3 of the 4 site digesters had aging heat exchangers that were struggling to maintain the desired heat range and were prone to blockages. It would be costly to shut down each digester in turn to change the respective heat exchanger as the client would lose income from reduced CHP output to the National Electricity Grid and have to move sludge’s to other sites incurring increased transportation costs. The existing heat exchangers were located inside a building with little free space around the large units, there was no space to install new units and then remove the old.
To replace the heat exchangers whilst keeping the digesters operational.
The Project Execution
Develop an accurate plan of works to facilitate the removal and replacement of a single heat exchanger unit, whilst keeping the respective digester at temperature. Including, isolation and drainage of water and sludge from the existing heat exchanger unit, overhead crane lift of the existing and new units, onsite make-up of pipework to connect the new unit to existing pipework.
Phase 1 – Execute the plan during an 8 hr window, record any additional risks and requirements during the works progress, commission heat exchanger to the client’s requirements.
Phase 2 – Review the phase one plan and update with any lessons learnt. Prepare the men and materials for phase 3.
Phase 3 – Remove and replace the remaining two heat exchangers simultaneously over a 16hr period utilising 2 teams working 8hr shifts.
GTS were able to reduce the client’s costs by adopting an innovative approach to this project whilst maintaining the required digester temperatures and minimising the loss of CHP output and transportation of sludge’s to other sites.