Request experts on the forum to kindly help us with the following problem with one of the two Gas Turbines.
The problem is being faced by my colleagues in a remote field so am posting their proximate experience here. Pardon me for any missed out information. Have tried my best to collate whatever I cud gather from them.
Brief Process Description:
Two Gas Turbines (GT1 & GT2) power a Gas Injection Plant
Machine Details:
Then Allison (Now Siemens) Make;
3 MW each @ 50Hz;
14000 RPM,
Model 501KB5
The Fuel to the Turbines is fed from a preceding stage of Booster Compressor (Boosts Gas Pressure from 6 Kg/Cm2 to 18 Kg/Cm2).
The Booster Compressor Cuts in at 18 Kgs and Cuts off at 21 Kgs. Cut in Cut Off periodicity is 3 - 4 Mins (Take 3 - 4 mins to Cut in and 3 - 4 Mins for Cut Off)
Downstream of Booster Compressor is a PCV (after 'Dominic Filters' in the diagram) which maintains pressure to GT inlets at 15-16 Kgs BUT this PCV is not functional AND hence is kept fully opened, manually. (One can alternatively say that the Gas Pressure to GT inlet is fluctuating at the same rate as the Cut-in Cut OFF cycle of Booster Compressor)
Operation of GTs is in Parallel. They are not connected to any larger state Grid. Both GTs normally share equal loads.
Nominal Plant Load is approx 4 MW. Each GT takes 2 MW in sharing mode.
Problem (described below) occurs atleast 4 - 6 times a day. About a month ago, when the problem started it was about once in four days. So clearly the problem is showing an an increasing trend.
The machines have been in 24x7 operations and havent been subjected to any major maintenance activity prior to the problem.
Problem Description:
GT1, the problematic guy, suddenly throws approx. 25% of the load.. The load is taken up by GT2 but due to this there is a 30-45 seconds of a turbulent period which causes the load to fluctuate on GT1. After 45 Seconds or so, the load is again equalized on both machines. Problem is more frequently noticed when machines are running above 1.8MW EACH.
Technicians have replaced the Fuel Control Card, Checked the Fuel Control Valves, MW Transducer. Seemingly, everything sounds and looks right. Except, for the PCV upstream, which as already said above, is currently out of line. Hence the Governor Inlet Pressure swings with the Cut-in Cut-OFF frequency of the Booster Compressor (which is roughly 3 - 4 Mins). But those with little experience with the machine, say that Fuel Controller has in past been able to handle similar upstream fluctuations and find little reason to doubt it.
Some Questions:
1) Obviously, given the info, what are the possible reasons which we shud be looking at to identify the problem
2) Would the Booster Compressor Discharge fluctuations weight in heavily to the problem? May be I have over emphasized this issue in the description (due to my personal bias, I guess) but would request experts here to kindly look the entire problem for other possible reasons too.
Thanks in adv and regards
Attaching a few available and relevant drawings for a perspective
The problem is being faced by my colleagues in a remote field so am posting their proximate experience here. Pardon me for any missed out information. Have tried my best to collate whatever I cud gather from them.
Brief Process Description:
Two Gas Turbines (GT1 & GT2) power a Gas Injection Plant
Machine Details:
Then Allison (Now Siemens) Make;
3 MW each @ 50Hz;
14000 RPM,
Model 501KB5
The Fuel to the Turbines is fed from a preceding stage of Booster Compressor (Boosts Gas Pressure from 6 Kg/Cm2 to 18 Kg/Cm2).
The Booster Compressor Cuts in at 18 Kgs and Cuts off at 21 Kgs. Cut in Cut Off periodicity is 3 - 4 Mins (Take 3 - 4 mins to Cut in and 3 - 4 Mins for Cut Off)
Downstream of Booster Compressor is a PCV (after 'Dominic Filters' in the diagram) which maintains pressure to GT inlets at 15-16 Kgs BUT this PCV is not functional AND hence is kept fully opened, manually. (One can alternatively say that the Gas Pressure to GT inlet is fluctuating at the same rate as the Cut-in Cut OFF cycle of Booster Compressor)
Operation of GTs is in Parallel. They are not connected to any larger state Grid. Both GTs normally share equal loads.
Nominal Plant Load is approx 4 MW. Each GT takes 2 MW in sharing mode.
Problem (described below) occurs atleast 4 - 6 times a day. About a month ago, when the problem started it was about once in four days. So clearly the problem is showing an an increasing trend.
The machines have been in 24x7 operations and havent been subjected to any major maintenance activity prior to the problem.
Problem Description:
GT1, the problematic guy, suddenly throws approx. 25% of the load.. The load is taken up by GT2 but due to this there is a 30-45 seconds of a turbulent period which causes the load to fluctuate on GT1. After 45 Seconds or so, the load is again equalized on both machines. Problem is more frequently noticed when machines are running above 1.8MW EACH.
Technicians have replaced the Fuel Control Card, Checked the Fuel Control Valves, MW Transducer. Seemingly, everything sounds and looks right. Except, for the PCV upstream, which as already said above, is currently out of line. Hence the Governor Inlet Pressure swings with the Cut-in Cut-OFF frequency of the Booster Compressor (which is roughly 3 - 4 Mins). But those with little experience with the machine, say that Fuel Controller has in past been able to handle similar upstream fluctuations and find little reason to doubt it.
Some Questions:
1) Obviously, given the info, what are the possible reasons which we shud be looking at to identify the problem
2) Would the Booster Compressor Discharge fluctuations weight in heavily to the problem? May be I have over emphasized this issue in the description (due to my personal bias, I guess) but would request experts here to kindly look the entire problem for other possible reasons too.
Thanks in adv and regards
Attaching a few available and relevant drawings for a perspective
