Pre-Construction Pipe Acceptance & Site Preparation Precautions

Strict full inspection of each basalt lined pipe before unloading and installation to eliminate defective products entering construction site:

1. Liner Appearance Inspection: Check basalt inner wall for cracks, chips, edge collapse, missing lining and offset. Any damaged liner pipe shall be rejected directly without on-site repair.
2. Dimensional Verification: Measure pipe outer diameter, wall thickness, flange parallelism and liner length; liner maximum retraction offset shall not exceed 2mm as industry standard.
3. Steel Shell Integrity: Confirm outer steel pipe without deformation, dent, penetrating welding hole and rust penetration; check factory hydrostatic test report and MTC certificate.
4. Construction Site Foundation Treatment: The pipe laying base shall be compacted flat, remove sharp gravel, steel bar residues; cushion with sand layer ≥100mm to avoid point extrusion damage to pipe shell.
5. Pipeline Layout Drawing Review: Confirm bend radius ≥3 times nominal bore; reserve straight pipe section of 5~12 times DN after each elbow to reduce direct material impact on basalt liner.

Hoisting, Transportation & Handling Anti-Collision Requirements

Cast basalt liner is brittle ceramic material; hard collision, dragging and eccentric hoisting will cause invisible internal cracks:

Lifting Operation Specifications

Use soft wide canvas slings only; prohibit steel wire rope direct binding pipe body to scratch outer shell and squeeze liner.
Two-point symmetric hoisting, hoisting point distance pipe ends 1/3 pipe length; single-point hoisting forbidden.
Lifting speed slow and stable, avoid sudden braking, swing collision with trench wall, steel support and other pipelines.

On-Site Movement & Stacking Rules

Forbid dragging pipes on concrete, steel plate and gravel ground; use roller cushion for short-distance shift.
Stack pipes with wood block separation between layers, stack height ≤1.2m, fixed anti-slip baffle on both sides.
Pipe ends shall be covered with foam protective caps to prevent liner edge chipping during turnover.

Pipeline Laying, Alignment & Slope Construction Key Points

1. Flat Laying Requirement: Adjacent basalt liner joints must be staggered, no liner protrusion facing slurry/material flow direction; convex step will accelerate local impact wear and liner peeling.
2. Straightness & Coaxiality Control: After pipe in place, adjust coaxiality of two connected pipes, misalignment error ≤1mm; severe offset will generate turbulent flow and stress concentration at liner joint.
3. Slope & Drainage Design: The whole pipeline shall be laid with uniform downhill gradient; set drainage valves at low points to avoid long-term static material deposition inside pipe.
4. Fixed Support Layout: Pipe supports shall be arranged at steel pipe section only; support contact surface pad rubber sheet, avoid rigid local pressure crushing basalt liner.

On-Site Cutting & Special Shaft Machining Control

If standard liner plates cannot fit corner and variable-diameter positions, finish cutting shall be processed off-site by professional manufacturers; random cutting basalt liner on construction site is prohibited, which will destroy liner edge stress balance and cause crack propagation during operation.

Flange & Flexible Coupling Joint Assembly Precautions

Connection Type	Core Construction Control Points	Forbidden Operation
Fixed Flange Connection	Full flat rubber composite gasket between two flanges; cross symmetrical bolt tightening, graded torque locking to uniform compression force	Single-side bolt one-time full tightening, hard metal gasket without buffer
Flexible Expansion Coupling	Reserve thermal expansion gap for high-temperature pipeline; coupling absorbs axial displacement and small angle deviation to release liner thermal stress	Force compression coupling without expansion allowance, long straight pipe without expansion joints

For high-temperature working conditions above 200℃, thermal expansion compensation joints must be installed every 30~50m straight pipeline; temperature change stress will crack continuous basalt liner without buffer structure.

Pipeline Hydrostatic Pressure Test Acceptance Standard

1. Test medium: Clean water without hard solid particles; prohibit slurry, muddy water containing gravel for pressure test to avoid liner scratch.
2. Test pressure: 1.5 times pipeline design working pressure, maintain constant pressure for 15 minutes, no leakage, steel shell deformation and liner separation allowed.
3. Air exhaust before pressure holding: Fully open all high-point exhaust valves to eliminate residual air inside pipe; air compression impact will burst basalt liner instantly during pressurization.
4. Pressure rising speed: Slow boost step by step, each pressure stage hold 3min; rapid one-time pressurization forbidden.

After passing hydrostatic test, drain all residual water inside pipeline and blow dry with compressed air to prevent lining bonding layer damp peeling under long-term water immersion.

Outer Steel Pipe Anti-Corrosion & Post-Construction Protection Measures

External Coating Construction Points

Buried pipeline: 3PE anti-corrosion coating construction after pipeline pressure test acceptance; repair coating damage at welding and flange positions synchronously.
Above-ground pipeline: Two layers red oxide primer + finish silver paint, fully cover steel shell to prevent atmospheric rust erosion weakening outer protection structure.

Post-Construction Pipeline Protection

Mark warning signs along pipeline trench, prohibit heavy vehicle rolling directly above buried basalt pipe.
Complete backfilling immediately after pressure test pass, use fine sand filling around pipe body, large hard stone backfill is strictly forbidden.
Before system formal operation, carry out low-load no-material water circulation pre-run for 2 hours to inspect joint tightness and liner stability.

Common Pipeline Failure Caused By Non-Standard Construction

Non-Standard Construction Behavior	Subsequent Pipeline Failure Consequence
Direct steel wire rope hoisting, dragging pipe on ground	Hidden cracks inside basalt liner, liner peeling after 1~3 months operation
Pipe misalignment, liner convex surface facing material flow	Local severe abrasion, through-hole leakage at liner joint
No expansion joint for long high-temperature pipeline	Temperature expansion stress crack whole section basalt lining
Fast pressurization without air exhaust during hydro test	Instant liner fragmentation, pipeline total failure
Hard stone direct backfill without sand cushion	Outer steel shell dent, liner extrusion collapse