Frequently Asked Questions on Operation of the Gates designed by GGPL
- When the gates open, do they cause a sudden flood in the d/s channel?
Godbole gates do not suddenly open out fully.
The angle of opening of gate is adjusted by the gate itself to suit the discharge to be passed out safely, while maintaining the u/s water level within the specified limits.
The gate may take several hours or even days to open or close fully, depending upon the rate of rise or fall of water level in the u/s reservoir. Hence sufficient time is always available for people on the d/s side to move to safer places at the times of floods.
- What can interfere with proper functioning of the gates?
- The fear that accumulated silt on the u/s side of the gate near the sill may obstruct the opening or closing of the gate is unfounded as no silt can accumulate near the gate sill due to continuous desilting being caused by the high velocity bottom jet, as long as the gate is open, even to a small extent.
- Entanglement of the floating debris between rubber seals and seal seats at sides or at bottom may prevent the gate from completely closing. Hence leakage of water through the sealing system is sometimes possible. Emergency mechanical hoists can be used to facilitate removal of the entangled debris.
- Excessively tight side seals which are twisted or torn can sometimes prevent complete closure of gates. In such cases, the hoist can be used to close the gate completely to reduce leakage until the seals are changed or properly adjusted.
Thus, except the above two reasons of entanglement of the floating debris & damaged rubber seals which may prevent complete closure, there is no other reason that can interfere with closing of the gate. Moreover the emergency hoist can always be used to ensure complete closure of the gate.
As far as opening of the gate is concerned, it is almost impossible to prevent it by any means, if the u/s water level rises above the designed F.R.L.
- The same gate appears to open at a slightly different levels of u/s water levels at different times, why?
Changes in silt contents cause changes in hydrostatic moments. Similarly, changes in coefficient of friction of rubber seals cause changes in frictional moments, due to these two reasons, a change of a few centimeters in the opening and closing levels are unavoidable
- If at any time on a particular project only some of the gates appear to open, does it mean that the gates which have not opened yet are defective?
Conversely, when the floods are receding, if some gates close earlier while other remain open for a longer period, does it mean that the gates which have not closed earlier are defective?
The number of gates that remain open at any given time depends upon the magnitude of the incoming discharge. A little patience is all that is required.
The remaining gates will open or close as the case may be as soon as the u/s water level changes by a few centimeters. This may take just 10 minutes or even 10 hours, depending upon the rate of change of the incoming discharge.