Assesment of the real penstock safety margin during transient operation
Overload Detection Module (ODM)
The overload detection module of HYDROSURGE software performs continuous diagnosis of any pressure event to detect the risk of exceeding the admissible maximum pressure over each section of the penstock.
From only one pressure tap on downstream end of the penstock, inside the plant, an assessment of the impact of the transient along each point of the penstock is conducted to detect potential security risk in each section.
So, the phenomena detection is performed in each transient signals thanks to data extracted by SPM:
- ODM detects any Mass Water Hammer phenomena to determine if the measured pressure on the penstock does not exceed the admissible maximum pressure profile,
- ODM detects any Wave Water Hammer phenomena (or rapid water hammer) to determine if the speed of the transient flow drop will not create a propagating pressure surge. This wave could exceed the admissible maximum pressure level over upstream sections of the penstock and damaging its structure.
- ODM detects any risks of Water Column Separation phenomena to determine if the speed of a sudden increase in flow rate leads to a propagating pressure drop wave. The depressurization could lead to cavitation over the upstream sections of the penstock and finally a large void cavity. This cavity that collapses when the pressure recovers causes strong overpressure in upstream sections of the penstock.
- ODM detects any risks of resonance by checking if the cyclical levels of the pressure are properly amortized. If not, these cycles drive to self-sustained pressure fluctuations and dangerous structural fatigue damage.
The mass water hammer phenomenon is only related to the inertia of the water column located upstream of the component which cuts the flow. Closure time is longer than the return time of the reflected wave from the top of the penstock.
The affected area is meanly the downstream part of the water system: penstock sections, manifolds, unit casings.
back to to phenomena
The wave Water Hammer phenomenon results from a quick drop in flow. The closure time is shorter than the return time of the reflected wave. Because of the wave propagation, the affected area is meanly the upstream sections of the penstock. This phenomenon is related to the overall compressibility of the water in the penstock.Thus, safety requires to quantify the maximum pressure profile reached along the penstock for each transient event.
HYDROSURGE is designed to detect early signs which may lead to Wave Water Hammer phenomena.
Water Column Separation phenomenon resulting from a rapid increase in flow. The opening time is shorter than the return time of the reflected wave. The affected area is meanly the upstream sections of penstocks. Thus, hydro safety requires to quantify the minimum pressure profile reached along the penstock for each transient event.
HYDROSURGE is designed to detect early signs which may lead to Water Column Separation phenomena.
Self sustained cyclical pressure fluctuations may cause low-cycle fatigue damages of penstocks. The whole sections of the penstock are affected.
HYDROSURGE is designed to detect early signs of behaviours which may lead to self-sustained cyclical pressure fluctuations for each transient event.
- See a visual of a known case of hydro acoustic penstocks resonances