What is the function of the following valve in water injection/ gas turbine 9FA?
VS2-1
VS2-2
VC4-1

 

Do you have a copy of the P&ID for the Water Injection system? To make good use of that you also need the Device Summary document provided with the equipment.

There should also be copies of the Operation & Maintenance Manuals available to everyone who works with the turbine-generator and auxiliaries in the plant. There is a System Description section for each system which describes components and operation.

I guess the two VSn-n devices are Stop Valves (or, Valve-Stop), and the VCn-n device is a Control Valve (or, Valve-Control). You need the P&ID to help you see where the components are in the system based on the numbers of the devices. (The reason for two stop valves is probably because there are low- and high flow manifolds in the Water Injection system—but the P&ID and the System Description will be most helpful and accurate.)

But my guesses are just that—without access to the P&ID for the Water Injection system at your site.

 

Thanks for your reply,
I checked the functional description and p&id but I didn’t found anything which realted to the operAtion of this valves.
My question is, how valves are working during preselect and baseload mode? ?

 

That WASN'T clear from your original post... at all.

Pre-Selected Load can be ANY load between 0 MW and Base Load. (Some people MISTAKENLY use Pre-Selected Load Control to load a machine to CPR-biased exhaust temperature control by entering a load reference that is very high, and while the machine will reach CPR-biased exhaust temperature control the Droop Speed Control reference (which is how the machine is loaded and unloaded) will often go VERY high even when the machine is limited by CPR-biased exhaust temperature control. Using Pre-Selected Load Control is a VERY BAD way to operate a machine.)

Typically Water Injection isn't started until the fuel flow-rate exceeds some value (it varies for each site and sometimes even for individual machines on the same site). So, unless the Pre-Selected Load Control Reference causes the fuel flow-rate to be above the setpoint at which Water Injection is enabled there will be no Water Injection flowing to the machine, and the Stop Valves and the Control Valve will both be closed.

All of the sheets of the P&ID are not shown so it's not possible to see where the discharge of the Stop Valves go and since this is a GE Belfort design it's not really clear what the Control Valve is doing (VC4-1A)--since it seems to bypass the Stop Valves entirely.

BUT, when the fuel flow-rate exceeds the Water Injection enabling setpoint the Stop Valves will open and the Control Valve will (usually--this IS a GE Belfort design so all bets are off without more information, which should be in the System Description) modulate to control the Water Injection flow-rate, which is usually also a function of the fuel flow-rate. As the fuel flow-rate increases the amount of Water Injection required to meet the emissions requirements of the site will increase, meaning the Control Valve will move to increase the Water Injection flow-rate. As the fuel flow-rate decreases the Control Valve will act to reduce the Water Injection flow-rate in order to meet the emissions requirements. (In other words, the amount of water being injected varies with fuel flow-rate.)

At Base Load the Stop Valves will be open and the Control Valve will also be modulating the Water Injection flow-rate--because the amount of fuel flowing at Base Load is not constant, throughout the day or the year. It will vary primarily with ambient temperature and axial compressor inlet temperature (if some kind of inlet air cooling system is used). So, the amount of Water Injection required to maintain emissions will also vary--though not by much, just a small amount.

We don't know if the machine you are working on burns only liquid fuel(s) or if it burns natural gas/LNG (Liquified Natural Gas) and liquid fuel(s). MOST 9FA machines have DLN (Dry Low NOx) combustors which don't use Water Injection when operating on most gaseous fuels, but do require water injection when burning liquid fuel(s). So, it's typical to see Water Injection only running when the machine is running on liquid fuel(s).

It would be helpful if you have other questions about the system if you would post the other sheets (pages) of the P&ID. And, for me--I would like to read the Water Injection System Description to see if I can understand what GE Belfort is doing with this particular Water Injection system.

Hope this helps you in your quest to understand the system better.

If you are experiencing problems with the Water Injection system by describing the problems--and giving some actionable data (trends of fuel flow-rate and Water Injection flow-rate and valve status indications (for example, there appear to be some limit switches on VC4-1A as well as on VS2-1, -2 & -3) we might be able to help with troubleshooting and resolution.