The 3D Model is the multidisciplinary tools to review the project from the front end to the detail phase. This shall be complete of all the systems present in the plant in order to verify the interaction of the different disciplines both above and underground. The systems to be represented are:

• Equipment
• Piping
• Sewers
• Structures
• Foundations, paved areas and roads
• Cable routings
• Instruments and boxes
• Building and substations

The reviews shall be conducted after preparing a dedicated procedure and check lists for each phase, after the review completion a list of open points shall be prepared and the following actions clearly identified and monitored. At the end of the activity all the parties involved shall concur in a minute of meeting that the Model is frozen for the verification executed.

The 3D Model is used to review the equipment layout, the aspects to be discussed are:

1. Construction accessibility - verification of the clearances for equipment, piping, cable installation with required means like cranes (a particular case is the columns or reactors erection), verification of the heavy paved areas location (with reinforced concrete) where heavy loads can be present during construction and maintenance, verification of the access to the different units.
2. Process layout - The location of equipment, both in plan and elevation, shall respects the process requirements of the P&ID. Moreover the location of equipment shall minimise the pipe and cable connections length following the process requirements (i.e. vapour lines in slope, operational valves accessible, minimum pump NPSH, air coolers distribution, etc.).
3. Maintenance accessibility and devices- Different items shall be verified for the easy maintenance, typical ones are the exchanger tube bundles extraction, pump electric motor removal, heater burners dismantling, etc. Where required by the contract monorails, bridge cranes, motor hoists and other special devices or tools shall be provided.
4. Safety distances - Depending on local regulation or licensor specification or other applicable standards, the safety distances between equipment, roads, fences, etc. shall be verified. Retaining wall shall be provided where required and the volume contained shall be higher than the maximum contained in the bigger equipment (sometimes is required 1,5 times). Hazop results shall be implemented.

The 3D Model can be reviewed different times, detailed check lists has the target to verify that the progress in the definition of the minor items is compliance with the requirements of the project. In this phase the piping shall match the p&I d's (i.e. slope, no pockets, locate at ground, etc.), the instruments installed on equipment or in line accessible or readable, ladders and platform shall permit an easy access to all operational points (valve handwheels and body, manholes, psv's, actuators, etc.). The inferences between structures, instrument boxes, pipes shall be avoided with dedicated checks (in automatic or visually).

Particular circuits, such as pump suction, steam condensate, transfer/vapour lines, shall be calculated the pressure losses.

Links between electronic p&I 2D and 3D Model can allow you to monitor automatically the progress and the correctness of the piping layout in terms of line components and process data associated with.