What is a Basis of Design or BOD? How to Write a Basis of Design for a Project?

The Basis of Design (BOD) is a very important document for every project. The basis of design or project design basis provides all the principles, business expectations, criteria, considerations, rationale, special requirements, and assumptions used for decisions and calculations required during the design stage. So, a basis of design is a project baseline and overview to kickstart the project activities.

The BOD is prepared by the Engineer or Designer with inputs from all departments. For oil and gas projects, the basis of design is usually prepared by process engineers. In this article, we will explore more about the Basis of Design, its purposes, writing methodology, responsibilities, etc.

What is a Basis of Design Document?

The Basis of Design document describes the technical approach planned for the project. Preliminary project technical details are incorporated in this essential document. The BOD is prepared during the pre-design stage and it serves as the basis for all the design calculations and other design decisions. Note that, BOD is not a substitute for code and standard guidelines or project design drawings. But a BOD simply includes the list of individual items to support the design work process based on the owner’s project requirements.

Even though the basis of design starts at the pre-design phase, the document is dynamic in nature. As the design work progresses, the basis of the design document is updated to include a specific description of the system and components, its function, how it relates to other systems, sequences of operation, and operating control parameters. However, BOD does not include detailed project information or calculations.

Purpose of Basis of Design Document

The basis of design for any project serves several important purposes like

• It documents the major process and assumptions behind specific decisions.
• A BOD concisely captures the owner’s requirements and vision into technical terms and design parameters.
• For the commissioning team, BOD is a very important document to evaluate the ability of a design.
• The BOD provides a listing of all major design decisions.
• This is the document that provides a technical document providing the thought process of design professionals for developing the plant.
• A project basis of design helps in calculating the life cycle cost analysis.

Responsibilities of the Basis of Design Document

As already stated earlier that the designers and engineers are responsible for creating and managing this document. They ensure that the document is complete in all respect. However, the client and commissioning manager review the document and approve it. Creating a quality Basis of Design for the project’s success by improving the communication and collaboration between the design consultant and client.

How to Write a Basis of Design (BOD)?

Writing a basis of design specification starts with the owner’s project requirement document. A lot of required data will be obtained from that document to start writing the BOD. In the following section, I will list the important parameters that are usually added to the basis of design for oil and gas projects. This will serve as a typical basis for design engineering examples.

Contents of a Basis of Design Oil and Gas Project:

Oil and gas projects typically include the following information on the basis of design documents.

• Project background: This section includes a briefing of the project.
• Document purpose: This section lists the requirement of this document.
• Project Interface
• Project Scope: This section includes the overall scope of the project in detail. A Separate scope of each discipline involved in that project is briefed. For example, a typical oil and gas basis of a design document may include the scopes or process team, piping team, pipeline teal, civil team, control and automation team, electrical team, etc.
• Design basis: This section lists all the design information or assumptions for each discipline. Separate sub-modules of individual disciplines are prepared as process design basis, piping design basis, pipeline design basis, civil design basis, electrical design basis, C&A design basis, etc.
• Design Philosophy: In this section, the following sub-modules (as applicable in that specific project) are included.
  • Operating, Control & Safeguarding Philosophy
• • Sparing & Maintenance Philosophy
• • Metering Philosophy
• • Sampling Philosophy
• • Design Philosophy Based on H₂S content
• • Vent and drain Philosophy
• • Tie-in & Shutdown Philosophy
  • Manning Philosophy
  • Pigging philosophy
  • Emergency Shutdown Philosophy
  • Technical Safety
  • Fire & Gas Philosophy
• Technical Assurance Review: This section ensures the safety and quality of the project by performing various quality reviews like Design review, HAZOP study, SIF, Alarm rationalization review, etc.
• Design Criteria: In this section of the project design basis, various calculation basis is provided. For example,
  • Sizing Criteria for pipes/pipelines
  • Capacity determination for Partial Relief Valve
  • Sizing Criteria for Partial Relief Valve Pit
  • Sizing Criteria for Chemical Injection (Demulsifier) Skid
  • Design Life
  • Site environmental conditions
• Codes and Standards: In this section of the basis of the design document, all the relevant codes and standards are listed along with their editions.
• Government Laws and regulations, if applicable
• Process specification of Technology provider, if applicable
• References and Appendices: This is the final section of the design basis. Here, all the references and appendices are attached to substantiate the above-mentioned decisions.

The above-mentioned points are the minimum required information to be produced in any basis of design document for oil and gas projects. The complete depth and information list will vary from project to project.

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