Install CSL Tubes on Piles: Installation and Sealing Checklist

Definition: Install CSL tubes on piles for drilled shafts, guiding contractors and inspectors to verify fixation, continuity, sealing, and complete records—excluding CSL testing—per approved project specifications and authority requirements.

Define tube size, spacing, and fixation to reinforcement cage.
Verify continuity with mandrel passes and tight, pressure-proof sealing.
Capture photos, readings, and signatures for a defensible tube record.
Interactive, commentable workflow with export and QR code verification.

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Checklist

Install CSL tubes on piles is the focused task of attaching, sealing, and documenting crosshole sonic logging conduits on drilled shaft reinforcement cages. This checklist covers CSL tube installation only—fixation, continuity checks, and sealing—excluding any CSL testing operations. It aligns with common practice for drilled shafts and bored piles, using steel or PVC tubes with smooth internal bores, reliable couplers, and pressure-rated caps. By following these steps, you avoid water ingress, concrete contamination, tube collapse, or blocked passages that compromise future sonic logging. You will also ensure consistent tube coverage around the cage, protect tubes during lifting and placement, and produce a complete, traceable tube record for review per approved project specifications and authority requirements. The outcome is a dependable setup that enables efficient, accurate future CSL without rework, delays, or claims. Use this interactive checklist to tick items, add comments and photos, and export to PDF/Excel with a QR-secured record.

This checklist standardizes CSL tube installation on drilled shaft piles, ensuring correct tube sizing, equal spacing, robust fixation to cages, and sealed ends. It prevents concrete ingress and blockage, keeping tubes aligned and continuous for future sonic logging without on-site rework.
Technicians verify continuity using dry mandrel passes, align tops to accessible elevations, and pressure test sealing to a defined hold period. Ties, spacers, and brackets maintain cover and prevent movement during lifting and tremie placement, documented with photos and readings.
The Tube Record consolidates tube IDs, locations, lengths, splice counts, pressure results, and sign-offs. Structured evidence reduces ambiguity, supports quality reviews, and accelerates approvals per approved project specifications and authority requirements, while clearly excluding CSL testing activities.
Interactive online checklist with tick, comment, and export features secured by QR code. Users attach photos, note corrective actions, and generate a shareable PDF/Excel package for engineers and inspectors, creating a tamper-evident trail and consistent installation outcomes across crews and shifts.

Pre-Installation Preparation

1. Review approved drawings for required number, tube diameter, and locations; mark the cage layout accordingly. Acceptance: plan matches mark-up; number of tubes confirmed. Evidence: annotated plan photo and supervisor acknowledgement.
2. Confirm tube type and size (smooth bore, nominal ID 50–63 mm) and compatibility of caps/couplers with concrete/grout. Acceptance: correct materials on delivery docket. Evidence: photos of labels and lot numbers recorded.
3. Verify tube segment lengths achieve toe level plus ≥150 mm projection above cut-off, accounting for splices. Acceptance: total length per design ±50 mm. Evidence: length measurements logged with tape photos.
4. Assemble tools/PPE: 35–40 mm steel mandrel ball, bottle brush, compressed air, thread sealant, butyl/PVC tape, O-ring caps, couplers, SS band clamps, tie wire, spacers, 0–0.6 MPa gauge and hand pump. Evidence: tool list and calibration dates recorded.

Tube Materials and Fabrication

5. Dry-fit tube segments on level ground; check straightness ≤5 mm per 1 m and no dents/kinks. Acceptance: joints mate fully. Evidence: straightedge photo and joint close-ups.
6. Clean bores with brush and air until a white cloth swab emerges clean. Acceptance: no debris or moisture. Evidence: before/after swab photos uploaded.
7. Assign tube IDs (T1–Tn) and tag with weatherproof markers 1.5 m below top. Acceptance: unique IDs visible. Evidence: ID list in Tube Record and tagged tube photos.
8. Assemble couplers per manufacturer; apply compatible thread sealant; tighten to 30–40 N·m using a torque wrench. Acceptance: full thread engagement; torque recorded. Evidence: torque log and joint photos.

Fixation to Reinforcement Cage

9. Position tubes equidistant around cage circumference per plan (e.g., 3–4 tubes typical). Acceptance: spacing tolerance ±10°; tubes parallel to cage. Evidence: layout photo with angle tape or template.
10. Tie tubes to vertical bars at ≤1.0 m intervals using SS strapping or 16-gauge tie wire with protective sleeves. Acceptance: slack ≤5 mm; no sharp bends. Evidence: tie detail photos every 2 m.
11. Install plastic spacers every 1.5–2.0 m to maintain tube cover ≥75 mm from cage edge and clear of tremie paths. Acceptance: cover verified with tape. Evidence: spacer locations photographed and logged.
12. Secure tube bottoms to base ring with rigid brackets to prevent flotation or displacement >10 mm during lifting and lowering. Evidence: photos and short video of trial lift showing stability.

Continuity and Alignment

13. Verify tube plumbness parallel to cage; deviation ≤15 mm over full length. Method: measure offsets at three elevations. Evidence: measurements recorded with annotated photos.
14. Perform dry mandrel test: drop/pull 35–40 mm steel ball through each tube from top to bottom. Acceptance: free passage without snagging. Evidence: per-metre pass/fail log and video snippet.
15. Stagger splices vertically by ≥300 mm between adjacent tubes to reduce congestion. Acceptance: spacing confirmed. Evidence: mid-cage joint photos with measurements.
16. Set tube tops to project ≥300 mm above cut-off elevation; mark each top with elevation. Acceptance: elevation within ±10 mm. Evidence: level/tape reading photos.

Sealing and Protection

17. Install bottom caps with O-rings; apply sealant to threads. Pressure test each tube to 0.2 MPa for 2 minutes (water or air). Acceptance: pressure loss ≤0.01 MPa. Evidence: gauge close-up photo with timestamp.
18. Wrap every joint with butyl tape and overwrap with PVC tape, 100 mm minimum overlap. Acceptance: continuous wrap, no gaps. Evidence: joint labels and wrap photos.
19. Fit top pressure-rated caps with valves; add temporary protective sleeves to prevent concrete ingress; tether caps to cage. Acceptance: caps secured; sleeves intact. Evidence: cap detail photos.
20. Protect tubes during cage handling and concreting: use tag lines; prohibit slings/hooks on tubes; monitor during lowering. Recheck top elevations post-placement within ±10 mm. Evidence: lifting photos and post-pour measurements.

Records and Handover

21. Complete Tube Record: tube IDs, lengths, locations, splice counts, mandrel results, pressure test data, materials lot numbers. Acceptance: all fields filled. Evidence: signed record by foreman and inspector.
22. Install durable as-built tag at cage top with tube IDs and date; ensure legible after placement. Evidence: close-up and context photos showing tag position.
23. After initial set, remove temporary sleeves and re-cap; confirm tubes are unobstructed at tops. Acceptance: no concrete ingress observed. Evidence: photos and short note of condition.
24. Submit as-built package: Tube Record, photos, pressure logs, and mark-ups to the engineer per approved project specifications and authority requirements; archive with QR link. Evidence: exported PDF/Excel and distribution list.

Selecting and Preparing CSL Tubes for Drilled Shafts

Proper CSL tube selection underpins reliable future logging. Use smooth-bore tubes with a nominal internal diameter around 50–63 mm so probes pass freely. Match couplers and caps to the tube material and ensure sealants are compatible with concrete alkalis. Before attachment, clean every bore using a bottle brush and compressed air until a white cloth emerges clean; leftover rust scale or PVC shavings will trap debris during the pour. Check straightness with a straightedge; small kinks dramatically increase drag on the CSL probe. Dry-fit segments on the ground and torque couplers to manufacturer limits for a gas- and water-tight assembly. Assign durable tube IDs (T1–Tn) and log lot numbers and lengths. Field example: a contractor cut rework time by half after instituting a prefit-and-clean step, catching two dented segments and a mismatched coupler before cage lift.

Use smooth bores; nominal ID 50–63 mm.
Clean until a white swab is spotless.
Torque couplers; verify full thread engagement.
Label tubes clearly and record lot numbers.
Reject dented or kinked segments immediately.

Fixation to the Reinforcement Cage Without Obstruction

Fixing tubes correctly keeps them continuous and accessible after the pour. Space tubes equally around the cage to the approved layout, typically three or four per pile depending on diameter. Tie at ≤1.0 m intervals with stainless strapping or protected tie wire; avoid sharp bends. Install plastic spacers every 1.5–2.0 m for consistent cover (≥75 mm from cage edge) and to keep tubes clear of tremie paths, rockers, and lifting points. Rigid brackets at the base prevent flotation when slurry or concrete displaces water. Confirm that splices are staggered between tubes to reduce congestion. Conduct a trial lift and rotate the cage to check that no tube snags rigging or formwork; adjust ties and spacers where needed. This proactive check often prevents crushed tees and lost continuity at the mat during lowering.

Tie at ≤1.0 m intervals; avoid sharp bends.
Maintain ≥75 mm cover using plastic spacers.
Stagger splices by at least 300 mm.
Perform a trial lift to verify stability.
Keep clear of tremie and lifting paths.

Continuity, Sealing, and Documentation That Stands Up to Review

Continuity and sealing determine whether a probe can traverse the tubes after curing. Run a dry mandrel test with a 35–40 mm steel ball to confirm unobstructed passage and log the results per tube. Seal the bottom with O-ring caps and apply thread sealant to joints. Pressure test each tube to 0.2 MPa for two minutes; acceptable loss is ≤0.01 MPa, which reveals pinholes before the pour. Protect top caps with sleeves and ensure they project ≥300 mm above cut-off so future access is simple. After placement, re-check top elevations and remove sleeves only when safe. Compile a Tube Record with IDs, lengths, locations, splice counts, mandrel results, pressure readings, and photos. This package accelerates approvals per approved project specifications and authority requirements while clearly excluding CSL testing operations.

Mandrel pass confirms continuity pre-pour.
Pressure test: 0.2 MPa, 2 minutes, ≤0.01 MPa loss.
Top projection ≥300 mm above cut-off.
Protect caps with sleeves during concreting.
Complete a signed Tube Record with photos.

How to Use This Interactive CSL Tube Installation Checklist

Preparation: assemble tubes, couplers, O-ring caps, torque wrench, mandrel (35–40 mm), hand pump with 0–0.6 MPa gauge, brushes, tape, spacers, SS straps, and PPE; review approved drawings and specifications.
Site readiness: set a clean assembly area, confirm cage lifting points, and brief the crew on handling tubes, tie spacing, and no-hook zones to avoid damage.
Open the checklist, start interactive mode, select project/pile ID, and assign tube IDs (T1–Tn) to prefill the Tube Record fields.
Tick each item as you complete it; attach photos of joints, gauges, elevations, and trial lifts directly from your device for traceable evidence.
Use comments to flag issues (e.g., kinked segment, failed pressure hold) and record corrective actions with timestamps and responsible persons.
Export the in-progress or final record to PDF/Excel for daily reports or submittals; include embedded photos and measurement logs.
Sign-off: capture digital signatures from the foreman and inspector after verifying completeness and compliance with approved project specifications and authority requirements.
Archive the final package in your project system and share the QR-authenticated link with stakeholders for future CSL access and verification.

Install CSL tubes on piles: fixation, sealing, records

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CSL Tube Installation on Piles

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Dmitry Volkov BridgeMasterDmitry

Dec 25, 2025

FAQ

Question: How many CSL tubes should I install on a pile and where should they go?

Most drilled shafts use three or four tubes, spaced equally around the cage to provide full coverage between probe paths. Larger diameters or critical elements may require more. Always follow the approved project specifications and authority requirements, and mark the layout on the cage to maintain equal angular spacing during installation.

Question: Can I use PVC instead of steel for CSL tubes?

Both steel and PVC are used. The critical factors are smooth internal bore, compatibility with couplers and caps, and the ability to remain watertight under pressure. Confirm material selection with the designer per approved project specifications and authority requirements, and ensure sealants and tapes are compatible with the tube material and fresh concrete.

Question: What should I do if the mandrel ball hangs up during the continuity check?

Stop and locate the obstruction by measuring the depth where the ball sticks. Disassemble the nearest joint, clean, and replace damaged segments or couplers. Re-run the mandrel test from both ends until it passes freely. Record the issue, corrective action, and retest results in the Tube Record with supporting photos.

Question: How do I prevent concrete or slurry from entering the tubes during the pour?

Use pressure-rated top caps fitted with temporary protective sleeves and ensure all joints and bottoms are sealed with O-rings and compatible sealant. Tether caps to the cage and keep tubes clear of tremie paths. After placement, recheck elevations and cap integrity, removing sleeves only when safe to do so.

Question: When do I grout the CSL tubes?

Grouting typically occurs after CSL testing and acceptance, which is outside this checklist’s scope. Coordinate timing, materials, and procedures per approved project specifications and authority requirements, and ensure tubes remain sealed and accessible until testing is complete.