Inter-Discipline Check
IDC
Inter-Discipline Check (IDC) is the EPC engineering review process where every engineering discipline (process, piping, mechanical, instrumentation, electrical, civil, safety) reviews each other's deliverables to surface inconsistencies before formal client release. IDC is the gating quality control between IFR and IFA status and is critical to project risk management.
Full Definition
Inter-Discipline Check (IDC) is the structured review workflow where every engineering discipline reviews the deliverables produced by other disciplines. Process engineering reviews instrumentation deliverables for control philosophy consistency. Instrumentation reviews piping deliverables for instrument-to-line tie-in consistency. Piping reviews mechanical deliverables for nozzle orientation and elevation consistency. Mechanical reviews civil deliverables for foundation loading consistency. Safety reviews all disciplines for HAZOP, safety device, and SIL classification consistency. IDC happens between IFR and IFA status: deliverables released for IFR are circulated for IDC review, comments are consolidated, and the IDC-cleared version goes out for IFA. See the cross-document verification page for the Pathnovo product that automates IDC.
Context & Detail
IDC scope and discipline coverage
IDC review covers process to instrumentation (control loops, interlocks, alarms), process to piping (line numbers, sizes, materials, slope, sloping), instrumentation to electrical (instrument power, cable routing, junction boxes), piping to mechanical (nozzle orientation, elevation, support loading), mechanical to civil (foundation loading, anchor bolt layout, equipment access), all to safety (HAZOP scope, safety device adequacy, SIL classification, emergency response). A typical greenfield refinery runs hundreds of IDC cycles per P&ID, isometric, and equipment package.
IDC comment lifecycle
IDC comments are classified by severity: Major (blocking, requires deliverable revision), Minor (non-blocking, can be addressed in next revision), Observation (informational). Comments are logged in the IDC comment register with reviewer, date, comment text, and proposed resolution. The deliverable owner addresses each comment and the resolution is signed off by the original commenter. Once all comments are closed, the deliverable advances to IFA.
IDC tooling
Traditional IDC workflow uses Adobe PDF markup tools, Excel comment trackers, and email round-trips. Modern EPC projects use document management systems (Aconex, ProjectWise, SharePoint, Documentum) with built-in markup, comment tracking, and audit trail. IDC cycle time typically runs 2-4 weeks per deliverable cycle. AI-powered cross-document verification can compress IDC by surfacing inconsistencies before human review.
Common IDC findings
Recurring IDC findings include: instrument tag inconsistency between P&ID and instrument index, line number mismatch between P&ID and line list, equipment tag mismatch between P&ID and equipment list, valve specification mismatch between P&ID and Piping Material Specification, nozzle orientation mismatch between P&ID and isometric, HAZOP recommendation closure missing in updated P&ID revision. Pathnovo's cross-document verification automates detection of all common IDC inconsistencies.
EPC Usage
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Every greenfield refinery, petrochemical plant, and gas processing facility runs IDC cycles on hundreds to thousands of deliverables. IDC is unavoidable on every EPC project regardless of size.
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P&ID IDC is the most visible: every P&ID revision triggers IDC review by instrumentation, piping, mechanical, electrical, safety, and operations disciplines.
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Indian PSU projects follow PSU-specific IDC conventions with formal IDC comment registers and discipline sign-off matrices. Each major Indian PSU has its own IDC procedure documenting roles, responsibilities, and timeline.
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Multi-EPC packages on mega-projects require coordinated IDC across multiple EPC contractors plus the integrating client engineering team. Interface deliverables (battery limit lines, utility connection drawings) require multi-party IDC.
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Brownfield revamp projects run IDC between existing plant deliverables and new modification scope. The IDC must verify consistency between the AFC baseline and the new IFC scope.
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AI-driven cross-document verification reduces IDC cycle time. Pathnovo's cross-document verification surfaces inconsistencies before human review.
How Pathnovo Handles It
Pathnovo's cross-document verification product automates IDC across 5+ document layers simultaneously: P&ID vs instrument index, P&ID vs line list, P&ID vs equipment list, P&ID vs piping material specification, P&ID vs isometric. The product surfaces every inconsistency as a structured discrepancy report so the IDC team focuses on engineering judgement rather than manual document comparison. Combined with C&E matrix vs P&ID verification, Pathnovo extends IDC coverage to SIS / IEC 61511 safety functions. Used by EPC contractors to compress IDC cycle time from weeks to hours while improving inconsistency detection rate.
Frequently Asked Questions
What does IDC stand for?
IDC stands for Inter-Discipline Check. In EPC engineering, IDC is the structured review process where every engineering discipline (process, piping, mechanical, instrumentation, electrical, civil, safety) reviews each other's deliverables to surface inconsistencies before formal client release as IFA.
Who participates in IDC?
All engineering disciplines participate in IDC review. Process engineering reviews instrumentation control philosophy. Instrumentation reviews piping tie-ins. Piping reviews mechanical equipment nozzles. Mechanical reviews civil foundation loading. Safety reviews all disciplines for HAZOP, safety device, and SIL classification consistency.
When does IDC happen?
IDC happens between IFR (Issued For Review) and IFA (Issued For Approval) status. Deliverables released for IFR are circulated for IDC review by other disciplines. Comments are consolidated, the deliverable owner addresses them, and the IDC-cleared version goes out for IFA. IDC cycles typically run 2-4 weeks per deliverable.
What are common IDC findings?
Recurring IDC findings include instrument tag inconsistency between P&ID and instrument index, line number mismatch between P&ID and line list, equipment tag mismatch between P&ID and equipment list, valve specification mismatch with PMS, nozzle orientation mismatch between P&ID and isometric, and HAZOP recommendation closure gaps in updated P&ID revisions.
How is IDC comment severity classified?
IDC comments are classified by severity. Major: blocking, requires deliverable revision before progression to IFA. Minor: non-blocking, can be addressed in next revision. Observation: informational, no action required. Each comment is logged with reviewer, date, comment text, and proposed resolution in the IDC comment register.
Can AI automate IDC?
Partially. Pathnovo's cross-document verification product automates IDC across 5+ document layers (P&ID vs instrument index, line list, equipment list, piping spec, isometric) by surfacing structural inconsistencies as a discrepancy report. The IDC team focuses on engineering judgement rather than manual document comparison.
What is the difference between IDC and HAZOP?
IDC is a document consistency check across engineering disciplines. HAZOP (Hazard and Operability Study) is a structured safety review that identifies process hazards and operability deviations. IDC verifies that deliverables are internally consistent; HAZOP verifies that the design is safe. Both are mandatory gating reviews on EPC projects but serve different purposes.
Related Pages
Cross-Document Verification
Automate IDC across P&ID, instrument index, line list, equipment list, piping spec, isometric.
C&E Matrix vs P&ID Verification
SIS / IEC 61511 safety IDC for SIF loops.
P&ID Data Extraction
Extract structured data from P&IDs supporting IDC review.
Tag-Document Register
Tag-to-document mapping across disciplines for IDC traceability.
IFR / IFA / IFC / AFC Standard Reference
Document status codes that IDC moves through.
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