The approval process for mechanical equipment drawings follows a six-step closed-loop workflow (based on procurement/engineering practices): ① Supplier submits drawings (2–4 weeks after order placement); ② Buyer reviews (dimensions/tolerances/materials/interfaces); ③ Modification and resubmission (feedback/comments returned); ④ Issuance of “Approved for Manufacture” (AFM authorization to start work); ⑤ Version control (revision markers + history); ⑥ Mutual sign-off (valid only upon signature)—suppliers must not cut material or begin production prior to approval.
I.
Submission (Supplier Submits)
Timing: Submit within 2–4 weeks of PO issuance (based on transformer procurement practices); Content: General assembly drawings, component drawings, electrical schematics, foundation drawings; Format: PDF drawings + STEP models + Bill of Materials (BOM); Version: Revision numbers marked (Rev. A/B/C); Milestones: Design inputs (specifications/interfaces provided by the buyer)—submission milestones must be included in the contract (delays imply delivery risks).
II.
Review (Buyer Reviews)
Dimensions & Tolerances: Critical dimensions, tolerances, and datums (GD&T); Materials: Consistent marking of material grades and surface treatments; Interfaces: Mounting dimensions, piping, and electrical interfaces (alignment with site conditions); Manufacturability: Internal radii, thin walls, and tool accessibility; Conflicts: Contradictions between drawings (based on Neway checklist)—the buyer’s engineering department reviews items point-by-point (critical dimensions highlighted in red for priority inspection).
III. Revise & Resubmit
Comments: Returned via mark-ups on drawings or itemized lists in documents; Resubmission: Supplier resubmits after modification, accompanied by a summary of changes; Iterative Process: Typically 1–3 rounds (more rounds for complex equipment); Timeframe: Deadline for confirmation per round (5–10 working days); Records: Audit trail of comments for each round—comments must be specific (e.g., change “incorrect dimension” to “change flange hole spacing to 160mm”).
IV.
Approved for Manufacturing (AFM)
AFM: Buyer issues a written “Approved for Manufacturing” notice; Authorization: AFM is the sole authorization to commence work (no material cutting, welding, or assembly allowed without approval; Source: TransformerGrid); Conditional Approval: Conditions must be clearly listed (e.g., “release pending sample confirmation”); Rejection: Major deviations may result in rejection and a redesign requirement—approval must be documented (written notice or system record, not verbal).
V.
Version Control
Revision ID: Unique revision number for each version (e.g., Rev. C); Revision History: Details of changes, dates, and authors recorded in the title block (Source: SKF OEM); Change Management: Post-approval changes require a formal process (ECN); Controlled Issuance: Old versions recalled or marked as obsolete; PDM System: Drawings archived and released via the system (Source: CAXA)—loss of version control leads to production chaos (using the wrong drawing version is a root cause of quality incidents).
VI. Dual Signatures
Signatures: Requires dual signatures from the Buyer’s authorized engineer and the Supplier’s Quality/Engineering manager; Responsibility: Signatures signify accountability (design, review, and approval roles must be segregated; the same person cannot perform multiple roles; Source: CAXA); Email Insufficiency: An “OK” via email cannot substitute for a signed document (Source: SKF); Date: Date of signing;
Archiving: Archive the signed copy (serves as the basis for acceptance/claims)—the signed drawing is the only valid version.
VII. Practical Implementation Points
First, incorporate milestones into the contract (deadlines for submission/confirmation); second, prioritize critical dimensions (verify interfaces before details); third, maintain a written record (conduct all feedback and approvals via email or the system); fourth, re-run the process for changes (any modification after approval requires an ECN);
fifth, verify against the approved version upon acceptance (inspect delivered goods against the approved drawings)—Mechanical equipment drawing confirmation involves a six-step process: Submission → Review → Modification → AFM → Versioning → Dual Signatures (work cannot commence without approval; only the signed version is valid).
