where/how to add pressure gages to measure stage pressures

[DonkeyPhysics]

Hi there,

I work for an electric company who periodically has to due efficiency tests on our plant turbines. Related to one of those, we're looking to modify a 5-stage, axial, condensing, geothermal steam turbine, to add pressure ports for stage pressures, to facilitate more detailed on-going monitoring.

It's unclear, however, both where would be ideal locations along the turbine to add the ports (i.e. inter-stage, mid-stage, etc), and also if something akin to pitot tubes exists for steam turbines. If no pitot tubes, what kind of pressure devices do exist (and are typical) for this type of usage? I assume we're not unique in wanting to do this.

Any thoughts on this subject? I'm still new enough that it's not yet clear to me what questions I should be asking to fully address the issue.

Thanks in advance.

-Alex-

 

[DonkeyPhysics]

fyi, the goal here for the monitoring is to be able to more rapidly identify leakages or other losses during normal operation.

 

[byrdj]

While not my expertise, I'll comment given no one else has yet.
the location of stage pressure connections for the primarly impulse design units I have seen are between the stationary diaghrams and thus are measuring the pressure as seen by the rotating bucket wheel. there is a "chamber" between the diagphrams that is some what shielded from any velocity with a gap between the two to allow the chamber to sense the stage pressure.

thus the pressure measurement is pure static and just a single pipe connection. there needs to either a cooling and condensation collector to prevent the pressure sensing device from being over heated with steam. if the condensation head is a concern for your performance calculations, I have seen the use of low flow nitrogen purge of the sensing lines during the gather of pressure measurements. I am not sure since I have not read them in a few decades, but ASME PTC6 may discuss.

as for a pitot tube, i have seen devices installed in steam flow piping to inform which direction the steam is flowing, they were reffered to as foward/reverse tubes. they act like a pitot in that two pressures are compared, but they were both dynamic.