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Control Oil and Hydraulic Oil in Gas Turbines
Difference between control oil and hydraulic oil in gas turbine
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hi dear,

What is the difference between control oil and hydraulic oil in gas turbine? and what the function of them? and what the main components of each?

1 out of 1 members thought this post was helpful...


>What is the difference between control oil and hydraulic oil
>in gas turbine? and what the function of them? and what the
>main components of each?

The best answer to these questions can be found on the Schematic Piping drawings for the Control Oil and Hydraulic Oil systems--supplied with every GE-design heavy duty gas turbine. (Most people and organizations in the world call these drawings P&IDs--Piping & Instrumentation Diagrams; GE calls them "Piping Schematics.")

If the heavy duty gas turbine was packaged and provided by GE, and it's an older unit (newer units don't have Control Oil systems), you should be able to find the Piping Schematics in Vol. III of the Operations and Service Manuals provided with the unit.

Also, in Vol. I of the Operations and Service Manuals you should find the System Descriptions tab, with a sub-tab for every system for which there is a Piping Schematic drawing. These, brief descriptions have some useful information, and is always the best starting point. NOTE: These System Descriptions are usually very generic in nature--while the Piping Schematics are almost always unit-specific and not hardly ever wrong or generic.

Now, for as much information as I can provide without knowing a LOT more about the unit you are working on/asking about, both systems use the same fluid--which is turbine lubricating oil (lube oil).

In general, the Control Oil system referred to the "hydraulic" tripping system which was used to be able to open the fuel stop valve(s). There were devices, some electric, some mechanical, some electro-mechanical, that controlled the flow of high-pressure Hydraulic oil to the fuel stop valve hydraulic actuator(s) to open the stop valve(s).

Usually, Control Oil was NOT used as the pressure/fluid for the hydraulic stop valve actuator--Hydraulic oil was used for that. But, Control Oil, operating through some electric or mechanical or electro-mechanical device either passed or blocked the flow of high-pressure Hydraulic Oil to the stop valve actuator. I know this sounds strange, but, once you examine the Piping Schematic drawings for the two systems, it will all become clear.

The stop valve can't open without high-pressure hydraulic oil--but the control oil system was used to pass or block the flow of high-pressure hydraulic oil to the actuator. It was all part of the safety and reliability of the turbine--to the designers of the control and protection systems at the time.

SOME Control Oil systems used Hydraulic Pump discharge pressure/flow; others used Main Lube Oil Pump discharge pressure/flow. So, some Control Oil systems were "high-pressure" systems, and some were "low-pressure" systems.

Again, without know what Frame size machine you are referring to, what "vintage" it is (the year it was built and installed and commissioned), and without being able to see the Piping Schematics for the unit in question, it's really difficult to say much more.

Oh, a LOT of confusion was caused by really worded Process Alarm text messages which were NOT properly specific. Some Process Alarms used the terms "Hydraulic Protective" when referring to Control Oil, and others used the same terms to refer to the Trip Oil system, which was the later version of Control Oil, but usually at low-pressure.

There have been different generations of turbines with different control and protection schemes over the decades. Wish I could be more specific!