Hi Dears!

GCV doesn't open by calibration 5 step procedure and at 100% percent of demand. it opens only 8 mm base on mechanical valve scale (0-40mm range). All LVDTs voltages are good, and display on HMI shows 100%, but actually the valve displacement shows 8 mm!

Please help me to find where is the problem, and How I can calibrate just servo valve?

 

Dear,

You haven't provided much information about the valve (type; manufacturer (Young & Franklin; Woodward; Fisher; etc.), the turbine it's mounted on, the turbine control system (Mark I, Mark II, Mark IV, Mark V, Mark VI or Mark VIe), etc.

Have you properly established Hydraulic pressure, and Trip Oil pressure, if necessary (some units require Trip Oil to stroke the GCV; many do not, but it's an important distinction). Does the turbine have an Auxiliary Hydraulic Pump, or do you have to CRANK the turbine to establish Hydraulic pressure?

One thing which can be said: Servo-valves are <b>>>NOT<<</b> calibrated. <b><i>ONLY LVDT FEEDBACK CAN BE CALIBRATED.</b></i> You may use the Manual feature of AutoCalibrate to stroke (move) a servo-operated device, but servo-valves are NOT calibrated--only LVDT feedback.

Usually when something like this happens on a GE digital Speedtronic turbine control system it's because the LVDT feedback has been improperly calibrated--usually when using AutoCalibrate. And that results in the Speedtronic thinking that 100% open is less than actual 100% open.

But, to be helpful, we need a LOT more information than was provided. It's noted you checked GE Mark V/VI, but we need to know which Speedtronic to be able to help you--and if it's a Mark V if you're using AutoCalibrate or Demand Displays to stroke the valve.

If you're having some problem with unit operation and suspect the GCV LVDT calibration or valve actuation to be the problem, please describe the problem and we can help troubleshoot that, as well.

This topic has been covered <b>many</b> times on control.com (LVDT calibration). MANY times. There is a 'Search' function on control.com, but it's recommended you use the Search 'Help' before beginning because it's not as intuitive as the typical Internet search engine.

But, if you'll take a few minutes and provide the requested information--and if you're having other issues which are being attributed to the GCV and you're just trying to stroke the GCV to see if it's working correctly, please describe the problem being attributed to the GCV.

 

Do you have a Moog in your system?

> Please help me to find where is the problem, and How I can calibrate just servo valve?

 

dear

what about primary and secondery oil pressure?
can you please share GCV operation principle like EHC or Moog?
which machine GE, Siemens, etc.?