Controls Retrofit for gas turbines
Why Holland-Controls retrofit gas turbine controls are a must for aging turbines
Scope of control system upgrade
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 PLCbased solution with open code providing exactly the same functionality as the old controller.
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 (middle picture)
- 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.
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.