How to plan automation modernization to minimize downtime?

The key element of automation modernization without downtime is proper preparation. The more work that can be completed before physical intervention in the installation, the shorter the actual production shutdown will be.

MJ Group applies a proven methodology based on three pillars that consistently reduce implementation risks and significantly shorten commissioning times.

Offline programming and simulation (virtual commissioning)

The traditional approach involves programming the controller only after the physical replacement of equipment on the shop floor. This often leads to extended downtime because every coding error requires additional debugging on a non-operational production line.

MJ Group uses a modern approach based on offline simulation and virtual commissioning. PLC code is developed and tested before it ever reaches the production environment.

For projects involving Siemens S7-1500 platforms, engineering teams use TIA Portal together with simulation tools such as S7-PLCSIM and Digital Twin environments. This enables verification of control logic, machine sequences, alarms, and communication structures long before installation.

Benefits include:

• Up to 80% of programming issues identified before commissioning.
• Commissioning time reduced from weeks to days.
• Operator and maintenance training before go-live.
• Reduced startup risk during production shutdown windows.

Prefabrication and preparation of control cabinets

In a traditional modernization project, replacing a control system means dismantling an existing cabinet, installing a new one, and wiring everything on-site during production downtime.

MJ Group reverses this process.

The new control cabinet is fully assembled, wired, tested, and documented in the workshop before arriving at the plant. Detailed audits and signal inventories make it possible to prepare dedicated harnesses and connection interfaces in advance.

As a result, site activities are limited mainly to:

• Positioning the new cabinet.
• Connecting prepared wiring harnesses.
• Verifying communication.
• Executing commissioning procedures.

This approach reduces installation work from several days to just a few hours and dramatically lowers the risk of wiring errors.

Audit and inventory before project execution

Every successful retrofit starts with a comprehensive technical audit.

Before any replacement work begins, MJ Group engineers perform a detailed analysis of the existing installation.

The audit typically includes:

• Inventory of all DI, DO, AI, and AO signals.
• Analysis of existing PLC source code.
• Identification of critical control functions.
• Assessment of sensors, actuators, and field devices.
• Verification of communication networks.
• Evaluation of safety systems and redundancy structures.
• Measurement and validation of operating parameters.

Many older installations contain undocumented modifications made over years of operation. The audit allows engineers to uncover hidden dependencies before modernization begins.

Without a proper audit, modernization becomes a high-risk exercise. With it, over 90% of potential implementation issues can be identified before the first power cable is disconnected.

The execution phase – from replacement to commissioning in just a few days

Once the audit is complete, the software has been tested offline, and the control cabinet is fully prepared, the project enters its most critical stage: implementation.

This is where planning, engineering, and execution come together to determine whether the modernization will succeed within the available shutdown window.

Replacement during a weekend shutdown – the hot-swap approach

For most manufacturing plants, the preferred modernization window is a planned weekend shutdown or holiday maintenance period.

MJ Group frequently executes migrations using a hot-swap methodology.

Rather than immediately removing the old control system, the new cabinet is installed alongside the existing infrastructure. Production sections are then transferred progressively to the new system.

The sequence typically follows:

1. Migration of non-critical auxiliary systems.
2. Verification of stability and communication.
3. Transfer of critical production sections.
4. Final shutdown and removal of the legacy controller.

This staged approach minimizes operational risk because the existing system remains available as a fallback option throughout most of the migration process.

FAT testing and intensive onsite supervision

Before deployment, every modernization project undergoes a Factory Acceptance Test (FAT).

Depending on the project scope, FAT can be performed either in the MJ Group workshop or directly at the client’s facility.

Typical FAT activities include:

• Verification of all I/O signals.
• Functional testing of control sequences.
• Simulation of emergency and fault conditions.
• Communication testing with SCADA, MES, and ERP systems.
• Cybersecurity and protocol verification.
• Validation of safety functions.

Following commissioning, MJ Group engineers remain onsite to support startup activities, optimize parameters, train operators, and ensure the system performs according to design expectations.

This post-commissioning supervision is often the difference between a system that merely functions and a system that delivers measurable operational improvements.

Example schedule: S5 → S7 migration

From the first shutdown activity to full production readiness, total downtime can often be reduced to 2–5 days, compared to 3–4 weeks using conventional modernization approaches.

Benefits of modernization – measurable results for engineers and decision-makers

Modernizing an outdated control system is not only about eliminating the risk of breakdowns. It delivers measurable operational, financial, and organizational benefits that directly affect production performance and competitiveness.

• • 10–30% increase in production efficiency through optimized control logic, faster diagnostics, and improved process stability.

• • 20–50% reduction in energy consumption, particularly in systems using variable speed drives (VSDs), intelligent load control, and advanced process regulation.
  • Improved cybersecurity through modern PLC platforms, network segmentation, encrypted communications, user authorization, and compliance with NIS2 requirements.
  • Extension of machine lifespan by 10–15 years while preserving mechanically sound infrastructure.
  • Industry 4.0 readiness through integration with MES, ERP, cloud analytics, remote diagnostics, OEE monitoring, and predictive maintenance systems.
  • Reduced spare parts inventory thanks to controller standardization across multiple production areas.
  • Improved operator ergonomics through modern HMI interfaces, alarm management, historical reporting, and enhanced process visibility.

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Most common mistakes in automation modernization

Based on experience gained from hundreds of retrofit projects, MJ Group has identified several recurring mistakes that frequently lead to delays, increased costs, and operational disruptions.

1. 1. Skipping the technical audit
      Starting a migration without a complete inventory of signals, devices, and control logic creates unnecessary uncertainty and significantly increases project risk.

1. 1. Programming directly during production downtime
      Writing and debugging software on-site can extend shutdown periods by several days. Offline testing should always be completed before implementation begins.
   2. Skipping FAT testing
      Factory Acceptance Testing allows engineers to identify communication, configuration, and logic issues before they affect production.
   3. Lack of a rollback strategy
      Every modernization project should include a clearly defined fallback scenario allowing temporary return to the legacy system if necessary.
   4. Insufficient operator training
      New systems introduce new procedures, interfaces, and diagnostics tools. Training should take place before startup rather than under production pressure.
   5. Poor timing of implementation
      Even a technically perfect project can become problematic if it is executed during peak production periods.

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Case study – wastewater treatment plant modernization by MJ Group

The challenge

An industrial facility in south-western Poland operated a wastewater treatment plant controlled by Siemens S5-115U controllers installed in the late 1990s.

The installation managed aeration, chemical dosing, pumping, and filtration processes. Over time, maintenance costs increased significantly due to:

• Frequent failures of I/O modules.
• Limited availability of spare parts.
• Absence of remote diagnostics capabilities.
• Growing cybersecurity concerns.

Each unexpected failure required onsite intervention and often resulted in costly operational disruptions.

The solution

MJ Group performed a complete inventory audit covering more than 400 I/O signals and 16 distributed control stations.

The modernization project included migration to:

• Siemens S7-1500 PLC platform
• ET200SP distributed I/O system
• WinCC Unified SCADA environment

The implementation involved:

• Migration of legacy STL code to modern SCL and LAD structures.
• Workshop prefabrication of control cabinets.
• FAT testing using PLCSIM and process simulations.
• Three-day implementation during a planned shutdown period.
• Parallel operation of old and new systems during migration.

The results

• • Downtime: 3 days instead of the planned 5 days.

• • Reliability: zero critical failures during the first six months of operation.
  • Remote diagnostics: complete process visibility through WinCC Unified Web Client.
  • Energy savings: 18% reduction in energy consumption through optimized aeration control.
  • Scalability: readiness for future MES integration and environmental reporting systems.

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Summary

Market pressure, cybersecurity requirements, and increasing maintenance costs leave little room for hesitation. Modernizing outdated automation is no longer a strategic option – it is a business necessity.

The challenge is not whether modernization should happen, but how to execute it without causing prolonged production interruptions.

Successful projects rely on a structured methodology that combines:

• Comprehensive technical audits.
• Offline programming and simulation.
• Control cabinet prefabrication.
• Factory Acceptance Testing.
• Hot-swap implementation strategies.

This approach has proven effective across industries ranging from automotive and food processing to energy generation and wastewater treatment.

FAQ – frequently asked questions about automation modernization

Does automation modernization always require stopping production?

No. By combining prefabrication, offline testing, and hot-swap implementation methods, actual downtime can often be limited to just 2–5 days and scheduled during weekends or planned maintenance periods.

How much does a retrofit cost compared to purchasing a new machine?

A retrofit typically costs between 30% and 60% of the purchase price of a new machine or production line. Return on investment is commonly achieved within 12–36 months.

Can a Siemens S5 installation be migrated to Siemens S7-1500?

Yes. This is one of the most common modernization projects performed by MJ Group. Existing control logic can be mapped and migrated to modern Siemens platforms using TIA Portal while retaining much of the existing field infrastructure.

How long does a modernization project take from audit to commissioning?

A typical migration project takes between 6 and 8 weeks from the initial audit to final commissioning. Actual production downtime is usually limited to 2–5 days.

Will the new system comply with NIS2 and cybersecurity requirements?

Yes. Modern automation platforms support network segmentation, encrypted communication, user authentication, audit trails, and other features required for compliance with current cybersecurity standards.

Sources

1. Senseye/PTC – The True Cost of Downtime 2023.
2. PwC – Digital Factory Transformation Survey 2025.
3. McKinsey & Company – Industry 4.0: How to succeed in the digital transformation.
4. Regulation (EU) 2023/1230 of the European Parliament and of the Council of 14 June 2023 on machinery.
5. Siemens – Modernization Guide: Migration from SIMATIC S5 to S7.
6. MJ Group – company materials and project experience.