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What is Front End Engineering Design or FEED Engineering? FEED vs Detailed Engineering

Written by Anup Kumar Dey in Civil,Instrumentation,Mechanical,Pipeline,Piping Design Basics,Piping Interface,Process,Project Management

Front End Engineering Design or FEED is an engineering design approach adopted prior to detailed engineering, procurement, and construction. It is an important engineering design phase that is used to control project expenses and thoroughly plan a project before bid submission. Benchmark studies have shown that FEED constitutes roughly 2% of the project cost but properly executed FEED projects can reduce up to 30% of costs during design and execution. In this article we will discuss more about FEED project details with respect to oil and gas projects.

What is FEED?

Front-End Engineering Design (FEED) is a crucial phase in the project lifecycle of oil and gas developments. It bridges the gap between project conceptualization and detailed engineering design. FEED focuses on defining the project scope, establishing technical requirements, and providing cost and schedule estimates. It aims to ensure that the project is well-defined before significant capital is committed. FEED serves as the blueprint for project execution, laying down the framework that guides detailed engineering, procurement, and construction phases.

Front-end engineering design is a basic engineering phase conducted after conceptual design or feasibility study. FEED is also known as Front End Loading or Front End Engineering (FEE).

Applications of FEED

Front End Engineering Design has its uses across various industries. Here are the sectors that use FEED at different stages of their applications.

  • Oil & Gas
  • Construction
  • Automation
  • Manufacturing
  • Chemical processing
  • Process Industry
  • Production line design
  • EPC
  • Power Generation
  • Refining
  • EPCIC
  • Equipment design
  • Process system design
  • Machine Vision
  • Pharmaceuticals
  • Petrochemicals
  • Food & Beverages

Purpose of Front-End Engineering Design

The main purpose of FFED or Front End Engineering Design is

  • to define the technical and project-specific requirements for an understanding of the clear project scope.
  • to prepare the project approach and basis of design for the system.
  • to develop a good project cost estimate for budget authorization.
  • to reduce the risk of the project.
  • to estimate the project duration and schedule during the detailed design phase.
  • to identify potential risks early to enable the development of mitigation strategies to address them.

A number of preliminary engineering documents are produced in the front-end engineering design phase (Click here to learn about all 12 phases of project implementation) which are used as the start-up documents for the detailed engineering design phase. Combinedly, these documents are known as the “FEED Package”. A good FEED package reflects all of the client’s project-specific requirements to avoid significant changes during the execution phase. The FEED package forms the basis for the design execution of EPC or EPCM projects.

Time Duration for FEED Project

FEED projects are fast-track engineering projects. The time duration for a front-end engineering design project is normally less than one year. So, it requires enough experience to execute FEED projects with safety within a short time period. Close communication between Project Owners and Operators (Client) and the Engineering Consultant is required to address all the client requirements in the FEED package.

Types of FEED Project

Depending on the extent of the detailing required during front-end engineering design phases, FEED projects can be categorized into three groups

  • Basic FEED
  • Intermediate FEED and
  • Extended FEED

Front End Engineering Design Deliverables

Considering Piping Engineering as the basis, the front-end engineering design deliverables for a FEED project can be listed as follows:

  • Basic FEED deliverables:
  • Intermediate FEED deliverables:
    • Deliverables mentioned in Basic FEED
    • Piping Purchase Specification
    • Piping Layout Design Basis
    • Piping Stress Analysis Design Basis
    • Interface Register
    • Demolition Scope details/drawings
    • Concept Notes on the overall plot plan
    • The assumption on the design basis
  • Extended Feed deliverables:
    • Deliverables mentioned in Basic and Intermediate FEED
    • Unit Plot Plan
    • Equipment Layout
    • Pipe-rack sections
    • Pipe thickness Calculation
    • Valve datasheets
    • Preliminary Stress Analysis for pipe routing/civil loading
    • Piping Support Standard
    • Special Item list
    • Piping Standard Assembly Drawings
    • Piping Scope of Work
    • Preliminary 3D Model

Typical FEED engineering deliverables with respect to the process engineering team are

Benefits of FEED in Oil and Gas Projects

The FEED phase offers several benefits, which significantly impact the overall success of oil and gas projects:

1. Enhanced Project Clarity

FEED provides a clear and detailed design blueprint, reducing ambiguity and setting well-defined project goals. This clarity helps in aligning all stakeholders and minimizing misunderstandings.

2. Improved Cost Control

By providing accurate cost estimates and identifying potential cost overruns early, FEED enables better financial planning and budget control. This reduces the likelihood of unexpected expenses during later stages.

3. Reduced Project Risk

Early identification and assessment of risks allow for the development of effective mitigation strategies. This proactive approach helps minimize delays and avoid costly setbacks.

4. Regulatory Compliance

FEED ensures that the project design adheres to regulatory requirements and industry standards. This compliance is crucial for securing permits and avoiding legal issues.

5. Optimized Project Schedule

A well-defined FEED phase contributes to a more accurate project schedule, helping to streamline the construction and commissioning phases. This reduces the risk of project delays and ensures timely completion.

Inputs required for FEED Project

Roughly the following inputs are required to proceed with a FEED project

  • FEED Engineering Scope of Work
  • Feasibility Study Report
  • Location and Details of the area where the plant will be built
  • List of Applicable Codes and Standards
  • Customers technical practices

Overall, the FEED phase is considered an important and critical planning tool.

What comes after front-end engineering design or FEED Engineering?

Front-End Engineering Design identifies all technical requirements, potential risks, and approximate costs of the proposed project. Once there is a green signal for the project execution, Detailed Design Engineering, Detailed Engineering, or DD Engineering comes into place. So, Detailed Engineering comes after FEED engineering.

What is a FEED study?

The Front-end engineering and design process is one of the most important pre-project planning activities. A typical FEED study consists of producing technical documents, confirming product specifications, clarifying the project scope, and estimating the approximate project cost.

What is pre-FEED engineering?

Pre-FEED Engineering is a preliminary step that is usually undertaken before starting the basic engineering work. Pre-FEED engineering is an optional project phase and may be skipped. In the pre-FEED stage, the technical and economic feasibility of the project is sometimes confirmed. Depending on the nature of the project and the uncertainties involved, pre-FEED work may be combined with conceptual work and studies.

What is the front end of a project?

The front-end phase of a project is the initial phase of a project when the project idea is conceived. The front-end phase of the project ends when the final decision to start or not start the project is made.

Differences between FEED and Detailed Engineering: FEED vs Detailed Engineering

Both FEED and detailed engineering are completely different terms in a project life cycle. FEED is the basic engineering with the aim of establishing the project costing. Whereas, detailed engineering is the actual detailed project work for design and construction. Some of the major differences between detailed engineering and FEED engineering are tabulated below:

FEED EngineeringDetailed Design Engineering
Front End Engineering Design is an up-front basic engineering phase. This is an early phase after conceptual design; which precedes Detailed Design.Detailed Engineering is the design phase when all design work is done in detail to put into construction and operation. It follows FEED; comes after project approval and before construction.
FEED develops a comprehensive design basis and outline of the project.Detailed Design finalizes all technical details required for construction and installation.
FEED is done mainly to assess the cost and produce preliminary basis documents. It provides a preliminary cost estimate and budget analysis.Detailed Engineering is the design phase when all design work is done in detail to put into construction and operation. It offers more accurate and detailed cost estimates based on the finalized design.
FEED is done with an acceptable level of accuracy. It is a high-level design with preliminary specifications and layout.Detailed engineering is done with utmost accuracy. It is a detailed design with precise calculations, materials, and dimensions.
The time requirement of FEED engineering is short.Detailed Engineering requires more time as compared to FEED.
The cost and manpower requirement for the FEED project is less.Detailed Design needs more manpower and the associated cost is also much higher than the FEED stage.
The FEED phase may not end with Detailed EngineeringAll Detailed Engineering projects usually have a FEED phase.
FEED outlines a preliminary project schedule with major milestones.DD develops a detailed construction schedule with specific tasks and deadlines.
The FEED phase identifies potential risks and develops preliminary mitigation strategies.The DD phase refines risk assessments with more detailed analysis and updated mitigation plans.
FEED allows for design changes and refinements as the project scope is defined.The detailed design phase focuses on finalizing and locking in design details with minimal changes.
During FEED, a FEED report is produced summarizing the design approach, cost, and schedule estimates.Detailed design generates detailed engineering documents, including drawings, specifications, and calculations.
Table 1: Detailed Engineering vs FEED Engineering

Front-End Engineering Design (FEED) is a pivotal phase in the lifecycle of oil and gas projects, setting the stage for successful execution and project delivery. By providing a comprehensive design blueprint, cost estimates, and risk assessments, FEED ensures that projects are well-planned and positioned for success.

Maximum Shear Stress Theory: Tresca Theory of Failure

Written by Anup Kumar Dey in Civil,Mechanical,Pipeline,Piping Interface,Piping Stress Analysis,Piping Stress Basics

Maximum shear stress theory provides failure criteria for mechanical components made of ductile material. This failure criterion is developed by the French mechanical engineer, Henri Tresca, and based on his name maximum shear stress theory is also known as the Tresca theory of failure. Due to their enormous contribution to the field of plasticity, Henry Tresca is popular as the father of the field of plasticity.

Maximum shear stress theory is one of the two main failure criteria that are widely used in recent times for predicting the failure of ductile materials. To establish the failure criteria of material, all failure theories compare a specific parameter with the same parameter for the uniaxial tension test. The maximum shear stress theory is no exception and the parameter for comparison in Tresca theory is maximum shear stress.

“The maximum shear stress theory states that the failure or yielding of a ductile material will occur when the maximum shear stress of the material equals or exceeds the shear stress value at yield point in the uniaxial tensile test.”

Maximum shear stress theory formula

Let’s deduce the mathematical form of the above-mentioned Tresca theory statement.
Considering principal stresses, at the yield point, the principal stresses in a uni-axial test, σ1 =σy; σ2 = 0 and σ3 = 0.
So the maximum shear stress at yielding: σsy =σ1/2. Therefore σsy = σy/2

Now assuming σ1 >σ2 >σ3; the maximum shear stress for the material is given by:

τmax=(σ1 -σ3 )/2

Now comparing these to maximum shear stresses following Tresca theory, failure will happen when τmax>=σsy

Safe Design Condition as per Tresca’s theory of failure

So the design of a mechanical component should be based on the following maximum shear stress theory equation

τmax<=σsy or (σ1 -σ3)<=σy

The factor of safety (N) can also be calculated based on maximum shear stress theory and given by N=σsy /τmax

Hence, the maximum permissible shear stress for designing a component as per maximum shear stress theory is given by τmax =σsy /N

The failure envelope for Tresca’s theory of failure is provided in Fig. 1 below:

Failure Envelope as per Maximum Shear Stress Theory
Fig. 1: Failure Envelope as per Maximum Shear Stress Theory

Steps for using the Maximum Shear Stress Theory

To use the maximum shear stress theory in problem-solving the following steps are necessary to be followed:

  • Step 1: Determine the three principal stresses (σ1,σ2, and σ3) from the tri-axial stress system using principal stress equations or Mohr’s circle method.
  • Step 2: Find out the maximum (σ1) and the minimum (σ3) principal stresses.
  • Step 3: Determine the value of the maximum shear stress τmax=(σ1 -σ3 )/2.
  • Step 4: Find out the allowable stress value of the material; allowable stress= σsy /N or σy /2N as mentioned above (N=Factor of safety)
  • Step 5: Compare the value calculated in step 3 with the allowable value found in step 4. If the Value at step 3 is less than the allowable value at step 4, then the design is safe as per the maximum shear stress theory.

Maximum Shear Stress Theory vs Von Mises Stress Theory

Von Mises and Tresca’s failure criteria are normally presented jointly with little discrimination between them. However, there are some differences between them which are tabulated below:

Maximum Shear Stress TheoryVon Mises Stress Theory
Maximum Shear Stress theory or Tresca theory of failure relates to the maximum shear stress of ductile materials.Von Mises’s stress theory represents the maximum distortion energy of a ductile material.
This theory is considered to be more conservative. The Tresca theory, generally provides higher safety margins in certain applications.Considered less conservative when compared with Tresca’s theory. It provides a more refined approach to determine yielding under complex loads.
Component cost designed based on Tresca theory increases.Component Cost is Optimized for the design based on Von mises theory.
Required only two principal stress equations (σmax and σmin) to calculate the maximum shear stress.Use all three principal stresses (σ1 ,σ2 , and σ3) in its equation for calculating Von Mises Stress.
Predicts yielding based on maximum shear stress differences.Predicts yielding based on a combination of all principal stresses.
Table: Tresca theory vs Von Mises theory

The following article describes the applicability of Tresca and Von-Mises Theory with respect to Piping and Pressure Vessel Applications: Tresca or Von Mises: Their Applicability in Piping and Pressure Vessel Applications.

The failure envelope for Tresca theory and Von Mises theory is given in Fig. 2:

Failure Envelope as per Tresca and Von Mises Stress Theory
Fig. 2: Failure Envelope as per Tresca and Von Mises Stress Theory

Limitations of Maximum Shear Stress Theory

While the Maximum Shear Stress Theory provides a valuable framework for predicting material failure, it has its limitations. Some of the key limitations include:

  1. Material Behavior: The theory is primarily applicable to ductile materials. For brittle materials, other criteria, such as the Mohr-Coulomb criterion, may be more appropriate.
  2. Complex Loading Conditions: In cases where multi-axial loading is present, the Maximum Shear Stress Theory may not fully capture the material behavior.
  3. Non-Isotropic Materials: The theory assumes isotropic material properties, meaning it may not apply to materials with directional dependence in their properties.
  4. Temperature Effects: The theory does not account for changes in material properties due to temperature variations, which can significantly affect yield strength.
  5. The maximum shear stress theory does not give accurate results for the state of pure shear stresses developed by the Torsion test.
  6. The Tresca theory provides conservative results leading to an increase in component cost.

Applications of Maximum Shear Stress Theory

Structural Engineering

In structural engineering, the Maximum Shear Stress Theory is often applied to predict the failure of beams, columns, and other structural elements subjected to various loading conditions. By analyzing the shear stresses in components, engineers can ensure that structures remain safe under expected loads.

Mechanical Design

Mechanical components such as gears, shafts, and fittings often experience complex stress states. Using the Maximum Shear Stress Theory allows designers to assess the likelihood of failure in these components, leading to safer and more reliable designs.

Geotechnical Engineering

In geotechnical applications, the Maximum Shear Stress Theory can be used to analyze soil stability under various loading conditions. Understanding the shear strength of soil is crucial for designing foundations, retaining walls, and other earth structures.

Piping Engineering

In piping stress analysis, the Tresca theory is widely used.

In conclusion, the Maximum Shear Stress Theory remains a cornerstone of material failure analysis in engineering. Its ability to predict yielding under complex stress states is invaluable across various fields, from structural to mechanical engineering. Despite its limitations, it serves as a reliable criterion for assessing material behavior and designing safe structures and components.

What is a Topographic Survey? | Cost of Topographic Survey

Written by Anup Kumar Dey in Civil,Pipeline,Piping Interface

What is a Topographic Survey?

A topographic survey identifies and measures the exact location, shapes, arrangements, and features of all-natural and manmade features on a specified land surface. It gathers data on land contours, the elevation of the terrain, etc required by engineers, architects, local government bodies, and contractors for accurate visualization for development/updation work. The topographic survey encompasses a broad range of surveying and mapping products, ranging from ground to aerial mapping and underground surveys.

Depending on the client’s requirement, a topographical survey picks up several different elements like

  • Man-made Structures and features
  • Buildings & structures
  • Boundaries and fence lines
  • Surfaces such as paving, tarmac, concrete, etc
  • Services such as power lines, telephone lines
  • Natural features
  • Drainage features such as inspection chambers
  • Street furniture like benches, bins, lamp posts, etc
  • Trees, bushes, and vegetation
  • Changes in surfaces
  • Ponds, lakes, watercourses
  • Ground heights/contours
  • Water levels

After the topographic survey, the collected information is compiled into an electronic CAD (Computer-Aided Design) file (AutoCAD, Microstation) to prepare a 2D plan drawing. Which can be printed as required. A topographic survey is also known as a contour survey.

Topographic Survey

Requirements of Topographic Survey

To correctly plan and execute any project with safety, a topographic survey provides accurate measurements explaining how the existing site is arranged. Hence, a Topographic survey is the starting point for the design and construction work of various projects like:

  • New buildings/structures/construction/architecture
  • Civil engineering projects like road design, bridge design, tunnel design, or improvements.
  • Land repurposing/environment restoration/land development
  • Utility design
  • Grading or drainage projects
  • Pipeline projects for pipe routing
  • The regulatory requirement for construction work
  • Re-positioning of boundaries
  • Geology, petroleum, and forestry

A topographic survey helps in preparing alignment drawings, preparing cross-sectional profiles, identifying existing structures, controlling locations, establishing elevation differences, and finding the presence of underground utilities like pipelines, electrical cables, etc.

Process of Topographic Survey

A topographic survey process consists of various steps like:

  • Receiving the client specification on the topographic survey that includes levels of survey details and information they are looking for.
  • Planning the time schedule with the client and negotiating the price.
  • Gathering Site data from the topographic survey.
  • Processing the data and preparing it as per the agreed format.
  • Quality assurance
  • Final handover of the report to the client.

Gathering survey data is the most important step. The time required for a topographic survey is dependent on

  • The size of the area to be surveyed and
  • The complexity of the terrain
  • The level or detail and accuracy required

Equipment /Tools for Topographic Survey

A topographic survey is conducted using various survey equipment and tools that measure distances and angles with extreme accuracy. Typical tools are

  • GPS survey equipment
  • Laser Scanning Tool to accurately record position points in plan and elevation.
  • Tripod-mounted robotic total station with appropriate software
  • Digital Levels
  • Differential Global Positioning System (DGPS)
  • Wireless computer unit
  • 3D Scanners
  • Electronic distance measurement (EDM) reflectors
  • Range poles, Pegs, Nails, Measuring tapes, Level Rods, Digging Tools, etc

Outputs from Topographic Survey

A wide range of information can be produced from topographic surveys. This information is used for producing topographic survey drawings. Some of the outputs from the topographical survey are:

  • Drawings – Plan and elevation drawings, sectional drawings, and lighting plans
  • 3D Point Clouds for producing 3D site models.
  • Photographs to get actual site information and feel
  • Schedules – Including chamber inverts and pipe/pipeline diameters.
  • A detailed topographical survey report mentioning major details.

Advantages of Topographic Survey

The main advantages of conducting a topographic survey are:

  • Reduction of risk from costly mistakes due to the absence of accurate site details.
  • A deeper understanding of land topography helps in the proper planning and cost estimation of the project.
  • The topographic survey includes recent changes and hidden information, thus making the design and construction work easier.
  • When shared in a GIS system, the topographical survey can serve as the ‘base map’ for multiple parties to share their design work, construction planning, and cadastral / land ownership information.
  • Governmental agencies use topographical surveys for enforcing construction and zoning regulations and evaluating existing infrastructure.

Cost of Topographic Survey

The cost of a topographic survey depends on various factors like

  • plot area size
  • plot location
  • how overgrown the area is
  • details required in topographic survey specification
  • accuracy required
  • specific requirements of equipment used.

The cost of a typical topographic survey ranges from $500 to $1,000 per day. So, the total topographical survey cost will add up as per the days required for completing the survey and generating the final report. Also, the topographic survey cost varies from one geographic region to the other.

Topographic Surveys by Drone

A topographic survey by drone technology or drone surveys has become quite popular in recent times. Increasingly clients are asking for ‘drone surveys’. The use of UAV (unmanned airborne vehicles) technology to provide rapid and thorough topographical surveys has increased to a large extent because:

Drone Topographic Survey
Drone Topographic Survey
  • A topographic survey using a drone is cheap and fast.
  • The method is accurate and repeatable with exhaustive data.
  • Surveying becomes easy and provides a good return on investment
  • Better insight from rich visual datasets captured by highly effective sensors.
  • Drones reduce the workload on topographic survey specialists
  • Easily map inaccessible areas.

However, note that there could be governmental restrictions on flying a drone over a specified area. So clearances must be obtained before conducting a topographical drone survey in those areas.

To learn more about the subject, some online-courses can be accessed by clicking here.

Further Studies on Topographic Survey:

Manual of Topographic Survey: report.pdf (usgs.gov)

Brownfield vs Greenfield: Differences Between Brownfield and Greenfield Oil and Gas Projects

Written by Anup Kumar Dey in Civil,Mechanical,Piping Interface,Project Management

The term “Brownfield vs. Greenfield” is frequently heard during project execution. This is a very meaningful term for the oil & gas industry. But, the term greenfield vs brownfield is not only related to oil & gas industries but is widely used in many industries like IT, Construction, Manufacturing, Building Services, etc. Overall, both these terms are related to any kind of project. In this article, we will find out more about Brownfield and Greenfield and their differences.

What is a Brownfield Project?

Brownfield projects are projects where some work has already been made. The site is already partly developed with the required infrastructure. From that point onwards, new developments will be started. Considering Oil & Gas, new expansion projects, revamp projects, yield improvement projects, redevelopment or enhancement of existing oil and gas facilities or fields, etc. come under brownfield projects. These sites may have a legacy of production, but they can also present challenges such as contamination, aging infrastructure, and regulatory hurdles.

Key Characteristics of Brownfield Projects:

  • Existing Infrastructure: Brownfield projects leverage existing drilling platforms, pipelines, refineries, and other facilities, which can reduce initial capital expenditures.
  • Environmental Concerns: Many brownfield sites may have residual contamination from previous operations, necessitating thorough environmental assessments and remediation efforts.
  • Regulatory Oversight: Brownfield developments often face stringent regulations regarding environmental safety, requiring compliance with cleanup standards set by government agencies.

What is a Greenfield Project?

A greenfield project starts from scratch. The site is not developed, and the required infrastructure for the project is normally not present. So a greenfield project starts afresh from scratch. For oil and gas, completely new projects in undeveloped places, like new refinery construction, new drilling locations, setting up of a chemical or petrochemical plant, etc. fall under greenfield projects.

Key Characteristics of Greenfield Projects:

  • Untapped Resources: Greenfield projects offer the potential for exploring new reserves, making them attractive for companies seeking to expand their resource base.
  • Modern Design Opportunities: Developers can implement the latest technologies and sustainable practices from the outset, leading to more efficient and environmentally friendly operations.
  • Regulatory Framework: Although greenfield projects still require permits and approvals, they generally face fewer legacy regulatory challenges compared to brownfield sites.

Examples of Brownfield and Greenfield Project Concepts

The above concept can be clearly understood from the following examples:

  • For the software industry, updating an existing application to add some new capabilities can be considered a brownfield. However, creating a completely new application is considered greenfield.
  • For the Real estate sector, constructing a new tower in an already developed society complex is considered a brownfield whereas constructing a completely new society complex is a greenfield project.
  • For a chemical plant, modification of the plant to increase productivity is considered a brownfield whereas constructing a new chemical plant is a greenfield project.

Differences between Brownfield and Greenfield Projects in the Oil and Gas Sector

From the above definitions and examples, it is clear that both brownfield and greenfield are completely different concepts. The major differences, subject to some basic parameters, are listed below:

Brownfield vs Greenfield
Fig. 1: Brownfield vs Greenfield

1. Brownfield vs Greenfield: Economic Consideration

From the economic point of view, as brownfield projects are normally small-sized, total initial money involvement is comparatively smaller. While brownfield projects can benefit from existing infrastructure that may reduce initial costs, they often incur additional expenses related to environmental cleanup and compliance. The complexity of these projects can lead to unpredictable costs and delays

On the other hand, greenfield projects are large projects, and starting from scratch, the initial project cost is larger. They may require significant upfront investment to establish new infrastructure, but they avoid the complications associated with remediation. The potential for modern, efficient designs can also lead to lower operational costs in the long run.

2. Greenfield vs BrownField: Space Constraint

Considering refinery projects, in brownfield projects space is limited so each element, piping, equipment, and structure need to be minutely checked and placed. Also, because of limited space pipe routing becomes critical as the designer has to use the available space only considering all construction activities as larger construction equipment may not be accessible. Also, there is limited storage space and parking space for project requirements.

On the other hand for new projects, there is much flexibility in design as the initial complete area is empty. So locating equipment and pipe routing becomes much easier. Also, better planning and optimization are possible in greenfield projects.

3. Brownfield vs Greenfield: Infrastructure Requirement

As brownfield projects are normally expansions or improvements of existing projects, the required infrastructure is available. It’s easy to arrange labor in already-developed places. Places are easily accessible for deliveries. Earlier design data, soil reports, etc are easily available.

Greenfield projects are new projects, and most of the time in undeveloped places, required infrastructure needs to be created during the project run which will impact the project schedule and deliveries.

4. Environmental Management

Brownfield: Environmental challenges are a significant concern for brownfield projects. Some sites may require extensive remediation to address soil and groundwater contamination. This process can be time-consuming and costly, affecting the overall project timeline and budget.

Greenfield: Greenfield projects typically start with clean land, allowing for straightforward environmental assessments. However, developers must still consider potential impacts on local ecosystems and biodiversity.

5. Regulatory Complexity

Brownfield: The regulatory landscape for brownfield projects is often intricate, with multiple agencies involved in overseeing remediation efforts and ensuring compliance with environmental laws. Navigating these regulations can be a major hurdle for developers.

Greenfield: While greenfield projects must comply with environmental regulations, they often face fewer historical constraints. However, companies must still engage in comprehensive planning to meet local zoning and environmental standards.

6. Community Impact and Stakeholder Engagement

Brownfield: Redeveloping brownfield sites often involves significant community engagement due to the historical impact of previous operations. Stakeholders, including local residents and environmental groups, may have concerns about contamination and the potential for gentrification.

Greenfield: Greenfield projects may face community opposition due to concerns about land use, environmental disruption, and impacts on local wildlife. Effective stakeholder engagement is crucial to addressing these concerns and fostering community support.

7. Strategic Opportunities

Brownfield: For oil and gas companies, brownfield projects can be strategically beneficial as they can often tap into remaining reserves in mature fields. Enhanced oil recovery techniques can be employed to maximize extraction from existing wells.

Greenfield: Greenfield projects represent opportunities for innovation and expansion into new markets. They allow companies to explore previously untapped reserves and implement cutting-edge technology from the start.

8. Greenfield vs Brownfield: Other differences

Other major differences between brownfield and greenfield are tabulated below:

Brownfield ProjectGreenfield Project
Brownfield projects have limited space and difficulty in further future development. Even finding the required plot size could be difficult.Greenfield projects have ample space, and future expansion is possible.
Easy accommodation for crew members as in the brownfield project they are already built.Accommodation in greenfield projects could be difficult, so it must be built beforehand.
Brownfield projects get easy access to local suppliersOn the contrary, greenfield projects have limited local suppliers in undeveloped locations.
Demolition requirements in brownfield projects can increase the project cost.Greenfield projects are completely new, so no demolition requirement.
Normally there are no governmental restrictions. However, they may be subject to strict regulations for remediation and safety.There could be governmental restrictions if deforestation or similar environmental issues arise. They usually face fewer legacy regulations but still require permits.
Local interference can delay projects.There is no chance of local interference as greenfield plots are usually new and in undeveloped places.
Brownfield development localizes communities in a limited congested region.Developing greenfield sites reduces traffic and congestion with a more pleasant environment.
Risk factors in brownfield projects are high due to environmental liabilities and public scrutiny.Lower risks in terms of legacy issues but still subject to market fluctuations.
The innovation potential is usually limited by existing infrastructure and past practicesHigh potential for innovation and sustainable practices in greenfield oil and gas projects.
Table 1: Brownfield vs Greenfield Projects

How to Choose between Greenfield and Brownfield Oil and Gas Project

Choosing between a greenfield and a brownfield oil and gas project involves careful consideration of various factors. Here’s a guide to help you make an informed decision:

1. Resource Availability

  • Greenfield: Assess the potential for untapped reserves in new locations. Consider geological surveys and exploration data.
  • Brownfield: Evaluate the remaining reserves in existing fields and the potential for enhanced oil recovery (EOR) techniques.

2. Cost Analysis

  • Greenfield: Estimate the total investment required for new infrastructure, including drilling, transportation, and processing facilities.
  • Brownfield: Calculate the costs associated with remediation and compliance with environmental regulations, alongside infrastructure upgrades.

3. Environmental Considerations

  • Greenfield: Conduct environmental impact assessments to understand the potential effects on ecosystems and local communities.
  • Brownfield: Evaluate the extent of contamination and the necessary remediation efforts to meet regulatory standards.

4. Regulatory Environment

  • Greenfield: Research zoning laws, permitting processes, and environmental regulations for new developments.
  • Brownfield: Understand the legal complexities and compliance requirements related to the cleanup of contaminated sites.

5. Market Demand and Economic Factors

  • Assess the current and projected demand for oil and gas products. Consider how each project aligns with market trends and pricing fluctuations.

6. Timeline and Feasibility

  • Greenfield: Evaluate the projected timeline for development, including exploration and construction phases.
  • Brownfield: Consider potential delays due to remediation efforts and regulatory approvals.

7. Community Engagement

  • Greenfield: Prepare for potential community opposition. Engage with local stakeholders early in the process to address concerns.
  • Brownfield: Involve the community in discussions about the benefits of revitalizing contaminated sites and ensuring safety.

8. Technological Considerations

  • Greenfield: Leverage modern technologies for exploration and extraction to enhance efficiency and reduce environmental impact.
  • Brownfield: Assess the potential for upgrading existing technologies to improve recovery rates and reduce operational costs.

9. Risk Assessment

  • Analyze risks associated with each type of project, including financial, operational, environmental, and reputational risks.

10. Long-Term Sustainability Goals

  • Consider how each project aligns with your company’s sustainability objectives. Greenfield projects may allow for the incorporation of sustainable practices from the outset, while brownfield projects can contribute to urban revitalization and pollution reduction.

The decision between a greenfield and a brownfield project in the oil and gas industry requires a comprehensive evaluation of resources, costs, environmental impacts, regulatory frameworks, community considerations, and long-term goals. Engaging with stakeholders and conducting thorough feasibility studies can help ensure that the chosen path aligns with both business objectives and responsible development practices.

To conclude, in the oil and gas industry, the choice between brownfield and greenfield projects involves a complex interplay of environmental, regulatory, financial, and community considerations. Brownfield projects can revitalize existing sites and maximize resource extraction but come with significant challenges related to contamination and regulatory compliance. Greenfield projects offer the opportunity for innovation and exploration but require substantial investment and careful community engagement.

Ultimately, the decision will depend on the specific context of the project, including resource availability, regulatory environments, and strategic goals.

What is Von Mises Theory of Failure? Formula for Von Mises Stress

Written by Anup Kumar Dey in Mechanical,Piping Stress Analysis,Piping Stress Basics

Von Mises Stress criterion is one of the widely used criteria for designing ductile material engineering components. To judge if a design is within design limits and will work safely for its design life, Von Mises Stress Criteria prove to be highly effective. Von Mises’s stress concept is developed from the distortion energy theory and a highly preferred failure theory used in the mechanical design industry.

This theory is devised by James Clerk Maxwell in 1865, but in 1913 it was rigorously developed by Richard Edler Von Mises, an Austrian Jewish scientist and mathematician. Accordingly, the theory is popular as Von Mises’s Stress theory. In this article, we will explore more details about Von Mises’s Stress.

What is Von Mises Stress?

Von Mises stress is an equivalent stress value based on distortion energy to decide if a ductile material will fail (yield or fracture) under a given loading condition. The Von Mises failure theory indicates that A material will fail if the Von Mises stress or effective stress of that material under load is equal to or greater than the yield limit of the same material under a simple uniaxial tension test.

Equation/ Formula for Von Mises Stress

Failure of any material is decided by a simple tension test. In this test when the material reaches the yield point, the material is considered as failed. Now failure by distortion energy or Von Mises Stress theory compares two kinds of distortion energy.

  • Case A: Distorsion energy for the actual case with complex loading conditions.
  • Case B: Distorsion energy for the same material in the simple tensile test during failure.

As per Von Mises’s Stress theory, Failure will occur if Case A>=Case B. Mathematically, this can be explained as below:

Distorsion Energy (ud) for the actual stress condition in terms of principal stress values (σ1, σ2, σ3)

Distortion Energy Equation

Again, the distortion energy for the uniaxial tension case at the time of failure is given as:

So, as per distortion energy theory,

Distortion Energy theory

Now, the formula for Von Mises Stress, σv is given by

formula for Von Mises stress

So, the above equation becomes, σv2>=σy2

So, the Von Mises failure condition can be simplified as follows:

Von Mises Failure Theory

In the cases of plane stress, σ3 = 0. The von Mises criterion reduces to,

Von Mises Stress for two dimensional plane stress

The failure envelope based on distortion energy or Von Mises Stress theory can be represented in two dimensions as follows:

Failure envelope as per the distortion energy theory
Fig. 1: Failure envelope as per the distortion energy theory

Steps for solving problems using the Von Mises Stress Theory

To use the Von Mises Stress theory in solving problems the following steps are required to be followed:

  • Step 1: Calculate the three principal stresses (σ1,σ2, and σ3) using principal stress equations or Mohr’s circle method.
  • Step 2: Find out the Von Mises Stress (σv) following the equations mentioned above.
  • Step 3: Determine the value of the allowable stress (σy/N) of the material. σy is the Yield Strength and N is the factor of safety.
  • Step 4: Compare the value calculated in step 2 with the allowable value found in step 3. If the Value at step 2 is less than the allowable value calculated at step 3, then the design is safe as per the Von Mises stress theory.

Applications of Von Mises Stress Theory

During the mechanical design of elements, It is the duty of every engineer to keep the Von Mises Stress (σv) value below the yield strength (σy) of that material to make the design safe. This theory finds wide application in Finite Element Analysis.

In piping stress analysis and structural beam design, Von Mises Stress theory is applied to make the piping or structural beams safe from various loading conditions.

Difference between Von Mises’s theory and Maximum Shear Stress Theory

As distortion is always associated with shear stress; there are some similarities between both failure theories. The main differences between the Von Mises theory and the maximum shear stress theory are listed below:

  • The Von Mises theory predicts ductile yielding with more accuracy as compared to the maximum shear stress theory. It is more real and less conservative than the maximum shear stress theory and hence, product cost reduces.
  • Von-Mises theory uses all three principal stresses (σ1,σ2, and σ3) in its equation, while the maximum shear stress theory uses only two (σmax and σmin ).

The following article describes the applicability of Tresca and Von-Mises Theory with respect to Piping and Pressure Vessel Applications: Tresca or Von Mises: Their Applicability in Piping and Pressure Vessel Applications

What is a Double Block and Bleed (DBB) Valve? Its Working and Application

Written by Anup Kumar Dey in Engineering Materials,Health & Safety,Mechanical,Pipeline,Piping Design Basics,Piping Interface

Oil and gas, petrochemicals, and pharmaceuticals rely heavily on complex pipe systems to transport fluids, gases, and chemicals. In these applications, maintaining a tight seal, isolating equipment, and facilitating maintenance are essential. A Double Block and Bleed (DBB) valve is such a critical component that combines these functions to enhance safety and operational efficiency. In this article, we will explore what DBB valves are, how they work, their applications, and why they are crucial in modern industrial processes.

What is Double Block and Bleed Valve (DBB)?

A Double Block and Bleed (DBB) valve is a specialized type of valve designed to provide a superior level of isolation and safety in fluid control systems. Essentially, it combines the functions of two separate valves and a bleed port into a single, compact unit.

Double Block and Bleed Valve is a single assembly of two inline block valves and one bleed valve. A DBB valve is like having three valves in one. The task of three separate valves is performed by this assembly while saving huge space, installation, and maintenance time, weight, and cost.

The main aim of using a double block and bleed valve system is to ensure that the fluid from upstream and downstream does not reach other components of the system. So, engineers can easily bleed off or drain the remaining fluid from the intermediate section and execute maintenance, repair, or replacement work. In a double block and bleed system, isolation is achieved both from upstream and downstream flow or pressure. The bleed valve is used to drain the cavity created between two block valves.

Components of DBB Valve

Let’s break down its components and functions:

Two Isolation Valves:

The “double block” part of the DBB valve consists of two isolation valves, typically ball or gate valves, arranged in series. These valves, when closed, create a double barrier that isolates the downstream and upstream piping, ensuring no flow passes through.

Bleed Valve:

The “bleed” portion of the DBB valve is a smaller valve, often a needle valve, located between the two isolation valves. Its purpose is to allow controlled bleeding of fluid or gas from the cavity between the two isolation valves. This is crucial for verifying the integrity of the seals and for safely releasing pressure.

An NPS 3/4-inch or 1-inch bleed valve is installed between two block valves for venting or draining as shown in Fig. 1.

Schematic of Double block and Bleed valve
Fig. 1: Schematic of Double block and Bleed valve

The image in Fig. 1 also serves as the double block and bleed valve P&ID symbol. In some companies, the P&ID system for the DBB valve can be represented as shown in Fig. 2.

Double Block and Bleed Valve P&ID Symbol
Fig. 2: Double Block and Bleed Valve P&ID Symbol

Working Principle of a Double Block and Bleed Valve

Two block valves provide isolation from the upstream and downstream flows. A set of gate, ball, needle, or globe valves is normally used as the block valves that are placed back to back. In the center cavity of the two-block valves, a third valve known as the bleed valve is positioned. Fig. 3 shows a typical double block and bleed valve diagram.

Double Block and Bleed valve diagram
Fig. 3: Double Block and Bleed valve diagram

The same double block and bleed arrangement can be obtained using three separate valves. But the single unit double block and bleed valve saves huge space, weight, installation time, and cost. Also, from the operation and maintenance viewpoint, single-unit double block and bleed valves are better as potential leak paths are significantly reduced in a single unit. Pressure drop is also minimized.

The operation of a DBB valve is relatively straightforward:

  • Normal Operation: In typical operational conditions, both isolation valves are open, allowing fluid or gas to flow through the valve as if it were a regular pipeline. The bleed valve remains closed.
  • Isolation: When maintenance or repairs are needed, the DBB valve offers a unique advantage. By closing both isolation valves, it effectively seals off the section of the pipeline in which it is installed. This isolation ensures that no fluid or gas can pass through.
  • Bleeding: After isolation, the bleed valve can be opened to release any trapped fluid or gas between the isolation valves. This step is crucial for safety and maintenance purposes, as it prevents pressure buildup that could be hazardous.

The main function of the bleed valve is

  • to drain/vent the cavity created between two isolation valves.
  • flow diversion
  • sampling and injection point connection
  • integrity or maintenance check connection to monitor leakage

Bleed valves can be vented to the atmosphere directly or a hose connection/piping system can be used for a closed disposal system.

Types of Double Block and Bleed Valves

Double Block and Bleed (DBB) valves ensure safe and dependable isolation of process fluids through a combination of block valves and a bleed valve. Depending on configurations, there are three types of DBB valves that are widely used:

  • Single valve systems,
  • Dual valve systems, and
  • Expanding gate valves.

Single Valve DBB

Single Valve DBB systems combine both block and bleed functions within a single valve body, featuring two separate sealing surfaces for effective isolation and a bleed function to vent trapped pressure. When closed, the primary and secondary seals create a double barrier, preventing fluid flow and ensuring isolation. A bleed port situated between the seals allows for the venting of any pressure or fluid once isolation is achieved, making the section safe for maintenance or inspection. Upon re-opening, the seals retract, restoring normal flow. The compact design of Single Valve DBB systems minimizes the need for additional piping and space, simplifying installation and maintenance. These systems are particularly useful in applications with space limitations and where moderate isolation integrity is sufficient.

Dual Valve DBB

Dual Valve DBB systems consist of two separate block valves and an independent bleed valve positioned between them, providing enhanced isolation integrity and maintenance flexibility. The first block valve is closed to prevent fluid from entering the isolated section, followed by the closure of the second block valve to create a dual barrier that ensures reliable isolation. Once both valves are closed, the bleed valve can be opened to vent any trapped pressure or fluid between the block valves, ensuring safety for maintenance personnel. During maintenance, the bleed valve is opened first to eliminate trapped pressure, followed by the opening of the block valves to restore normal operation. This setup offers enhanced safety through an additional layer of protection against leaks or failures and allows for independent maintenance of each block valve without compromising isolation integrity. Dual valve DBB systems are particularly suitable for high-integrity applications such as oil and gas pipelines, chemical processing plants, and other critical isolation scenarios.

Expanded gate valve DBB

Expanding gate valves are a type of DBB valve that utilize an expanding gate mechanism to achieve effective isolation, featuring a gate that expands laterally against the valve seats to create a tight seal. When the valve is closed, the gate presses firmly against the seats on both sides, establishing a double block and ensuring a strong barrier against process flow. A bleed port located between the expanded gates can be opened to vent any trapped pressure or fluid once the gates are fully expanded. Upon opening the valve, the gate retracts from the seats, allowing fluid to flow through. This mechanism provides a positive seal with minimal leakage, ensuring high integrity isolation, while its robust design is suitable for high-pressure and high-temperature applications. Expanding gate valves are commonly employed in the oil and gas industry, particularly in critical service scenarios where reliable isolation is crucial.

Codes and Standards for Double Block and Bleed valves

Double Block and Bleed Valves or DBBVs are designed and manufactured based on any of the governing codes

  • API 6D
  • API 607
  • API 6FA
  • BS6755-Part 2
  • ASME B16.34
  • EEMUA 182
  • API 598
  • BS EN ISO 17292
  • ISO 14313

Benefits of Double Block and Bleed Valve

The advantages of double block and bleed valve can be summarised as follows:

  • Compact design
  • Provides sealing against pressure from both the upstream and downstream ends of the valve.
  • The capability of venting the cavity in between the block valves.
  • Around 60% savings in weight and 70% savings in installation time.
  • High reduction of leak paths, ensuring low probability of hazard. Improved safety in operation.
  • Great savings in space as compared to a conventional arrangement using separate valves.
  • Can be used as chemical injections and sample points.
  • Prevent product contamination.
  • Remove equipment from service for cleaning or repair
  • Reduced Stresses from load and vibration
  • Uninterrupted flow for negligible pressure drop

Applications of Double Block and Bleed Valve

Double Block and Bleed Valve or DBB is widely used in systems requiring critical isolation. The major uses of DBB Valve include

  • Oil & Gas, Chemical, and Petrochemical industries.
  • LNG and Natural Gas industrial processes.
  • Isolate instrumentation such as level gauges, pressure indicators, etc.
  • Liquid pipelines and manifolds.
  • Prevent product contamination.
  • Transmission and storage, refined products transmission lines.
  • Meter Calibration.
  • Chemical injection and sampling.
  • Liquid service near waterways or municipalities.
  • Instrument drain connections.
  • Remove equipment from service for repair or cleaning.

Factors affecting Double block and Bleed Valve (DBB) Selection

The parameters that affect the selection of a double block and bleed valve are

  • Process Media and Application
  • Temperature and Pressure
  • Toxicity and Operating Environment
  • The material of Valve Parts

Depending on requirement various types of DBB Valve configuration is available in the market. In general, three types of double block and bleed valves are available; Single unit DBB, Cartridge Type Standard Length DBB, and Three Piece Non-Standard Length DBB.

Why DBB Valves Are Crucial

  • Safety: DBB valves are essential for maintaining safety in high-pressure systems. By providing double isolation and a bleed port, they reduce the risk of hazardous incidents during maintenance or emergencies.
  • Efficiency: DBB valves streamline maintenance procedures by allowing technicians to isolate specific sections of a pipeline without shutting down the entire system. This minimizes downtime and improves operational efficiency.
  • Cost Savings: Reduced downtime, minimized risk of leaks, and increased system reliability contribute to significant cost savings over the long term.
  • Compliance with Regulations: Many industry standards and regulations require the use of DBB valves for critical applications. Using DBB valves helps ensure compliance with these safety standards.

DBB vs DIB

A double isolation and bleed valve, or DIB, is a single valve with two seating surfaces. In a closed position, each of these seating surfaces provides a positive seal against pressure from a single source. There is a means of draining/venting from the cavity between seating surfaces. So, DIB looks almost similar to DBB and is quite confusing among many. The main differences between DBB and DIB valves are listed below:

Double Block and Bleed Valve (DBB)Double Isolation and bleed valve (DIB)
A DBB Valve provides sealing against pressures from both sides of the valve.A DIB provides an additional sealing against pressure from one side of the valve.
A DBB Valve has two unidirectional self-relieving seats which are independent of outside mechanisms for pressure relieving.A DIB uses one or two bi-directional seats which are not self-relieving requiring an external pressure-relieving mechanism.
In a DBB, if the first seal leaks, the second will not provide sealing in the same direction.DIB provides an additional pressure barrier from the main pressure barrier.
DBB vs DIB

Double Block and Bleed (DBB) valves are indispensable in the oil and gas industry, providing a reliable means of isolating and managing sections of pipelines and process systems. Their ability to offer double isolation and safe depressurization makes them a critical component in maintaining safety and efficiency in operations. By understanding their functionality, advantages, and applications, industry professionals can better appreciate the role of DBB valves in ensuring the safe and effective operation of oil and gas facilities.