Field Audit Protocol

Thermal Mismatch Verification Procedure v1.0

Purpose

This protocol enables first-line supervisors to verify thermal compatibility of material joins before fabrication begins. Used on active sites in Mount Joy industrial corridor, validated against NIST reference standards.

Objective: Prevent catastrophic joint failure through pre-emptive measurement and gap specification.

Required Equipment

Measurement Suite:
• Digital caliper (±0.01mm accuracy, NIST-traceable)
• Infrared thermocouple array (−200°C to +500°C range)
• Laser distance measurer (±0.1mm @ 10m)
• Strain gauge rosette (for stress mapping)

Reference Materials:
• Certified material samples (each alloy batch)
• Thermal expansion coefficient cards (laminated)
• Gap spacer calibration blocks (0.1mm to 10mm increments)

Digital Companion:
• Tablet running ledger.html offline bundle
• Synced to ledger.json material database

Protocol Steps

STEP 01
Material Identification & Certification

Verify mill certificates for both materials. Cross-reference alloy designation against ledger.json database.

  • Mill certificate present and legible
  • Alloy designation matches design spec
  • Heat treatment history documented
  • α value extracted from certified database
STEP 02
Baseline Dimension Capture

Measure L₀ at ambient temperature (record T₀ ±0.5°C). Take three measurements per dimension, average result.

  • Ambient temperature logged
  • Primary axis length measured (×3)
  • Secondary axis length measured (×3)
  • Standard deviation < 0.05mm confirmed
STEP 03
Operating Envelope Definition

Establish maximum expected ΔT from operational specifications. Apply 1.5× safety factor to nominal ΔT.

  • Maximum operating temperature defined
  • Minimum operating temperature defined
  • Worst-case ΔT calculated
  • Safety factor applied (≥1.5)
STEP 04
Mismatch Computation

Execute calculation using ledger.html calculator or manual formula. Record all intermediate values.

δ = |α₁ − α₂| × L₀ × ΔT_design
Where ΔT_design = ΔT_nominal × 1.5
  • ΔL₁ computed and recorded
  • ΔL₂ computed and recorded
  • Mismatch δ calculated
  • Result compared against failure thresholds
STEP 05
Gap Specification & Physical Verification

Specify required gap tolerance (δ × 1.15). Verify physical spacers match calculation before welding/bonding begins.

  • Gap tolerance specified on drawing
  • Spacer blocks calibrated to tolerance
  • Physical fit check performed dry
  • Supervisor sign-off obtained

⚠ Critical Failure Points Observed in Field

Case 001: Steel-aluminum truss joint, La Grange greenhouse dome (2025-03). Gap omitted entirely. Failed at 147°C differential. Cost: $4.2M replacement.

Case 002: Titanium-copper heat exchanger, Mount Joy pilot plant (2025-09). Gap undersized by 3.2mm. Micro-fracture network detected at 89% design temp.

Lesson: The calculator does not fail. The omission does.

Audit Log Template

Record Format (JSON-compliant):
{
  "audit_id": "TIMESTAMP_SITE_MATERIAL_PAIR",
  "auditor": "NAME_CERT_ID",
  "T0_Celsius": VALUE,
  "L0_meters": VALUE,
  "deltaT_design_Celsius": VALUE,
  "material_primary": "ALLOY_ID",
  "material_secondary": "ALLOY_ID",
  "computed_mismatch_mm": VALUE,
  "specified_gap_mm": VALUE,
  "verification_status": "APPROVED|CONDITIONAL|REJECTED",
  "supervisor_signature": "CRYPTO_HASH"
}

Deployment Checklist

Before this protocol leaves the desk: