During the R2 outage we carried out repairs to the CW drum screen concrete beams (Drum Screen 3 & 4). The beams had degraded over the years and needed restoring to a condition that removes any operational risk and makes them fit to last the rest of station life. Working with Civil Design Group and the contractor Mansells we devised a combination of concrete and carbon fibre repairs. One of the major challenges was to ensure we created a safe working environment to gain access to the beams. This involved installation of an access system and a series of cradles that provided the working platform.
Picture 1 shows the cradle and concrete beam supporting frame work. (A substantial structure)
Picture 2 shows the frame work with the support chains attached, which were designed to support the concrete beams whilst the repair work was to be undertaken. This was to eliminate the risk of the beam collapsing whilst the operatives were carrying out the structural repairs.
Picture 3 shows one of the eight access cradles being lifted into position above drum screen 3.
Picture 4 shows the cradle being installed into the working position. Due to the complexity of the lift a trial was conducted prior to this at Barnsley. This proved really beneficial as this allowed Apollo and Specialist crane hire to make some adjustments to the lift, which led to the lifting operations on site being carried successfully and safely.
Picture 5 shows the access cradles being lowered into the drum screen chamber
Picture 6 shows the access cradles being lowered into the drum screen chamber from a difference angle
Picture 7 shows the existing rebar once the concrete had been removed.
Pictures 8 & 9 show the new rebar installed to the under side of the concrete beam
Picture 8 (previous) & Picture 9 show the new rebar installed to the under side of the concrete beam.
Picture 10 shows the shuttering being installed.
Picture 11 shows the shuttering being removed form the beam.
Picture 12 shows the repair once the shuttering had been removed
Picture 13 shows the repair and also the cored holes which were to allow the Cathodic protection to be installed.
Picture 14 shows the testing of the cathodic protection being carried out by the Mansell operatives.
Picture 15 shows the Carbon fibre wrap being applied by the Mansell operatives.
Picture 16 shows the beam once all of the repairs have been carried out and the Poxitar coating had been applied to the surface of the beam.
Picture 17 shows the Apollo operatives preparing the cradles to be removed form the chamber.
Pictures 18 & 19 shows one of the cradles being removed form drum screen 4
Pictures 18 (above) & 19 show one of the cradles being removed form drum screen 4
Pictures 20 and 21 show cape roped access team refitting the mesh panels to drum screen after the cradles had been removed.
Pictures 20 (above) and 21 show cape roped access team refitting the mesh panels to drum screen after the cradles had been removed.