Fundamentals of Construction Planning in Plant Projects
Published on 2024-11-01
Construction planning in plant projects follows fundamental principles that ensure efficiency and smooth execution. The key principles include:
- Bottom to top
- Inside to outside
- Large to small
- Long lead items first, short lead items later
- Higher quantity first, lower quantity later
- Earlier commissioning first, later commissioning last
Bottom to Top
Underground work is prioritized before above-ground and overhead work. The vertical construction sequence is generally divided into:
- Underground installations
- Ground-level work
- Above-ground structures
- Installation at height on the steel structure
The most crucial aspect of this principle is completing ground-level work as early as possible to establish a stable work area. In plant construction, the installation of heavy equipment is common, and cranes are essential for almost all installations. Unlike commercial buildings or factories, plants are designed with maintenance and equipment replacement in mind, which also require crane access. Therefore, plant design inherently ensures that all major components can be installed using cranes.
When planning crane operations, attention is often given to the installation site and the movement of the crane boom, but key considerations include:
- Adequate space for crane assembly and disassembly
- Strong ground conditions capable of supporting the crane and the load
- Accessible routes for crane and equipment transportation
To meet these requirements, ensuring a well-prepared ground surface is essential. Major underground installations in plants include cooling water piping, equipment foundations, and underground pits. The success of early-stage construction planning depends on completing deep underground work as soon as possible.
Inside to Outside
Plant sites typically have limited access points, with heavy equipment entry often restricted to a single location. As construction progresses, access routes become even more constrained, making it essential to build from the inside out.
Unlike a simple front-to-back approach, an inside-out strategy allows construction to expand in all directions, ensuring efficient site utilization. For chemical process plants and similar facilities, the manufacturing process dictates the site layout, with feed-in points on one side and product-out points on the other. However, within these constraints, flexible layout planning can enhance constructability.
Large to Small
The principle of installing large components before smaller ones is intuitive but critical. Large equipment requires larger cranes, which demand significant space. For example, a 3,200-ton crane may need an assembly area of approximately 40m × 200m. Installing large equipment first simplifies subsequent construction planning by reducing spatial constraints and crane-related interferences.
Size considerations extend beyond weight and dimensions. Crane operations depend on the relative position of the crane and the installation site, including the required boom length and counterweight. Therefore, large-to-small sequencing must account for crane logistics as well.
Long Lead Items First, Short Lead Items Later
Long lead items, typically requiring six months or more for procurement, are often specialized and produced by a limited number of vendors. If these items are also large, their installation schedules become critical path activities. Until these installations are complete, surrounding areas remain inaccessible for subsequent work.
Managing long lead items requires coordination across engineering, procurement, and construction teams. Due to their impact on project schedules, project managers and project control managers must oversee their progress comprehensively.
Higher Quantity First, Lower Quantity Later
Construction planning prioritizes tasks with higher quantities to maximize efficiency. Advantages of this approach include:
- Easier material procurement and inventory management
- Better work front availability
- Improved progress monitoring and forecasting accuracy
- Higher workforce efficiency and skill development
- Early defect detection and quality improvements
However, low-quantity items should not be neglected. While their individual numbers may be small, their diversity often accounts for a significant portion of the total project volume. Special attention must be given to vendor-supplied items, as their quantities and installation complexities often become apparent only after detailed design is finalized.
Earlier Commissioning First, Later Commissioning Last
The final phase of plant construction involves commissioning and startup. Construction priorities must ultimately align with commissioning schedules. Even if other prioritization factors suggest different sequencing, commissioning-driven execution planning remains fundamental.
In projects executed under consortiums or joint ventures, different contractors may handle various project stages. In such cases, aligning execution plans with later-stage requirements is crucial. Since different contractors may have conflicting interests, strong project management oversight is essential.
Conclusion
As outlined above, construction planning in plant projects follows well-established principles to optimize efficiency and minimize delays in later phases. By adhering to these fundamental strategies, projects can achieve structured execution, ensuring seamless progress toward commissioning and startup.