Drive power describes how much work per unit time is supplied to a system to execute mechanical processes reliably and economically. In practice, it determines how fast and forcefully hydraulic tools operate — such as concrete demolition shears, hydraulic rock and concrete splitters, steel shears, combination shears (Combi-Shears HCS8), multi cutters, tank cutters, or rock splitting cylinders. For the application areas of concrete demolition and special deconstruction, strip-out and cutting, rock excavation and tunnel construction, natural stone extraction, as well as special operations, an appropriate drive power determines cycle times, tool life, energy demand, and result quality.
Definition: What is meant by drive power
Drive power is the provided power of a drive system — typically an electric motor or internal combustion engine — including downstream components such as pump, gearbox, and hydraulic control. It is specified in watts or kilowatts. In hydraulics, usable power is the product of pressure and flow rate, minus losses due to friction, throttling, and conversion losses. A distinction is made between power input (input power), power output (pump output), and the effective power available at the tool tip, taking efficiency into account. Relevant parameters include rated power, continuous power, short-term peak power, and duty cycle.
Hydraulic basics: pressure, flow rate, and efficiency
In hydraulic systems, tool force and speed are derived from pressure and flow rate. System pressure creates force; flow rate determines movement speed. Idealized, the following applies: Power ≈ pressure × flow rate. For cylinder drives, this yields: Force ≈ pressure × piston area and Speed ≈ flow rate ÷ piston area. In reality, these relationships are influenced by efficiencies. Mechanical, volumetric, and hydraulic losses reduce the power arriving at the concrete demolition shear, the splitting wedge, or the cutting edge. High efficiency lowers heat generation, reduces power input, and increases productivity.
Relation between drive power and tool performance
Available drive power sets limits: if the flow rate is insufficient, cycle and return times increase; if pressure is too low, crushing, splitting, or cutting forces decrease. With concrete demolition shears, too little power leads to longer bite-through times and higher thermal load. With rock and concrete splitters, setting and splitting phases are prolonged, affecting takt sequences and precision. Steel shears, multi cutters, combination shears, and tank cutters likewise require sufficient power to maintain a stable cutting speed at consistently high force — especially in heterogeneous cross-sections or high-strength materials.
Calculation and sizing in practice
For design, desired tool forces and target takt times are translated into hydraulic parameters. Practice-oriented principles:
- Determine required force: Material strength, cross-section, reinforcement, crack formation, and the desired separation line define the necessary peak force at the concrete demolition shear or splitting wedge.
- Define required speed: Specifications for takt time, return time, and operator rhythm define the flow rate.
- Derive power: Pressure level and flow rate yield the required drive power of the hydraulic power pack, including safety and efficiency reserves.
- Account for efficiency: Realistically factor in line losses, oil viscosity, valve and throttling losses, hose lengths, and couplings.
- Consider the load spectrum: Continuous vs. intermittent duty, peak loads, and thermal balance influence sensible motor and pump sizing.
Drive power in the application areas
Concrete demolition and special deconstruction
Here, reinforcement density, concrete grade, and component geometry determine the required crushing or splitting force. Higher pressure delivers more force; more flow rate shortens the cycle. A well-balanced drive power avoids unnecessary heat and reduces wear on concrete demolition shears and combination shears.
Strip-out and cutting
In selective deconstruction, controlled, reproducible power is key. Constant flow rates provide predictable takt times; moderate pressure levels protect components when installations near the cut must be preserved. Power reserves help handle unforeseen material changes.
Rock excavation and tunnel construction
In rock, the combination of high peak force and sufficiently fast follow-up is decisive. Rock and concrete splitters benefit from high pressure for splitting wedge forces, while adequate flow rate shortens setting cycles. Robust power helps absorb load peaks in inhomogeneous rock.
Natural stone extraction
Stable pressure values and finely metered feed rates are important for clean separation joints. Constant drive power improves the reproducibility of splitting lines and reduces microcracks.
Special operations
In special situations — confined spaces, elevated ambient temperatures, or long hose lines — drive power must compensate for temperature- and line-induced losses. Mobile hydraulic power packs with appropriate power reserves and matched oil viscosity ensure functionality.
Hydraulic power packs: selection by drive power
Hydraulic power packs — i.e., matching hydraulic power units — provide the system pressure and flow rate that tools such as concrete demolition shears, rock and concrete splitters, steel shears, or tank cutters require. Key selection factors:
- Pressure level: High-pressure hydraulics (e.g., up into the range of several hundred bar) enable high tool forces with compact piston areas.
- Flow rate: Determines takt time and productivity. Larger pumps increase speed but also power input and heat.
- Drive type: Electric or combustion engine depending on power supply, emissions, and mobility.
- Cooling and filtration concept: An adequate oil circuit with high-performance filtration and suitable cooling stabilizes efficiency over the working day.
- Single- or multi-circuit operation: Supplying several tools in parallel requires matched power and the ability to hold pressure.
Concrete demolition shears: influence of drive power on crushing force and cycle
The crushing force of a concrete demolition shear results from hydraulic pressure and the geometry of the drive. Cycle time primarily depends on flow rate. Dense reinforcing steel and thick-walled components require high peak forces and sufficiently fast follow-up. Too little drive power shows up as jerky movement, rising oil temperatures, and increased stress on the cutting edges. Careful tuning of pressure, flow rate, and valve technology ensures controlled separation and lower wear.
Rock and concrete splitters: influence of drive power on the splitting process
Splitting works via the wedge principle: high pressures generate the necessary splitting force, while a stable flow rate accelerates setting and readjustment. In heterogeneous concrete and hard rock, short, strong load impulses improve efficiency, provided the power pack and lines transmit these peaks with low losses. For natural stone extraction, sensitive power metering helps guide splitting lines precisely.
Energy efficiency, thermal management, and efficiency
Any unnecessary throttling converts power into heat. Efficient systems reduce pressure losses in valves, avoid overly long lines, and use a suitable oil viscosity. Good thermal management stabilizes efficiency, protects seals, and extends oil service intervals. Rule of thumb: Bring power to where it is needed — do not burn it off in the bypass.
Operating conditions, maintenance, and oil management
The callable drive power depends strongly on the condition of the hydraulic system. Clean oil, intact filters, properly vented lines, and tight-sealing valves keep pressure and flow rate at setpoint. Temperature window and viscosity should match the environment. Regular seal and coupling checks prevent creeping power losses. For concrete demolition shears, rock and concrete splitters, and other tools, good care ensures reproducible force and constant takt times.
Practical tips for determining power demand
- Characterize the component or rock (strength, reinforcement, moisture, cross-sections, accessibility).
- Define the process (crushing, splitting, cutting) and target takt times.
- Estimate force demand based on material and geometry; plan a moderate safety margin.
- Derive flow rate from the desired cylinder movement times.
- Select the hydraulic power pack according to pressure, flow rate, cooling, and operating environment.
- Check hose lengths, couplings, and valve technology for pressure loss.
- Trial under real conditions; log oil temperature and cycle times and adjust.
Documentation and monitoring of drive power
Continuous recording of pressure, flow rate, and oil temperature makes it possible to detect deviations early and keep drive power stable. In recurring tasks — for example in special deconstruction or natural stone extraction — documented parameters ensure reproducible quality. Tools and hydraulic power packs from Darda GmbH benefit from clear limit values, clean media, and regular condition checks to reliably deliver the planned power to the worksite.