Concrete Removal
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NOTE : Diver operations shall be continuously monitored and recorded using ROV.
If ROV is not available the hand held or head mounted camera will be
utilised.
1. Measure out where concrete has to be removed and mark positions of
longitudinal and circumferential cut positions.
2. Using eithe r the concrete saw or HP water jet make two circumferential
cuts approx. 1 - 1.2m apart.
3. CAUTION - If the concrete saw is used to cut the concrete coating.
Due to the uneven coating thickness the following procedure will be
used to prevent potential damage to the pipe O.D.
The blade will be set to 12mm less than the minimum depth of coating.
The div er will constantly monitor the depth of cut in the coating while
the cutting is in progress. The 24" pipeline has a weight coat of 50mm
thick, therefore the blade will be set to cut to a max. depth of 38mm.
An inspection will be carried out after each cut.
4. Two longitudinal cuts are made at the 12 o'clock position, 12mm apart.
5. Two further cuts are made at 4 o'clock and at 8 o'clock positions.
6. If HP water jetting technique is used the steel reinforcement bars and
mesh must still be cut manually using bolt cutters or the concrete saw.
7. remove the 25mm wide section of concrete at the 12 o'clock position.
8. Insert the hydraulic spreader and/or wedges to spread the 120 degree
segments of concrete apart. Loosened segments can be driven apart by
driving steel wedges into the saw cuts.
9. Larger sections of concrete will be recovered to the vessel in a work
basket.
2.3 Corrosion Coating Removal
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1. Corrosi on coating can be chipped and scraped off manually and/or
removed using HP water jet.
2. It must be ensured that section of pipe are held within the Seahorse
clamps have already had the corrosion coating removed.
3. Critica l areas requiring a high surface finish fer NDT etc. may be
polished with hydraulic wire brush.