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Orifice in parallel with Control Valve

Orifice in parallel with Control Valve

Orifice in parallel with Control Valve

Hello to everyone,

In our Steam Turbine Seal Steam System we have the main control valve which opens at start up, run down and low load operation.
We also have a bypass manual valve in parallel with the control valve, in case the control valve fails.
The bypass valve is isolated during normaloperation.
Finally we have a third parallel line with an orifice. This line has two manual valves,
one before and one after the orifice, which are open during normal operation.
Coming from an electrical backround I cannot understand the purpose of the third line.

I would be gratefull if anyone could explain to me the abovementioned.

Thank you in advance,


RE: Orifice in parallel with Control Valve

I would THINK it is to provide a warming/draining flow to the feed lines to the steam seal station. Given the feed valves are closed when the unit is above minimun loading, condensation could accumulate in the supply piping without the orificed flow

RE: Orifice in parallel with Control Valve

Thank you for the answer!

Just to clarify, you are saying that condensation could accumulate in the supply line UNTIL the closed control valve?
After the control valve, in bigger loads, we have the seal steam pressure provided by the HP turbine glands.
Could we have condensation after the control valve as well, if it wasn't for the orifice??

RE: Orifice in parallel with Control Valve

I would ASSUME the slope of the pipe from the closed SSFV to the header would allow for drainage

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