Clash Detection & 3D Model Review Workflows for EPC Projects: 30%, 60%, 90% Freeze Milestones

In modern industrial plant design, federating 3D models across piping, civil/structural, electrical, instrumentation, and HVAC requires a rule-based Clash Matrix: - **Test 1: Piping vs. Structural Steel (Hard Clash, 0mm Tolerance):** Identifies pipe centerlines, flanges, or secondary supports physically cutting into structural columns, beams, or bracing. - **Test 2: Insulation Outer Diameter vs. Structural Steel (Clearance Clash, 25mm Tolerance):** Ensures thermal insulation jacket is not compressed against structural steel, which destroys thermal efficiency and causes corrosion under insulation (CUI). - **Test 3: Piping vs. Electrical & Instrument Cable Trays (Clearance Clash, 150mm):** Prevents piping from running directly above open instrument trays, protecting sensitive wiring from thermal radiation or flange leakage. - **Test 4: Valve Handwheel / Stem vs. Walkways & Platforms (Ergonomic Clearance, 500mm):** Verifies full stroke opening without striking handrails or forcing operators into awkward postures.

Clashes fall into three distinct engineering categories: 1. **Hard Physical Clashes:** Two solid geometric objects intersecting in 3D space (e.g., an 8-inch pipe piercing a vertical web stiffener). 2. **Soft Clearance Clashes:** Violation of a required thermal, electrical, or safety buffer zone (e.g., high-voltage electrical conduit routed within 300mm of an uninsulated steam pipe). 3. **Workflow & Maintenance Envelopes:** Encroachment into temporary operational spaces (e.g., piping routed across a heat exchanger tube bundle withdrawal zone or blocking a vessel manway hinge swing).

Formal client model reviews mark project progression: - **30% Review:** Validates plot plan spatial layout, civil battery limits, underground pipe corridors, and major equipment footprint. Clashes are primarily high-level architectural interferences. - **60% Review:** Focuses on main process lines, primary pipe rack routing, inline valves, major cable trays, and structural pipe racks. At this stage, 80% of all interferences must be cleared. - **90% Review (Freeze Gate):** Covers all small-bore piping, secondary steel, instrument impulse tubing, junction boxes, lighting poles, and pipe supports. Achieving zero unresolved clashes is the contractual prerequisite for extracting IFC isometrics.