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Posted by Bob D. on July 30, 2008 at 12:40:45:
In Reply to: Fuel switch posted by Carleton Langley on July 22, 2008 at 21:45:26:
If you only have the one gas service, and it's interruptible, you could put the ignitor permanently on CNG or LPG, or you could have a smaller "firm" service put in just for the ignitor, or you could look into converting your ignitor to an electronic unit, I believe they are called "Class 3 Special".
With the feedwater valves, there are a few other things to think about, such as how many other pneumatic loads you have out in the plant, do you want to swap over to electric actuators, stuff like that. I'd have a chat with a good, independent system integrator, not neccessarily my service rep. Remeber, if a saleman's lips are moving . . . .
For Lead/Lag, I usually install F&T "spill traps", in piping parallel with the water columns, at a level just above the normal water level. As steam from the header condenses in the idle boiler, the water level rises up to the spill trap, and no further, then spiills to drains or the B/D flash tank. Even combination stop & non-returns usually leak enough steam back to keep a stand-by boiler hot. But it all depends . . . . .
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