Adaptation Cooling Water Outfall, Qatar

During a maintenance shutdown in March 2010, diver inspections revealed that the outfall head (T-head diffusor) of a cooling water system was completely lifted of the GRP pipeline. At the area around the outlet box the installed scour protection system was found to be partly washed away with a local scour. Thyssenkrupp Uhde contracted DMC to investigate potential reasons for the failure of the outlet box and to propose repair/adaptation measures to improve the performance of the system.

The detailed assessment of the outfall system revealed that the trigger of the diffusor box failure at the seabed was excessive air entrainment at the weirbox located on land. The high air content led to extreme flow velocities, turbulences and pressure peaks above original design assumptions.
The limited size of the outfall chamber of the weirbox (3x10x20m) did not allow to de-aerate the discharged water of up to 14m3/s. Since an extension of the outfall chamber was impossible a non-standard solution had to be found and assessed in view of feasible installation and reliable operation.

Role DMC

DMC provided advice during the tests and carried out the detailed design entailing examination of the complex jet conditions of the two phase flow at the outfall openings in the sea.