The six typical phases of an engineering design and construction project

Phase 1 – feasibility study

A workable process design is generated, project costs are analysed, systems are identified and the initial plot layout is proposed. The design is reviewed for safety and environmental considerations. All disciplines are involved.

The objective of a concept or feasibility study is to review a number of alternative project schemes to give sufficient information to enable a client go or no-go decision on whether to progress the most promising base case design.

Our example project was worth over £150 million and involved gas processing and transportation. The study was lead by the client team, with the project goals and objectives both in technical and commercial terms being established and assessed.

Conceptual studies typically last for three to six months, during which many alternatives are considered. This was the case on the example project where different compressor and turbine arrangements, gas feedstocks, flowrates and layouts were reviewed. Additionally, a cost estimate to ±30–40 per cent was generated, including preliminary costs for major equipment and factored estimates for piping, civil, electrical and instrumentation needs.

Engineers from each discipline were involved in brainstorming ideas, leading to fundamental savings in the total project cost.

Phase 2 – front-end engineering

Detail is added to generate an agreed process design and contractual information. All disciplines are involved.

During front-end engineering design (FEED), an engineering solution is developed with sufficient detail to enable a ±20 per cent estimate to be established. Additionally the project schedule is further developed, and commercial contracts prepared for product and feedstock supply. During this phase the project team expands and input is provided from engineering, estimating, planning and legal departments. For our project this took about eight months to complete.

Engineering development There were now about 40 people on the project team, who came from all the major engineering disciplines. An engineering manager with multidisciplinary knowledge directed the work, providing leadership and expertise to ensure that a robust and safe design was progressed.

The FEED led to the creation of primary design documents such as process flow diagrams, equipment lists and equipment data sheets. We developed piping and instrumentation diagrams (P&IDs) showing valves, instruments and safety devices, which then enabled a piping layout to be started. A three dimensional computer-aided design (CAD) model was used to create a common platform for all piping, civil and electrical interfaces.

Project development

Planners, project managers, procurement engineers and estimators developed a project schedule, control budget and cost estimate. The project team also participated in team workshops to voice ideas, generate cost-reduction schemes, improve communication and avert any anticipated problems in the detailed engineering phase ahead.

Phase 3 – detailed engineering

Mechanical work on technical bid analysis, procurement work on commercial bid analysis and quality control confirm acceptability of plant. When purchased, confirmed vendor data is used to complete the designs for electrical and instrumentation systems, piping and foundation/structural work. All disciplines are involved.

The project team takes the FEED design and implements rigorous design calculations, safety and environmental auditing, interdisciplinary review and operability checks. The workload rises as numerous documents and information are transferred between parties. This is the busiest time in the design phase of the project. In our project, over 150 people worked against tight deadlines for 12 months.

Project dynamics

What was previously a process-led design now revolves around requisitioning disciplines, such as piping and mechanical. This gives procurement a mountain of data to cope with and the project manager a headache (typically!). Changes to the design now have an impact upon all disciplines and importantly upon the project cost and schedule. For this reason, all changes are highlighted from a base design.

For brownfield projects, site visits are necessary to define the interfaces with the existing plant. This is the case for both pipework and instrumentation where interfacing with older systems can generate unique problems.

Ultimately the objective is always to generate a safe design that meets the client’s requirements. It is important that engineering decisions are taken with a commercial awareness and the engineering and procurement teams work closely to realise that commercial perspective.

Procurement

Procurement involves specification, tendering, technical and commercial review, order placement and expediting to ensure that the services and materials purchased are fit for purpose, cost effective and delivered to site to meet the design and construction schedule. In selecting a vendor, procurement interacts extensively with the engineering disciplines, a relationship that continues right through to construction.

Gains for graduate engineers

Working in a small, project-focused team provides early responsibility and rapid progression towards achieving chartered status. The skills required change as working methods including engineering software develop, which means that the young engineer has to balance sound engineering judgement with flexibility to embrace the available tools. On-the-job and seminar-based training play a key role in improving performance and the development of technical and management skills is encouraged.

Phase 4 – construction

Construction engineers construct the plant according to design detail.

Construction is a huge undertaking – this is where real money can be lost. The construction manager has to juggle schedules, materials and the workforce to achieve mechanical completion. Successful integration of vendor design information is critical for ensuring that the construction runs smoothly; this includes all items such as pipe fittings, foundation designs, valve dimensions, insulation details etc.

Subcontracting

In our project, construction subcontractors were engaged in a sub-alliance to the main project alliance. They had to interpret all design documentation, establish site facilities and undertake both civil construction and mechanical, electrical and instrument (ME&I) installation. The 3D CAD system was available at site with design engineers providing support to ensure the design intent was implemented.

Project engineers co-ordinated the workforce both on site and in the office. For them this was the most stressful (yet rewarding) time. Although delivery schedules made the work intensive, the huge effort ensured that all necessary activities were performed to allow the equipment to be installed prior to commissioning.

Phase 5 – commissioning

A team of engineers from a selection of disciplines commission the plant.

During the commissioning phase, the new plant is divided into process and technical systems and tested over a designated period. Process systems have limits based on design conditions, valve isolations, safety restrictions and equipment tie-ins. Technical systems include control, emergency shutdown (ESD), electrical and utility systems.

Commissioning occurs in three stages:

• Pre-commissioning: the installation, including all instrument loops, equipment items and electrical supplies, is checked and tested against the design. Operating manuals are developed, operators trained and the final commissioning plan confirmed.
• Commissioning: commissioning proves system functionality. Safety, control and utility systems are established, then process fluid is introduced and operating conditions generated where feasible. Many anomalies arise through commissioning, but when successful, expectations are realised and there is enormous satisfaction for the entire project team.
• Performance testing: when commissioned the plant must pass acceptance criteria. This includes mechanical completion and performance criteria in terms of process, safety, environmental and availability requirements. This can last for 3–12 months.

Safety

Commissioning requires special attention to safety, especially during start-ups. Working practices, such as permits to work and isolation methods help prevent accidents, but it is always up to the individual to act responsibly and consider the safety of themselves and others at all times. Nothing is too important to prevent it being undertaken safely.

Gains for graduate engineers

Graduates are actively involved in commissioning and for many it is the first taste of site work. The experience gained on site can enhance a graduate engineer’s design skills and certainly provides ample anecdotal material to use on peers and colleagues!

Phase 6 – operation and maintenance

The operations team is responsible for the day-to-day plant operation, while maintenance keeps the plant in an operable and safe condition.

Traditionally, when the plant is fully commissioned and handed over to the client, the project is over. However, it is increasingly common to provide operations, maintenance and engineering support. These services can be provided as part of the project or brought in under a separate contract.

Operations

In our example, the operators had to ensure that the plant met the dayto- day production targets and product quality issues. In addition, the operations team was trained to run the plant safely and operate a suitable shift system to run 24-hours a day. Operations were ongoing and required a routine and procedural emphasis to ensure that personnel maintained safe working practices while satisfying production demands.

Maintenance

The key objectives are to maintain the plant and equipment in good working order, retain a high plant availability and keep the site safe. There are three main functions of plant maintenance:

• Routine maintenance: the planned refit of equipment such as pump seals and filter elements to ensure that the plant is fit for operation. The vendors are brought in to assist where specialist equipment is involved or warranties can be affected.
• Monitoring/running checks: for plant items in continuous operation, running checks are made to ensure that the equipment is in a satisfactory condition. These service checks are used to avoid future breakdowns.
• Incidental maintenance: required in response to unforeseen failures that necessitate repair of the plant and/or replacement of damaged items.

In our example, plant sparing was addressed in the design by the provision of duty/standby equipment for critical services, while layout studies ensured safe access for known maintenance activities. This ensured that the plant could continue to meet production targets while individual items were undergoing maintenance.

Safety

In our project, plant safety was of primary importance. All activities were controlled and co-ordinated to minimise risk to personnel by implementing permit to work systems, adhering to operating and maintenance procedures and employing people to monitor and control safety. Each phase required input and commitment from many different individuals and companies to produce a safe, well-designed plant that met the client’s objectives and was designed on time and under budget.