A simple method for lock gates leakage measurement

Didier Bousmar, Gil Zorzan

Friday 3 july 2015

14:45 - 15:00h at Amazon (level 1)

Themes: (T) Water engineering, (ST) Hydraulic machinery and industrial flows

Parallel session: 16E. Engineering - River

Different types of gates and valves can be used for navigation locks equipment. Due to wear and aging, or due to misuse or accidents, the water tightness of the seals of those gates and valves may be deficient. When the lock is on an artificial waterway whose water supply is provided by pumping, each lost volume leads to extra pumping costs. It is thus necessary to estimate the actual leakage in order to plan appropriate maintenance works. Direct measurement of the leakage is difficult: the damaged sections are not always clearly identified, or may be underwater; the leakage discharge varies with the water level in the lock chamber; and successive manoeuvre of the gates may lead to differences in the leakage discharge, as seals compression is not perfectly reproduced. An indirect measurement method was therefore developed based on the recording of water level variations in the lock chamber during one night without traffic, with all gates and valves closed. When the water level in the lock chamber equals the upstream reach water level, the head on the seal of the downstream gate is maximal and the downstream leakage discharge is also maximal. As a result, the chamber will empty and the water level will decrease. The downstream leakage discharge then decreases while the upstream leakage discharge increases. A conceptual modelling of the leakage discharges enables curve fitting and estimation of the discharge for each water level in the chamber. This method has been successfully tested on several locks in Wallonia, Belgium, with different types of gates (mitre, transversal, lifting, flap). Analysis of 10 days time series highlight the variability of leakage discharge due to gate manoeuvring. In some cases, the method could be applied to very short recordings of less than one hour. Lastly, results were satisfactorily compared to ADCP measurement for one lock group.