Leaking Penstocks
CLIENT - National Hydroelectricity Power Project
CONTRACTOR - CICO
WORK PERFORMED : July to September 1994
WATER PROOFING OF CHAMERA HTDEL PROJECT
1.) The power house of the chamera
Hydroelectricity Power Project is situated at Khairi in the Chamba district of Himachal
Pradesh, India. The installed capacity of the project is 540 MW. with 3 Turbine generators
of equal capacity. The three generators are fed from a common tunnel which is near the
surge tank into the three penstock tunnels. The project is under the aegis of the national
Hydroelectricity Power Corporation (NHPC) India.
2.) The NHPC officials had been plagued with
continuous water leakages inside the penstock tunnels. Unable to solve this vexing
problem, NHPC officials approached CICO Group of companies to inspect the locations
of water ingress and to suggest immediate remedial measures to stop the water leakages, as
continuous leakage of water inside the penstock could lead to serious damages.
3.) Senior technical personnel of CICO after
inspection suggested the use of POLYGROUT, - a water-reactive expandable chemical
for sealing of the leakage.
LEAKING PENSTOCKS
4.) The surrounding rock
of the tunnels had been grouted by cement grouts through deep holes inside the rock. These
holes are referred as direct holes. However, leakages from these direct holes were more
pronounced in the upper half of the tunnels. In addition, high leakage concentration was
found near the construction joints of the concrete lining of the tunnels.
5.) The rectification work consisted of :
6.) In both the cases
100x6 mm diameter nozzles were used through which POLYGROUT was injected under a maximum
pressure of 2 Kg/Cm2. The nozzles were fixed in the newly drilled holes near the
construction joints or in the direct holes by means of quick setting mortar which attains
stability within 10 minutes of mixing. CICO No.3 alongwith ordinary Portland Cement
provided the Quick setting compound.
7.) In addition to the penstock tunnels some
other spots where water was leaking were also successfully sealed with POLYGROUT. The
spots included anchor bolts of the turbine generator and portions of the vertical walls
and raft of the turbo-generator building.
The work was carried out within a limited period to
the full satisfaction of the NHPC Authorities. |
