Powering Up Progress: Pre-Commissioning, Commissioning, and Start-Up in EPC Megaprojects

Article Overview

In the world of large-scale EPC (Engineering, Procurement, and Construction) projects, transitioning from construction to operational status is not a single handover event—it's a detailed, multi-phased process that defines the success and safety of the facility. This article titled “Powering Up Progress” sheds light on the crucial final stages of EPC megaprojects: pre-commissioning, commissioning, and start-up. These are the steps that power up a plant—quite literally—taking it from a static installation to a live, functioning asset.

You’ll learn how systems and subsystems are structured for phased commissioning, what mechanical completion truly involves, and how loop tests, service readiness, and energization checks are carried out. The article also examines how owner/operator teams collaborate with EPC contractors and OEM vendors to ensure readiness, safety, and performance compliance.

Whether you're a commissioning manager, construction planner, quality engineer, or operations lead, this is your guide to powering up progress the right way.

System and Sub-System Definition

This section defines the foundational architecture of large-scale EPC projects. Systems and subsystems are the building blocks for process plant commissioning. A system refers to a complete operational unit (e.g., a utility water system), while a sub-system is a manageable portion of the system (e.g., a cooling water pump). Proper systemization enables phased turnover and early commissioning, especially in modular and fast-track projects.

Typical Examples:

1A. Mechanical Completion (MC)

Mechanical completion is the formal milestone where construction is declared complete. All components are checked for conformity to design and construction scope. It’s the starting point for pre-commissioning. A strong MC process reduces commissioning risks by ensuring all deliverables are properly installed, tested, and documented.

MC Activities Include:

• Completion of field erection, alignment, and bolting
• Installation of all piping, valves, instruments, and equipment
• Hydrotesting and reinstatement
• Verification of painting, insulation (hot and cold), and tagging
• Documentation of as-built drawings and test records

System Walkdowns:

• Joint verification by QA/QC, commissioning, and client teams
• Identification of remaining work, non-conformities, and documentation gaps

Deliverables:

• Mechanical Completion Certificate (MCC)
• Punch List categorized by A/B/C
• Turnover dossiers

2A. Loop Testing (Part of Pre-Commissioning)

Loop Testing verifies that field instruments correctly communicate with the control system. It ensures that process automation logic is implemented and functions correctly. Each loop—from field device to DCS/PLC—is verified for signal integrity and operational control.

Scope:

• Input/output signal checks
• Alarm and interlock logic simulation
• Instrument calibration and validation

Tools:

• HART communicator
• Loop checklists and calibration reports

2B. Service Tests (Functional System Checks)

These tests validate the readiness of auxiliary systems like HVAC, lighting, compressed air, telecoms, and CCTV. Service systems must be operational before energisation and process introduction begin.

Common Service Tests Include:

• HVAC performance testing
• Emergency power generator black start
• Water flushing and flow measurement
• Firewater system integrity test
• Communication testing (PA, telephone, telecom, CCTV)

3. Pre-Commissioning Activities

Pre-commissioning is the phase that ensures all mechanical and electrical components are clean, verified, connected, and operable. It bridges the gap between construction and commissioning.

Key Tasks:

• Air blowing and water flushing
• Instrument line drying
• Cable meggering and insulation resistance tests
• Control logic simulation

4. Commissioning Activities

Commissioning makes systems live. Activities verify that all subsystems work as designed under operational load conditions. It ensures systems respond safely, predictably, and efficiently.

Activities Include:

• Energization of motors and panels
• Rotating equipment solo run and coupled run
• Control valve functional checks
• Logic interlock verification (ESD/PSD)
• Vendor-assisted performance testing

5. Start-Up

This critical phase introduces feedstock, ramping up systems to design conditions. Start-up bridges the EPC handover to the operations team. It validates that plant production, quality, and safety systems operate in harmony.

Typical Start-Up Activities:

• Line flushing with process fluids
• Loading of catalyst/reactor beds
• Heating or cooling cycles
• Integration of utility systems with main process

6. Handover Tests and Performance Verification

This is where the plant must prove contractual performance guarantees. Testing verifies if capacity, emissions, reliability, and safety meet design standards.

Key Elements:

• 72-hour reliability run
• Flow, pressure, and temperature performance verification
• Vibration and noise level checks on rotating equipment
• Functional Safety Validation

7. Roles and Responsibilities

Each stakeholder plays a crucial role during commissioning. Without clear accountability, coordination breakdowns occur.

RoleResponsibilitiesCommissioning ManagerMilestone planning, execution tracking, team coordinationHSE ManagerSafety reviews during energization, live testing, and fluid introQA/QC LeadVerification of documents, punch list clearance, test validationVendor RepInstallation support, troubleshooting, performance testingOwner Ops TeamInterface with EPC, readiness for takeover and O&M preparation

8. Punch List Categories and Closure

Punch items are deviations identified during walkdowns and testing. They’re grouped by urgency and risk.

Categories:

• A – Critical (must close before start-up)
• B – Important (must close before performance testing)
• C – Minor (can be deferred post-handover)

Efficient punch management reduces commissioning delays and ensures seamless start-up.

9. Statistical Snapshot

• 70–80% of schedule overruns are linked to late commissioning readiness
• Projects with phased subsystem handover save 15–20% time
• 10–15% of commissioning hours are lost to unclear role delegation
• Structured punch list systems improve closure rates by 35–40%

10. EPC Megaproject Timeline: Construction to Start-Up

11. Best Practices

Global best practices include

• Systemization early during construction
• Live dashboards for punch closure and test tracking
• Involving O&M team in walkdowns and FATs
• Engaging vendors for on-site training and performance runs
• Continuous risk assessments before live energization

References

1. International Association of Oil & Gas Producers (IOGP) – “Commissioning and Start-Up Guidelines for Oil and Gas Projects” – www.iogp.org
2. API RP 1FSC – Recommended Practice for Facilities Systems Completion Planning and Execution – American Petroleum Institute (API), 2013.
3. Long International – “Commissioning and Startup – Project Completion & Handover Practices” – www.long-intl.com
4. CCPS – Center for Chemical Process Safety – Guidelines for Safe Process Operations During Commissioning and Start-Up, Wiley-AIChE, 2010.
5. Whatispiping.com – “Understanding Pre-commissioning and Commissioning Phases in EPC Projects” – www.whatispiping.com
6. Shell Global Commissioning Standards (confidential project use)
7. BP Project Execution Guidelines – commissioning logic and system turnover standards
8. Chevron Project Management System (CPMS) – handover and energization practices
9. Wood Group – Engineering completion and turnover practices
10. Siemens Energy – Startup and commissioning manuals for GT/ST/HRSG and power systems