This is the second article in a series about the typical stages and phases of complex engineering projects. Each article looks at one stage and how Assai supports the requirements and common challenges of that stage – ultimately contributing to the efficient, timely, (cost-)effective and safe delivery of projects. 

Conceptual design stage amongst entire engineering project
Conceptual Design: the next stage after the Feasibility Study.

Conceptual Design in a nutshell

The Conceptual Design stage – sometimes ‘Concept Selection’, ‘Conceptual Engineering’ or ‘FEL-1’ (if FEL project planning is used) – starts after a positive outcome of the Feasibility Study: the project seems technically achievable and commercially viable. This next stage marks the start of the design process, and the three subsequent stages (Pre-FEED, FEED /Front-End Engineering Design, Detailed Design) will each go a level deeper, expanding the design with more details and more accuracy.

In this stage, engineers analyze the engineering challenge to come up with (realistic) requirements and solutions. First, design ideas are generated on how the project could be implemented (‘ideation’). Next, gathered design ideas and alternatives are evaluated (‘concept evaluation’) – on their strengths, weaknesses, cost and benefits – to decide on the optimal solution, which meets the requirements and maximizes profits for the client/owner. Cost estimates (on CAPEX/capital expenditures and OPEX /operational expenses) are still quite rough at this stage: easily +/- 50%.

The main objective of this stage is to produce a proper conceptual design that provides enough detail and quality input for management to make a decision on proceeding with pre-FEED (or FEED / ‘Define’ / ‘FEL-3’, if Conceptual Design and pre-FEED are combined as ‘Select’ phase). Fundamental design choices in this stage will have a big impact on the rest of the project. The duration of this stage varies depending on the nature, location, size and complexity of the project.

Who is involved in Conceptual Design?

The client/owner may assign own engineers and/or involve an engineering company at this stage (and a process licensor, if applicable). Engineers from various disciplines are involved to come up with design ideas and elaborate them, in their respective areas of expertise. Project management becomes more crucial now to manage planning & progress and ensure timely completion of all required activities & deliverables.

A dedicated Document Controller is usually not required at this stage, but could be valuable. Having an eDMS application will help team members and external parties to find, store & share all project deliverables centrally, define standards, collaborate, review & approve, track actions, plan and report.

Once the conceptual design is ready, management (e.g. a board of directors) will decide – based on all relevant information and expert advice – whether or not to move on to pre-FEED or FEED. The outcomes of design analyses (e.g. economics) or changes to internal/external factors and circumstances can also influence this go/no-go decision.

Key deliverables & outputs

More types of deliverables are produced now by qualitative and quantitative engineering analyses, design activities, cost estimation, studies and meetings.

Typical deliverables of this stage may include:

  • Functional requirements (FR)
  • Preliminary design basis
  • High-level design drawings and diagrams (e.g. plot plan)
  • Models and simulations (e.g. thermal simulation)
  • Technical analyses (e.g. mechanical/structural)
  • Commercial analyses (economics/financial)
  • Risk register

Typical deliverables for projects involving (chemical) processes:

  • Block Flow Diagram (BFD) –  A simplified and more informal overview than a Process Flow Diagram (PFD), providing a high-level logical overview of the process structure and streams.
  • Material Balance – Overview of materials involved (input and output).
block flow diagram (BFD) example
Block flow diagram (BFD) example

Some of the deliverables created during Conceptual Design will be handed over to the next project stage (pre-FEED or FEED) – as essential input to take the design to the next level. Among the other deliverables, a selection may need to be retained as-is, for future reference or to meet regulatory/audit requirements.

How Assai supports Conceptual Design

During Conceptual Design, the number of deliverables, companies, people and actions starts to increase. Having an eDMS in place helps to keep everything well-organized, efficient, secure and compliant.

Assai provides out-of-the-box support for all project stages (and operations), with over 30 years of experience. The following Assai features are key in supporting the Conceptual Design stage:

document overview during conceptual design
Assai reports and dashboards provide live insight and overview at any level.

Plus, as mentioned in the previous article:

  • Assai is a proven, reliable, user-friendly and secure “single source of truth” for all your project deliverables, such as documents, drawings, correspondence and technical queries. Everything is traceable and can be reported on.
  • Setup & configuration of an Assai Cloud (SaaS) environment – for any number of projects, documents and users – is a breeze.


We hope you found this article about the Conceptual Design stage interesting and useful. Please let us know if you have any questions or feedback, or if you would like to explore with us how Assai could support your project(s).

A short summary of what was discussed in this article:

  • Conceptual Design happens after a positive outcome of the Feasibility Study and forms the start of the engineering design process.
  • Interdisciplinary teams generate ideas and solutions to solve the engineering problem at hand.
  • If the conceptual design is accepted, the next stage is pre-FEED, or FEED if Conceptual Design and pre-FEED are combined (as ‘Select’ phase).
  • The number of different document types, companies, people and actions starts to increase, which makes an eDMS a value-added tool to keep things well-organized, efficient, secure and compliant.
  • Assai offers an eDMS solution based on more than 30 years of worldwide experience and industry best practices. It provides true out-of-the-box support for all project stages – specifically also Conceptual Design – and projects of any size (plus operations).

Download the 50+ page PDF!

If you would like to read all articles in a 50+ page PDF which you can print or distribute in your organization, you can download them via the form below:

Previous stage: Feasibility Study

Next stage: pre-FEED

All articles in this series:

Feasibility Study
Conceptual Design (current article)
Detailed Design
Procurement & Fabrication
Construction & Installation

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