When is it convenient to make intermediate maintenance stops for the spindle and how can they be scheduled without affecting deadlines?

Q: When is it convenient to make intermediate maintenance stops for the spindle and how can they be scheduled without affecting deadlines?

Intermediate stops are justified by increasing torque/push trends, loss of feed, high abrasiveness or chamber pressure instability (EPB/Slurry), as well as preventive maintenance milestones for tools, seals and greasing. The periodicity is indicative and depends on DN/L and terrain (e.g., 60-150 m in highly abrasive soils; 150-300 m in mixed; 300-600 m in competent silts/clays). In order not to impact the timeline, they are scheduled in windows synchronized with shift changes and logistics (sludge, supply), running parallel jobs (topographic recalibration, pump overhaul) and using pre-assembled spare parts kits and timed checklists. Re-entry is performed with soft torque/pressure ramps, earth balance verification and recording in the ITP with intervention and QA/QC minutes.

In works of pipe jacking (microtunneling) y Direct Pipe, The intermediate stops are justified by head wear, torque/thrust trends, abrasiveness y pressure conditions. They are programmed in planned windows (logistics/HSE) to inspect, replace tooling, regrease and recalibrate, maintaining the average production of the schedule.

Objective signals for deciding to stop

Machine trends: sustained increase in par y thrust, drop of feed at equal set-point, increase of consumption (foams/sludge).
Terrain and abrasiveness: step by gravels/cobbles, sandstones or hard layers; index of abrasiveness high in polls.
Pressure conditions: instability of chamber pressure (EPB/Slurry), level losses or abnormal leaks.
Geometry and tolerances: need for recalibrate guidance (laser/gyro) or fine corrections before a critical section.
Preventive maintenance: hours/meters of service achieved for spades/cutters, stamps, lubrication y bolts.

Indicative periodicity (adapt to DN/L, terrain and method)

Very abrasive soils (gravels/cobbles, siliceous sands): review every 60-150 m o 20-40 h of effective progress.
Mixed soils (alternations): each 150-300 m o 40-80 h.
Competent silts/clays (low abrasiveness): each 300-600 m o 80-120 h.

These are ranges referencesThe decision is made by trend data (torque/thrust/pressure/returns) and the risk to face a critical stretch without intervention.

How to schedule them without penalizing the deadline (production tactics)

Synchronized windows: aligns the stop with shift changes, arrival of materials or emptying of sludge plant.
Parallel work: while intervening in the spindle, run topographic recalibration, line inspection, pump maintenance and HSE review.
Pre-assembled spare parts packages: spades/cutters, stamp kits, and pernery ready in the well; minimizes downtime.
Timed checklists: target times per task (access, blocking, replacement, testing, start-up).
Intelligent Re-entry: takes up with gentle ramps pressure/torque and pressure/torque land balance to avoid settlements.

Safe sequence (HSE + QA/QC) for shutdown

Blocking and consignment (LOTO) energy/ferro-fluid; atmosphere verification at the front.
Stabilizes the frontPressure stable chamber (EPB/Slurry) or wedges/frame depending on method.
Inspection and replacements: head tooling, stamps, perimeter lubrication, bolts; adjustment of clearances.
Recalibration: guided laser/gyroscopic, total stations, total stations, sensor tests.
Testing and start-up: check-ups of leaks, pressure and returns; registration in the ITP and updating of the as-built of production.

Where to place them in the layout?

Before critical sections: low sensitive infrastructures, areas, areas of NF high or change of lithology.
After completing modulesper beaten length (e.g., every N rings or meters of driving defined in the plan).
In operational accesseswhen the well logistics allows fast lifting/repositioning and safety of the equipment.

Control metrics (to decide to continue vs. stop)

Average torque/thrust and peaks (weekly trend).
Chamber pressure y flow rates (EPB/Slurry).
Wear rate (number of tools/cutters replaced per hour/meter).
Geometric quality (axis/slope deviation) and land balance.

Necessary documents and means

Maintenance ITP with stopping points, responsible parties and target times.
Critical spare parts inventory (with batch traceability).
Registrations torque/thrust/pressure/returns and minutes signed intervention agreements.
Lifting/lowering plan well insurance for consumables and head tools.

If you want us to set up your preventive shutdown plan married to geotechnical and production targeting, our team of geotechnical Technical assistance and engineering can be integrated into the construction schedule and the ITP.

To expand programming criteria and best practices, it is useful to contrast with the BTS/ICE Specification for Tunnelling (3rd ed.), which includes guidelines for maintenance and operational control in mechanized tunnels.