S
SB
Question Regarding Inversion Masking
______________________________________________________________________
Dear CSA,
I've been following this thread (I read this whenever I get time) and I appreciate the time and energy you devote to the community. Please continue this thread. As your last two posts are not appearing when I open this thread, I'll be good if this discussion is continued in other thread (part II as Neo said).<pre>
L86CB L4Y l27qel L3CP l63fdl
---|/|-------||--------|/|-------||-----|/|--------( ) L3STCK2
| |
| L43FTG |
|----||----|</pre>
L3STCK2: Start check 2
L86CB : Compressor bleed valve or IGV position lockout
L4Y : Loss of master protective
l27qel : Emergency lube oil pump under-voltage
L3CP : Customer permissive to start
l63fdl : Distillate fuel supply pressure switch
L43FTG : Transfer to Gas
As already said I'm also on this journey with you and Neo. I've learned to read the Rungs and interpret how it'll work. I've managed to get some of the Application Code running in our Speedtronic Mark VI, and I've a question regarding inversion masking.
let me read the Rung:
when L86CB is logic "0" AND L4Y is logic "1" AND l27qel is logic "0" AND L3CP is logic "1" AND l63fdl is logic "0" OR L43FTG is logic "1" L3STCK2 will be logic "1".
now interpreting it:
When there is NO compressor bleed valve or IGV position lockout AND loss of master protective timer is complete AND Emergency lube oil pump is NOT undervoltage AND Customer permissive to start is selected AND Distillate fuel supply pressure is NOT low OR transfer to gas is selected, start check 2 is completed.
Coming to my question, I think the signal l27qel and l63fdl are inverted.
For l27qel: When EOP is not under-voltage, the NC contacts will remain closed and thus it will allow L3STCK2 to pickup. When EOP is under-voltage the NC contacts will open and will prevent L3STCK2 to pickup. Thus when the contacts are closed then only L3STCK2 coil is allowed to pick up. This ensure when the contacts are closed EOP is not under-voltage and the switch is also in healthy condition, thus doing the work of supervision too. Instead, had GE had chose the contacts to close when EOP is under-voltage, we wouldn't have known even if the circuit is intact or not.
For l63fdl, When the distillate supply pressure is not low the NC contacts will remain closed thus alowing L3STCK2 to pickup. When the distillate fuel supply pressure is low, the NC contacts will open, thus preventing L3STCK2 from picking up. Thus here also the contacts must be close, which ensures that the distillate supply pressure is normal and the switch circuit is intact.
Am I right? I've tried hard to understand the concept of inversion masking by reading (and re-reading) your explanations in this thread. Please correct me if I'm wrong.
______________________________________________________________________
As you asked about the machine at our site in http://control.com/thread/1403711658#1404062279. It is a PG5361. It is having conventional combustors. The machine is duel fuel capable. It can be operated on Natural Gas or Naptha, but it is operated on NG only since last 10 years. out of two machines, one was installed in 1988 and the other in 1996. Both the machines can be operated in Droop and Isochronous mode. Our plant generally (not all the time though) remains separated from the grid. Both the machines exhausts in HRSG. This arrangement is having a By-Pass stack.
______________________________________________________________________
Dear CSA,
I've been following this thread (I read this whenever I get time) and I appreciate the time and energy you devote to the community. Please continue this thread. As your last two posts are not appearing when I open this thread, I'll be good if this discussion is continued in other thread (part II as Neo said).<pre>
L86CB L4Y l27qel L3CP l63fdl
---|/|-------||--------|/|-------||-----|/|--------( ) L3STCK2
| |
| L43FTG |
|----||----|</pre>
L3STCK2: Start check 2
L86CB : Compressor bleed valve or IGV position lockout
L4Y : Loss of master protective
l27qel : Emergency lube oil pump under-voltage
L3CP : Customer permissive to start
l63fdl : Distillate fuel supply pressure switch
L43FTG : Transfer to Gas
As already said I'm also on this journey with you and Neo. I've learned to read the Rungs and interpret how it'll work. I've managed to get some of the Application Code running in our Speedtronic Mark VI, and I've a question regarding inversion masking.
let me read the Rung:
when L86CB is logic "0" AND L4Y is logic "1" AND l27qel is logic "0" AND L3CP is logic "1" AND l63fdl is logic "0" OR L43FTG is logic "1" L3STCK2 will be logic "1".
now interpreting it:
When there is NO compressor bleed valve or IGV position lockout AND loss of master protective timer is complete AND Emergency lube oil pump is NOT undervoltage AND Customer permissive to start is selected AND Distillate fuel supply pressure is NOT low OR transfer to gas is selected, start check 2 is completed.
Coming to my question, I think the signal l27qel and l63fdl are inverted.
For l27qel: When EOP is not under-voltage, the NC contacts will remain closed and thus it will allow L3STCK2 to pickup. When EOP is under-voltage the NC contacts will open and will prevent L3STCK2 to pickup. Thus when the contacts are closed then only L3STCK2 coil is allowed to pick up. This ensure when the contacts are closed EOP is not under-voltage and the switch is also in healthy condition, thus doing the work of supervision too. Instead, had GE had chose the contacts to close when EOP is under-voltage, we wouldn't have known even if the circuit is intact or not.
For l63fdl, When the distillate supply pressure is not low the NC contacts will remain closed thus alowing L3STCK2 to pickup. When the distillate fuel supply pressure is low, the NC contacts will open, thus preventing L3STCK2 from picking up. Thus here also the contacts must be close, which ensures that the distillate supply pressure is normal and the switch circuit is intact.
Am I right? I've tried hard to understand the concept of inversion masking by reading (and re-reading) your explanations in this thread. Please correct me if I'm wrong.
______________________________________________________________________
As you asked about the machine at our site in http://control.com/thread/1403711658#1404062279. It is a PG5361. It is having conventional combustors. The machine is duel fuel capable. It can be operated on Natural Gas or Naptha, but it is operated on NG only since last 10 years. out of two machines, one was installed in 1988 and the other in 1996. Both the machines can be operated in Droop and Isochronous mode. Our plant generally (not all the time though) remains separated from the grid. Both the machines exhausts in HRSG. This arrangement is having a By-Pass stack.