# The life cycle of an industrial plant > A plant lives for decades, across several phases — from feasibility study to decommissioning. Understanding these phases means knowing where cost, safety and performance are actually decided. - Source : https://industryhub.site/en/learn/foundations/cycle-de-vie-installation - Track : foundations - Level : Discovery - Reading time : 5 min - Language : English ## In brief An industrial plant moves through successive phases: feasibility study, design, construction, commissioning, operation, modifications, decommissioning. Most of the future costs and the safety profile are decided very early, right at the design stage. ## A plant is the long game A controller stays in service fifteen to twenty years; a valve or a structure, thirty to fifty. An industrial plant is not designed for today, but for decades. It moves through well-identified phases, each with its own stakes. ## The phases 1. **Study & feasibility.** You define the need, cost it, compare options. This is where the [business case](/en/learn/economics/business-case) plays out — and where most future costs are already committed. 2. **Design (engineering).** Process diagrams, drawings, specifications, equipment selection. **80% of the total cost of ownership is determined at this stage**, while almost nothing has been spent. 3. **Construction & installation.** Civil works, assembly, wiring. This is where the bulk of the CAPEX goes out. 4. **Commissioning.** You verify, test, start up. A critical step: this is where you catch design errors before production. 5. **Operation & maintenance.** The longest phase, years long. This is the reign of OPEX: energy, maintenance, parts. 6. **Modifications (revamping).** The plant evolves: new equipment, new standard. Every modification follows a formal **management of change** (MOC), so as not to degrade safety. 7. **Decommissioning.** End of life: shutdown, clean-up, recycling. A cost often underestimated. ## The cost lesson The central paradox: **the cheapest decisions to make commit the most spending**. Fixing an error costs roughly **ten times more at each phase crossed** — a pencil stroke at design, a fortune once the plant is built. Hence the importance of getting design right: it is the highest-leverage moment. This whole-life cost logic is formalised by asset management ([ISO 55000](/en/standards/iso-55000)), and ties directly to the notions of [CAPEX, OPEX and cost of ownership](/en/learn/economics/capex-opex). ## Why it matters for automation The control system accompanies all these phases: you design it, test it at commissioning, maintain it, modify it. Thinking "life cycle" from the start — documentation, spare parts, obsolescence, cybersecurity — avoids ending up, in ten years, with a controller no one supports any more.