Reasons for CPD Varying on Frame 9

Dear All,

What are the all possible reason for less CPD? In one of our Frame-9E machine CPD is 0.3 bar less than other similar GT.

We are planning to inspect the below at available chance
1. IGV position
2. CPD transmitter calibration
3. Filter house inspection
4. Bleed valve inspection

Please add your input, what else can be inspected?

take care
g.rajesh
 
grajesh,

This question is related to the performance of heavy duty gas turbines--a topic which has been covered MANY times before on control.com (and we know you're a very constant reader of most of the heavy duty gas turbine-related posts on control.com).

Machine conditions (internal clearances of the axial compressor, and of the turbine buckets with the shroud blocks; the condition of the seals between the transition pieces; the conditions of the axial compressor blades, and the turbine nozzles); exhaust duct back-pressure; time since last off-line water wash; time since last CI or HGPI or MI; etc. All of these can have significant impact on axial compressor/unit performance, in addition to the things you've listed.

Even two brand new "identical" units, built one right after the other in the same factory, and installed side-by-side on the same site with the same equipment, and commissioned at the same time will NEVER have exactly the same operating conditions and/or performance. There are just too many variables--too many. Even brand new fuel nozzles have a tolerance (as a set) which may make the output of the two machines radically different (not necessarily the CPD, but this example is about two new, "identical" units.

Please write back to let us know the results of your investigation. Also, how will you be verifying the accuracy of the IGV LVDT feedback ("calibration")? Will you be using a machinist's protractor to measure the actual IGV angles and comparing them to the calibrated feedback, not just the position reference? (What is the null bias current value for the IGVs for this machine?)

Thanks--and we look forward to hearing back from you!
 
Thank you CSA as your usual supports.

Last offline wash carried out on Dec 2014 and another one planned next month Nov 2015.HGPI carried Dec 2013 and CI planned in Mar 2015.We are measuring IGV angle by protector and confirming. IGV current bias is 2.7.

We'll keep you updated after our offline water wash.

thanks again

take care
g.rajesh
 
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