Case study 02 · Bolt pocket infilling
Five times the output on a critical-path task
Two simple changes took bolt pocket infilling from about 6,000 a month to 30,000, taking 17 weeks off the programme.
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Case study 03 · Nuclear marine works
92% faster segment preparation, with 2.5 million litres of water saved
Before 4,221 tunnel segments could be coated, each one had to be high-pressure cleaned and, by design, taped. We questioned both. A new cleaning method achieved the same finish in a fraction of the time and water, and the taping step was removed altogether.
At a glance
92%
less time to prepare each segment
2.5m litres
of water avoided, 89% less
£2.5m+
expected savings across both changes
Context
The challenge
Ahead of thick coating, every segment in the cooling system had to be cleaned at 340 bar to remove dust, oil, grease and surface laitance. Each took 45 to 50 minutes and around 675 litres of water, and the wastewater then had to be removed from the tunnels.
The design also called for scrim tape on segments in the tunnel invert: a manual step that added time and created a risk of non-conformance.
Our approach
How we tackled it
We observed both processes during off-site trials, then worked with the designers, subcontractors and materials team to challenge them.
Challenge the specification
We could not see what value the scrim tape added for the client, and it raised the risk of non-conformance and rework after coating. We made that case to the designers, and the step was removed from 1,477 segments.
Trial a better method
Through controlled trials with the subcontractor and materials team, we changed the cleaning method and equipment. The new approach reaches the same surface standard in about four minutes per segment.
Outcome
The results
- Preparation time cut by 92%, from 175 days to 14 across all 4,221 segments.
- Water use cut by 89%, avoiding around 2.5 million litres (enough to fill an Olympic swimming pool), with 89% less wastewater to remove from the tunnels.
- At least 10 weeks off the programme, reaching the value-adding coating step sooner.
- Removing the scrim tape saved 525 hours (65 working days) of programme and a non-conformance risk.
- Expected savings of around £2m from the new cleaning method and more than £550K from removing the tape.
Nuclear marine works
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