Classification and tiered management of changes
Scientific classification and tiered management of MEP engineering changes are the foundation for controlling the impact of changes. According to the classification systems of GF-2017-0201 and GB 50500, MEP engineering changes can be divided into three major categories: design changes, construction scheme changes, and contract condition changes. Design changes are the most common type of change, including modification of design drawings, adjustment of technical parameters, replacement of equipment models, and optimization of pipeline routing. From the perspective of impact severity, they are classified as follows: general changes (cost within RMB 50,000 or schedule impact within 3 days) are approved by the supervision engineer; important changes (cost of RMB 50,000–200,000 or schedule impact of 3–10 days) require joint approval by the owner's representative and the design unit; major changes (cost exceeding RMB 200,000 or system scheme adjustment) require approval by the owner's senior management.
Approval process and time-limit control for change visas
Standardized approval processes and strict time-limit control are the core elements of change visa management. Change visas should follow the basic principle of approval before implementation. The complete process includes six steps: change initiation, technical review, cost estimation, tiered approval, implementation tracking, and settlement confirmation. The contractor should submit the change price report within 14 days after the change instruction is issued, and the owner should confirm it within 14 days after receipt. The owner should establish a change time-limit management ledger to avoid passive acceptance due to overdue periods. Marriott MIDS requires the complete process of change visas not to exceed 30 days, and major changes not to exceed 45 days.
Cost accounting and dispute resolution mechanism
The accuracy of change visa cost accounting and the dispute resolution mechanism are important guarantees for cost control. Change cost accounting should be based on the pricing principles agreed in the contract: where an applicable unit price exists in the contract, the contract unit price shall be used; where no applicable unit price exists but a similar unit price exists, the similar unit price shall be referenced; where neither an applicable nor a similar unit price exists, the contractor shall propose a reasonable unit price subject to the owner's confirmation. Dispute resolution system: on-site negotiation (disputes within RMB 30,000), written coordination (disputes of RMB 30,000–100,000), third-party mediation (disputes exceeding RMB 100,000 are entrusted to a cost consulting agency).
Proactive prevention and control of change risks
The best strategy for change visa management is prevention first and control as supplementary. Proactive prevention and control measures include quality assurance at the design stage, detailed integrated pipeline design before construction, and precise alignment at the procurement stage. BIM integrated pipeline technology can identify approximately 80% of pipeline collision issues in advance. Before construction, the BIM team completes the integrated MEP pipeline model for collision detection and spatial optimization. Closed-loop management requires the establishment of a complete change archive management system, and all process documents of each change should be archived for reference.