load test pull.
- Pre-tension and guide: keep taking up slack constantly while cutting with concrete demolition shears or during splitting.
- Set down and secure: place the load in a controlled manner, relieve the pulley block, and dismantle it.
Practical examples from the application areas
Strip-out and cutting
A wall panel is separated using concrete demolition shears. A compact pulley block is rigged beforehand to a certified ceiling beam and holds the panel under slight tension. After separation, the component is lowered along the egress route without damaging the surroundings.
Rock excavation and tunnel construction
A block loosened with rock and concrete splitters jams in the fracture. The pulley block pulls horizontally along a slide path until the block is free, then guides it to a safe resting position.
Natural stone extraction
After scoring and splitting a raw block, a hand-operated pulley block serves as a finely dosed pulling means to avoid microcracks and remove the block with minimal internal stress.
Special operation in a sensitive environment
Where sparks or exhaust gases must be avoided, a manually operated pulley block can be used to position power units, multi cutters, or tank cutters—with reduced noise and no additional energy source.
Typical mistakes and how to avoid them
- Sheave diameters that are too small increase rope wear.
- Rope routed over sharp edges: always use edge protectors.
- Missing backstop leads to load drift: use suitable holding clamps.
- Incorrect rope routing neutralizes the mechanical advantage: check the sequence of parts.
- Dynamic loads during cutting or splitting underestimated: plan with sufficient reserve.
Maintenance, inspection, and service life
Before each use, perform a visual and functional check for cracks, deformations, burr formation, damaged hooks, or spread shackles. Inspect ropes for broken wires/strands, crushing, and kinks. Keep sheave bearings clean and lubricate according to the manufacturer’s instructions. After defined intervals, a more in-depth inspection should be carried out by competent persons. Clean, dry storage increases service life.
Calculation and documentation
For load estimation, volumes and materials are considered; concrete, masonry, and natural stone differ in density and fracture behavior. Safety allowances must be included for uncertainties. The selected pulley block configuration, component load capacities, and the load path are documented. This supports a reproducible and safe working method in projects with Darda GmbH tools.
Terms and distinctions in everyday use
In common usage, pulley block, tackle, rope hoist, or chain hoist are sometimes used interchangeably. A grip hoist, by contrast, works with clamps and is a pulling device for linear movements. Deflection pulleys change direction and are not complete pulley blocks, but can be used together with them to adapt pulling direction and load path to site conditions.
Legal and organizational notes
The use of pulley blocks falls under general requirements for lifting and moving loads. The applicable rules of technology, operating manuals, and company instructions must be observed. Stated load capacities and component markings are binding. These notes are general in nature and do not replace a case-by-case assessment.