In chemical engineering, three terms appear throughout project development: Process Design Package, basic engineering, y detailed engineering. Yet their respective roles and relationships are not always clear to new engineers, investors, or project managers.
Key questions include:
- What is each stage responsible for?
- Why can the design not be completed in a single step?
- How do international technology licensors and engineering companies divide these responsibilities?
- Why do major EPC contractors rarely develop their own process technologies?
This article explains the complete design workflow of a chemical project and the commercial logic behind this division of responsibilities.
A simple way to understand the relationship is:
- En Process Design Package defines the process technology and the conditions required to make the desired product.
- Basic engineering converts that process technology into an engineering scheme that can be evaluated, estimated, and developed further.
- Detailed engineering translates the approved scheme into drawings and specifications that can be used for procurement, fabrication, construction, and installation.
Process Design Package: Defining the Core Process Technology
A Process Design Package, commonly abbreviated as PDP, is a front-end engineering package that defines the process and the associated scope through drawings, calculations, specifications, and technical documents.
Koch Modular describes a PDP as a front-end engineering package that uses drawings and specifications to define the overall scope of supply. In practical terms, it explains what the plant is intended to produce, how the process works, and which technical principles and operating conditions are critical.
A paper presented by the engineering team of Saudi Basic Industries Corporation (SABIC) at an American Institute of Chemical Engineers (AIChE) conference noted that a PDP is normally developed during the project feasibility stage. Three major deliverables—Process Flow Diagrams (PFDs), Piping and Instrumentation Diagrams (P&IDs), y equipment datasheets—may account for approximately 60% of the total engineering hours required to prepare the package.
Another AIChE paper describes a PDP as a collection of documents containing sufficient process and technical information for an engineering company to prepare a Front-End Engineering Design package or proceed directly to detailed engineering.
A typical PDP may include:
- Design basis and process design data
- Process Flow Diagrams
- Preliminary process P&IDs
- Equipment process datasheets and equipment lists
- Interlock descriptions
- Preliminary equipment layout drawings
- Fluid lists and piping material classes
- Process safety design criteria
- Utility requirements
- Process datasheets for pressure relief devices and environmental data
In short, the PDP is the central technical reference for the process plant. It contains the principal process technology and often incorporates the licensor’s proprietary knowledge and intellectual property.
Without this package, the engineering contractor cannot reliably proceed with the subsequent design stages.
Figure 1. A modern chemical plant, where extensive piping networks, columns, and process equipment illustrate the complexity of chemical engineering projects.
Basic Engineering: Bridging Process Requirements and Engineering Implementation
Terminology for this stage varies between companies and regions. Common terms include Basic Engineering, Basic Engineering Design Package (BEDP), and the more broadly used Front-End Engineering Design (FEED).
DEC Engineering’s terminology describes the progressive relationship between these stages: the PDP provides the foundation for the plant’s core process documentation, while the BEDP adds enough engineering detail for a qualified contractor to begin detailed engineering, procure long-lead equipment, and prepare for construction.
If the PDP defines the temperature and pressure required for a chemical reaction, basic engineering determines the reactor capacity and materials of construction, the required pipe sizes, and the space needed to install and operate the system.
Typical basic engineering activities include:
- Developing the process P&IDs in the PDP into engineering-level P&IDs suitable for detailed design
- Preparing preliminary specifications for major equipment, with sufficient detail to request quotations for long-lead items
- Determining preliminary pipe sizes, material classes, and insulation requirements
- Developing a preliminary 3D model and general plant layout
- Conducting a Hazard and Operability Study (HAZOP)
- Preparing a more accurate capital cost estimate, commonly within approximately ±10% to ±15%
Under the internationally used Front-End Loading (FEL) framework, project development is commonly divided as follows:
- FEL-1—Feasibility: Preliminary process definition, block flow diagrams, and a cost estimate with an accuracy of approximately ±50%
- FEL-2—Conceptual Design or Pre-FEED: A more developed process package, PFDs, preliminary P&IDs, and a cost estimate with an accuracy of approximately ±30%
- FEL-3—FEED or Basic Engineering: A substantially higher level of design definition, including procurement-level equipment datasheets, to support the Final Investment Decision (FID)
Why is the project divided into multiple design stages? The main reason is that design changes are relatively inexpensive during early project development. Once detailed engineering or construction has begun, the same changes can cause substantial cost increases and schedule delays.
Industry studies indicate that a well-executed FEED can significantly reduce project cost and execution time, although the actual improvement depends on project complexity, design maturity, and execution conditions.
PFDs and P&IDs in Basic Engineering: Different but Complementary Roles
A common question is why basic engineering needs P&IDs if the detailed engineering contractor will later issue complete construction-level P&IDs. Is this duplicated work? Which document is more important during basic engineering: the PFD or the P&ID?
The two documents define different aspects of the plant and are therefore complementary.
A PFD defines the overall process configuration. It shows material flows, heat integration, and the locations of major reaction and separation operations. It helps answer fundamental questions such as:
- Is the process route technically feasible?
- Is it thermodynamically and chemically sound?
- Is the selected process economically reasonable?
- What combination of equipment should be used?
For example, the PFD may establish whether the process requires a fixed-bed or fluidized-bed reactor, or whether extractive distillation or azeotropic distillation should be used. Once these choices have been made, the subsequent engineering work is built around them.
A P&ID converts this process configuration into an operable engineering system. It defines how pumps, valves, instruments, equipment, and control loops are connected. It also establishes the process control and safeguarding philosophy.
Construction-level P&IDs developed during detailed engineering may include sampling points, piping slopes, tracing requirements, and other installation details. Basic engineering P&IDs do not necessarily define every construction detail. Their primary purpose is to preserve the essential process, control, and safety logic so it is not unintentionally altered during detailed design.
In chemical projects, understanding how equipment must be operated to produce a consistent, qualified product is more important than simply producing a complete set of drawings.
Equipment configurations can often be reproduced, but process know-how is much harder to replicate. A technology licensor may know:
- The appropriate temperature ramp rate during the most heat-sensitive stage of a reaction
- The optimum crystallizer agitation speed
- The required supersaturation level for seed addition
- The conditions needed to obtain the target crystal size distribution
- The control response required during startup, shutdown, or process disturbances
This knowledge is expressed through the operating principles in the PDP and implemented through the PFDs and P&IDs developed during basic engineering. It is a major part of the value provided under a technology licensing agreement.
A PFD primarily defines which process operations and equipment combinations are required. A P&ID defines how those systems must be operated, controlled, and protected. Together, they create an engineering framework that can be implemented in a real plant.
If a PFD Includes Control Logic, Is a Basic Engineering P&ID Still Necessary?
A sufficiently detailed PFD can include material and energy balances, major control loops, critical interlock triggers and actions, design conditions, alarm limits, and shutdown set points. An experienced engineer may therefore be able to understand the principal operating strategy from an extensively developed PFD.
However, a PFD has inherent limitations. Many engineering decisions cannot be adequately documented on it.
Process safety details
A safety valve shown on a PFD is only a symbol. The design must also define:
- Required relief capacity
- Materials of construction
- Discharge destination, such as a flare system or local vent
- The effect of flare-system backpressure on relief capacity
- Isolation and maintenance requirements
These decisions are normally documented on the P&ID and supported by the relevant calculations. They are also essential inputs to HAZOP studies and regulatory safety reviews.
Where Chinese regulations or standards apply, the documentation must comply with the relevant Chinese national standards (GB or GB/T standards) and local regulatory requirements. These should not be interpreted as international standards.
Startup and shutdown arrangements
PFDs mainly describe normal process operation. They generally do not contain all the auxiliary piping required for:
- Startup circulation and heating
- Shutdown, draining, and purging
- Catalyst regeneration
- Aislamiento de los equipos
- Maintenance access
- Depressurization and cleaning
These connections must be defined on the P&IDs.
Valve operating requirements
A control loop shown on a PFD does not fully define how its valves should operate. The P&ID must specify matters such as:
- Whether an isolation or shutdown valve fails open or fails closed
- Whether manual block valves are required upstream and downstream of a control valve
- Whether a bypass line is required
- How valves respond when an interlock is activated
Without this information, equipment and instruments cannot be correctly specified or procured, and plant safety cannot be properly evaluated.
Engineering handover requirements
The detailed engineering contractor must convert the design into construction documents. To do so, the contractor needs the P&IDs to determine:
- Piping pressure classes
- Materials of construction
- Insulation and heat-tracing requirements
- Connection types
- Instrument connections
- Drain, vent, sampling, and flushing arrangements
A PFD may state that a stream must be heated to 200°C. The P&ID and related specifications define the piping material, wall thickness, insulation, tracing method, and control arrangement needed to achieve that requirement safely.
A basic engineering P&ID is therefore not simply an additional drawing. It converts process requirements into a system that can be designed, procured, constructed, operated, and maintained safely.
It also provides a common coordination platform for process, safety, piping, equipment, instrumentation, electrical, civil, and structural disciplines. Omitting this step transfers major technical decisions to the detailed engineering team, which may not possess the same depth of process knowledge. This can substantially increase late-stage changes and project risk.
Detailed Engineering: Producing Construction-Ready Documentation
This stage is known as Detailed Design o Detailed Engineering.
HEDCO describes detailed engineering as the stage in which each engineering discipline completes the most comprehensive technical design required to ensure that the plant can be installed safely, without technical conflicts, and with appropriate construction cost efficiency.
Koch Modular provides a similar description: engineers and designers systematically define every component of a modular process system. Equipment, piping, structural steel, instrumentation, electrical systems, and control systems are evaluated, optimized, and designed in sufficient detail for fabrication and construction.
If the PDP defines what the process must accomplish and basic engineering defines the systems required to accomplish it, detailed engineering specifies exactly how those systems will be fabricated, installed, connected, and constructed.
Typical detailed engineering deliverables include:
- Construction-level equipment drawings and fabrication details
- Complete piping 3D models and piping isometrics
- Bills of Materials (BOMs) and procurement specifications
- Instrument indexes, loop drawings, and wiring diagrams
- Electrical single-line diagrams and layout drawings
- Civil foundation drawings and structural steel details
- Construction and installation instructions
Detailed engineering documents are used directly for procurement, fabrication, installation, and site construction. Producing these documents is a central responsibility of the EPC contractor.
Key Differences Between the Three Design Stages
| Comparison | Process Design Package (PDP) | Basic Engineering (FEED/BEDP) | Detailed Engineering |
|---|---|---|---|
| Project stage | Feasibility or conceptual development | After the PDP and before detailed engineering | After FEED and before construction |
| Primary question | What process should be used? | What equipment and engineering systems are required? | How should the plant be fabricated, installed, and constructed? |
| Main deliverables | PFDs, preliminary P&IDs, and process equipment datasheets | Engineering-level P&IDs, long-lead equipment specifications, and a preliminary 3D model | Construction drawings, isometrics, BOMs, and wiring diagrams |
| Cost-estimate accuracy | Approximately ±30% to ±50% | Approximately ±10% to ±15% | Sufficiently developed to support construction budgeting |
| Typical responsible party | Technology licensor or process owner | Engineering company, owner, licensor, or a joint team | Multidisciplinary EPC engineering team |
| Principal knowledge involved | Proprietary process technology and know-how | Engineering definition and integration | Construction-level engineering information |
How the Three Stages Work Together
The three stages form a continuous sequence:
- En PDP establishes the process route, operating window, material and energy balances, and core technical requirements.
- Basic engineering converts those requirements into an integrated plant concept, defines the major equipment and control philosophy, and reduces uncertainty before major investment commitments.
- Detailed engineering develops the approved concept into the drawings, models, specifications, and material lists required for procurement and construction.
Weakness in any one stage affects all subsequent work.
An incomplete PDP may leave critical process conditions undefined. Insufficient basic engineering can allow safety, operability, layout, or cost issues to remain unresolved. Poor detailed engineering can lead to procurement errors, site conflicts, rework, and construction delays.
The design workflow from the Process Design Package to detailed engineering.
Which International Companies Develop Process Design Packages?
Companies capable of supplying process design packages generally possess proprietary reaction technology, catalyst systems, process integration expertise, or specialized separation technologies.
They can be grouped into several broad categories.
Established Petrochemical Technology Licensors
| Empresa | Core fields | Representative technologies |
|---|---|---|
| Honeywell UOP | Refining, aromatics, olefins, and natural gas processing | Parex™ for para-xylene separation and Butamer™ isomerization |
| Tecnología Lummus | Ethylene cracking, ethylbenzene/styrene, and polypropylene | Licensed technologies used in large ethylene projects |
| KBR | Ammonia, refining, and olefin recovery | KBR Purifier™ ammonia technology |
| Technip Energies | Ethylene furnaces, LNG, and hydrogen | A broad portfolio of licensed process technologies |
| Axens | Hydrotreating, reforming, and biofuels | Commercialization of IFPEN technologies |
| thyssenkrupp Uhde | Coal chemicals, fertilizers, chlor-alkali, and nitric acid | Established licensed process technologies |
Technology-Licensing Divisions of Chemical Producers
| Empresa | Core fields | Representative technologies or characteristics |
|---|---|---|
| Dow | Polyethylene, polyurethane, ethylene oxide, and ethylene glycol | UNIPOL™ gas-phase technology |
| ExxonMobil | Para-xylene crystallization and refining | PDPs supplied through its licensing operations |
| BASF | Acrylic acid and butadiene extraction | Technologies frequently integrated with catalyst supply |
| Shell | Gasification, ethylene oxide, and ethylene glycol | Shell Catalysts & Technologies |
| INVISTA | PTA, PET, adiponitrile, and nylon 6,6 | P8 PTA and nylon 6,6 polymerization technologies |
Providers of Specialized Separation Technologies
Separation and purification are as important as reaction engineering in many chemical processes. Companies with specialized capabilities include:
| Empresa | Core technology | Aplicaciones |
|---|---|---|
| Air Products | PRISM® hollow-fiber membrane separators | Bio-LNG and offshore operations |
| Linde Engineering | HISELECT® membrane technology | Natural gas decarbonization and hydrogen recovery |
| Honeywell UOP | Parex™ and Molex™ adsorption separation | Para-xylene and normal-paraffin separation |
| Sulzer | Distillation, crystallization, and membrane separation | Bio-based polymers, including PLA |
Specialized Process Technology Companies
| Empresa | Core field | Industry position |
|---|---|---|
| Stamicarbon | Urea technology | Technology used across a substantial share of global urea capacity |
| Johnson Matthey | Methanol synthesis, gas-to-liquids, and fuel cells | Strong catalyst and process expertise |
| Topsoe | Ammonia, methanol, hydrogen, and sulfuric acid | Established Danish technology licensor |
These companies primarily commercialize process knowledge: reaction pathways, catalyst formulations, operating windows, and process configurations. They may support engineering development, but they are not necessarily responsible for producing all construction drawings or executing civil installation.
Figure 2. A large chemical processing facility illustrating the engineering complexity of a modern plant.
Division of responsibilities between technology licensors and EPC contractors.
Which International Companies Perform Detailed Engineering?
After receiving the PDP and basic engineering documentation, EPC contractors and specialist engineering companies convert the design into procurement packages, fabrication drawings, construction documents, and physical plant infrastructure.
Major European and North American EPC Contractors
| Empresa | Core fields | Características |
|---|---|---|
| Bechtel | Energy, petrochemicals, and LNG | One of the largest US engineering and construction companies |
| Fluor | Refining, chemicals, pharmaceuticals, and mining | Major international engineering and construction contractor |
| KBR | Ammonia, refining, and olefins | Combines technology licensing with EPC capabilities |
| Technip Energies | Ethylene and LNG | Combines proprietary technology with engineering execution |
| McDermott | Storage tanks, ethylene cracking, and LNG terminals | Services extending from FEED to EPCIC |
| Saipem | Offshore oil and gas and onshore petrochemicals | Major Italian engineering contractor |
| Técnicas Reunidas | Refining and petrochemicals | Spanish engineering and construction company |
| Linde Engineering | Gas separation, FEED, and detailed engineering | Major German engineering organization |
Japanese and South Korean EPC Contractors
| Empresa | Core fields | Representative strengths |
|---|---|---|
| JGC | LNG, refining, and petrochemicals | Known for disciplined project execution |
| Chiyoda | LNG liquefaction plants | Experience with large LNG projects in Qatar |
| Samsung E&A | Refining and chemicals in the Middle East and Southeast Asia | Major South Korean EPC contractor |
| Hyundai Engineering | Refining and chemicals in the Middle East and Southeast Asia | Major South Korean EPC contractor |
Specialist Engineering Companies and Other International Contractors
| Empresa | Core fields | Características |
|---|---|---|
| Worley | Detailed engineering for oil, gas, and chemicals | Australian-founded global engineering company |
| Wood | Energy and chemical engineering | UK-headquartered engineering company |
| Petrofac | Oil and gas lifecycle services | UK-headquartered service provider |
| MAIRE | Polyolefin and fertilizer EPC projects | Its group includes urea technology licensor Stamicarbon |
| Hargrove | Chemical-industry engineering | US engineering and project services company |
| Audubon Engineering | Energy infrastructure | US provider serving industrial processing and oil and gas projects |
These EPC companies typically maintain large multidisciplinary teams covering process, piping, mechanical equipment, instrumentation, electrical systems, civil works, and structural engineering. Their role is to convert process and engineering documentation into a safe, operable physical plant.
Figure 3. A large chemical plant at night, illustrating the scale and technical complexity of modern industrial construction.
Common International Contracting Models
Technology licensors and EPC contractors generally work together under one of three models.
The Owner Contracts Separately with the Licensor and EPC Contractor
Under the traditional model, the owner purchases a process license and PDP from a technology licensor. The owner then uses that package to tender the basic engineering, detailed engineering, procurement, and construction scope to an EPC contractor.
This is one of the most common arrangements.
The Licensor Supplies Both the PDP and Basic Engineering
Some licensors provide both the PDP and a more developed basic engineering package. They may also form strategic partnerships with selected EPC contractors and submit an integrated technology-and-engineering proposal.
For example, after INVISTA licensed nylon 6,6 technology to China Resources Chemical Innovative Materials, Chemtex provided engineering, procurement, and construction services.
The EPC Contractor Provides Its Own Process Technology
Some EPC companies have acquired or independently developed technologies in specialized fields, such as small modular plants and water-treatment systems.
This model exists but remains less common in major commodity chemical projects, where established licensors control many of the leading process technologies.
Why Do Major EPC Contractors Rarely Develop Their Own Process Design Packages?
If an EPC contractor possesses extensive detailed engineering capability, why does it not simply develop its own process technology and provide both licensing and EPC services?
The main reason is that technology licensors and EPC contractors operate under fundamentally different business models.
Intellectual Property and Project Services Require Different Business Models
A process package is primarily an intellectual property product. A licensor may invest in developing a technology once and then license it repeatedly across multiple projects.
Decades of operating data, experiments, scale-up results, and process optimization can be applied to many plants. Once the technology has been commercialized and validated, each additional license may require relatively limited incremental development work.
EPC contracting, by contrast, is project-based. Each project requires a customized team and may involve hundreds of engineers and construction personnel. The contractor also assumes substantial schedule, cost, procurement, and construction risks.
Technology licensing therefore depends on repeatable intellectual property, while EPC contracting depends on project execution and risk management. The required organizational capabilities are different.
Process Development Requires Long-Term Investment
Developing a mature process that can be licensed commercially usually requires:
- Laboratory research
- Bench-scale testing
- Validación a escala piloto
- Demonstration-plant operation
- Scale-up engineering
- First-of-a-kind commercial application
- Long-term operating data
The complete development cycle may take 10 to 20 years and require investment measured in hundreds of millions of US dollars, depending on the technology.
For publicly listed EPC companies focused on project turnover and quarterly financial performance, this investment model can be difficult to justify. Privately held industrial groups may be better positioned to support technology development over longer periods.
Process Know-How Creates a High Barrier to Entry
A PDP involves much more than PFDs and material balances. It is supported by extensive tacit knowledge that is difficult to obtain from public information.
Algunos ejemplos son:
- Catalyst deactivation behavior at specific impurity concentrations
- Long-term equipment performance under abnormal operating conditions
- Special control logic required during startup and shutdown
- Fouling, corrosion, and plugging behavior
- Product-quality sensitivity to small changes in operating conditions
- Scale-up limitations identified through pilot and commercial operation
Technology licensors accumulate this knowledge through decades of operating feedback from multiple plants. It may reside in proprietary databases, internal standards, design methods, and the experience of senior engineers.
An EPC contractor cannot readily reproduce this knowledge through reverse engineering. Producing a P&ID may take weeks; developing the experience required to understand and validate every design decision can take decades.
Technology Performance Guarantees Create Additional Risk
Licensed process packages are often accompanied by a performance guarantee. If the completed plant cannot achieve the contractually specified capacity, product quality, energy consumption, or other performance targets, the technology licensor may be liable for penalties.
Providing such a guarantee requires extensive confidence in the technology and sufficient operating data to define its performance envelope.
An EPC contractor that provides both the technology and the full project execution scope may also face potential conflicts between process performance, equipment cost, construction cost, and schedule. Owners may prefer an independent licensor whose technical responsibilities and guarantees are clearly defined.
EPC contractors may likewise prefer to avoid technology-development risks that could threaten the financial performance of an entire project.
Attempts to Combine Technology and EPC Capabilities Face Significant Barriers
Some EPC companies have attempted to expand into technology licensing.
China National Chemical Engineering Group, for example, has promoted a T+EPC, or “Technology plus EPC,” model based on internal development and technology acquisition. South Korean engineering companies have also accumulated proprietary capabilities in selected refining and aromatic-process applications.
However, several barriers remain:
- Established licensors already hold extensive patent portfolios around major process routes
- EPC companies may lack pilot plants and opportunities for industrial validation
- Owners often require a long operating record before accepting a new process technology
- Performance guarantees for an unproven technology can create substantial financial exposure
As a result, only a limited number of EPC companies have successfully developed both broad process-licensing portfolios and full EPC execution capabilities.
Specialization Improves Project Efficiency
The separation between technology licensing and EPC execution reflects the benefits of industrial specialization.
Technology licensors focus on research, process development, scale-up, proprietary equipment, catalysts, and operating know-how. EPC contractors focus on engineering integration, procurement, construction, commissioning support, cost control, and schedule management.
Modularization of technical knowledge makes this division possible. A PDP packages proprietary process knowledge into a controlled set of documents and specifications that can be transferred to an engineering contractor without disclosing every aspect of the licensor’s underlying research.
This structure reduces coordination costs while allowing each participant to concentrate on its strongest capabilities.
When a major chemical plant is developed, its process technology may come from licensors such as Honeywell UOP, INVISTA, or Linde, while its engineering and construction may be executed by companies such as Bechtel, Fluor, JGC, or Samsung E&A.
The completed plant is therefore the result of coordinated work among technology licensors, owners, engineering companies, equipment suppliers, and construction contractors.
Conclusión
The three principal stages of chemical plant design perform distinct but closely connected functions:
- En Process Design Package defines the process route, technical requirements, and proprietary operating knowledge.
- Basic engineering or FEED converts that technology into an integrated engineering concept and resolves major design, safety, cost, and operability questions.
- Detailed engineering produces the construction-ready documents required for procurement, fabrication, installation, and commissioning.
None of the three stages can fully replace the others.
The quality of the PDP determines whether the core process is technically sound. The quality of basic engineering determines whether that process can be converted into a safe, operable, and economically viable plant. The quality of detailed engineering determines whether the design can be accurately constructed and reliably operated.
The division of responsibilities between technology licensors and EPC contractors is therefore not an unnecessary separation. It is an established project-delivery structure based on different technical capabilities, commercial models, and risk profiles.
