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I am hoping to get some help in determining the cause of excessive H2 loss in our generator. We have been going through about 3 to 4 bottles/day compared to a normal of about 1/2 to 1 bottle/day (or 5 psig per day compared to about 1 or less). This has occurred following a purge incident while the unit was offline but not immediately, as immediately after for about two weeks usage was normal and then suddenly a sharp increase. The background information is as follows and any ideas are appreciated:
GE 7FA simple cycle turbine.
seal oil flow, DP, and scavenging flow rates are normal, and in fact scavenging flow rates on the E-One DHCP have been reduced from total flow of 3000sccm to 2500sccm in an effort to slow H2 losses (no noticeable effect on either purity or H2 usage).
Purge incident was due to power loss from substation (not at our plant) trip caused by weather.
CO2 Purge valve line-ups have been closed since the incident due to a stuck solenoid valve. we have done this so that we don't lose H2 through the CO2 header and out the CO2 inlet line which is normally valved into the purge vent line via another solenoid.
As mentioned after purge for about two weeks H2 usage was normal and then we had a couple of normal runs (about 10 hours on separate days) over the course of a week. then we went on an extended run (for us) of 5 days and toward the end of that run is when we can determine that the usage increased.
Logic would point to a relationship between the purge incident and H2 increase even with the two weeks of normalcy, but what exactly could that have done to cause this? We are leaning toward seal damage but aren't seeing any other indicators of seal damage or possibly something having to do with the CO2 valving closed off. However it seems highly unlikely to be related to the CO2 valve as it is closed (double blocked) at the header and therefore isn't connected to any other piping. The only reason CO2 valving is suspect at all is because it is an abnormal condition, but in reality it seems almost impossible to be the cause.
Thanks folks and hopefully someone can help because I dread the thought of a very expensive and time-consuming seal replacement if that is not the cause.
GE 7FA simple cycle turbine.
seal oil flow, DP, and scavenging flow rates are normal, and in fact scavenging flow rates on the E-One DHCP have been reduced from total flow of 3000sccm to 2500sccm in an effort to slow H2 losses (no noticeable effect on either purity or H2 usage).
Purge incident was due to power loss from substation (not at our plant) trip caused by weather.
CO2 Purge valve line-ups have been closed since the incident due to a stuck solenoid valve. we have done this so that we don't lose H2 through the CO2 header and out the CO2 inlet line which is normally valved into the purge vent line via another solenoid.
As mentioned after purge for about two weeks H2 usage was normal and then we had a couple of normal runs (about 10 hours on separate days) over the course of a week. then we went on an extended run (for us) of 5 days and toward the end of that run is when we can determine that the usage increased.
Logic would point to a relationship between the purge incident and H2 increase even with the two weeks of normalcy, but what exactly could that have done to cause this? We are leaning toward seal damage but aren't seeing any other indicators of seal damage or possibly something having to do with the CO2 valving closed off. However it seems highly unlikely to be related to the CO2 valve as it is closed (double blocked) at the header and therefore isn't connected to any other piping. The only reason CO2 valving is suspect at all is because it is an abnormal condition, but in reality it seems almost impossible to be the cause.
Thanks folks and hopefully someone can help because I dread the thought of a very expensive and time-consuming seal replacement if that is not the cause.