Tryckslag

Tryckslag is a term used to describe a sudden transient change in pressure within a fluid- or gas-filled system. It denotes a pressure spike (positive) or a pressure drop (negative) that occurs when flow conditions change rapidly, such as by closing or opening a valve, starting or stopping a pump, or other abrupt boundary movements. In fluids, these events propagate as pressure waves, which can reflect at system boundaries and create complex transient pressure fields.

Causes of tryckslag include rapid valve actuation, pump trips, piston movements in hydraulic or pneumatic systems, ruptures, and other operational transients. The magnitude and duration of the pressure change depend on the system’s compressibility, inertia, and elasticity, as well as the speed of the initiating disturbance. The phenomenon is a central concern in fluid dynamics and acoustics and is often analyzed as a pressure transient or shock in pipelines and vessels.

Measurement and effects: Tryckslag is monitored with pressure sensors and characterized by peak pressure and negative or positive overshoot, rise time, and duration. Large or fast transients can cause mechanical stress, fatigue, pipe ruptures, valve damage, or equipment malfunction, making accurate assessment and mitigation important.

Applications and mitigation: Engineers study tryckslag to prevent damage in hydraulic, pneumatic, and gas systems. Mitigation strategies include surge tanks or expansion vessels, slow-closing valves, snubbers, relief valves, and appropriate damping or control strategies to minimize peak pressures.

See also: water hammer, pressure transient, shock wave, acoustics, fluid dynamics. Etymology: the Swedish term combines tryck (pressure) and slag (strike or spike), reflecting a sudden pressure event.