Expansion of the stepped down-pipe gallery in E-CL Mejillones
Client:
Budget:
Project management:
Execution period:
Status:
Location:
Cobra Chile Servicios S.A
2,535,133, 85  €
Alex Ledezma / Cobra Chile Servicios S.A.
September 2013 - July 2014
Completed
Mejillones, Antofagasta (Chile)

Description

Works completion includes the elimination of the turbulent regime originally produced in the water evacuation system diffusers for the cooling circuit water of the two new units at the E-CL thermal power station in Mejillones. These units are designated:

- CTA: Angamos thermal power station
- CTH: Hornitos thermal power station
The turbulent regime in the submarine outflow pipeline diffusers is seen on the water surface as a water geyser from the circuit, which reaches heights of up to four metres when the cooling circuit is operating at maximum.
In order to eliminate this geyser, the Cobra Engineering Department designed two underwater chambers of 20 x 10 x 10 metres, containing hydraulic jumps and designed to produce an outgoing water flow through the outflow pipeline in non-turbulent regime.
These chambers would have to be connected to the original down-pipe (existing down-pipe gallery) and would operate as the system bypass and spillway, buried below the Mejillones beach level and thus hidden from the public.

• Most significant works data:
The reinforced concrete chambers had to be executed on the same area of beach at an approximate elevation of ten metres below sea level, which meant that water was present throughout the works in the construction pits in which a continuous (day and night) dewatering system had to be dimensioned in order to progress with the work.
The new chambers were connected to the main gallery during two plant shutdowns (when the units were stopped in order to carry out scheduled maintenance tasks), each of fifteen days, with the following jobs having to be executed during each shutdown:
- Demolition of the chamber access and exit window, which had to be by hand because the difficult access to the area and required fifteen persons engaged in continuous demolition work, in two 12-hour shifts, seven days a week.
- Execution of the partition wall in the original gallery, the purpose of which is to divert the water flow towards the new chambers.


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