FEED, or front-end engineering design, turns a selected concept into a defined plant. It ends with a package of documents that an owner can approve, a lender can review and a contractor can bid on.
Post 1 placed FEED as the third of five project stages. Post 2 covered the design basis that FEED starts from. This post goes through what the package contains, using the same $100M specialty chemical plant.
What FEED has to produce
A FEED package answers three questions.
- What are we building? A scope defined well enough that two engineers would design the same plant from it.
- What will it cost? A Class 3 estimate, typically accurate to between −20% and +30%.
- How will we build it? A schedule, a contracting plan and a list of risks.
The documents are produced in a set order, because each one is calculated from the one before.
The documents and what each one decides
Table 1. Main FEED deliverables
| Group | Document | What it decides | If it is skipped |
|---|---|---|---|
| Process | Design basis | The agreed starting assumptions | Rework when capacity or specifications change |
| Process | Heat and material balance with PFDs | Every stream: flow, composition, temperature and pressure | Equipment sized on guesses |
| Process | P&IDs | Every pipe, valve, instrument and control loop | Scope missed in the estimate, late design changes |
| Process | Equipment list and datasheets | Size, duty and material of each item | Vendors cannot quote, so costs are factored |
| Process | Utility summary | Peak and normal demand for power, steam, cooling and gases | Undersized utilities found at start-up |
| Safety | Hazard review (HAZID or HAZOP) | Safeguards the design needs | Safety changes made during construction |
| Safety | Relief and hazardous area studies | Relief device loads, electrical classification | Wrong equipment ratings, permit delays |
| Layout | Plot plan and equipment layout | Where everything sits and how it is reached | Piping and civil quantities unknown |
| Electrical and controls | Single-line diagram, load list, instrument index | Power supply and control system size | Electrical cost, often 10% or more, estimated blind |
| Project | Class 3 estimate and basis of estimate | The budget and its accuracy range | Approval based on an unreliable number |
| Project | Schedule and long-lead list | Duration and what to order first | Late equipment drives the completion date |
| Project | Execution plan and risk register | How the work will be contracted and what could go wrong | Disputes over scope during construction |
A package for a small plant may combine some of these. None of the questions in the third column can be left unanswered.
PFD and P&ID: the two drawings to know
Owners are asked to review both drawings, and they serve different purposes.
Table 2. PFD and P&ID compared
| Process flow diagram (PFD) | Piping and instrumentation diagram (P&ID) | |
|---|---|---|
| Purpose | Shows how the process works | Shows how the plant is built and controlled |
| Shows | Main equipment, main streams, key operating conditions | Every line, valve, instrument, control loop and relief device |
| Typical count | 10 to 20 sheets | 80 to 150 sheets |
| Used for | Heat and material balance, equipment sizing | Hazard review, cost estimate, construction, operation |
| Owner should check | Capacity, feeds and products match the design basis | Operators can start, stop, isolate and maintain each item |
The sheet counts are for a plant of the example's size. The P&IDs are the most important drawings in the package, because the hazard review, the estimate and the construction scope are all taken from them. For a worked example of both drawings, see How to Read a PFD and a P&ID.
How the Class 3 estimate is built
A Class 3 estimate is built up from the documents and is no longer factored from a single number. Each line has a source in the package.
Table 3. Estimate build-up and the source of each line
| Cost element | Amount | Share | Where the number comes from |
|---|---|---|---|
| Equipment | $30,000,000 | 30% | Vendor budget quotations against datasheets |
| Bulk materials | $15,000,000 | 15% | Quantities taken from P&IDs and layout |
| Construction labour | $22,500,000 | 22.5% | Hours estimated from quantities and local rates |
| Engineering and project management | $12,500,000 | 12.5% | Planned hours by discipline |
| Owner's and other indirect costs | $10,000,000 | 10% | Permits, spares, commissioning, owner's team |
| Contingency | $10,000,000 | 10% | Set from the risk register |
| Total installed cost | $100,000,000 | 100% |
Equipment is under a third of the total. The rest is the cost of installing it, connecting it and managing the work. An estimate that prices the equipment well and factors everything else has not reached Class 3. The methods are covered in Engineering CAPEX and OPEX Estimation for Process Plants.
What FEED does not include
FEED stops short of construction drawings. Piping isometrics, structural steel details, cable schedules and vendor fabrication drawings belong to detailed engineering, which follows approval. That work typically costs three to five times as much as FEED, so it should start only after the investment decision.
Eight questions to ask when you receive a FEED package
- Is the design basis signed, and are any holds still open?
- Does the heat and material balance close, and does it match the capacity in the design basis?
- Have the P&IDs been through a hazard review, and are the actions closed or listed?
- How much of the equipment cost is backed by vendor quotations?
- Does the estimate state its class, its accuracy range and its exclusions?
- Is contingency tied to named risks?
- Which items have the longest delivery, and when must they be ordered?
- What is outside the battery limits, and who pays for it?
A package that answers all eight is ready for an investment decision. A gap in any of them is a reason to extend FEED before committing the full budget.
Takeaway. A FEED package defines the scope, the cost and the plan. Judge it by whether each number in the estimate can be traced to a document in the package.
The plant, its capacity and its costs in this series are an illustrative example. The ranges and percentages are typical industry values and do not replace an estimate prepared for your project.
