Hamon UK were awarded a contract in May 2019 following a 3-year tender process to convert RWE Little Barford Power Station, UK to a conventional plume abated Cooling Tower. This 727MW net capacity power station comprises two banks of 14 cells (28 cells total) fed by 14 risers (2 cells per riser). The total flow rate is 41,832m3/hr. The cooling tower was originally designed with a wet / dry pack in crossflow configuration to provide a design plume point of 4°C and 92% RH.

The project

Hamon received the RFQ to repack this cooling tower with the view to restoring the original design duty conditions. As an option, Hamon offered to convert the cooling tower to a more conventional induced draught, plume abated design with tube bundles. The conversion is to be undertaken on a riser-by-riser basis always leaving 26 cells operational.

Due to problems with the original design, the pack could not be cleaned without major intervention and the maintenance of the wet / dry pack cores was almost impossible. As a result, the Client had planned for repacking these towers every 10 years. With the pack in poor condition, we established that the Cooling Water was around 3.4K higher than the original design criteria. The conversion offered an improvement in performance expressed as an improvement against the original design cold water temperature and the ability to adopt conventional cleaning and other maintenance regimes, whilst also improving Legionella Control compliance to modern norms.

Site activities commenced in January 2020.

The challenges

There have been many challenges with the main issues to overcome being:

• · Make best use of the existing EKKI and Redwood structure
• · Unusual bays sizes and structural elevations
• · Incorporation of new FRP structure for the new components
• · Tube bundles could not be located on the usual frames, so mounted on outside frames
• ·  Existing Riser pipe water feed flanges at low level are all different (offset centrelines and varying elevations)
• ·  Restricted access to one long side of the Cooling Tower
• ·  Operating during the COVID-19 pandemic; site was closed for just 4 weeks, resuming 14th April whilst we adapted and implemented new risk control measures to protect the workforce and to ensure essential UK national infrastructure was kept in operation.
• · Incorporation of additional works added by RWE (amendments to Contract)
• · Testing of two cells when all others were operating in old configuration.

The solutions

The first riser has now been completed and with successful interim testing (thermal, plume and drift loss) by Hamon was completed 19th June 2020. The tests show that we have achieved the guaranteed criteria for thermal, plume and drift loss for this first riser.

Health & Safety: to date we have zero Lost Time Accidents and zero First Aid Incidents.