We have one Frame 6 MarkVIe controlled 30 MW Gas Turbine. Control system was upgraded from MarkIV to MarkVIe during Major Inspection in February 2012.

Just now we finished its HGPI. During HGPI 2nd and 3rd stage buckets and shrouds were replaced, remaining parts were reused. After start up we have observed reduction in GT exhaust temperature by @ 30 deg C compared to that before shutdown. There are no changes in IGV, SRV & GCV positions. Our inlet filters are replaced and inlet DP came down. Also we have noticed reduction in GT fuel gas without any significant changes in it's calorific value. Comparison of data taken at different load before and after are as follows.

what may be reason of reduced fuel gas flow and exhaust temperature?



















<pre>
COMPARISON AT
25 MW 20 MW 15 MW 10 MW 5 MW FSNL
Gas Turbine BEFORE AFTER BEFORE AFTER BEFORE AFTER BEFORE AFTER BEFORE AFTER BEFORE AFTER
Data
DW MW 23.9 25.2 19.8 19.7 15 15.2 9.4 10 4.8 5.2 FSNL FSNL
Speed RPM 5104 5124 5098 5119 5065 5122 5131 5101.8 5114 5130 5100 5125.5
NG FLOW SM3/Hr 9000 8500 8300 8000 7200 6800 5600 5400 5300 5300 3000 3000
TTXM Deg.C 565 556 560 508.9 524 455 451.2 401.7 396.2 343.6 329.5 279
CPD Kg/cm2 8.9 8.6 7.7 8 7 7.6 6.7 7.1 6.2 6.7 5.7 6.3
CTD Deg.C 370.9 334.3 345.7 325.3 334.1 318.1 323.1 319.7 311.6 306.7 299.4 292
CTIM Deg.C 36 28.6 36 28.4 35.2 28.6 34.2 33 32.8 33.8 32.6 26.4
CSGV % 83.1 59.5 60.9 57 56.1 56.9 56.1 57 56.1 56.9 56.1 57
Spread Deg.C 39.9 33.5 21 14.2 24 10.8 24.7 11.9 32.8 33.8 32.6 6.5</pre>
Please share your views

 

How is IGV operation?

Have you calibrated it and verified its angle?

take care
G.Rajesh

 

It pretty well looks like you did a good job on the HGPI. You should really try and compare Base Load before and after an inspection, that will give you more reliable results. You should be happy, your fuel flow is down, TTXM is less at the same load, your machine is more efficient..!!

 

> How is IGV operation?

> Have you calibrated it and verified its angle?

Not during this shutdown