This guide explains the drivers for upgrading turbine controls, the main options and a sensible sequence for a migration. It also covers the checks that owners should make so that the new system does not trade one set of problems for another.
Signs that controls are becoming a risk
Common signs include difficulty finding spare cards and power supplies, failing displays, loss of vendor support, limited documentation, and a growing number of unexplained trips. Software on old workstations that run unsupported operating systems adds cyber risk.
Another sign is the effort needed to make a small change. If simple alarm or logic changes require rare skills or take weeks, the system is a constraint on operations.
Upgrade options
The scope can range from replacing individual modules to replacing the entire turbine control system, including the logic, the operator interface, the protection and the input and output hardware. A partial upgrade, such as new operator stations only, is cheaper but leaves the core hardware at risk.
A full replacement gives a new platform with current support, and it allows better diagnostics and integration with plant control. Choose by risk and by what the plant can accept in outage time.
Scope decisions: what to replace
Decide whether to replace the field wiring, junction boxes and sensors at the same time. Old wiring may have degraded insulation and old sensors drift. Replacing them adds cost but reduces the risk of chasing faults after the new controller is running.
Also decide whether to retain the turbine’s existing speed, temperature and vibration sensors, and whether to upgrade fuel valves and actuators. The best results come when the controller, the sensors and the actuators form a coherent set.
Protection functions and safety
Overspeed, flame detection, over-temperature and vibration protection are safety functions. Any change to them needs careful design and testing, and often involves independent protection hardware. Never migrate protection logic by transcription alone; review each function against the turbine manufacturer’s requirements.
Ask for a documented design review and a written test plan for every protective function.
Software migration and documentation
Recover the existing logic, set points, tuning and alarm lists before the old system is removed. Where documentation is missing, reverse engineer it from the running system and the drawings. Mistakes in this step produce operating differences that are found only under rare conditions.
Keep a clear record of changes and approvals, and store backups of both old and new configurations.
Cybersecurity
Modern controllers are networked, and that creates new risks. Plan network segmentation, access control, patching, logging and backup for the new system. Decide how remote access will be provided, if at all, and who is responsible for maintaining security over time.
Include security requirements in the specification, not as an afterthought.
Outage planning and testing
Most of the work can be prepared offline: factory acceptance testing with simulators, cabinet build and loop checks. The outage is for removal, installation, wiring, loop testing, functional tests and first firing.
Plan enough time. Tests that are compressed at the end of an outage tend to be skipped, and problems then appear on first start. Use the outage to combine controls work with inspections described in gas turbine inspection intervals.
Commissioning and tuning
After first fire, tuning of start sequences, fuel schedules, temperature control and load response takes time. Allow for several starts and load runs, and keep the control engineers on site until the machine has run reliably.
Train operators on the new interface before handover. Provide quick reference guides and keep the old drawings for comparison.
Pitfalls on controls projects
The most common pitfalls are incomplete recovery of the old logic, underestimated field wiring condition, tight outage schedules that squeeze testing, unclear responsibility between the controls supplier and the turbine supplier and operators who see the new screens for the first time at start-up.
A clear scope document, a single project manager and a realistic outage plan help with all of them.
Documents to require at handover
Ask for the final logic and configuration files, as-built drawings, loop sheets, test reports and sign-off records, set point lists, backup copies stored in two places, the cybersecurity design and the training records.
These documents make the next change simpler and protect the owner from being tied to one supplier for support.
Questions to ask a controls supplier
Ask for references on the same turbine model, the planned support period for the platform, the way software updates are delivered, the training offered and the spares strategy. Ask who will be on site during first fire and for how long.
Also ask what happens if the supplier is acquired or stops supporting the platform. A good answer includes source code or configuration escrow and a clear support commitment.
Business case and links to lifecycle cost
The cost of an upgrade should be compared with the cost of unplanned outages, the cost of scarce spares and the value of longer life for the turbine. Our article on gas turbine lifecycle cost shows how to include controls in a lifecycle view.
Where a turbine is remanufactured, as with a reman GE Frame 6B, the controls scope is usually defined as part of the package, so ask what is included.
Who writes this
Legacy control systems on installed turbines are a recurring issue for the engineers who maintain them. Our USP&E turbine team contributed the practical points. USP&E, which does EPC and O&M work as principal rather than agent, reports 25,000 MW contracted since 2002 and 150+ power projects in 45+ countries and 24+ years in the field. Learn about our asset refurbishment work, including remanufactured GE Frame 6B units.
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Questions about turbine controls upgrades
When should I upgrade turbine controls?
When spares are scarce, support is gone, trips are unexplained or changes are difficult. Plan before a failure forces the decision.
Do I have to replace everything?
No. Scope ranges from module replacement to a full system, and sensors and wiring should be reviewed with the controller.
How long does an upgrade take?
Preparation and factory testing are done in advance. Site work fits an outage, whose length depends on scope and testing.
What about cybersecurity?
Include network design, access control and patching in the specification from the start.
Weighing a controls upgrade?
Send us the turbine model, control system type and fault history, and our engineers will outline the options and the outage they need.
For a first conversation, use the turbine enquiry form, ring +27 10 822 2324 or send the details to info@uspeglobal.com. Turbines and parts available now are in the natural gas turbine inventory.