Water hammer and/or mass oscillations may occur. Due to the elasticity of the pipes, the compressibility of the water and of air bubbles, pressures pulsations propagate in closed conduits through the water at a propagation speed being lower than the speed of sound in water of 1440 m/s. If no precaution is taken water hammer may become destructive. For any modification of the control system the effect on pressure pulsations and water hammer must be checked. In systems with open channel transients lead to free surface variations.
etaeval offers its services for transient and unsteady measurements in hydro plants. Typical quantities for unsteady measurements are pressures at various locations, flow rate, levels, power, speed of rotation, valve openings needle or guide vane strokes, etc. Typical sampling frequencies for transient measurements are in the range of 10 Hz to 10 kHz. Higher sampling rates are used for measurements of mechanical vibrations. Simultaneous data acquisition is often needed at distant positions and fiber cable of wireless data transmission are applied.
Properties of unsteady measurements:
- measurements of unsteady signals
- distributes measurements location within the hydraulic system
- suited for pumps and turbines
- analysis of water hammer, surge chamber level, mass oscillations
The combination of prior performed <a href="index.php?transient_simulations_en">transient simulations (water hammer and mass oscillation)</a> and their validation by measurements in the hydraulic system are often of special interest. A validated model allows on site to reduce the closing times to the minimum allowed limits without endangering the power plant and its elements. Such a procedure can be optimized and risk minimized if both, simulation and measurement, are performed by etaeval.