To avoid a single point failure, i.e. redundancy.

saludos.
a.

well done albetio.
looks like the OP works for a contractor and you work for a manufacturer, am I wrong ?

"If you want to acquire a knowledge or skill, read a book and practice the skill".

It might just be one is "abondoned in place". the "gate" to allow both to be in service would probalbly be more cmplicated than either.

A control diagram would be useful

I have seen turbines with multiple, redundant over-speed trip systems. I have never seen multiple redundant governors. I don't know how that could work. One of the systems may be OST and the other is a governor. The other possibility is that the TG governor is not a governor, but just an actuator for the electronic governor. They make an actuator that mounts in place of the old TG governor to actuate the governor valve. I have considered doing this. It makes the retrofit simpler. Search for Woodward TG Actuator. This is from their web site:

TG-13E & TG-17E Actuators

Woodward’s TG-13E/TG-17E self-contained electro-hydraulic actuators are used in the replacement of TG governors with an actuator and electric control system. The TG-13E and 17E proportional electro-hydraulic actuators convert an electrical signal to a corresponding proportional output shaft position in order to position the valve that controls the flow of steam (or energy medium) to the turbine. The actuators are intended for controlling small steam turbines that drive loads such as alternators, dc generator pumps, compressors, fans or papermaking machines.

Johnny Pellin

I reviewed the post from the last time you asked this question, I had forgotten. The first time, you didn't describe the hydraulic governor as a TG. That was the clue the led to the TG Actuator. A picture or a control diagram would solve the mystery for certain. It sounds like you have a Tri-Sen electronic governor with a Woordward TG hydraulic actuator. The Peak-150 panel must be just for the user interface. It would be possible to have two electronic governors (Tri-Sen and Woodward Peak-150) with some sort of control logic to select between the two. But, I can't understand why anyone would do that. But, I would bet you dollars to donuts that the TG "governor" is just a dumb actuator and not a true governor, at all.

Johnny Pellin

Thanks a lot all of you fit your views.

J Pellin and Rdbj , I will get back to your query if I locate a control diagram .rotw, I did read Heinz Bloch but not much help with this specific doubt

J Pellin , I agree it may not be a real governor as you said because in the field they always use wrong terminologies

I appreciate your detailed and dedicated reply( as you always do)

Thanks again!

Also the electronic governors may be adjusting the set points of the mechanical governors.
The electronic governor would provide control of the normal operation and the mechanical governor would provide loss of load protection.
This would be similar to a grid connected generator with a droop governor. The loading can be controlled by adjusting the set point, manually or automatically. On loss of grid connection, (load loss), the droop function of the mechanical governor allows a few percent increase in speed and continues in droop control mode.

Bill
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