{"id":19080,"date":"2025-10-11T12:54:34","date_gmt":"2025-10-11T10:54:34","guid":{"rendered":"https:\/\/www.darda.de\/injection-pressure"},"modified":"2026-04-02T16:06:03","modified_gmt":"2026-04-02T14:06:03","slug":"injection-pressure","status":"publish","type":"page","link":"https:\/\/www.darda.de\/en\/knowledge\/injection-pressure","title":{"rendered":"Injection pressure"},"content":{"rendered":"
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The term injection pressure describes the local pressure acting at the contact surface between tool and workpiece when hydraulic forces are transferred onto a limited area. In the practice of demolition, deconstruction, and rock excavation, injection pressure largely determines whether concrete breaks in a controlled manner, steel is separated, or natural stone splits along existing planes of weakness. For applications by Darda GmbH – such as with concrete demolition shears or rock and concrete splitters<\/a> – the safe determination, adjustment, and monitoring of this pressure is crucial for efficiency, precision, and component preservation.<\/p>\n

Core idea:<\/strong> system pressure provides energy, whereas injection pressure<\/em> focuses that energy at the interface to initiate cracking, plastic flow, or separation. Clear target values, reproducible settings, and continuous observation of the process improve outcomes and reduce rework.<\/p>\n

Definition: What is meant by injection pressure?<\/h2>\n

Injection pressure is the contact pressure<\/em> p between an acting force F and the effective contact area A (p = F\/A). It occurs where jaws, wedges, blades, or shears transfer load into the workpiece. Injection pressure is not identical to the system or hydraulic pressure in the power unit; it is the result of force transmission (cylinder area, lever kinematics, wedge geometry) and the real, often dynamically changing contact area. In concrete, sufficient injection pressure leads to microcracks, crack initiation, and controlled separation. In steel, it determines whether plastic flow begins and a shear or separating cut succeeds. In rock, injection pressure induces radial tension around the borehole that is used for splitting. Units and scale:<\/strong> contact pressure is typically expressed in MPa (N\/mm\u00b2); local maxima can substantially exceed average stress if contact is highly concentrated.<\/p>\n

Physical fundamentals and distinction from system pressure<\/h2>\n

Hydraulic power units<\/a> generate system pressure, which is translated into forces via cylinders. The resulting force acts through tool geometries (jaw levers, wedge faces, cutting edges). Decisive is the local contact pressure<\/strong> on the workpiece: it depends on the real contact (roughness, positive fit, edge radius) and load distribution during deformation. The smaller the effective contact area, the higher the injection pressure – up to the point where material limits, safety requirements, or tool wear impose constraints. In practice, transient effects (dynamic loading rate, slight misalignment, stick-slip) can change contact areas milliseconds before separation and thus shift pressure peaks.<\/p>\n

Injection pressure in application: concrete demolition shears and stone and concrete splitters<\/h2>\n

Across the Darda GmbH portfolio, different tools rely on injection pressure as their operating principle. Two central examples are concrete demolition shears as well as stone and concrete splitters; in addition there are combi shears, multi cutters, steel shears, tank cutters, and special stone splitting cylinders. Correct positioning, stable support, and controlled pressure ramp-up improve repeatability and reduce unintended collateral effects.<\/p>\n

Concrete demolition shears<\/h3>\n

Concrete demolition shears transfer hydraulic force through jaws into reinforced concrete. Serrated contact surfaces concentrate injection pressure to crack the concrete cover and expose the reinforcement. Balancing sufficiently high contact pressure with the protection of adjacent components is essential, for example in concrete demolition and special deconstruction or during strip-out and cutting. Edge radii, tooth wear, and jaw overlap influence how quickly microcracks coalesce into a through-crack; timely repositioning prevents overloading of reinforcement or attachments.<\/p>\n

Stone and concrete splitters<\/h3>\n

Splitters use wedges and counter-wedges to apply injection pressure in boreholes to build radial tensile stresses. Critical factors include wedge angle, lubrication, borehole diameter and depth, as well as the homogeneity of the material. In rock excavation and tunnel construction and in natural stone extraction, precise injection pressure enables controlled, low-vibration rock removal. Consistent borehole quality and correct standoff from free faces accelerate crack initiation and produce straighter split planes.<\/p>\n

Other tools<\/h3>\n

Combi shears, multi cutters, steel shears, and tank cutters apply injection pressure at cutting edges or pressing faces to shear or separate cross-sections. Stone splitting cylinders focus pressure in linear contact zones, for example in natural stone sizing or special operations. Matching blade clearance and support conditions to the material thickness improves cut quality and reduces burr formation.<\/p>\n

Influencing variables on injection pressure<\/h2>\n