J
Can any body help me to understand the servo valve P&ID diagram of GE Frame 9E, There is Hydraulic symbols. Please tell me about the P&ID Sketch Condition (Running) (Tripping) or (Shutdown). Servo valve 65GC1.
Thanks
Thanks
V
Voyager2kbc
The servo valve is always working on a neutral position or a Null position given by the position of a spool located inside the servo valve. This null position is maintained through a hydraulic oil nozzle acting over the middle of the spool. This nozzle is attached to a torsion motor who has two coils. Depending on if you want to increase or decrease the load, those coils, through the current that reaches to them, will make the torsion motor moves the nozzle to the right or to the left. This will also make the spool moves to the same direction as the torsion motor moves. Under the spool there are son ports (P1, P2) that remain closed while the spool is in the middle position or null position, but when the nozzle makes the spool moves, some of these ports (P1, P2) opens and some closes, making the hydraulic oil enter by one side (port) and going out by another side (port). When the turbine reaches the load that you want, then the torsion motor, through the currents at the coils, makes the nozzle to point again to the middle position or null position and will remain always in this position, unless a variation of load is required. If the spool is not able to return and to remain at the null position, you have to replace it.
Voyager2kbc
Voyager2kbc
P
Process Value
this thread has quite a bit of info on the working of a servo. It does not use the symbols used in the PID but it will give you a good idea of working of a servo (flapper nozzle type).
http://www.control.com/thread/1289667103
http://www.control.com/thread/1289667103
I don't know why people just freak out when they see "hydraulic symbols". It's like they are the devil incarnate, or something worse, even.
If you have a machine packaged and provided by GE, you should be able to find in the drawings and instruction (service) manuals provided with the unit a drawing called, appropriately enough, 'Piping Symbols'. It can be used to decipher those hydraulic symbols.
But, just in case you can't find the Piping Symbols drawing, this little piece of information might help you. On opposite sides of the servo representation are two parallel lines, enveloping the servo representation. The Piping Symbols drawing says those two lines mean that the device between the two lines is "infinitely positionable". Which is another way of saying, the device between the lines is usually never fully open nor fully closed, but can be at any position in between fully open or fully closed.
An electro-hydraulic servo-valve is not going to be operated at any *one* of the positions depicted by the symbol. Those positions just indicate that flow can go through the servo valve in the directions indicated by the arrows, but the flow can be "throttled" (reduced or increased) by small changes in the position of the servo-valve spool piece.
If you would just redraw the symbol on paper with pencil, using each of the positions shown for a single instance, you will quickly see what the symbol is trying to show you. Which is how oil can be ported to and from the actuator to open and close the gas control valve. The infinitely positionable portion of the symbol means that the flow can be increased or decreased as required to put the gas control valve at the desired position.
So, while the symbol seems to indicate three or four distinct positions, the "envelope" (the parallel lines on either side if the symbol) indicate that it can be in *any* intermediate position in order to throttle the flow as required.
Lastly, as Voyager2kbc has said, when the gas control valve is at the desired position the flow of hydraulic oil through the servo valve is essentially at zero because the gas control valve does not need to be opened or closed. In reality, the only time there is flow through the valve is when it needs to be opened or closed from its current position.
When the unit is shut down or when gas fuel flow is not to be flowing the servo-valve is moved to the position to prevent high-pressure hydraulic oil from reaching the gas control valve actuator and also to allow any oil in the actuator to drain out, thereby allowing the great big spring on the valve to keep the valve closed.
As a point of clarification, the servo-valve of a TMR (Triple Modular Redundant) Speedtronic control system will have three coils, and the servo-valve of a SIMPLEX or DUAL redundant Speedtronic control system will have two coils.
If you have a machine packaged and provided by GE, you should be able to find in the drawings and instruction (service) manuals provided with the unit a drawing called, appropriately enough, 'Piping Symbols'. It can be used to decipher those hydraulic symbols.
But, just in case you can't find the Piping Symbols drawing, this little piece of information might help you. On opposite sides of the servo representation are two parallel lines, enveloping the servo representation. The Piping Symbols drawing says those two lines mean that the device between the two lines is "infinitely positionable". Which is another way of saying, the device between the lines is usually never fully open nor fully closed, but can be at any position in between fully open or fully closed.
An electro-hydraulic servo-valve is not going to be operated at any *one* of the positions depicted by the symbol. Those positions just indicate that flow can go through the servo valve in the directions indicated by the arrows, but the flow can be "throttled" (reduced or increased) by small changes in the position of the servo-valve spool piece.
If you would just redraw the symbol on paper with pencil, using each of the positions shown for a single instance, you will quickly see what the symbol is trying to show you. Which is how oil can be ported to and from the actuator to open and close the gas control valve. The infinitely positionable portion of the symbol means that the flow can be increased or decreased as required to put the gas control valve at the desired position.
So, while the symbol seems to indicate three or four distinct positions, the "envelope" (the parallel lines on either side if the symbol) indicate that it can be in *any* intermediate position in order to throttle the flow as required.
Lastly, as Voyager2kbc has said, when the gas control valve is at the desired position the flow of hydraulic oil through the servo valve is essentially at zero because the gas control valve does not need to be opened or closed. In reality, the only time there is flow through the valve is when it needs to be opened or closed from its current position.
When the unit is shut down or when gas fuel flow is not to be flowing the servo-valve is moved to the position to prevent high-pressure hydraulic oil from reaching the gas control valve actuator and also to allow any oil in the actuator to drain out, thereby allowing the great big spring on the valve to keep the valve closed.
As a point of clarification, the servo-valve of a TMR (Triple Modular Redundant) Speedtronic control system will have three coils, and the servo-valve of a SIMPLEX or DUAL redundant Speedtronic control system will have two coils.
