The seven stages of chemical engineering technology from concept to industrialization (Issue 63/100) -- Basic design

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The seven stages of chemical engineering technology from concept to industrialization (Issue 63/100) —— Engineering translation: basic design. Dear friends: Hello everyone! In the previous issue, we discussed scheme design and approval for planning; the main framework of the installation has been established, and the planning procedures are also in progress. In this issue, we discuss the most crucial aspect of the engineering transition phase: basic design. If scheme design is about providing a framework for the device, then foundation design is about adding muscles and blood vessels to that framework. It is the direct input for detailed design, and it represents the phase of the entire engineering transition process with the greatest amount of work and the most intensive professional collaboration. The quality of the basic design determines whether the detailed design will go off track, as well as whether the facility will be able to operate safely, stably, and cost-effectively in the future. In this issue, we will discuss the in-depth positioning, core tasks, and working logic of basic design. I. The role of basic design: Basic design lies between conceptual design and detailed design. Scheme design addresses questions such as \"where the equipment will be placed and what it will look like\", while basic design deals with issues like \"what model to use for each piece of equipment, what material to use for each pipe, and how to implement each control circuit\". During the scheme design phase, the equipment layout remains at the level of \"suggested arrangements\" – namely, the approximate locations of the main equipment as well as the span and height of the framework. During the basic design phase, the equipment layout must evolve from a \"proposal\" to a \"final design\" – each piece of equipment is positioned precisely based on its actual dimensions and the location of its connections, with careful consideration given to the access paths for operation and maintenance, the routes for lifting, and the elevation levels related to gravity flow. During the scheme design phase, the representation of the process system relies primarily on the PFD and PID of the process package. During the basic design phase, it is necessary to verify and refine this foundation: the data on the PFD must be confirmed again one by one, the PID should include more engineering details, and the completeness of the five operating conditions (normal operation, startup, shutdown, accident handling, maintenance and replacement) must be checked item by item. During the scheme design phase, the consumption of utility services remains at the estimated values provided in the process package. During the basic design phase, it is necessary to accurately calculate the demand and peak operating conditions at various points for the utility systems, based on the actual selection of equipment and piping layout, in order to provide reliable input for the design work related to these utility systems. Once the basic design is completed, the “genes” of the device are essentially determined. The subsequent detailed design is the “expression” based on this gene – determining how to arrange the pipelines, how to calculate the structures, and how to wire the instruments. If the selection of a certain device or the design of a certain control scheme is inappropriate during the preliminary design phase, trying to make changes in the detailed design phase will have significant consequences. II. Core tasks of foundation design Foundation design involves a wide range of aspects, and its core tasks can be summarized as follows. First, the process system design is further refined. This is of utmost importance in the basic design. Based on the PID of the process package, complete engineering information is added—the start and end points and diameters of all pipes, the specifications and pressure ratings of all valves, the tag numbers and ranges of all instruments, as well as the port numbers and connection methods of all equipment. It is particularly important to conduct the integrity check for the five operating conditions. Normal operation is the main aspect of plant operation, but the four abnormal conditions of startup, shutdown, accidents, and maintenance, although accounting for a small proportion of time, encompass the majority of safety risks throughout the plant’s lifecycle. During the basic design phase, it is essential to ensure that the system has complete piping and instrumentation schemes for these five operating conditions. Operation during startup: How does the system gradually establish a liquid level, increase temperature and pressure, and enable the entire process to operate? Is the design of the pipelines used for startup sufficient, and are the interfaces for nitrogen purging and airtightness testing properly provided? Parking mode: How to safely empty or transfer the materials in the system, and how to prevent materials with high freezing points from solidifying in the pipes. Emergency operating conditions: How does the system initiate automatic interlock actions in the event of a power outage, water outage, steam outage, or failure of critical equipment? What state does the device enter after these interlock actions occur, and what actions are required from the operator? Maintenance mode: How to isolate and purge each piece of equipment before maintenance, and whether nitrogen purging interfaces and exhaust ports are properly installed. Second, the equipment layout is refined. Develop the proposed equipment layout from the process package stage into a formal equipment layout. Based on the actual dimensions of the selected equipment and the orientation of its ports, each piece of equipment is precisely positioned on the drawings, with careful verification of the access paths for operation and maintenance, the locations of the inlet and outlet pipes, the space required for core extraction, and the lifting routes. At the same time, basic information is provided to the structural engineering team – the weight of each large-scale device, its vibration characteristics, and the locations of the key load-bearing points – so that they can design the framework, pile foundations, and equipment bases accordingly. Third, the pipeline material grade is further refined. During the process package phase, only an index table of pipeline material grades was completed; during the basic design phase, this needs to be developed further into a detailed table of pipeline material grades, specifying the exact specifications and material requirements for all fittings, valves, flanges, gaskets, and bolts within each grade. Fourth, utility system design. Circulating water, steam, compressed air, nitrogen, chilled water – the layout of the pipelines for each utility system, pipe diameter calculations, and equipment selection are all completed during the preliminary design phase. The utility systems must be capable of meeting the demands under peak conditions – multiple large pumps may start operating at the same time during startup, and the steam demand can be twice that of normal operation ； Under accident conditions, emergency cooling may require chilled water to remove a large amount of heat in a short period of time. If the utility systems are designed only for normal operating conditions, they may not be able to meet the demands during startup or in case of an accident, which could put the entire plant at a disadvantage. Fifth, preparation of the preliminary estimate for the basic design. Prepare a preliminary estimate based on the equipment list, piping estimates, civil works estimates, and electrical and instrumentation estimates. The estimation accuracy should be around ±10%; it is the key document for project cost control and also serves as a benchmark for budget control during the subsequent detailed design phase. Sixth, the compilation of each special chapter. A special section on safety facility design, a special section on fire protection design, a special section on environmental protection facility design, and a special section on occupational health and safety protection facility design – all four of these sections need to be prepared and reviewed during the preliminary design phase. The preparation of special sections cannot be delayed until the detailed design is completed, as they directly influence the design direction of the subsequent construction drawings. The specific contents of each special article will be discussed in detail over two subsequent issues. III. Division of labor and cooperation between the design unit and the process package provider. The preliminary design is usually entrusted to a professional engineering design firm to carry out. The role of the process package provider at this stage is to provide technical support – by clarifying technical questions raised by the design team, confirming or correcting any issues related to the process package data that arise during the design process, and participating in the review of key design solutions. Choosing a design firm with relevant experience ensures better quality and timeliness in the preliminary design. How can you tell if a design firm has experience? It’s not about how many projects are listed in the company profile, but rather about the specific teams they assign to a project – the project manager, the chief process engineer, the chief equipment engineer – and what types of installations they have worked on in the past. An experienced team, upon receiving the process package, can quickly identify which are the critical equipment, which are the critical control loops, and where amplification risks may exist. A team lacking experience in similar projects may allocate equal effort to everything, falling short in critical areas and over-designing minor aspects. When the design contract is signed, the process package is included as a technical attachment to specify the deliverables and depth requirements of the design firm. Before signing the contract, it is recommended that the core team of the design firm review the process package thoroughly and submit their questions and suggestions. If they finish reading the process package without raising any questions, it might be a warning sign – either they didn’t read it carefully or their understanding of the process is insufficient; either situation is not conducive to future cooperation. IV. Review stages for the basic design The basic design is not completed in one go or submitted in a single submission. There are several key review points in between that require close attention from the project team. After the PFD verification is completed, a meeting to confirm the process plan should be held. The design agency conducted an independent analysis of the data in the PFD of the process package; if any discrepancies were found, it was necessary to analyze the reasons for those discrepancies one by one – to determine whether they stemmed from differences between the calculation assumptions and basic design of the process package, or from issues that needed to be corrected within the process package itself. Only after the data from both parties is aligned can further work on refining the PID be carried out. After the PID refinement is completed, a special review on the integrity under five operating conditions should be conducted. This review cannot be a mere formality – every aspect must be checked carefully: whether there are sufficient piping for driving, where parking materials should be placed, whether the interlock actions work properly in case of an accident, and whether the maintenance isolation plans are feasible. Operation representatives and driving experts must participate in this review, as their on-site experience can help identify issues that designers sitting in the office would not think of. After the equipment layout plan is approved, the load conditions must be formally submitted to the structural engineering team. This process of specifying conditions requires the joint approval of the supervisors from the fields of engineering, equipment, and structure, to ensure that the load data submitted is accurate and complete. If the load associated with a heavy piece of equipment is overlooked, it may not be discovered until the detailed design stage, at which point it turns out that the cross-sections of the beams and columns are insufficient; adjusting the structural design in such a case comes at a high cost. V. Some Insights The quality of the basic design largely determines the smoothness of the subsequent engineering implementation process. There are a few insights I can share. First, the preliminary design phase is the most critical period for implementing the concept of \"proactive risk management\". HAZOP analysis, SIL classification, 3D model review, and constructability review – these safety and design reviews are carried out in the initial design phase; identifying issues at this stage and making corrections on the drawings results in the lowest costs. If problems are discovered only after the detailed design is completed or even after construction has begun, the cost of redoing work will be dozens or even hundreds of times higher. Second, the process engineering team has a heavy workload during the preliminary design phase, but progress pressures should not be used to pass incomplete designs on to teams in subsequent stages. Every set of design conditions—such as the pipe locations for the mechanical engineering team, the load data for the structural engineering team, and the pipe diameters and material grades for the piping engineering team—should be verified before being submitted. Under inaccurate conditions, the downstream department carries out the digestion; a detailed design is created based on that, and then revisions are made. This chain reaction involves not just one department – it’s possible that four or five departments may have to redo their work simultaneously. Third, the preparation of the special report cannot wait until the basic design is completed. The special section on safety facility design is currently the only section for chemical projects that still requires review by the relevant government authorities, and the review process can be quite lengthy. If submission for review is delayed until the basic design is fully completed, and revisions or additions are required if the review is not approved, it may affect the progress of the detailed design. The reasonable approach is to prepare a special report for review once the main design plan has been finalized in the preliminary design phase; while awaiting the approval from that review, other tasks related to the detailed design can be carried out simultaneously, thereby removing the review period from the critical path. Preview for the next issue: Issue 64 – Detailed design: The final step in creating construction drawings. The foundation design is complete, and the ‘genes’ of the device have been determined. Next comes the detailed design – pipeline stress analysis, 3D piping design, simultaneous in-depth work by various specialties related to structural and electrical automation, preparation of technical specifications for long-cycle equipment, and review and filing of construction drawings. This is the last mile in producing the construction drawings, and it is also the critical point at which the cost of design changes begins to increase sharply. To be continued in the next issue.