{
  "schema": "piping-hdpe-bead-bend/v1",
  "object_id": "c16-hdpe-bead-bend",
  "bead": {
    "H": "height from pipe surface to crest",
    "W": "complete double bead width",
    "W_over_H": [
      2,
      2.5
    ],
    "V_depth_max_over_H": 0.5,
    "uniformity": "size and shape all around joint",
    "surfaces": "external and internal; examine internal if accessible",
    "bead_removal": "prohibited under selected route",
    "molded_fitting_exception": "slight fitting-side irregularity only if pipe-side shape and V correct; not pipe-fabricated fittings"
  },
  "trial": {
    "frequency": "first fusion each day for each operator",
    "production_gate": "pass bend test before installed butt fusion",
    "cooling": "complete before cutting",
    "t": "actual pipe wall thickness, mm",
    "ring_axial_width_mm": "max(300,30*t)",
    "strips": "four at 90 degrees apart",
    "strip_width_mm": [
      {
        "condition": "t <= 17",
        "value": "25"
      },
      {
        "condition": "t > 17",
        "value": "1.5*t"
      }
    ],
    "fixture_offset_each_side_mm": "max(25,4.3*t)",
    "bend_min_deg": 90,
    "tension_surface": "concave interior pipe wall and fusion root",
    "cross_section": "no voids/discontinuities",
    "bent_acceptance": "no fusion-area failures in all four strips",
    "failure_action": "new trial, full cooling and repeat test"
  },
  "paired_unit_qualification": "rounded source inch equivalents retained privately; formulas use coherent mm basis",
  "drawing_procedure_difference": "graphic 1.5t or 25mm minimum versus procedural 17mm piecewise boundary preserved; no silently reconciled threshold",
  "purpose_distinctions": [
    "procedure qualification",
    "bonder qualification",
    "daily trial",
    "production examination",
    "installed pressure test"
  ]
}