April 2021

Engineering and Construction

Retrofit: A viable alternative to greenfield construction

Retrofitting/revamping—also referred to as modernization, derating or rerating—is an update of a plant or an existing piece of equipment to improve efficiency and/or capacity, and to make it adequate for a new design or operating condition through the modification or replacement of some of its parts.

Das, S. C. D., Fluor Daniel India Pvt. Ltd.

Retrofitting/revamping—also referred to as modernization, derating or rerating—is an update of a plant or an existing piece of equipment to improve efficiency and/or capacity, and to make it adequate for a new design or operating condition through the modification or replacement of some of its parts. New parts/equipment may be added to make the equipment and/or the plant adhere to demand. High-efficiency internals replace old ones, and some equipment parts are removed and replaced with new ones. For example, FIG. 1 shows a sketch for a typical fluid catalytic cracking (FCC) reactor-regenerator revamp. In this case, the existing regenerator is being retrofitted to cater to increased demand by replacing the cyclones, the dome, the air distributor, slide valve, spent catalyst deflector and linings (all highlighted in yellow and blue ink), while retaining the existing shell. The number of cyclones and the air distributor configuration were revised, and the existing design was checked for adequacy for loading conditions.

FIG. 1. Sketch of a typical FCC regenerator retrofit.


Several reasons exist why retrofitting a plant or unit is the most efficient option for owner-operators. Clients and investors are looking to optimize investment costs and are seeking a quick return on investment (ROI) and the production of better products. New greenfield projects are challenging due to their high investment costs and construction time frames. Owners are also looking for quick solutions to enhance the quality and quantity of existing energy products. Whether it is a large oil and gas project or a small chemical project, each company strives to increase existing plant capacity and product quality in a timely manner (i.e., reducing downtime).

Retrofitting/revamping includes the following objectives:

  • Increased equipment design life
  • Improvement in efficiency/throughput
  • Relocation of equipment/machinery
  • Testing of the latest technology
  • Increased energy savings
  • Improvement of maintenance and safety of operation
  • Adherence to environmental strains or legislational changes
  • Quick ROIs.

These objectives make retrofitting a sought-after solution for energy companies.

Retrofitting from a detailed engineering point of view

Equipment and internals have a set lifecycle per the client’s project-specific requirement. Most of the static, rotating and fired equipment, as well as the piping, have a design life of 20 yr–30 yr—whereas, internals (e.g., tubes and column internals) are designed to last for 10 yr–20 yr. Accordingly, corrosion allowances are built into the design. After a certain period of usage (i.e., age of equipment), equipment and components are degraded due to pressure, temperature, weight, vibration, environment, site conditions and flow transients. Most equipment undergoes at least one revamp during its lifecycle.

The author’s company has recently executed a study and detailed engineering activity for retrofitting a chemical plant. The old plant was in operation, producing products that adhered to local regulations. The author’s company carried out the study to ensure that the plant’s equipment and facilities were still fit for service. Fitness for service (FFS) purpose or mechanical integrity is a set of quantitative methods used to determine the integrity and remaining life of degraded components and to help operators make run-or-repair decisions.

Project managers and engineers visited the plant site for an initial evaluation. From visual inspection, various fabrication deficiencies and concerns were flagged by the team. These observations included the following:

  • Standard products for various equipment components (e.g., nozzle flanges, blind flanges, studs and bolts) were not used (FIG. 2).
    FIG. 2. Standard products for equipment components were not used.
  • Geometrical configurations (thickness and diameter) for various equipment components did not comply with that of standard products.
  • Mismatch of equipment details with that shown in as-built drawings.
  • Defects and cracks in equipment were clearly visible.
  • The subpar quality of fabrication, welding and repair work were clearly noticeable (FIG. 3).
    FIG. 3. The quality of fabrication, welding and repair was subpar.

Based on these observations, an adequacy check of the plant and its equipment was carried out based on available drawings, documents and site survey reports. Most of the facility and equipment failed this adequacy inspection, based on the following:

  • Code of construction (ASME vs. local standard)
  • Operation methodology
  • Source of equipment
  • Fabrication quality
  • Product standardization.

Most of the equipment was fabricated and operated as per local codes and plant operation methodology. These are based on FFS and do not meet the requirements or codes mentioned in the fabrication/as-built documentation. The client who purchased the plant decided to retrofit/revamp the existing plant and to increase capacity to make retrofitting economically viable.

In a separate project, a Middle Eastern client purchased equipment from a Western country and transported it to the proposed site. Most of the equipment was retrofitted/revamped to make it suitable for the design and operating conditions of the proposed plant. This was a challenging management decision, as many cost factors involved in retrofitting (such as the cost of existing equipment, logistics, transportation, retrofitting and reinstallation) needed to balance out the costs of new equipment fabrication and installation. The risk involved in anticipating the cost of retrofitting vs. new equipment installation was substantially high due to the uncertainty in estimating all types of cost in retrofitting. FFS relies on comparing the demand on the degraded component/equipment (e.g., the load exerted in-service in the form of pressure, temperature, weight, vibration and flow transients) to the components’ capacity to sustain demand.

With greenfield plants being capital intensive and having longer construction timelines, retrofitting an existing plant and equipment can be a viable option to meet product demand. Operating companies must have proper planning and documentation to greenlight a retrofitting project to meet current market demand and to maintain a grasp on the latest technologies and environmental legislation. Some of the key factors to consider include:

  • As-built drawing test reports and material certificates
  • Periodical equipment health check reports during planned maintenance and inspections
  • Remaining-life assessments for equipment, based on present operating and design conditions
  • New regulations and legislational changes
  • Planned capacity/efficiency improvements
  • The quality of the finished product.

All these factors must be assessed meticulously before greenlighting a retrofit on an existing plant. Other factors appear when equipment modifications, relocations, reinstallations and testing are carried out. These costs can impact an owner’s planned retrofit project budget. Technical risks include:

  • Specificity of works and experience of engineers/designers
  • Primary parties involved in the project (such as fabricators and construction contractors)
  • Technology used and compatibility between new design specifications and the original design
  • Technical safety margins on upgraded machines
  • Conservation measures during standstills
  • Logistics and security on working sites.

Various equipment codes boilers, pressure vessels, storage tanks and pumps also need to be verified during a retrofit project.


Retrofitting a plant or existing equipment is a viable option for oil and gas operators, as well as for chemical manufacturers. All parties must efficiently optimize their workflows to optimize costs and to increase the quality of the facility’s products, while adhering to regulations. The items presented here will help operators to minimize risk during retrofitting operations. HP

The Author

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