Benefits of upgrading aged gas turbine control systems

As older gas turbines begin to operate beyond their original life expectancy, applying a new control system becomes a necessity. A gas turbine control system has a tendency to age faster than the equipment it is controlling which is likely to have a negative impact on the turbine itself. A complete or partial control system retrofit minimizes gas turbine failures and is the core business of Holland-Controls.

At Holland Controls we provide you with the means to increase reliability and up-time. Whether you need a full (turn-key) retrofit or modular upgrades, our team can engineer a solution that:

  • Achieves a higher reliability

  • Uses the latest technology making your gas turbine futureproof
  • Generates more up-time until decommission

  • Reduces costs for maintenance

  • Improves diagnostic capabilities

  • Includes very detailed documentation and support

  • Uses an open, expandable system architecture that facilitates future modifications or extensions

  • Offers modular upgrades to build in more reliability and functionality

From full turn-key retrofit to part retrofits

Holland-Controls is one of the few companies that offer a modular retrofit service for gas turbines control systems. We survey the system in detail looking through alarm logs, interrogating the software and hardware to deliver a survey report which is highly detailed.

Next step is to make an upgrade program that will offer a cost effective solution to the worst affected areas of the control system. This enables the client to gain greater reliability and functionality for minimum investment.  

Reduce the cost of ownership of your current installation and talk to us before an upgrade becomes a matter of urgency. 

Highly qualified staff with long term experience.

Structured project execution according ISO-9001-2018.

Proven experience in gas turbine control system retrofit

Holland-Controls are able to support all existing gas turbine controls systems and offer overhaul facilities and spare parts for the FT/Entronic controls. We have in-depth experience of supporting and retrofitting gas turbines from Rolls-Royce, Solar, GE, Ruston, Siemens, P&W both DLE, none DLE, and dual fuel.


Types of gas turbine retrofit

Control system retrofits can take place in various shapes and formats. This depends on the criticality of the gas turbine system involved, the money that can justifiably be spent on it, the requirements,  and the competence already available on site.

Life cycle of control systems

Any piece of electronics follows a life cycle curve roughly looking as shown on the right.

The initial high failure rate (Y-axis) is commonly referred to as ‘infant mortality rate’ and occurs during the first half year. Through burn-in periods at the manufacturer, during in-house tests and through warranty clauses, this period is well covered.

After the system has proven itself there is a window of 10 to 15 years with only a few failures; thereafter the mortality rate goes up again.

At roughly the same time spare parts, due to obsolescence and support availability decreases. And the old technology is no longer thoroughly understood by the new generation of engineers not trained on these systems.

This typically means that control systems start to fail when support and repair become harder to accomplish and often at a high cost. Even if the system is still functional, it has reached end of economical life. This is further accelerated by the fact that new technology offers technical and cost-saving operational advantages.

The consequence is that one must make a choice: either invest heavily in spare parts and know-how on site –or– ensure that systems are being modernised before the end of the life cycle is reached.

Note that the ‘amplitude’ of the curve depends several factors such as mechanical stress, thermal stress, corrosion, type of component and complexity of the system.

Innovations in controls systems

Whereas developments on the mechanical side are fairly steady, control systems have made quantum leap improvements compared to systems of 15 to 30 years ago and still advance every year. Yet a control system only cost a fraction compared to the turbine it is controlling.

It is this combination which makes it so attractive to consider upgrading the control system: the investment-effect ratio is high. In fact in quite a few cases it will reduce the stress on the turbine itself and thus lengthens its life beyond the cost of a controls upgrade.

This is possible by achieving fewer trips from high power and operating closer to the limits without exceeding them.


  • Visualisation and trending of all engine parameters on a large screen in a comfortable control room.

  • High speed trending with low hysteresis and storage over many years.

  • Pre & post event-triggered trending with resolutions for special conditions such as starts and trips.
  • No more missed events, no need for that spurious fault to re-occur to properly diagnose it. The order of events is accurate, leaving no doubt as to what came first. Compare the stored data with data of 1, 2 or 3 years ago, or longer if desired.

  • Distinction of events is dramatically better. Whereas older systems contain one indication light to indicate ‘a’ fault, current systems will point you exactly to the faulty device – further supported with a historical trend of that device.


Current PLCs are much more accurate. Self-calibrating high definition analog to digital conversion is the norm nowadays. This makes it possible to operate gas turbines closer to their limits – safely.

Examples are exhaust gas temperature limit and compressor surge limit. You are less likely to burn an engine out. Or you can operate with one engine less because you know you are safely on that limit. Think of the savings in fuel costs and CO2 emission!

All modern PLCs support safety levels up to SIL-3. This is much better than the average trip-relay string your current system might still use. This means that with one single system it is now possible to carry out both the control and safety functions.

It is now also possible to carry out certain control functions such as engine purging in safety logic. This is very important if there is a boiler located in the exhaust stack. With conventional systems and architectures this is complicated to accomplish.

High performance components

  • Modern components have a much higher reliability compared to their predecessors.

  • More intelligence can be put in the control system if needed when compared with discrete systems. Changes are easy to program. For example, stopping the engine with a cooling-down cycle instead of just cutting the fuel reduces the number of overhauls on your engine while keeping its performance. The gas compressor does not have to be depressurised on each stop saving on CH4 emission. Be green and save money at the same time.
  • Availability can be increased by adding redundant field instrumentation which is then processed by the CPU using intelligent voting. Notorious problematic sensors no longer shut you down.

  • Coupling to DCS or remote systems is easy to accomplish. There is no more need to limit dispatching with only a subset of the information available locally.

Legislation applicable to gas turbine installations


Over the years legislation has changed. The following is relevant in this context:

CE - European Conformity. Especially with regards to radiofrequency emission and susceptibility many older systems fail resulting in unnecessary shutdowns or operational inconvenience when using radios and such. Also outside Europe it makes sense to ensure equipment is c marked.

ATEX - This refers to the explosion hazard always present in the oil and gas industry, and the approved (!) technologies to overcome this.

PED - This refers to high pressure systems, for example transport gas, fuel gas and steam.

SIL - Safety Integrity Level refers to the level in which a system acts safe in case of malfunctioning in order to prevent injury or death.


CO/NOx, CO2 and CH4 emission reduction measures through taxes and limits. Legislation was changed to improve transparency of the market, and to overcome flaws in previous standards having resulted in accidents. It is allowed to continue using an installation if it was truly installed according to the legislation in place at the time.

But it is not always wise to do so, as it makes it hard to carry out improvements on the installation without breaking current legislation. With respect to the environment it is often better to demonstrate that a company is already taking it’s measures rather than waiting for the authorities to step in with law.

Options for implementing controls upgrades


Control system upgrades can take place in various shapes and formats. This depends on the criticality of the system involved, the money that can justifiably be spent on it and the competence already available on site.

Case 1: Limited Upgrade

If a particular component is causing trouble, but the installation is not highly critical then Holland-Controls can ensure that only the troubled component is replaced. An example of a limited upgrade we did is of a section of an Allison KB-5 control panel for a non-critical backup generator. The speed & temperature controller was a ‘black box’ constantly causing availability problems. Spare parts were no longer available.

Holland-Controls has reverse engineered the functionality of the box. We installed a PLC based solution with open code providing exactly the same functionality as the old controller.


Another example is the modernization of the generator excitation system for a Solar Taurus power generation set. The old set of loose electronic boards was constantly causing spurious overexcitation issues and was difficult to troubleshoot. By modernizing this to a processor based Automatic Voltage Regulator (AVR) all these issues are solved (see image).

The regulation is accurate, safety is restored and diagnosis is easy through the network connection and event based logging system.

Case 2: Control-system only upgrade

PLC manufacturers tend to obsolete their current systems every 10 to 15 years. Thereafter they are still supported with spare parts but at a significant price and supply time. Also auxiliary components get poorer, relays start to demonstrate bad contacts, electronic converters hit the end of their life cycle by failing more frequent.

In case the instrumentation on the engine is sufficiently modern, then it is worthwhile considering to only upgrade the control system. The two common scenarios are:

  • Replacement of backplanes. In this case the existing panel is stripped of all hardware except the field terminals. The new hardware connects onto the existing terminals.

  • Full panel replacement. Through an extensive site-survey and design phase it is ensured that the existing cables will fit onto the new control system’s terminals.

Case 3: Control-system upgrade & field modernisation

This is the most common of all. When a control system requires upgrading, then it often makes sense to also modernise the field instrumentation, for example:

  • Replacement of the hydraulic fuel valve by an electric version.

  • Replacement of switch-type sensors (temperature, pressure, level) by analog types in order to dramatically improve the diagnostics capability of the system.

  • Adding strategic protection and redundancy previously missing.

Case 4: Full upgrade – Proven engines deserve reliable controls

Sometimes we see systems that haven’t been touched for years. When the time has come to upgrade these systems then it is not possible to limit oneself to the control system only. Field instrumentation has meanwhile become completely outdated, field cabling is brittle, junction boxes are still of the heavy explosion proof type and so on.

In that case it is best to basically strip ‘everything with a wire’ such that after the retrofit the system is as new again as before the retrofit, but now to today’s standards and practices.

Turn-key upgrades

Upgrades can be performed turnkey in which case Holland-Controls takes care of the complete spectrum through the following actions:

  • Site survey and specification

  • Engineering and drafting of hard and software

  • Specification and writing of software and HMI

  • Building of the new control system

  • In-house control system test followed by a customer

  • Witnessed Factory Acceptance Test

  • Removal of old- and installation of new control system and instrumentation

  • Loop checking, system checks and start-up

  • Final handover & documentation

  • Training of operators and technicians

Holland-Controls is also open to joint efforts as long as the scope can be clearly split. Many offshore platforms have maintenance contracts with a certain company. In such a case that company can take care of the installation aspect under Holland-Controls supervision and procedures.

Demand on your installation

The level of criticality depends on the application the unit is in. Redundancy of gas turbine engines is the most important parameter here. Most installations, when newly built, have one or two units spare. This makes it possible to do routine maintenance on one unit, running the remaining units and still have one spare in case of sudden mishaps. 

However, applications change. Offshore platform power generators tend to feed newly built satellite platforms. On gas compression stations the volume of gas being pumped increases every year. And with the free gas and electricity market the term ‘running season’ seems to be no longer applicable.

The result is that the demand for availability of the installation increases year by year – while at the same time the true availability of the installation decreases due to aging.

The control system plays an important role in two aspects here:

  • the availability of the system itself
  • the quality of information it can provide to the operator about malfunctioning of the unit or system it is controlling
Would you like to know more about our solutions? Feel free to reach out to us via our contact page.